DVS_Bericht_380LP

MAY 4 – 6, 2022 VIENNA, AUSTRIA
2022
DVS-BERICHTE
Conference Lectures
and Poster Sessions
Organizers:
• DVS – German Welding Society
• ASM International – Thermal Spray Society (TSS)
• IIW – International Institute of Welding
Supporting Partners
Media Sponsors

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• laser cladding and am stations
laser power up to 22 kW!
• mega-ts station
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• Powder and wire flame spray station
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MAY 4 – 6, 2022 VIENNA, AUSTRIA
Conference Abstracts
(including proceedings on USB stick)
Organizers:
• DVS – German Welding Society
• ASM International – Thermal Spray Society (TSS)
• IIW – International Institute of Welding
Supporting Partners
Media Sponsors

The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie;
detailed bibliographic data are available in the Internet at http://dnb.d-nb.de.
Bibliographic information published by the Deutsche Nationalbibliothek
The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie;
detailed bibliographic data are available in the Internet at http://dnb.d-nb.de.
DVS-Berichte Volume 380
ISBN 978-3-96144-180-8 (Print)
ISBN 978-3-96144-181-5 (E-Book)
DVS-Berichte Volume 380
ISSN 0418-9639
ISBN Cover: 978-3-96144-180-8 © mRGB / stock.adobe.com (Print)
ISBN 978-3-96144-181-5 (E-Book)
The conference abstracts are printed in form of manuscripts.
ISSN 0418-9639
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Preface
WELCOME TO ITSC 2022 IN VIENNA, AUSTRIA
Second attempt:
After the cancellation of the ITSC 2020 in-person event, we will meet face-to-face for the first time after two years in
Vienna, Austria for ITSC 2022. ITSC 2022 will be held in the Austria Center Vienna (ACV).
There are lots of event highlights for ITSC interested attendees, who are looking for new coating solutions and who
want to learn more about practicable possibilities of surface treatment technologies. Under the slogan “Surface
Solutions”, ITSC invites visitors to a “3-Day Exposition”, to understand the versatility of different coating
technologies and to discover how flexible thermals spray can be.
The “Industrial Forum” is another characteristic of ITSC. This Forum will include practical demonstrations on
industry related topics, products and solutions.
One highlight will be offered at ITSC 2022 for the first time. “Thermal Spray in a Nut Shell” will be held on the first
conference day. This session will cover thermal spray processes with its main applications and its significance for
different branches. All registered visitors, conference and exposition, are welcome.
Last but not least ITSC offers new technology oriented topics, such as Cladding Technologies which have also
become more and more inter-testing for end users. Cladding also fulfills many requirement specifications in an
excellent way.
ITSC 2022 will also feature the latest improvements in the field of Additive Manufacturing (AM). For that, thermal
spray offers magnificent technological basis for new AM applications.
A fixed point of the technical program will be again the Session “Young Professionals”. ITSC 2022 is again
supporting young talents becoming part of the worldwide thermal spray family.
In total, ITSC never offered more highlights!
We look forward to welcoming you in Vienna, Austria!
Düsseldorf, April 2022
DVS – German Welding Society
Dipl.-Ing. Jens Jerzembeck
Head of Research and Technology

Committees and Endorsing Sponsors
General Chairs:
W. Krömmer The Linde Group (DE)
W. Lenling TST Coatings (US)
Technical Chairs:
K. Bobzin RWTH Aachen University (DE)
D. Lima National Council (CA) (Us)
DVS Representatives:
K. Bobzin RWTH Aachen University (DE)
B. Brommer DVS – German Welding Society (DE)
F. Ernst KS Huayu AluTech GmbH (DE)
F. Gärtner Helmut-Schmidt-University of the Allied
Forces (DE)
T. Grund Chemnitz University of Technology (DE)
S. Hartmann obz innovation gmbh (DE)
H. Heinemann RWTH Aachen University (DE)
X. Huang TSCC Thermal Spray Committee of
Chinese Surface Engineering Association
(CN)
J. Jerzembeck DVS – German Welding Society (DE)
T. Klassen Helmut-Schmidt-University of the Allied
Forces (DE)
W. Krömmer The Linde Group (DE)
T. Lampke Chemnitz University of Technology (DE)
T. Linke Nemak Dillingen GmbH (DE)
E. Lugscheider RWTH Aachen University (DE)
H. Maier Leibniz University (DE)
G. Mauer Forschungszentrum Jülich GmbH (DE)
K. Möhwald Leibniz University (DE)
M. Nabavi Oerlikon Metco AG (CH)
K. Nassenstein GTV Verschleißschutz GmbH (DE)
M. Öte Schaeffer Technologies AG & Co. KG
(DE)
F. Prenger Grillo Werke AG (DE)
C. Rupprecht Technische Universität Berlin (De)
F. Schreiber DURUM Verschleiss-Schutz GmbH (DE)
F. Tiggemann Flowserve Flow Control GmbH (DE)
W. Tillmann University of Dortmund (DE)
R. Vaßen Forschungszentrum Jülich GmbH (DE)
C. Wasserman TeroLab Surface Group SA (CH)
S. Weinreich DVS – German Welding Society (DE
W. Wietheger RWTH Aachen University (DE)
ASM-TSS Representatives:
S. Fowler-Hutchinson SAINT-GOBAIN CERAMICS-
SGP (US)
E. Irissou National Research Council (CA)
C. Kay ASB Industries (US)
H. Koivuluoto Tampere University of Technology (FI)
J. Koppes ST Coatings (US)
K. Laul Delta Airlines (US)
A. McDonald University of Alberta (CA)
C. Moreau Concordia University (CA)
K. Shinoda National Institute of Advanced Industrial
Science and Technology (JP)
K. Sridharan University of Wisconsin (US)
A. Vackel Sandia National Laboratories (US)
J. Veilleux Universite de Sherbrooke (CA)
J. Villafuerte Centerline (CA)
Endorsing Sponsors:
Asian Surface Technologies, PTE. Ltd. (SG)
BIL Belgisch Instituut voor Lastechniek (BE)
CEREM/CEA (FR)
Commission of the European Community (BE)
DGO – Deutsche Gesellschaft für Galvano- und Oberflächentechnik e. V. (DE)
DGM – Deutsche Gesellschaft für Materialkunde e. V. (D)
DKG – Deutsche Keramische Gesellschaft e. V. (DE)
DVS – Research Association (DE)
GTS – Gemeinschaft Thermisches Spritzen e. V. (DE)
International Thermal Spray Association (US)
Japan Thermal Sprayers Association (JP)
JTSS – Japanese Thermal Spray Society (JP)
TSSEA –Thermal Spraying & Surface Engineering Association (GB)
TWI The Welding Institute (GB)
VDI Verein Deutscher Ingenieure (DE)
VTS – Vereniging voor Thermische Spuittechnieken (NL)
ZMB – Zentrum Metallische Bauweisen e.V. RWTH Aachen (DE)

TIME SCHEDULE ITSC 2022 CONFERENCE AND EXPOSITION (Session Overview)
12:00 – 18:00 ITSC 2022 Exposition, ACV, Hall X2 (Level -2)
Wednesday, May 4, 2022
Time Hall D Hall G1 Hall G2 Hall -2.32/33 Hall K2
09:00
Opening:
• Welcome
• Plenary Lecture
• TSS Hall of Fame /
TSS President’s Award
10:30 Coffee Break, ACV, Hall X2
10:50 Aviation Industry I Modeling & Simulation I Arc Spraying Pre- & Post-Treatment Thermal Spray in a Nut Shell
12:30
Lunch Break, ACV, Hall X2
Kick-off ITSC 2022 Exposition, Hall X2
Poster Session, ACV, Hall X2
14:00 Automotive Industry HVOF/HVAF Spraying I Precision Melt Engineering Suspension Spraying I Thermal Spray in a Nut Shell
15:20 Coffee Break, ACV, Hall X2
15:40
17:00
Session
“Young Professionals”
with Awards Presentation
• ITSC Best Paper Awards
• Oerlikon Metco Young
Professionals Award
17:45 End of ITSC 2022 Conference Program
18:00
Exhibitor Networking Reception, ACV, Hall X2
Poster Session, ACV, Hall X2
10:00 – 16:00 ITSC 2022 Exposition, ACV, Hall X2 (Level -2)
Thursday, May 5, 2022
Time Hall D Hall G1 Hall G2 Hall -2.32 / 33 Hall K2
09:00 Aviation Industry II HVOF/HVAF Spraying II New Processes I Metal Coatings I
10:40
Coffee Break, ACV, Hall X2
Poster Session, ACV, Hall X2
11:00 Industrial Gas Turbines Modeling & Simulation II Wear Protection I Nanomaterial Coatings
12:40
Lunch Break, ACV, Hall X2
Poster Session, ACV, Hall X2
Thursday, May 5, 2022
Industrial Forum I:
Coatings, Applications,
Materials
Industrial Forum II:
State of the Art in
alternative Surface
Technology Processes
Time Hall D Hall G1 Hall G2 Hall -2.32 / 33 Hall K2
13:40 Cold Gas Spraying I Modeling & Simulation III Medical Industry Electronics & Sensors
15:20
Coffee Break, ACV, Hall X2
Poster Session, ACV, Hall X2
15:40 Cold Gas Spraying II Ceramic Coatings High Entropy Alloys I General Plant Engineering
17:20 End of ITSC 2022 Conference Program
Industrial Forum III:
Equipment & Diagnostics
Industrial Forum IV:
Equipment & Diagnostics
19:00 Social Event Evening in the Heuriger (winery event)
10:00 – 14:00 ITSC 2022 Exposition, ACV, Hall X2 (Level -2)
Friday, May 6, 2022
Time Hall D Hall G1 Hall G2 Hall -2.32 / 33 Hall K2
09:00 Additive Manufacturing Laser Cladding New Processes II Wear Protection II
10:40
11:00 Metal Coatings II Cold Gas Spraying III
12:40
13:40 Suspension Spraying II Cold Gas Spraying IV
Coffee Break, ACV, Hall X2
Poster Session, ACV, Hall X2
Characterization & Testing
Methods I
Lunch Break, ACV, Hall X2
Poster Session, ACV, Hall X2
Characterization & Testing
Methods II
15:20 End of ITSC 2022 Conference Program
Renewable Power
Generation
High Entropy Alloys II
Industrial Forum V:
Equipment & Diagnostics
Industrial Forum VI:
Others, Process Peripheral
Process, Diagnosrics,
Sensors & Controls

Table of contents
Preface
Time Schedule
Lectures
Aviation Industry I
Atmospheric Plasma Spraying of Environmental Barrier Coatings – A Parametric Study ........... 1
A. Lynam, A. Rincon Romero, F. Xu, M. Bai, T. Hussain
Evaluation of CMAS Resistance and Failure Behavior for Phase Compo-site Thermal Barrier
Coatings .................................................................................................................................... 14
X. Ma and P. Ruggiero, G. Wildridge
Deposition and characterization of silicon coatings by HVOF spraying .................................... 25
K. Bobzin, L. Zhao, W. Wietheger, E. Burbaum
Automotive Industry I
Environmentally friendly protective coatings for brake disks ..................................................... 32
A. Wank, C. Schmengler, A. Krause, K. Müller-Roden, T. Wessler
Young Professionals Session
Effects of Powder Feedstock Pre-Heating on Polymer Cold Spray Deposition…..…………….. 32
T. W. Bacha, D. A. Brennan, Ü. Tiitma, F. M. Haas, J. F. Stanzione
Aerosol Deposition of BiVO4 Films for Solar Hydrogen Generation………… ........................... 56
A. Elsenberg, T. Emmler, M. Schieda, F. Gärtner, T. Klassen
Microstructure and Wetting Performance of High-Pressure Cold Sprayed Quasi-Crystalline
Composite Coatings .................................................................................................................. 63
R. Jafari, J. Kiilakoski, M. Honkanen, M. Vippola, H. Koivuluoto
Thermally Sprayed Al2O3 Ceramic Coatings for Electrical Insulation Applications .................... 72
P. Junge, C. Rupprecht, M. Greinacher, D. Kober, P. Stargardt
Effects of Polymer Crystallinity on Deposition Efficiency and Porosity in Cold Spray of PEKK . 82
M. S. Kaminskyj, M. S. Schwenger, D. A. Brennan, F. M. Haas, Joseph F. Stanzione, III
The numerical analysis of plasma sprayed YSZ particles behavior in the microtextured substrate
boundary layer .......................................................................................................................... 89
T. Kiełczawa, P. Sokołowski

Pull-off Testing and Electrical Conductivity of Sn-based Metal Powder Mixtures Cold Sprayed
on Carbon Fiber Reinforced Polymers .................................................................................... 100
A. C. Liberati, H. Che, P. Fallah, S. Yue, P. Vo
A novel method of fabricating water-cooled heat sinks with complex internal structures using
wire-arc spray ......................................................................................................................... 123
J. Palumbo, S. Chandra
Modeling & Simulation I
Spraying Parameters Selection based on Predicted Equipment Status: a Study on Measured
Voltage………………………………………………………………………………………………… 130
X. Guidetti, A. Rupenyan, E. Fallahi Sichani, M. Nabavi, and J. Lygeros
Effect of thermal shrinkage on the dynamics of droplet impact in a thermal spray process .... 141
S. Morteza Javid, L. Pershin, and J. Mostaghimi
Development of robotized spraying trajectory of multi-featured parts in cold spray additive
manufacturing system ............................................................................................................. 160
W. Li, Y. Yao, H. Wu, S. Deng, H. Liao, S. Costil
The Characteristics of In-Flight Ti-6Al-4V Particles and the Coatings Formed by the Inner-
Diameter High-Velocity Air-Fuel (ID-HVAF) Process .............................................................. 164
P. Khamsepour, J. Oberste-Berghaus, M. Aghasibeig, C. Moreau, A. Dolatabadi
Comparison of microstructure and residual stress of HVOF double carbides coatings deposited
on magnesium substrate ......................................................................................................... 172
L. Łatka, E. Jonda, M. Godzierz, M. Górnik, A. Tomiczek
High end hard metal coatings for the toughest demand in paper industry .............................. 179
H. Jungklaus, A. Blutmager
Arc Spraying
Improved environmental safety of pipelines using highly efficient wire arc spraying…… ......... 189
T. Hohnen, F. Lichtenthäler, M. Stark
Influence of Process Parameters on Overall Costs of Surfaces Coated by Wire-Arc
Spraying .................................................................................................................................. 194
M. A. Knoch, R. Wolf
Potentials of thermal spraying processes in silane-doped inert gases ................................... 199
M. Rodriguez Diaz, M. Szafarska, M. Nicolaus, K. Möhwald, H. J. Maier
Adapting the thermal spraying technique to metalize 3D-printed polymers' surfaces to improve
erosion, thermal, and wear resistance ................................................................................... 205
W. Tillmann, M. Abdulgader, A. Wittig, A. Adesunikanmi
Thermal Barrier Coatings based on Arc Spraying of Amorphous Fe-based Alloys and NiCrAlY
for Cryogenic Applications ..................................................................................................... 211
M. Hauer and A. Gericke, B. Allebrodt, K.-M. Henkel

Precision Melt Engineering
Potential Use of Plasma Sprayed Heating Coatings in Die Casting and Injection Molding .... 220
S. Gor, T. Hohlweck, D. Fritsche, A. Schacht, N. Wolff, B. Pustal, H. Heinemann, A. Bührig-Polaczek, C. Hopmann, K. Bobzin
Measurement routine for analysing the thermal impact of Additive Manufacturing processes on
deformation ............................................................................................................................ 226
K. Mäde, L. Oster, M. N. Bold, U. Reisgen, J. Schleifenbaum
Pre- & Post-Treatment
Stripping of thermal sprayed oxid coatings by means of laser techniques, water jet and a newly
developed hybrid method ....................................................................................................... 233
M. Staschik, C. Rupprecht, M.-L. Röhricht, Y. Kuche, E. Uhlmann
Analysis and Comparison of In Situ Coating Thickness Measurements Using Two Different
Sensing Techniques .............................................................................................................. 240
U. Hudomalj, E. Fallahi Sichani, L. Weiss, M. Nabavi, K. Wegener
Increase in surface strength by hammering and solid rolling of volumes produced by means of
Extreme High-Speed Laser Material Deposition .................................................................... 249
S. Koß, L. Sayk, C. Krull, L. Reiff, U. Krupp, J. H. Schleifenbaum
Suspension Spraying I
Antiviral Properties of HAp/Titania Composite Coating Fabricated by Suspension and Solution
Precursor Plasma Spray Technology ..................................................................................... 259
M. M. Abir, Y. Otsuka, Y.Miyashita
Development of thermal sprayed silicon carbide coatings by an innovative suspension/solution
precursors approach .............................................................................................................. 268
A. Rincon Romero, A. Lynam, H. Memon, F. Venturi, T. Hussain
Thermal Spray in a Nut Shell
Optical diagnostic tools for thermal spray processes ............................................................. 272
J. Zierhut
Aviation Industry II
Cold Spray Take off ............................................................................................................... 279
A. Nardi, Helmut P. Höll
Industrial Gas Turbines
Optimization of segmented thermal barrier coatings (s-TBC) for high-temperature
applications ............................................................................................................................ 288
B. A. Yalcinyüz, G. Thomas, Y. Hentschel, C. Rupprecht, F. Kamutzki, A. Gurlo

Cold Gas Spraying I
Strategies and analyses for robot trajectory optimization in thermal and kinetic spraying ..... 299
H. Wu, S. Liu, M. Lewke, W. Li, R.-N. Raoelison, A. List, F. Gärtner, H. Liao, T. Klassen, S. Deng
Cold Gas Spraying II
Perspective of 3D near-net-shape additive manufacturing by cold spraying: an empirical study
using pure Al powders ............................................................................................................ 306
M. Sokore, H. Wu, W. Li, R.-N. Raoelison, S. Deng, H. Liao
Sublayer-Assisted Cold Spray Metallization of Carbon Fiber Reinforced Composites ........... 314
T. Zhang, E. Padyyodi, R.-N. Raoelison, J.-C. Sagot
Cold Spray Nozzle Design for Deposition of Adhesive Perfluoroalkoxy Alkane as an Icephobic
Coating ................................................................................................................................... 327
Z. Leclerc, L. E. McMunn, R. N. Ben, B. Jodoin
The stimulation of grain structure evolution in Aluminium cold spray by Monte Carlo method 334
P. Yu, S. Yin, R. Lupoi
HVOF/HVAF Spraying II
Nitriding effect on HVAF FeMnCrSi coating ........................................................................... 347
W. Rafael de Oliveira, A. Renan Mayer, A. G. Marenda Pukasiewicz, G. Biscaia de Souza
Exploring miniaturized HVOF systems for the deposition and near net shape forming of
Ti-6Al-4V ................................................................................................................................ 356
J. Oberste-Berghaus, M. Aghasibeig, A. Burgess, P. Khamsepour, C. Moreau, A. Dolatabadi
Modeling & Simulation II
Modeling study on stress distribution at MCrAlY-YSZ interface influenced by pores and micro
bulges ..................................................................................................................................... 364
Z. Xu, J.-F. Wen, K. Yuan
Gain insight about thermal spray processes using Artificial Intelligence and Big Data
Analysis ................................................................................................................................... 369
L. Fassl, M. Nabavi, A. Schwenk
Numerical Investigation of the Effect of a Nozzle Extension on the Plasma Jet ...................... 377
K. Bobzin, H. Heinemann, S. R. Dokhanchi
Modeling & Simulation III
A physics based model for ultrahigh strain rates in Cold Spray ............................................. 383
S. Msolli, R.-N. Raoelison, Z.-Q. Zhang

Novel Method of Predicting Deposition Efficiency in Cold Spray by Incorporating Sphericity into
1D Numerical Models ............................................................................................................. 389
O. C. Ozdemir, S. Muftu
Effect of cathode-plasma coupling on plasma torch operation predicted by a 3D twotemperature
electric arc model ............................................................................................... 395
R. Zhukovskii, C. Chazelas, V. Rat, A. Vardelle, R. Molz
Ceramic Coatings
Microstructural Characterization and Oscillating Sliding Wear Investigations of the Aqueous
Suspension Sprayed HVOF WC-12Co Coatings ................................................................... 413
F.-L. Toma, A. Meyer, O. Kunze, I. Shakhverdova, F. Härtwig, A. Potthoff, M. Mayer, J. Pötschke, S. Makowski
As-sprayed Highly Crystalline Yb2Si2O7 Environmental Barrier Coatings (EBCs) by
Atmospheric Plasma Spray (APS) ......................................................................................... 422
F. Arhami, C. Moreau
New Processes I
High Velocity Flame spraying (HVOF) of Ceramic – Polymer Composite Filaments ............. 432
M. Sauter, A. Killinger, A. Grebhardt, C. Bonten
Effect of compressed air flow rate on the microstructure and properties of NiCoCrAlYTa
coatings via a Novel HVOAF process fueled with ethanol ..................................................... 437
S. Liu, H. Wu, Z. Yu, S. Xie, M. Arab Pour Yazdi, M. Moliere, H. Liao
Development of a low power plasma reactor for the local deposition of YSZ thermal barrier
coatings at atmospheric pressure .......................................................................................... 447
S. Segondy, C. Rio, S. Landais, C. Guyon, F. Rousseau
Evaluation of Mechanical Properties of Dense HAD Al2O3 Coatings by Nanoindentation
method .................................................................................................................................. 453
K. Sanami, M. Shahien, A. Yumoto, K. Shinoda, and J. Akedo
Wear Protection I
Cavitation Erosion in WC-10Co-4Cr Coating ......................................................................... 461
A. Algoburi, R. Ahmed, M. Nazarinia
Development of near net shaped coatings for reduced postprocessing costs in valves ........ 467
K. Bobzin, W. Wietheger, E. Burbaum, M.Schulz
Medical Industry
Cold spray of hydroxyapatite coatings: interest of PEEK as an intermediate layer ................ 475
D. Chatelain, A. Denoirjean, V. Guipont, F. Rossignol, N. Tessier-Doyen

Production of Titanium Dioxide with Optimum Heterojunctions and Coating Production via Cold
Spray ...................................................................................................................................... 483
A. Hawkins, D. Guo, A. Steeves, F. Variola, B. Jodoin
Copper-embedded facemasks for the destruction of Covid-19 and other pathogens ............ 489
L. Pershin, M. Ringuette, M. Sain, J. Mostaghimi
Driving Factors on the Fatigue Resistance for Titanium Plasma Sprayed Coated Samples .. 493
A. Venturoli, G. Conoscenti, R. Chiesa
High Entropy Alloys I
Enhancing the wear resistance of the medium-entropy alloy CrFeNi by minor alloying
constituents of BSiC for surface protective coatings by thermal spraying .............................. 504
T. Lindner, B. Preuß, M. Löbel, L.-M. Rymer, N. Hanisch, T. Lampke
Interparticle bonding and interfacial nanocrystallization mechanisms in cold sprayed metallic
glass ....................................................................................................................................... 511
N. Fan, C. Huang, P. Yu, W. Chen, R. Lupoi, L. Liu, S. Yin
Design of High Entropy Alloys for Thermal Spray Processes Using Machine Learning ......... 522
S. Kamnis, A. K. Sfikas, S. Gonzalez
Influence of Microstructure on Hardness and Electric Resistivity of Flame-sprayed High Entropy
Alloy Coatings ....................................................................................................................... 534
S. Pal, R. Bhaskaran Nair, A. McDonald
Metal Coatings I
On the applicability of iron-based alloy coatings to different wear conditions.......................... 543
T. Varis, J. Lagerbom, T. Suhonen, S. Terho, J. Laurila, P. Vuoristo
Nanomaterial Coatings
Investigation of novel nano-carbide WC/CoCr coatings applied by HVAF .............................. 553
K. Bobzin, W. Wietheger, E. Burbaum, L. M. Johann, L. J. Rempe, V. Matikainen, U. Kanerva, M. Karhu, J. Lagerbom,
K. Kaunisto, J.-F. Lartigue
Wear resistant nano-carbide WC-CoCr coating by novel powder manufacturing method ..... 559
V. Matikainen, J. Lagerbom, K. Kaunisto, V. Heino, K. Bobzin, W. Wietheger, E. Burbaum, L. M. Johann, J.-F. Lartigue, U.
Kanerva, M. Karhu
Electronics & Sensors
Flame-Sprayed NiCoCrAlTaY Coatings as Damage Detection Sensors ............................... 565
A. S. Ogunbadejo, A. McDonald, S. Chandra
Influence of the process parameters on the electrical resistance of mullite coatings ............. 575
K. Bobzin, W. Wietheger, E. Burbaum, K. Radermacher

Suspension sprayed thin metallic coatings for electric panel heaters .................................... 581
H. Kummer, M. Winkelmann, F. Wüst, S. Hartmann, F. Trenkle, P. Krieg, A. Killinger
General Plant Engineering
Refurbishment of damaged railway material by cold spray .................................................... 586
F. Delloro, M. Tebib, T. Lesage
HVSFS Al2O3-TiO2 Coatings of Porous Aluminium Substrates ............................................... 596
M. Sauter, V. Martínez García, A. Killinger
Industrial Forum I: Coatings, Applications, Materials
Functional Coatings made by Brazing ................................................................................... 601
I. Rass
Additive Manufacturing
Additive Manufacturing by Thermal Spray Deposition of Metals on 3D-Printed Polymer
Substrates .............................................................................................................................. 607
Ram gopal varma Ramaraju and S. Chandra
Metal Knitting: A method to control morphology and properties in cold spray additive
manufacturing ........................................................................................................................ 614
R. F. Váz, H. Canales, J. Sanchez, U. Ocaña, V. Albaladejo, I. Garcia Cano
Metal Coatings II
Fatigue properties of cold sprayed bell metal .......................................................................... 622
O. Kovarik, J. Daniel, J. Cizek, J Kondas, J. Cech, J. Siegl, R. Singh
Thermal Spraying of a Novel Nickel-free High Strength and Corrosion Resistant Austenitic
Steel ........................................................................................................................................ 631
A. Mohr, O. Schwabe, K. Ernst, H. Hill, P. Kluge
Suspension Spraying II
Current Trends in the Development of Suspensions and Liquid Precursors for Thermal
Spraying: Case of Zn2TiO4 .................................................................................................... 637
A. Meyer, F.-L. Toma, O. Kunze, A. Böhme, B. Matthey, A. Potthoff, Arno Kaiser, Tim Gestrich, Christoph Leyens
Performance of Suspension Sprayed YSZ Thermal Barrier Coatings on INCONEL®718
Substrates Produced by Laser Powder Bed Fusion ............................................................... 645
F.-L. Toma, S. Gruber, A. Selbmann, S. Tkachenko, O. Kunze, K. Zabransky, C. Leyens, L. Čelko, M. Tajmar
Laser Cladding
Study on the microstructure development in a laser-cladded tantalum layer ......................... 654
K. Yuan, Z. Pi, X. Pang

Effect of Nb Content on Structure and Properties of Martensitic Stainless Steel Laser Cladding
Layers .................................................................................................................................... 660
K. Du, E. Huang, Z. Pi, X. Chen, Z. Zheng
Cold Gas Spraying III
Assessment of agglomerated ceramic powders under impact by cold spraying .................... 666
G. Celeste, V. Guipont, D. Missoum-Benziane, G. Kermouche, S. Sao-Joao, S. Girard-Insardi, D. Chatelain
Particle Acceleration Through Coaxial Co-Flow Nozzles for Cold Spray Applications ........... 676
A. K. Sharma, A. Vashishtha, D. Callaghan, C. Nolan, S. Bakshi, M. Kamaraj, R. Raghavendra
Cold Gas Spraying IV
Systematic Study of the Effects of Powder Preconditioning on Flowability and Deposition in
Polymer Cold Spray ............................................................................................................... 683
D. A. Brennan, T. W. Bacha, Ü. Tiitma, F. M. Haas, J. F. Stanzione, III
Aerosol Cold Spray Technology for Ceramic and Metal Coating Deposition ......................... 695
V. Leshchynsky, G. Kubicki, J. Sulej-Chojnacka, A. Eleseddawy, R.Maev
New Processes II
Coating of Aluminium with high deposition rates through Extreme High-Speed Laser Material
Deposition .............................................................................................................................. 701
S. Koß, S. Vogt, M. Göbel, J. H. Schleifenbaum
Hybrid aerosol deposition as an outstanding prospective for dense barrier ceramic coatings
deposition on different substrates .......................................................................................... 709
M. Shahien, K. Shinoda and J. Akedo
Ultrasonic atomization as an alternative route for metal powder production .......................... 716
P. Sokołowski, P. Kustroń, M. Korzeniowski, A. Sajbura, T. Piwowaczyk, R. Szostak – Staropiętka, R. Kiełbasiśnki
Characterization & Testing Methods I
Quality assessment of thermally sprayed stainless steel coatings based on polarisation curves
with 3.5 % NaCl gel electrolyte .............................................................................................. 723
M. Grimm, P. Kutschmann, C. Pluta, O. Schwabe, K. R. Ernst, T. Lindner, T. Lampke
Dynamic impact wear analyses of selected cobalt based HVOF sprayed coatings ............... 729
S. Houdkova, J. Duliskovic, J. Daniel
Characterization & Testing Methods II
Elastic measurements of plasma spray refractory metal coatings using thermal cycling of bilayered
beams ....................................................................................................................... 736
A. Vackel, E. Peleg, J. Varga, M. Blea, C. Schmidt, E. Gildersleeve

Evaluation of electric conductivity and mechanical load capacity of copper deposits for
application in large winding components for electrical high-voltage machines made with cold
spray additive manufacturing ................................................................................................. 743
T. Braun, E. Uhlmann, R. Häcker, M. Jäger, H. Rauch, K. Brach, R. Singh, J. Kondas
Characterization of the microstructure, mechanical properties and corrosion behaviour of
submicron WC-12Co coatings produced by CGS and HVAF compared with sintered bulk
material .................................................................................................................................. 750
N. Cinca, O. Lavigne, H. Koivuluoto, S. Dosta, S. Conze, S. Hoehn, R. Drehmann, C. Kim, V. Matikainen, F. S. Silva, R. Jafari,
E. Tarrés, A.V. Benedetti
Wear Protection II
Anisotropy of Ti6Al4V deposited by cold spray ...................................................................... 756
O. Kovarik, J. Cizek, J. Kondas
Investigation of the effect of low-temperature annealing and impact angle on the erosion
performance of nickel-tungsten carbide cold spray coating using design of experiments ...... 763
M. Kazasidis, E. Verna, S. Yin, R. Lupoi
Tribological properties of hybrid plasma sprayed coatings ..................................................... 773
T. Tesar, R. Musalek, J. Medricky, J. Cizek, F. Lukac, J. Dudik, S. Houdkova
Renewable Power Generation
Protective Mo and Fe coatings by CS and RF-ICP for PbLi coolant environments in generation
IV fission reactors .................................................................................................................. 780
J. Cizek, J. Klecka, L. Babka, H. Hadraba, J. Kondas, R. Singh, M. Pazderova
A decade of development, optimization and scale up of a thin barrier layer for metal-supported
solid oxide fuel cells ............................................................................................................... 789
L. Leblanc, R. Hinckley, M. Alinger, T. Striker
Tungsten-Steel Functionally Graded Coatings for Nuclear Fusion Applications Manufactured by
Cold Gas Spraying ................................................................................................................. 798
G. Mauer, K.-H. Rauwald
High Entropy Alloys II
Niobium and molybdenum as alloying constituents in Al0.3CoCrFeNi to develop eutectic highentropy
alloys for HVOF spraying .......................................................................................... 809
B. Preuß, T. Lindner, L.-M. Rymer, T. Lampke
Systematic research on the formation of heterogenous microstructure in FeCoNiCrMn high
entropy cold spray .................................................................................................................. 815
P. Yu, N. Fan, S. Yin, R. Lupoi
Towards Highly Durable High Entropy Alloy (HEA) Coatings Using Flame Spraying ............ 827
A. Kenyi, R. Bhaskaran Nair, A. McDonald

Industrial Forum V: Equipment & Diagnostics
Influence of (future) refrigerants on the cooling of thermal spray equipment ......................... 834
R. Mulzer
Digital process chains for 3D laser cladding and LMD/DED additive manufacturing ............. 840
R. Beccard and A. Bartling
Industrial Forum VI: Others, Process, Peripheral
Thermal Spraying 4.0 – digitalization of old equipment vs. buying new equipment? ............. 843
C. Hambrock
Process Diagnostics, Sensors & Controls
Improvement of In-flight Particles Diagnostic System to Monitor Process Stability in Thermal
Spray Processes .................................................................................................................... 848
W. Jibran, A. Nadeau, C. Desmarais
Development of an arc-based diagnostic procedure for process characterization in DC plasma
spraying ................................................................................................................................. 856
G. Thomas, M. Limburg, S. Mihm, C. Rupprecht, H. Gruner
Importance of Evaluation Procedure of Particle State in Atmospheric Plasma Spraying ....... 868
U. Hudomalj, E. Fallahi Sichani, L. Weiss, M. Nabavi, K. Wegener
Investigation on laser cladding processes using high-resolution in-line atomic emission
spectroscopy .......................................................................................................................... 876
M. Schmidt, S. Gorny, N. Rüssmeier, K. Partes
Poster Sessions
Applications – Automotive Industry
Evaluation of the Chromium carbide deposited by HVOF for high pressure die casting
molds ..................................................................................................................................... 884
A. R. Mayer, H. D. C. Fals, L. A. Lourençato, A. G. M. Pukasiewicz
Applications – Aviation Industry
Development of Compatibilizing Sublayer for Metallizing CFRP Structures by Cold Spray ... 893
T. Zhang, E. Padayodi, R. N. Raoelison, J.-C. Sagot
Superfinishing of HVOF Sprayed WC-CoCr Coating for applications in Aviation Industry as a
Hard Chromium Replacement ................................................................................................ 900
M. Vostřák, S. Bejblíková, J. Antoš, L. Kameník, V. Voldřich

Applications – Electronics and Sensors
Assessment of High Entropy Alloys as Thermally Sprayed Heating Elements ...................... 907
K. Bobzin, H. Heinemann, A. Schacht
Applications – Power Generation – Industrial Gas Turbines
Heterogeneous Thermal Barrier Coatings with Engineered Gradient Interfaces .................... 913
R. Musalek, T. Tesar, J. Medricky
Equipment/Consumables – Process Diagnostics, Sensors & Controls
Inline characterization of thermal spray processes by thermographic spray spot analysis .... 919
M. Ider, C. Rupprecht, G. Thomas
Pre- & Post-Treatment
Thermo-Mechanical Finite Element Analysis of the Laser Heat Treatment of WC-17Co
Thermally Sprayed Coating .................................................................................................... 928
M. Manoj, R. G. Burela, D. Dzhurinskiy, A. Babu, A. Gupta, D. Harursampath
Properties – Ceramics Coatings
Yttria coatings as wear protection layer in the semiconductor industry .................................. 939
M. Nicolaus, M. Benedde, K. Möhwald, H. J. Maier, R. Walther
Properties – Characterization & Testing Methods
Cold spraying onto notched surfaces: Scanning acoustic microscopy as a tool for evaluation of
the interface quality ................................................................................................................ 945
M. Koller, M. Janovská, M. Ševčík, H. Seiner, J. Kondas, R. Singh, J. Cizek
Thermal Spray and other Processes – Additive Manufacturing
Additive Manufacturing feasibility of WC-17Co cermet parts by Laser Powder Bed Fusion .. 951
K. Papy, A. Sova, A. Borbely, J.-M. Staerk, J. Favre, Z. Roulon, J. Sijobert, P. Bertrand
Thermal Spray and other Processes – Cold Gas Spraying
A Machine Learning Based Approach for Cold Spray Deposition Porosity Prediction from
Processing Parameters .......................................................................................................... 961
S. Roy, K. Ravi
Thermal Spray and other Processes – Laser Cladding
The typical defects in laser cladding and process control method ......................................... 977
X. Wang, C. Xia, X. Deng, K. Du, Y. Yu

Thermal Spray and other Processes – Modeling & Simulation
Correlation between process parameters and particle in-flight behavior in AC-HVAF ........... 984
K. Bobzin, H. Heinemann, K. Jasutyn
Numerical Study of Ceramic Retention Mechanism in Cold Spraying .................................... 990
A. Elkin, A. Lama, S. Dautov, P. Shornikov
Thermal Spray and other Processes – Plasma Spraying
Preparation and Property of Thermal Spraying Aluminum Bronze Polyester Abradable Sealing
Coating ................................................................................................................................. 1000
T. Liu, J. Liu, D. Guo, D. Zhang
Authors and Co-Authors ...……………………………………………………… ………... 1006
Index to Advertiser ...…………………………………………………………........………... 1018

Atmospheric Plasma Spraying of Environmental Barrier Coatings –
A Parametric Study
A. Lynam, A. Rincon Romero, F. Xu, M. Bai, T. Hussain
Environmental barrier coatings (EBCs) are required to protect SiC based composites in high temperature, steam
containing combustion environments found in the latest generation of high efficiency gas turbine aeroengines.
Ytterbium disilicate has shown promise as an environmental barrier coating, showing excellent phase stability at high
temperature and a coefficient of thermal expansion close to that of SiC; however, its performance is dependent on
the conditions under which the coating was deposited. In this work, a parametric study was undertaken to
demonstrate how processing parameters using a widely used Praxair SG-100 atmospheric plasma spraying torch
affect the phase composition, microstructure and mechanical properties of ytterbium disilicate environmental barrier
coatings. Ytterbium disilicate coatings were deposited using 5 sets of spray parameters, varying arc current and
secondary gas flow. The phases present in these coatings were quantified using x-ray diffraction with Rietveld
refinement, and the level of porosity was measured. Using this data, the relationship between processing parameters
and phase composition and microstructure was examined.
Abradable coatings are used throughout gas turbine engines to increase efficiency in the compression and
combustion phases of the turbine. Abradable coatings are soft enough to be worn away by turbine blade tips (without
damaging the tip itself), allowing for tighter clearances to be used, limiting leakages and increasing efficiency. Using
the optimum process parameter window determined in this work, a low density abradable Yb2Si2O7 layer will be
deposited in future research.
1 Introduction
As performance and efficiency gains in gas turbines are constantly sought, the temperatures under which Ni based
superalloys must operate is approaching their limit. Thermal barrier coatings have allowed turbine inlet temperatures
of ~1500°C, improving thrust outputs, thermal efficiency and a reduction of harmful emissions [1]. However, this
temperature is now approaching the melting point of the Ni alloys, so it is clear that new material solutions must be
sought. One such solution is the use of SiC/SiC ceramic matrix composites (CMCs). CMCs show excellent high
temperature mechanical properties, have a temperature limit ~200 °C higher than Ni based superalloys and have a
lower density than their metallic counterparts (improving thrust to weight ratios) [2]. Nevertheless, SiC/SiC CMCs are
not without drawbacks. At high temperatures in oxidising environments SiC will form a protective SiO2 layer. However,
in the presence of steam, as found in gas turbines, the usually protective SiO2 will form volatile silicon hydroxide
(Si(OH)4), resulting in a recession of SiC [3].
Naturally, SiC based CMCs must be protected from such environments; one approach to do this is through coating
the CMC, known as an environmental barrier coating (EBC). Similarly to how thermal barrier coatings (TBCs) have
been employed to protect nickel superalloys from high temperatures, EBCs can be used to protect CMCs from steam
recession. To be effective, the EBC must have; low silicon volatilisation, a coefficient of thermal expansion (CTE)
similar to that of the CMC, chemical compatibility with the CMC and phase stability over the range of operating
temperatures [4]. For over 30 years, silicates have been investigated for use as EBCs due to their combination of
properties and the ease with which they can be deposited using thermal spray techniques, primarily atmospheric
plasma spraying (APS) [5, 6]. More recently, rare-earth silicates, specifically ytterbium monosilicate (Yb2SiO5 or
YbMS) and ytterbium disilicate (Yb2Si2O7 or YbDS), have come to the fore due to their low CTE (4.1 x10 -6 and
6.3 x10 -6 K -1, respectively), excellent phase stability and the fact they are monomorphic over the operating
temperature range [7-9].
One practical way in which the efficiency of gas turbines can be increased is to reduce leakages that occur during
the compression and combustion stages of the turbine. This can be achieved by reducing the clearances between
the moving parts within the turbine, for example between the blades and the casing. Due to the high operating
temperatures within the turbine, the blades will expand and contact the casing if the clearance is too low; high loads
and large vibrations could also lead the blade to impact the casing. To get around this, abradable seal coatings can
be employed. Such coatings are soft enough to be worn away by the turbine blade tip (without damaging the tip
itself), allowing for tighter clearances to be used, limiting leakages and increasing efficiency, whilst still (in the case
of an abradable EBC) providing protection from steam recession. Abradable seals are typically made up of a matrix
phase to which pore forming phases (e.g. polyester, removed in a heat treatment) and/or solid lubricants (e.g. hBN
or LaPO4) are added to provide abradability [10, 11]. While research into abradable EBCs is still in its infancy, studies
have been conducted into a hBN containing YbDS APS deposited EBCs, and within industry patents regarding
polyester and solid lubricant containing EBCs have been granted [12-14].
In this study, a parametric investigation was undertaken to optimise a YbDS coating deposited by APS. The effect of
secondary gas pressure and arc current were investigated, the phase composition, microstructure and level of
DVS 380 1

porosity were characterised for all the coatings. The aim of this study was to determine an optimum deposition
condition for a YbDS system, which would then be used as a base for future research in to an abradable EBC.
2 Methodology
2.1 Materials
An EBC system was deposited using APS. The system is comprised of a SiC substrate (JAI Engineers, UK), an
intermediate Si bond layer and YbDS acts as a protective top layer. Commercially available Si, Metco 4810, and
YbDS, Metco 6157 (both Oerlikon Metco AG, Switzerland) were used as feedstocks for the respective layers. The Si
powder had a nominal size range of 15-75 µm and contained < 1.5 wt. % SiO2 and a balance of Si. The YbDS powder
had a nominal size range of 11-90 µm, contained a nominal composition of 23–30 wt. % SiO2 and balance of Yb2O3,
with a maximum of 5 vol. % of unreacted Yb2O3 and YbMS. Prior to spraying, the powders were treated at 80 °C for
12 hours using a box furnace (Elite Thermal Systems, UK) to remove any moisture.
Reaction bonded SiC discs with a diameter of 25 mm and thickness of 10 mm, were used as the substrates. These
were grit blasted using a blast cleaner (Guyson, UK) with SiC (220 mesh) particles at a pressure of 9 bar. Following
surface preparation, the substrates were sonicated in industrial methylated spirit (IMS) using a FB-505 ultrasound
probe (Fischer Scientific, UK) in pulse mode (1 s pulse every 2 s) at 60% amplitude. Finally, the substrates were
dried using compressed air.
2.2 Coating Preparation
A SG-100 plasma spray system (Praxair Surface Technology, USA) was used to deposit the coatings. The spray gun
was fitted with a 02083-175 anode, 02083-120 cathode and a 03083-112 gas injector. Ar was used as the primary
gas and H2 was used as the secondary gas.
The Si bond coat spray parameters are shown in Table 1.
Table 1. Si APS parameters optimised from preliminary experiments not discussed in this work.
Current (A) Ar (PSI) H2 (PSI) Carrier (PSI) Voltage (V) Power (kW)
600 85 35 30 45 27
The YbDS spraying parameters are shown in Table 2. During the plasma spraying process, three variables can affect
the composition and microstructure of the coating for a given feedstock: the stand-off distance, the arc current and
the secondary gas pressure. During coating deposition, the stand-off distance was fixed at 150 mm. A parametric
study was conducted varying arc current and secondary gas pressure to assess how this affected YbDS phase
retention and porosity in the coating. The S (referring to “standard”) set of parameters refers to a centre point around
which arc current (C referring to current) was changed to a lower (C1) and higher (C2) level as was secondary gas
pressure (H referring to H2 pressure with H1 and H2 being with low and high level, respectively). Due to the highly
amorphous nature of the as-sprayed coatings, an annealing heat treatment was conducted to form crystalline phases
[15]. This was done at 1200 °C (Elite Thermal Systems Ltd., UK) for two hours, with heating and cooling rates of
5 °C/min in air.
Table 2. YbDS APS parameters.
Spray Parameter Current (A) Ar (PSI) H2 (PSI) Carrier (PSI) Voltage (V) Power (kW)
S 400 95 40 30 51 20
C1 300 95 40 30 52 16
C2 500 95 40 30 49 25
H1 400 95 30 30 32 13
H2 400 95 50 30 53 21
The temperature and velocity of both the Si and YbDS feedstock particles were measured at 50, 100 and 150 mm
stand-off distances using a Tecnar Accuraspray 4 (Tecnar, Canada). A stand-off of 150 mm was used as this
corresponded to the particles temperature and velocity as they impinged the substrate. Stand-offs of 50 and 150 mm
were used in order to better understand the history of the particles and how the condition changed in-flight. The
Accuraspray has a large measurement volume, 3 mm in diameter and 25 mm allowing for temperature and velocity
data as an average of all of the particles passing through the measurement volume to be measured [16]. As particles
pass through the focal plane of the Accurapsray system, pulses are generated by two slits in the sensor, knowing
the time between the pulses and the distance between the slits the particles velocity can be calculated. Temperature
is measured using a two-colour pyrometer. The signal amplification factor and exposure time settings were different
for the different spray parameters and stand-off distances but were comprised in the range of 20-32 times and
2 DVS 380

16-41 ms respectively. The response time was set to 1 s. Before the data was acquired, a period of 60 s was allowed
for flame stabilization. A series of 60 measurements were acquired over a time frame of 60 s, then averaged to give
the resulting values.
2.3 Sample Preparation for Characterisation
The coated substrates were cut using Qcut 200 precision cutting machine (Metprep, UK) and abrasive diamond cutoff
wheels (Metprep, UK) with a cutting speed of 0.025 mm/s. The cross-sections were mounted in Conducto-Mount
(Metprep, UK). The mounted samples were then ground using a diamond lapping disc and then silicon carbide
metallurgical abrasive papers (Metprep, UK) with grit sizes of P240, P400, P800 and P1200 sequentially. Lastly, the
ground samples were polished using diamond polishing pads to a surface finish of 6 μm and finally 1 μm.
2.4 Scanning Electron and Optical Microscopy
The morphology of the YbDS powder, the microstructure of the coating and the surface topography of the coating
were characterised using a FEI XL30 scanning electron microscope (SEM) (Thermo Fisher Scientific, USA) operated
in secondary electron (SE) and backscattered electron (BSE) modes, using an accelerating voltage of 20 kV, spot
size of 4 nm and working distance of ~10 mm. The SEM was equipped with energy-dispersive x-ray spectroscopy
(EDX) (Oxford Instruments, UK) which was used to perform elemental analysis. The level of porosity was measured
using ImageJ image processing software (National Institute of Health, USA). BSE images were converted into black
and white maps upon setting a threshold. Then, the automated function “Analyse particle” was employed, which
measured the area percentage of the image covered by porosity, returning an overall value per image. An average
of the five images of each coating was calculated and the standard deviation was calculated and presented as the
error associated with each measurement. BSE images were also used to measure the thickness of the coatings.
2.5 X-ray Diffraction
The phase analysis on the feedstock powder and as-sprayed coating was conducted by XRD using a D8 Advance
(Bruker, UK) from 10 to 80° 2θ, using Cu Kα radiation (0.154 nm wavelength), a 0.02° step size and 0.1 s per step
using Bragg-Brentano geometry. Phase identification and measurement of the degree of crystallinity in the coatings
was completed using EVA software (Bruker, UK) supported by data from the PDF-2 database (ICDD-PDF). Phase
quantification (in wt. % according to Hill and Howard [17]) was performed using Rietveld refinement in TOPAS V5
(Bruker, UK) with reference to the guidelines outlined by McCusker et al. [18]. The instrumental broadening was
accounted for by employing a fundamental parameters approach where the details of experimental set-up such as
radiation source, slits, detector, etc. are used for instrumental function calculations instead of its direct determination
by measuring sample without any physical broadening effects [19]. For all of the phases observed standard structures
were taken from the Crystallography Open Database and used in the refinements.
3 Results and Discussion
3.1 Powder Size and Morphology
SEM analysis was carried on the YbDS powder to understand its morphology. As shown in Figure 1, the powder
was round and hollow in morphology.
Figure 1. SE SEM image of YbDS powder.
DVS 380 3

Figure 2. Diffractogram of Metco 6157 powder.
XRD of the powder is shown in Figure 2, the composition of the powder was mainly monoclinic YbDS (C2/m, 82-
0734) with small amounts of monoclinic YbMS (I2/a, 40-0386). The phase composition of the powder was quantified
using Rietveld refinement, the powder was found to contain 95.1 wt. % YbDS and 4.9 wt. % YbMS.
3.2 In-flight Particle Characteristics
The particle velocity and temperature measured at three different stand-off distances are shown in Figure 3. Both
particle velocity and surface temperature increased as the arc current and H2 in the plasma gas composition were
increased. Increasing the arc current increases the velocity and length of the plasma jet, resulting in higher particle
temperatures and velocities. Compared to Ar, H2 has increased thermal conductivity and specific heat capacity
leading to higher arc voltages, so the higher proportion of H2 in the plasma gas, the more energetic the plasma [20].
Particle temperature and velocity also decreased as the stand-off distance was increased for all of the tested spray
parameters. The particle temperature exceeded the melting temperature of YbDS (1850 °C) [21] for all of the tested
spray parameters except H1 at 100 and 150 mm stand-off distance. While this ensures that the feedstock will be
molten as it impacts the substrate, work by Richards et el. [5] has shown that at high temperatures (1000-3000 °C)
the high vapour pressure of SiO2 led to Si depletion from the molten material, resulting in the formation of YbMS and
Yb2O3 phases in the YbDS coating.
4 DVS 380

Particle Temperature (°C)
Particle Temperature (°C)
3500
3000
2500
2000
1500
1000
50 100 150
Stand-off Distance (mm)
S C1 C2 H1 H2 YbDS Melting Point
Particle Velocity (ms -1 )
Particle Velocity (ms -1 )
180
160
140
120
100
80
60
50 100 150
Stand-off Distance (mm)
S C1 C2 H1 H2
Figure 3. Graphs showing particle velocity and surface temperature measured with a Tecnar Accuraspray 4 at three different
stand-off distances for the five sets of parameters.
DVS 380 5

3.3 Phase Composition
The diffractograms for the as-sprayed coatings are shown in Figure 4. The phases found in all five samples were
found to be highly amorphous—as expected in APS coatings for EBCs. Due to the high cooling rate of the particles
after they have impacted the substrate during APS, amorphous structures are formed [22-24]. In all of the
diffractograms two broad amorphous humps are visible between ~25° - 35° and ~40° - 70°. Despite the largely
amorphous phase composition crystalline phases were identified in some of the coatings. In the H1 coating peaks
corresponding to monoclinic YbDS (C2/m, 82-0734) can be seen, corroborating what was seen in Figure 3, that the
feedstock was not fully molten when using this low power parameter combination. In the C2 and H2 coatings, a
relatively intense peak can be identified at ~29°. This peak likely corresponds to cubic Yb2O3 (I213, 74-1981) (222),
as no Yb2O3 was detected in the feedstock powder this indicates that SiO2 is being lost during spraying using these
two parameter combinations. Similar findings have been reported in YbDS APS coatings by Bakan et al. [25]. C2
corresponds to the highest arc current while H2 corresponds to the highest level of H2 in the plasma gas mixture,
these were the two highest power sets of parameters used in this investigation, and, referring to Figure 3, caused
the highest feedstock particle temperatures during spraying leading to the greatest rate of SiO2 loss. The amorphous
and crystalline content of the coatings was quantified for each coating. Coating S was found to have 12.4 %
crystallinity, C1 11.6 %, C2 18.8 %, H1 33.1% and H2 13.5 %.
Figure 4. Diffractograms for the as-sprayed coatings.
Heat treatment prompted crystallisation of the phases in the coatings, the diffractograms of the annealed coatings
can be seen in Figure 5. Monoclinic YbDS (C2/m, 00-082-0734) and monoclinic YbMS (I2/a, 40-0386) phases were
identified in all the coatings. In coatings C2 and H2, cubic Yb2O3 (Ia-3, 74-1981) was assumed to be retained after
annealing although, due to overlapping peak positions (at 29° around the dominant Yb2O3 peak (222)) with YbDS
(201) and YbMS (013), this is not clear from the diffractograms.
6 DVS 380

Figure 5. Diffractograms of the annealed coatings.
The phase composition of the annealed coatings was quantified by Rietveld refinement. The respective phase
compositions of all of the coatings are shown in Table 3. The phase composition of the coating is incredibly sensitive
to the spraying parameters used in its deposition. In every coating except C1, the amount of YbMS was greater than
the amount of YbDS. Generally, increasing the arc current and the amount of H2 in the plasma gas composition leads
to increased particle temperatures, in turn leading to a higher rate of SiO2 loss and a shift towards more Yb-rich
compositions.
Table 3. YbDS and YbMS content for all the deposited coatings.
Coating YbDS Content (wt. %) YbMS Content (wt. %)
Yb2O3 Content (wt.
%)
S 34.4 65.6 -
C1 45.7 54.3 -
C2 30.8 67.2 2.0
H1 78.7 21.3 -
H2 35.2 63.5 1.3
3.4 Microstructure
Figure 6 shows BSE SEM images of the microstructures of the as-sprayed YbDS coatings deposited using the five
sets of parameters. The EBC system comprises the YbDS top layer, a Si bond layer and the SiC disc. In all of the
as-sprayed coatings, individual splats are visible. The as-sprayed coatings produced by spray parameters S, C1 and
H1 exhibit a porous, loose structure with poorly bonded splats. The inter-splat bonding improves in coatings C2 and
H2 with increasing arc current and the amount of H2 in the plasma, respectively as fewer individual splats are visible
and the structure is more homogeneous. Microcracking and un-melted particles are apparent in every sample
regardless of the spraying parameter.
Figure 7 shows BSE SEM images of the microstructures of the YbDS coatings deposited using the five sets of
parameters after annealing. During annealing, sintering of the splats has improved the inter-splat bonding, and the
density of the coatings has improved. As a result of the sintering, the morphology of the pores has changed after
DVS 380 7

annealing from porosity surrounding individual splats to small round pores, identified in Figure 7a. In Figure 7b
(coating C1) a large inter-layer crack can also be seen. The main difference between the different microstructures is
the level of porosity and the coating thickness; coatings C1 and H1 in particular had poor deposition efficiency.
Generally, porosity decreased, and deposition efficiency increased with increasing arc current. The level of porosity
has been measured and is represented in Table 4, along with the as-sprayed coating thickness. As arc current and
the amount of H2 in the plasma gas is increased, porosity is reduced while coating thickness is increased. Porosity
is also reduced upon annealing.
Table 4. Porosity measurements, taken using ImageJ, for coatings deposited using the five sets of spraying parameters.
Spray Parameter
Porosity (as
sprayed) (%)
Porosity
(annealed) (%)
Coating Thickness
(µm/pass)
S 11.4 7.2 28.6
C1 15.6 8.3 22.2
C2 5.7 5.6 31.0
H1 11.1 9.8 24.6
H2 9.1 6.2 35.7
8 DVS 380

A
YbDS
Si
SiC
B
C
D
E
Un-melted particle
Figure 6. BSE SEM images of as-sprayed YbDS coating microstructures deposited using the five sets of spraying parameters
with (a) corresponding to S parameters, (b) C1, (c) C2, (d) H1 and (e) H2.
DVS 380 9

A
Pores
Si
YbDS
SiC
B
Inter layer crack
C
D
E
Figure 7. BSE SEM images of annealed YbDS coating microstructures deposited using the five sets of spraying parameters
with (a) corresponding to S parameters, (b) C1, (c) C2, (d) H1 and (e) H2.
Another feature of the microstructures shown in Figure 6 and Figure 7, was the presence of brighter and darker
phases, indicating the presence of heavier and lighter elements respectively within these phases. This is especially
noticeable in coatings C2 and H2 after annealing, Figure 7c and Figure 7e. These can be seen more clearly in
10 DVS 380

Figure 8. Figure 8 shows a higher magnification image of the YbDS coating microstructure deposited using the
S parameters, with the brighter and darker phases clearly visible. EDX analysis of the phases showed the darker
phases to be Si and O rich compared to the lighter phase. Previous works have shown that these bands do not
represent distinct equilibrium phases but in fact, combinations of equilibrium phases, in this case YbDS and YbMS,
with the contrast coming from the proportion of each within the band [5, 22]. This indicates that in all of the coatings
some degree of SiO2 volatilisation is occurring as per the mechanism proposed by Richards et al. [5].
Element (at. %) Yb Si O
Spectrum 1 26.9 10.9 62.2
Spectrum 2 21.3 15.6 63.1
Spectrum 3 27.3 10.6 62.1
Spectrum 4 21.5 15.4 63.1
Figure 8. A high magnification SEM image of YbDS coating microstructure, deposited using S parameters. Spectrums 1 and 3
show EDX analysis of a brighter appearing phase while spectrums 2 and 4 show EDX analysis of a darker phase. Compared to
the lighter phase the darker phase is Yb rich and Si depleted.
As the presence of Yb2O3 could not be determined in the annealed C2 and H2 coatings by XRD, EDX analysis was
conducted on suspected particles. Figure 9 shows the composition of such a particle. The EDX analysis of the particle
shows it to be almost Si free, containing only 1.2 at. % Si.
Figure 9. EDX analysis of a Yb2O3 particle in coating H2, spectrum 1 contained 35.1 at. % Yb, 1.2 at. % Si and 63.7 at. % O.
DVS 380 11

4 Conclusions
YbDS coatings were deposited using APS, with the arc current and amount of H2 in the plasma gas being
systematically changed. Particle velocity and temperature data was recorded for all of the spray conditions and the
phase composition and microstructure of the respective coatings were investigated. After spraying the coatings
contained mainly amorphous phases and had loose, porous microstructures, so an annealing heat treatment was
required to crystallise the coatings and sinter the microstructures to produce better inter-splat bonding. Increasing
the arc current and secondary gas pressure was found to increase particle temperature and velocity with the spray
plume. This in turn led to reduced porosity and increased deposition efficiency in the coatings. Un-melted particles
and cracking within the microstructures were observed regardless of the spray parameters used.
In all of the coatings, phase composition changes from the feedstock powder were observed, in fact the only coating
to retain a majority YbDS composition was the H1 coating however particle temperature data suggests this was due
to the feedstock not being completely molten during spraying. In all the other coatings a high proportion of YbMS
was detected and, in the case of the two highest power spray conditions, C2 and H2, Yb2O3 was detected. This was
due to SiO2 volatilisation and loss during spraying, the rate of which increased as secondary gas pressure and arc
current (and hence particle temperatures with the spray plume) were increased. In order to produce optimised EBC
systems, YbDS phase content must be maximised, in order to best match the CTE of the SiC CMC it is protecting.
Given this constraint, it can be concluded that low power spray conditions, in this study H1, are required for maximum
YbDS phase retention. What has not been demonstrated in literature is the effect of different ratios of YbDS:YbMS
on the thermocycling behaviour of EBCs.
12 DVS 380

References
1. Padture, N.P., Advanced structural ceramics in aerospace propulsion. Nature Materials, 2016. 15(8): p.
804-809.
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Springer. p. 77-98.
3. Opila, E.J., Oxidation and Volatilization of Silica Formers in Water Vapor. Journal of the American Ceramic
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resultant from in situ plasma spray processing. Ceramics International, 2020. 46(13): p. 21328-21335.
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composites and Si3N4 ceramics. Journal of the European Ceramic Society, 2005. 25(10): p. 1705-1715.
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of the American Ceramic Society, 2013. 96(7): p. 2298-2305.
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under isothermal heat treatment. Journal of the European Ceramic Society, 2020. 40(7): p. 2667-2673.
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coatings: A story of porosity. Ceramics International, 2021.
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North American Technologies: USA.
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Corporation: USA.
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barrier coatings. Journal of the European Ceramic Society, 2021. 41(6): p. 3696-3705.
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17. Hill, R. and C. Howard, Quantitative phase analysis from neutron powder diffraction data using the Rietveld
method. Journal of Applied Crystallography, 1987. 20(6): p. 467-474.
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50.
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review. Journal of Applied Crystallography, 2004. 37(3): p. 381-390.
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plasma spraying. Journal of Thermal Spray Technology, 1993. 2(1): p. 79-91.
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Springer Berlin Heidelberg.
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coatings. Journal of the European Ceramic Society, 2019. 39(4): p. 1477-1486.
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high temperature steam atmosphere. Journal of the European Ceramic Society, 2019. 39(10): p. 3153-
3163.
24. Vaßen, R., et al., Environmental Barrier Coatings Made by Different Thermal Spray Technologies.
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Techniques: A Preliminary Comparative Study. Journal of Thermal Spray Technology, 2017. 26(6): p.
1011-1024.
DVS 380 13

Evaluation of CMAS Resistance and Failure Behavior for Phase Composite
Thermal Barrier Coatings
X. Ma and P. Ruggiero
G. Wildridge
Environmental degradation of thermal barrier coatings (TBC) by molten deposits such as calcium magnesium
alumino-silicates (CMAS) is one of the most vital factors resulting in the failure of thermal barrier coatings, while
turbine engine inlet temperatures are kept increasing for higher fuel efficiency. A new phase composite ceramic
had been developed and evaluated for the topcoat of a durable thermal barrier coating (TBC) system with low
thermal conductivity property and improved erosion resistance. The present work is to continue the effort to
exploring the behavior of CMAS resistance of the phase composite TBC at high temperatures. The effects of
CMAS attack and thermal exposure on the TBC degradation were investigated in experimental runs. In addition, a
YAG-modified layer over the top of the TBC was applied with the attempt to improve CMAS resistance of the TBC
system. The evaluation of CMAS resistance was focused on the most important characteristics of coating
microstructure, CMAS penetration, and failure mode and test condition factors. The mechanisms for the
CMAS infiltration and the TBC damages were discussed based on the analyses of the CMAS corroded
samples in details.
1 Introduction
Recently, the increase in combustion chamber temperatures of gas-turbine engines and their operation in particle
(silicate sand, ash and dust) -contaminated environments leads to ingestion, adhesion and infiltration of molten
calcia–magnesia–alumino–silicate (CMAS) in thermal barrier coatings (TBCs) on hot-section components. The
adhesive CMAS molten on TBC surfaces and its mitigation into the ceramic topcoat in TBCs could result in much
severe coating degradation and early failure [1-3].
In a typical zirconia-based 8YSZ-TBC system, it is
particularly vulnerable to high temperature CMAS
attack. The mechanisms of CMAS attack and damages
had been investigated and identified [4-6]. In
general, molten CMAS adheres to the TBC surfaces
and starts penetrating into the TBC through the
cracks, pores in APS-TBCs and grain boundaries in
EB-PVD TBCs. Then, the CMAS could cause the
deteriorious changes of chemical and mechanical
properties the TBCs. Upon cooling and solidifying of
the molten CMAS penetrated, the TBC layer becomes
rigid and induces strain which could cause
TBC cracking, delamination and even spallation due
to the thermal expansion mismatch between the
TBC and CMAS. The TBC chemically modified by
CMAS penetration and chemical reaction can also
become phase structurally unstable and further
reduce its lifetime. Chemical interactions occur between
the molten or semi-molten CMAS and TBC is
Figure 1. Thermal conductivity data of as-sprayed and
heat treated at 1300 O C/25 hours for a typical phase composite
TBC.
quite complicate, depending on chemical compositions, basicity, temperatures and coating structures, typically,
classified into several different mechanisms [7].
There are some general approaches that researchers have taken to improve TBC CMAS resistance by modifying
TBC chemistry [8-13]. Common methods include: (1) To add some solute dopants such as Al 3+ and Ti 4+ to TBC and
results in the crystallization of the penetrating CMAS glass front arresting it and sequentially slow down the CMAS
migration inward; (2) To add active oxides into TBC as to capture the molten CAMS by promoting the interaction;
(3) to change and inhibit interaction by some additives to alter the basicity of CMAS/TBC system; (4) to use
zirconate material for topcoat.
In our previous work, a concept of phase composite ceramic had been proposed for the topcoat of a durable and
low-k TBC system, and showed promising performance related benefits over conventional single phase TBCs,
including durability, material affordability, thermal stability and low thermal conductivity [14, 15], as shown in Fig. 1.
The present work is to continue the effort to exploring the TBC behaviors of CMAS attack at different test condi-
14 DVS 380

tions. In addition, the attempt to further improve the TBC CMAS resistance was made by modifying the chemical
composition of the top layer of the TBC. Investigation was focused on the macro surface, reaction layers and phase
composition of all the tested samples. The characteristics of the resistance to CMAS corrosion of the low-k TBC
and YAG (yttrium aluminum garnet: Al 5O 12Y 3) additive were studied and the related mechanisms were discussed.
2 Experimental
2.1 Preparation of coating specimens
TBC specimens used in CMAS tests are listed in Table 1. The TBC samples were produced by Curtiss-Wright
Surface Technologies (“CWST”) using a F4 plasma torch (Metco, Westbury, NY) for ceramic topcoats and a Jet
Kote-3000 HVOF torch (Stellite, Goshen, IN) for a metallic CoNiCrAlY bondcoat (CO-210-24, Praxair) onto Haynes
188 disk substrates (25 mm in diameter). A rough CoNiCrAlY flash layer over the dense alloy bondcoat was applied
by HVOF process to improve the interface bonding between the bondcoat and the topcoat. An interlayer of t’ phase
zirconia was deposited over the bondcoat prior to applying the phase composite topcoat. For the sample #G3, a
mixture of the low-k TBC (sample #G2) and yttrium aluminum garnet (YAG) was applied as a top layer, as shown in
Fig. 2.
Table 1. List of the TBC samples used for
CMAS corrosion tests.
Table 2. List of the TBC samples for CMAS attack tests.
The optimal spray parameters were employed for fabricating the composite phase TBC, and more details were
disclosed in previous work [14]. For comparison, regular 8YSZ TBC (Sample #G1) also were prepared. The TBC
specimens have a typical porosity of 13~15% and a topcoat thickness of about 200 µm.
2.2 CMAS attack test
CMAS corrosion tests were performed by applied CMAS sands on the surfaces of the TBC samples given in Table
2. The CMAS sand was obtained from a commercial source (AFRL-02 test dust, PTI Inc., USA). AFRL-02 test
dust is made from 34% Quartz, 30% Gypsum, 17% Aplite,
14% Dolomite and 5% Salt. DSC/DTA scans data showed
that the CMAS sand has a melting temperature at 1150-
1200 O C [16]. The sand was mixed with alcohol into a slurry,
then brushed evenly on the surfaces of the TBC samples. The
CMAS sand dosage on the surfaces were controlled at about
35±2 mg/cm 2 . For the TBC samples #G2-25-5, 15, 35, they
have a CMAS dosage mass at 5, 15 and 35 mg/cm 2 , respectively.
All the CMAS deposited TBC samples were tested in a box
furnace in air isothermally at 1250±25 O C for different durations
as given in Table 2. The test samples were placed inside
the furnace, then started to heat to the isothermal temperature
at a rate of about 50 O C/min. After the tests were done, the
furnace power was turned off and the samples stayed inside
until the furnace cooled down to room temperature.
Figure 2. Microstructure of a typical TBC sample
#G3 with a modified top layer by adding YAG to the
matrix of the phase composite TBC.
2.3 Coating characterization
The microstructures and some material properties of the TBC samples had been evaluated and characterized using
different technologies in as-sprayed and tested coating conditions. The coating microstructures on crosssections
and eroded surfaces were examined by optical microscope and SEM. The chemical compositions in selected
samples and coating sections were analysed by energy-dispersive-x-ray spectroscopy (EDXS) equipped
with the SEM. The tested samples #G3-5 and #G3-120 were analyzed by SEM/EDXS method. In addition, the
tested samples #G1, 2, 3-5 were examined by X-ray diffraction (XRD) method for phase identification, phase quan-
DVS 380 15

tity and lattice parameter measurement. The XRD examination was carried out using a computer-controlled diffractometer
(MiniFlex 600, Rigaku, Tokyo, Japan), with CuK-alpha 0.154 nm radiation.
3 Results and Discussion
3.1 Effect of CMAS dosage on TBC behaviour
The TBC specimens #G2-25-5, 15, 35 were tested in air at 1250 O C for 25 hours, with the surface dosages of
CMAS sand of 5, 15 and 35 mg/cm 2 , respectively. Figure 3 shows the optical top views of three TBC samples #G2-
25 (-5: 5mg/cm 2 ; -15: 15 mg/cm 2 ; -35: 35mg/cm 2 ) after the CMAS exposure. The damage of the CMAS existence to
the TBC samples are obvious, and the degree of damages tends to become more severe with the increase of the
CMAS dosage. The damage modes for those TBC samples are identified as surface buckling at 5 mg/cm 2 mass
load, major cracking and local delamination or spallation within the ceramic layers at 15 mg/cm 2 , and TBC catastrophic
spallation at the bondcoat/topcoat interface at 35 mg/cm 2 . The observation of the distribution of the molten
CMAS adhered on the TBC surfaces indicates that discontinuous coverage at low dosage of 5 mg/cm 2 ; locally concentrated
coverage at medium dosage of 15 mg/cm 2 ; and nearly complete coverage at the high dosage of 35
mg/cm 2 .
Figure 3. Top views of the TBC samples after CMAS tests at 1250 O C for 25 hours, with different CMAS dosages. Sample
A: #G2-25-5, 5 mg/cm 2 ; Sample B: #G2-25-15, 15 mg/cm 2 ; Sample C: #G2-25-35, 35 mg/cm 2
The surface morphologies and the cross-section microstructures of the tested TBC samples are examined and the
paths of CMAS infiltration into the coatings are schematically shown in Fig. 4. The CMAS infiltration process progresses
in a sequences of: (1) Wetting and spreading of molten CMAS on the TBC surfaces. The whole wetting
process starts with short-time spread-out stage and the long-time liquid-flow stage. Gu et al. found that the CMAS
begins to melt and wet the surface of the samples at 1250 °C, and the dynamic contact angle decreases dramatically
with time during this spreading process. The wetting contact angles are in the range of 3 to 20 O , depending on
the substrates [16]. In the thermal sprayed TBCs, the contact angles also should be associated with the surface
morphologies including roughness, grain sizes defects and so on. (2) When the spreading process reaches a
steady state, the CMAS infiltration process follows. It is believed that the infiltration starts from the locations of coating
defects. In Fig. 4, Several types of coating defects are indicated in TBC topcoat. Crack type-1 is for the intrinsic
coating cracks formed during coating process, typically, in micro-size. Crack type 2 is for the cracking caused by
the CMAS penetration and associated strain, typically, in macro-size. Crack type 3 is for the cracking consequentially
resulted from the cracking type-2, and will lead to coating delamination, spallation and or buckling. Coating
porosity in both micro- and macro-sizes plays key roles as preferred start points for CMAS penetration. (3) When
the molten CMAS enters into the coating, it will continue to penetrate inward through the coating defects primarily
macro-pores and widely open cracks.
The effects of CMAS dosage on the penetration behaviours of the tested TBC samples can be explained as illustrated
in Fig. 4 (a), (b) and (c). In the case (a) with a low CMAS dosage, the molten CMAS is only dispersed locally
16 DVS 380

due to not sufficient mass and or the surface wetting situation. The low coverage reduces the number of CMAS
infiltration possible start points through surface macro-sized defects (interconnected pores and open cracking). In
the case (b) with a medium dosage, the CMAS coverage is increased and there are more defective locations available
for CMAS penetration. In the case (c) with a high dosage, the coating surface should be fully covered by a
layer of molten CMAS, and so the chance for CMAS infiltration is maximized. Also the CMAS layer can provide
sufficient supply for continuously penetration from the coating surface to inner coating, finally reach to the interface
of topcoat and bondcoat.
Figure 4. Schematic of the effect of CMAS dosage on the damage mechanisms in the TBCs. (a) Low dosage with local
coverage; (b) medium dosage with high coverage; (c) high dose with full coverage.
The concentration of sand particles such as PM2.5 have been investigated in different environments. In the earth’s
atmosphere, relatively low levels of fine dusts are ∼5–35 μg/m 3 [17]. However, some natural events such as volcanic
eruptions and dust/sand storms led to elevated fine particulate levels as high as 13,000 μg/m 3 [18]. Those
dust particles ingestion into gas turbine engines can cause severe hot section components damage for both military
and commercial aircraft operating. Now, the safe operating level for GTEs is presently set to ≤2000 μg/m 3 [19].
In this study, the effect of CMAS dosage on the CMAS attack severity was confirmed, and the aggressive attack
was confirmed at 35 mg/cm 2 , therefore, this condition was used in follow-up CMAS exposure tests.
3.2 Effect of YAG additive on CMAS corrosion
The TBC samples #G1, 2, 3-5 were tested in air at 1250 O C for 5 hours with the CMAS dosage of about 35 mg/cm 2 .
The YAG addition to the low-k material was applied as the top layer of about 100-150 µm as shown in Fig. 2. The
test was focused on the effect of the YAG additive in the TBC sample #G3-5 to improve CMAS resistance by comparing
with the TBC samples #G1-5 and G2-5. The top views of the morphologies of the tested TBC samples were
observed under optical microscopes and are presented in Fig. 5.
All the tested samples were damaged by the CMAS attck in different degree. The 8YSZ TBC sample #G1-5 seems
to be the worst one with large area spllation and mass loss, as well as deep penetration in the topcoat. Meanwhile,
multi-layered delamination and separation is identified from the top viewed photo. In the low-k TBC sample #G2-5,
the coating damage with large cracking is found and seems that CMAS penetration is limited to the near surface
region within the topcoat, but there is spallation loss of the ceramic material in nearly half of the whole coating area.
The YAG-modified TBC sample #G3-5 exhibits improved CMAS resistance by reducing the material loss and limit-
DVS 380 17

ing the coating attack to some local areas. Instead of coating spallation, main coating failure takes place in a way of
topcoat buckling locally. The visual inspection on those TBC samples before and after cooling from 1250 O C to
room temperature, verified that the coating damages happened during cooling time.
With the most interest in the YAG contained low-k top layer, the microstructures of the composite material layer
were examined after the CMAS test and are shown in Fig. 6. A distinct layer with a thickness about 100 µm from
the coating surface is identified. It is assumed that the layer is formed by CMAS infiltration in the layer, and the
“dark grey“ phase could be some new phases due to the reaction between the CMAS and the YAG composite material.
Based on the depth of the CMAS infiltration, it can be concluded that the addition of YAG to the low-k material
matrix has inhibited the mobility of the CMAS attack frontier, and thus slows down the coating damage in some
degree. This positive effect of YAG or similar additives to a TBC system had been investigated and confirmed by
some researchers [20-22]. Turcer et al. revealed that YAlO3 ceramic can reacted with CMAS, and the reaction zone
comprises three regions of reaction-crystallization products, including Y-Ca-Si apatite solid-solution (ss) and
Y3Al5O12 (YAG)(ss).
In addition, the low-k TBC (#G2-5) shows better CMAS resistance than the regular 8YSZ-TBC (#G1-5). Iis behavior
can be explained by co-doping of RE oxides into ZrO2, and result in the formation of disordered solid solution structure
that will have lower diffusion coefficients and hence suppressed reactivity with CMAS [23, 24].
Figure 5. Surface photographs of the TBC samples after the CMAS exposure test in air at 1250 O C for 5 hours. (a)
TBC sample #G1-5: 8YSZ; (b) TBC sample #G2-5: Low-k; and (c) TBC sample #G3-5: YAG modified low-k.
Figure 6. Microstructures of the TBC sample #G3-5 with YAG additive in low-k material topcoat. (a) CMAS attacked coating
near surface region; (b) Close look on the attacked zone.
18 DVS 380

3.3 XRD analysis of the reaction between CMAS and YAG
To better understand the reaction between CMAS and YAG in the CMAS corrosion test, some test samples were
manufactured and then tested by isothermal heat at 1250 O C for 5 hours. The test samples for the testing are given
in Table 3. Three TBC materials (G1, G2, G3) were well mixed with CMAS sand at a weight ratio of 1:1(wt.%), then
placed in a ceramic crucible separately prior to the reaction tests in air at 1250 O C. For comparison purpose, a G3
powder sample and a G3 TBC sample were included in the XRD analyses.
The results of phase identification by XRD analyses are given in Table 3. The results show that there is no major
new phase formed in the sample #G1-S5 after the heating of the mixture of G1 (8YSZ) powder with CMAS sand for
the duration of 5 hours. Pujol et al. found that liquid-state CMAS will lead to the phase transition from stable t‘-ZrO2
to unstable m-ZrO2 causing the change of volume of lattice, which can result in the failure of the 8YSZ-TBCs
[25, 26]. In the test sample #G1-S1, the fact of no m-ZrO2 phase in the tested sample indicates that there is no
majoe reaction between the G1 material and CMAS and no resultant phase transition. In addition, the CMAS with
glassy structure (non-crystalline) is not detected in the XRD spectrum.
With the most interest in the reaction potential of the
Table 3. List of test samples for CMAS reaction tests
TBC materials #G2 and #G3 with CMAS, the XRD
and XRD phase analysis results.
patterns for the test samples #G2-S5 and #G3-S5 are
shown in Fig. 7 In the sample #G2-S5, a crystaline
phase Ca2Mg[Si2O7] is identified in Fig. 7 (a). Wu et
al. iInvestigated the CMAS corrosion behavior of the
similar co-doped ZrO2 TBC system at 1300 O C, and
found some new reaction phases like
Zr84.4Y5.6Ta5.1Ca4.9 were formed after reacting with
CMAS for 50 hours [27]. In this test, no similar reaction
products were detected in the XRD, maybe duo
to the difference in the test conditions (temperature,
time, CMAS type,...). However, the formation of crystaline
Ca2Mg[Si2O7] is beneficial for inhibiting CMAS
mobility and attack severity based on Nitin‘s et al.
discovery in the TiO2-Y2O 3 -ZrO2 TBC system, where
the TiO2 promoted the formation of crystalline phase formation [8].
In the sample #G3-S5, a reaction product NaO26Si6Y9 is confirmed in Fig. 7 (b). The XRD analysis determines the
phase composition as: ZrO2 phase at 28.7±0.4%, Al5O12Y3 phase at 39.9±0.6%, and NaO26Si6Y9 phase at
31.4±0.9%. The reaction product NaO26Si6Y9 contains the elements Si, Na from the CMAS, and Y from YAG additive
and or the co-doped low-k G2 material, and so it is no doubt that the CMAS is reactive to the YAG and or the
RE oxide-doped TBC material. Based on the finding in the sample #G1-5, in which the CMAS has minor and slow
reaction with the Y2O3-doped ZrO2, it can be assumed that the major reaction should happen between the CMAS
and the YAG (Al5O12Y3) additive in the sample G3-S5. In addition, the large quantity of NaO26Si6Y9 phase at
31.4±0.9% means that the YAG additive is very reactive with the CMAS, and can result in quick reaction to transit
liquid CMAS into crystalline solid product, which is expected to slow down the moving frontier of the CMAS infiltration
in the TBC topcoat and sequentially inhibits the CMAS corrosion and TBC damage.
DVS 380 19

Figure 7. XRD analyses of the ceramic materials mixed with CMAS sand after heated at 1250 O C for 5 hours.
(a) Low-k (#G2-S5) material with CMAS; (b) Low-k+YAG (#G3-S5) with CMAS.
One of the methods for improving TBC CMAS resistance was investigated is to modify the TBC with the addition of
active oxides or their compounds including RE oxides, TiO2, and YAG. Godbole et al. found that the Y-containing
system formed both garnet A2B8(TO4)6O2 and apatite A3B2T3O12 [28, 29]. Y3Al5O12 (rare earth Y aluminate garnet,
YAG) is stable in the CMAS-TBC system, and further can form more stable new reactant components. As a
positive result, the formation of crystalline phases such as apatite and garnet has a two-fold effect on melt
infiltration mitigation through a reduction in the melt volume and through changes in the melt viscosity due to
changes in the composition of the residual melt. Conclusively, our CMAs reaction tests are consistent with the
previous related studies, and confirm that the co-doped TBC (#G2) and the YAG-added TBC (#G3) can promote
the formation of some crystalline products, and eventually to change the properties of both CMAS and the phase
components in the TBCs.
3.4 TBC durability test under CMAS attack
The long-exposure CMAS corrosion tests were conducted for TBC samples #G1, G2 and G3-120 at 1250 O C for
120 hours with a purpose to further investigate the degree of the CMAS attack and the failure mechanisms of the
TBC samples with different chemical compositions. First, it is confirmed that the CMAS attack becomes more severe
and leads to more damage to those TBC samples with the increase in exposure time. Figure 8 show the top
surface views and the cross-section microstructures of the TBC samples after the 120-hours CMAS corrosion test.
Second, in the TBC sample #G1-120, the worst CMAS attack to the 8YSZ topcoat was observed. The topcoat has
delaminated and spalled almost completely mainly at the bondcoat and topcoat interface, which indicates that the
TBC has lost the protection of the topcoat. The TBC sample #G2-120 shows nearly full coverage of the ceramic
coating, but it is obvious that the
coating has suffered multiple layered
separation and partial spallation,
and thus lead to a lot material
loss. It seems that the coating damage
occurs mostly within the low-k
ceramic layer and at the 8YSZ layer
and the low-k layer interface. Third,
the TBC sample #G3-120 exhibit the
best CMAS attack resistance among
the three TBC samples, thought the
CMAS attack and coating loss still is
quite visible. A small area of original
coating surface is reserved with
spallation, and the rest of the coating
area is removed evenly, maybe
indicating a more even CMAS attack
in the coating region.
The microstructures of the tested
TBC samples reveal the CMAS
penetration into the coatings in dif-
25mm dia.
20 DVS 380
Figure 8. Morphologies and microstructures of the TBC samples after CMAS
corrosion tests at 1250 O C for 120 hours. (a) TBC sample #G1-120; (b) TBC
sample #G2-120; (c) TBC sample #G3-120.