Bericht 336_Leseprobe

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International Thermal Spray<br />

Conference & Exposition2017<br />

June 7 – 9, 2017, Düsseldorf/Germany<br />

2017<br />


Foto: GTV Verschleißschutz GmbH<br />

Conference Abstracts<br />

(including proceedings on USB stick)<br />

Organizers:<br />

! DVS – German Welding Society<br />

! ASM International – Thermal Spray Society (TSS)<br />

! IIW – International Institute of Welding<br />

Supporting Partners<br />

Media Sponsors

Lectures<br />

PENTA: Anovel high spray rate APS gun<br />

Plasma Spraying I<br />

T. Schläfer, A. Wank, C.Schmengler and K. Müller-Roden, Luckenbach/DE<br />

Multi-electrode APS has proven significant advantages with regard to spray rates, deposit efficiency and<br />

component life time. So far, three-cathode and three-anode spray guns have been established successfully in<br />

several industrial sectors where high spray rates are mandatory. Based on the successful three-anode plasma<br />

spray gun DELTA, the five-anode APS gun PENTA was developed to further increase productivity. With its gross<br />

power of up to 125 kW it allows very high spray rates and thus significantly reduced coating times. This paper<br />

focusses on the development ofhigh spray rate parameter settings for producing oxide ceramic coatings. All<br />

coatings will be investigated with regard totheir microstructures. Furthermore, economical benefits ofthe fiveanode<br />

technology will be highlighted.<br />

Novel approaches for thermal spray deposition of fully dense ceramic and metal coatings<br />

with well bonded lamellae<br />

C. Li, S.Yao, J.Tian, C. Li, G.Yang, X.Luo and Y. Wei, Xi’an/CN<br />

It has been well accepted that thermal spray coatings present atypical lamellar structure with limited lamellar<br />

interface bonding. It has been agreat challenge to deposit afully dense coating with fully bonded lamellae. In this<br />

report, three different novel approaches are introduced to deposit fully dense ceramic coatings and metal alloy<br />

coatings. With the deposition of aspecific ceramic coating, it was found that there exists an intrinsic bonding<br />

temperature corresponding to the glass transient temperature ofspray material. Achemical bonding is formed at<br />

the interface upon splatting of amolten ceramic droplet, as far as the maximum interface temperature between the<br />

spreading splat and the solid splat reaches over the intrinsic bonding temperature. Moreover, itwill be presented<br />

that asimple critical bonding temperature in alinear relation with the melting point of coating materials can be<br />

utilized to deposit fully dense ceramic coatings bycontrolling the deposition temperature. Furthermore, with metal<br />

alloy coatings, aself-bonding mechanism is proposed utilizing the ultra-high temperature molten droplet for dense<br />

coating with fully bonded lamellae. Using specially designed core-shell structured powders, it was demonstrated<br />

that abulk-like metal coating is deposited by creating ultra-high temperature molten droplet. It will be found that<br />

such coatings present excellent properties and performance comparable to bulk materials. Moreover, itwill be<br />

shown that, for ductile metal alloys, the solution-impermeable dense metal coatings can be deposited byusing the<br />

novel in-situ shot-peening assisted cold spraying.<br />

Porosity characterization and its effect onthermal properties ofAPS sprayed alumina<br />

coatings<br />

W. Tillmann, O. Khalil and M. Abdulgader, Dortmund/DE<br />

In the present work, three different APS alumina coatings were fabricated using three fused and crushed alumina<br />

powders of different particle size fine, medium and coarse. The influence of the particle size onthermal properties<br />

and micro-structural features ofthe produced coating were investigated by thermal insulation test and detailed<br />

image analysis technique, respectively. The analyzed micro-structural features include the total porosity, pore size<br />

(fine, medium, and large) and cracks. All types of cracks were considered in calculations as voids and were<br />

evaluated according totheir sizes aspores. All spray parameters except the particle size were fixed throughout the<br />

spraying process. The results revealed that the fine starting powder has produced the densest coating with the<br />

lowest total porosity and that the total porosity increases with an increasing particle size. This was expected as<br />

DVS <strong>336</strong> 1

powders ofsmaller particle size will reach ahigher in-flight temperature and velocity than powders of bigger<br />

particle sizes aslong asthe same spray parameters are applied. However, adetailed image analysis investigation<br />

on the three produced coatings showed that the fraction of fine pores and cracks versus the total porosity is<br />

substantially higher in coatings produced by using fine starting powders than those produced using medium and<br />

coarse powders. In this work, aconnection between the thermal insulation and the porosity fraction, which includes<br />

fine pores and cracks, was revealed.<br />

New investigations of the arc instabilities inaone-cathode-one-anode plasma generator<br />

via special wavelet-analysis<br />

S. Zimmermann, M.Mudra, O. Bornschlegl, S.Schein, G. Haderer, J. Marques and J. Schein Neubiberg/DE<br />

Plasma generators are frequently used in awide field ofapplications. These applications include thermal coating,<br />

plasma-welding, preprocessing ofsurfaces, sterilization and propulsion systems. The industrial use of plasma<br />

generators demands a high level of accuracy and reproducibility which has to be monitored throughout the<br />

process. Rather than analyzing results of e.g. acoating process (by electron microscopic) one prefers to have an<br />

online assessment of the plasma generator. The plasma generated is defined by various parameters (e.g.,<br />

temperature, conductivity…) which can be measured with suitable measuring systems. Determining all plasma<br />

parameters inone setup isvery costly and requires abig setup. Inindustrial facilities itisoften suitable to measure<br />

one or two physical quantities and derive the plasma parameters from these measurements. This paper focuses on<br />

the evaluation of the electric current consumed by the plasma generator and the sound emitted by the whole<br />

system. Aquick analyzation ofthese signals – that may result in an online assessment –was accomplished by<br />

using the wavelet transform. Multiple experiments were performed to gain reliable and significant data (behavior of<br />

the arc/plasma).<br />

Aviation &Power Generation Industry I<br />

Practical aspects ofsuspension plasma spray for thermal barrier coating on potential<br />

gas turbine components<br />

X. Ma and P. Ruggiero, Charlotte/US<br />

Suspension Plasma Spraying (SPS) process has attracted extensive efforts and interests to produce finestructured<br />

and functional coatings. In particular, thermal barrier coating (TBC) applied bySPS process gains<br />

increasing interest due toits potential for superior thermal protection of gas turbine hot-section components as<br />

compared to its conventional APS-TBC and even EB-PVD TBC. Unique columnar architecture and nano- and submicron<br />

sized grains in a SPS-TBC demonstrate some advantages of thermal shock durability, low thermal<br />

conductivity and high-temperature sintering resistance. This work will look into some practical aspects ofSPS<br />

process for TBC application before itbecomes areliable industry method. The spray capability and applicability of<br />

SPS to achieve uniformity thickness and microstructure on curved substrates was evaluated indesigned spray<br />

trials tosimulate industrial parts with complex configurations. The performances of SPS-TBCs in erosion, free<br />

falling ballistic impact and indentational loading tests were tested and evaluated to simulate SPS-TBC<br />

performances in turbine service conditions. The behaviors ofSPS-TBCs in those tests were correlated tokey test<br />

factors including grit incident angles, impact object sizes, indentation head sharpes and coating surface curvatures.<br />

Finally, aturbine blade was coated and sectioned toverify SPS sprayability in multiple critical sections. The SPS<br />

trials and test results demonstrate that SPS is promising for innovative TBCs, but some challenges need to be<br />

addressed before it becomes aneconomic and reliable industrial process, especially for gas turbine components.<br />

2 DVS <strong>336</strong>

Effect of spray parameters on the microstructure and porosity content of gadolinium<br />

zirconate TBCs deposited by suspension plasma spray<br />

S. Mahade, Trollhättan/SE, D. Zhouand R. Vassen, Jülich/DE<br />

Gadolinium zirconate (GZ) is considered as a promising top coat candidate for high temperature (>1200°C)<br />

thermal barrier coating (TBC) applications. Suspension plasma spray (SPS) technique has shown the capability to<br />

generate awide range of microstructures which includes the more desirable columnar microstructure. In this study,<br />

GZ single layer TBCs were deposited by axial SPS process. The variable parameters include the standoff distance,<br />

solid load content of the suspension and input power. The cross section and top surface of the as sprayed TBCs<br />

were analyzed by SEM. The phase content inthe as sprayed TBCs was analyzed by XRD. The porosity content of<br />

the assprayed TBCs was measured using image analysis. Inthe SEM analysis, it was observed that alower solid<br />

load content in the suspension favoured the formation of acolumnar microstructure. Additionally, at lower solid<br />

load content, increase in standoff distance resulted in columnar microstructure with high porosity content in the<br />

TBC. However,with higher solid content suspension and alteration ofinput power, only adense vertical cracked<br />

microstructure can be obtained.<br />

High feed rate plasma spraying of YSZ from various suspensions<br />

R. Musalek, J. Medricky, J. Kotlan, T. Tesar, F.Lukac, P. Ctibor, K. Illkova and T. Chraska, Prague/CZ<br />

In this paper, yttria-stabilized zirconia (YSZ) coatings were prepared by plasma spraying of ready-to-spray<br />

suspensions provided by three different manufacturers. High-enthalpy hybrid water-argon plasma torch WSP-<br />

H500 was successfully used for deposition of coatings with porous and columnar microstructure consisting of<br />

tetragonal non-transformable phase. Sensitivity of the deposition process to variation ofdeposition conditions was<br />

also evaluated by the change ofsuspension injection point position. Slight differences in the microstructures of the<br />

deposited coatings (in particular character of porosity and mutual bonding of the microsplats) were reflected in<br />

slight but measurable differences in hardness and wear resistance of the coatings indicating changes in the<br />

coating cohesion. Tensile adhesion/cohesion strength of the coatings was found to be in the range of 9to15MPa.<br />

High coating porosity desirable for low thermal conductivity combined with high suspension feed rate (from about<br />

100 to 120 ml/min in this study) makes the WSP-H coatings promising for further development for example in<br />

thermal barrier coatings applications.<br />

Medical Industry I<br />

Sporicidal efficacy of thermal spray copper alloy coating with varying degrees of<br />

roughness<br />

R. Shafaghi, L.Pershin, M. Riguette and J. Mostaghimi, Toronto/CA<br />

This study was focused onthe biocidal efficacy on spores of copper alloy sheet and copper alloy coating at two<br />

different surface topographies. Endospores can remain viable in adormant state for centuries. Our work compares<br />

the effectiveness inkilling endospores of copper alloy coating and sheet metal. Atwin-wire arc spray system was<br />

used for coating of stainless steel coupons. The feedstock was CuNiZn wire, the coating thickness was 400 µm.<br />

The copper alloy sheet metal had the same composition and is registered as antimicrobial by Environmental<br />

Protection Agency (US). Uncoated stainless steel coupons were used ascontrols in all experiments. The surface<br />

was polished to two roughness levels Ra=3.5 µm, and Ra=0.1 µm. The surface topography was analysed by a<br />

stylus profilolemeter and 3D image analysis. EDS and FIB were used tocharacterize the elemental composition<br />

and structure flower-like nanostructures and endospores. The results obtained in this study indicated that changes<br />

in Ra values of 0.1 and 3.5 μm had no significant impact on the biocidal activity of sheet metal and the coating on<br />

E. coli, S. epidermidis and B. subtilils. The coating was as effective as the EPA certified sheet metal inthe<br />

destruction ofvegetative cells within 5minutes. This study indicates that degradation of B. subtilis endospore<br />

begins within 2hours after exposure to the coating. By day seven, only extensively degraded endospores and<br />

nanostructures were visible on the both surfaces. Our results show that thermal spray copper alloy coatings were<br />

as effective ascertified antimicrobial sheet metal in the destruction ofendospores within hours however; the<br />

coating was more effective in killing after one week of exposure.<br />

DVS <strong>336</strong> 3

Transpiring thermally sprayed alumina layers with integrated fluid flow tubes<br />

M. Rodriguez Diaz, K. Möhwald, N.Loftfield, M.Kästner, E. Reithmeier, S. Knigge, B.Glasmacher and H. J. Maier,<br />

Garbsen/DE<br />

Osteoarthritis in the hip or knee is one of the most common diseases in industrialized countries. The implantation<br />

of an endoprosthesis as a joint replacement represents the most effective way to treat serious pathological<br />

changes in these joints. The lifetime of an endoprosthesis can be shortened by aseptic inflammation and<br />

osteolysis. The main cause for the aseptic inflammations, osteolysis, and thus, the failure of the endoprostheses<br />

are abrasion particles ofthe acetabular cup inlays that are caused by the tribological load of the prosthesis. This<br />

research project aims atdeveloping coatings with enhanced tribological behaviour for endoprostheses byanactive<br />

hydrodynamic lubrication ofthe joint with synovial fluid. Inaddition, biocompatibility, as well as the increase of the<br />

strength under static and cyclic loading need be realized. In the current approach, adeterministic fluid flow tube<br />

structure isformed inathermally sprayed alumina layer bythe introduction of aleachable placeholder. This tube<br />

structure allows the transverse transport ofthe synovial fluid through the alumina layer. Furthermore the synovial<br />

fluid can be transported into the lubricating gap of the sliding surfaces by leaving the alumina layer through the<br />

porous surface. First results will be presented and the ramifications in correlation to applications will be discussed.<br />

Experimental analysis of impact behavior of ultra-high molecular weight polyethylenenano<br />

ceramics composite particles by isolated particle deposition method using<br />

downstream injection cold spray technique<br />

K. Ravi, Sendai/JP and Lyon/FR, K. Ogawa, Sendai/JP, O.Lame, Lyon/FR, and J.-Y. Cavaillé,Sendai/JP<br />

Recent advances has made possible to obtain Ultra High Molecular Weight Polyethylene (UHMWPE) coatings by<br />

cold spray technique with nano-ceramic additives with the feedstock. However, the exact role ofnano particles is<br />

largely not understood. In this work, isolated depositions of UHMWPE particles with 0%, 2%, 4%, 10% offumed<br />

nano alumina (FNA) onAlsurface were performed at different gas/particle temperatures. Particle velocities and<br />

particle temperatures were controlled byvarying the carrier gas pressure and temperature. The impact behavior of<br />

UHMWPE was analyzed using SEM, FIB and high-speed camera. Increase ingas temperature and percentage of<br />

FNA showed asignificant variation in the deposition volume. FIB analysis showed that successful depositions were<br />

influenced by degree ofdeformation of particle. Further, addition ofFNA helped in deposition ofparticles that have<br />

required alesser degree of deformation. Finally, high speed camera showed that particles are moving atan<br />

incidence velocity of 180-200m/s and rebound velocity of40-50m/s. This suggests that particles lose asignificant<br />

amount of their kinetic energy during the impact.<br />

Process Diagnostics, Sensors &Controls<br />

The arc movement as asource ofprocess instability for single-cathode-anode systems –<br />

anew method for direct investigation<br />

G. Thomas, Technical University of Berlin, Berlin/DE, S. Mihm, Mägenwil/CH, M. Limburg, Berlin/DE, and H.<br />

Gruner, Mägenwil/CH<br />

The almost uncontrollable arc movement in a single-cathode-anode system limits the efficiency and process<br />

stability of this global used DC plasma spraying technique. Asuccessful approach to stabilize the arc anode<br />

attachment and thus to increase process efficiency was the replacement of the convergent-cylindrical nozzle<br />

geometry by aconvergent-divergent nozzle geometry with Laval contour. However, the advantages of this nozzle<br />

design were connected to an increased anode erosion caused by an excessive heat input from the anode<br />

attachment ofthe arc. Prerequisite for an optimization of the arc movement isits technical measurement and the<br />

dedicated correlation out of it with the plasma jet and the trajectory of injected powder particles. For this purpose<br />

Technical University ofBerlin developed anew optical analysis method based on high-speed video recording to<br />

examine the arc movement, its position and intensity. The software based data together with the simultaneous<br />

measured voltage of the corresponding DC-arc clearly show for example the dependence ofthe arc movement<br />

from the position ofthe cathode tip in relation tocenter axis of the anode, impressively demonstrated for anew<br />

three-zone anode (convergent, conical and divergent). Thus anew tool is given to the developer of new anode<br />

geometries for increasing process efficiency and the lifetime of the single-cathode-anode system.<br />

4 DVS <strong>336</strong>

Investigation of the usefulness of particle jet monitoring in aproduction environment<br />

L. Leblanc, R. Hinckley and C.Spinicci, Malta/US<br />

In the thermal spray process, particle state at impact is among the key factors influencing the quality,<br />

characteristics and properties of the deposit formed. Measuring and eventually controlling in-flight particle jet<br />

characteristics can help ensure the repeatability of desired coating properties. Moreover, monitoring particle jet can<br />

lead to cost savings by allowing replacement of consumable parts onaneed-basis rather than on apreventivebasis.<br />

However, successful use of in-flight particle sensors inaproduction environment requires developing an<br />

implementation strategy that minimizes impact on coating cycle time, limits operator intervention and reduces<br />

analysis time, while still generating useful data. The usefulness of in-flight particle sensor in ahigh yield production<br />

environment isinvestigated. Apreliminary study was first conducted todefine astrategy to implement the data<br />

acquisition process using an ensemble in-flight particle monitoring system that allows real-time measurements of<br />

average particle temperature and velocity and overall particle jet profile. Data was collected to capture<br />

representative torch and particle jet behaviors over the life of several consumable hardware sets. Evolution ofthe<br />

particle jet parameters over time is compared to that of some of the process parameters, as well as to the<br />

deposition efficiency and one selected characteristic ofthe coating deposited. Some trends are identified, and<br />

potential benefits and drawbacks of using in-flight particle monitoring inahigh yield production environment are<br />

highlighted.<br />

In situ acoustic monitoring of thermal spray process using high-frequency impulse<br />

measurements<br />

W. Tillmann, F. Walther, W. Luo, M. Haack, J. Nellesen and M.Knyazeva, Dortmund/DE<br />

In order to guarantee their protective function, thermal spray coatings must be free from cracks, which expose the<br />

substrate surface toe.g. corrosive media. Cracks in thermal spray coatings are usually formed because of tensile<br />

residual stresses. Most commonly, the crack occurrence isdetermined after the thermal spraying process by<br />

examination of metallographic cross-sections of the coating. Recent efforts focus on in situ monitoring ofcrack<br />

formation bymeans of acoustic emission analysis. However, the acoustic signals related to crack propagation can<br />

be absorbed by the noise of the thermal spraying process. In this work, ahigh-frequency impulse measurement<br />

technique was applied to separate different acoustic sources by visualizing the characteristic signal of crack<br />

formation via quasi-real-time Fourier analysis. The investigations were carried out on atwin wire arc spraying<br />

process, utilizing FeCrBSi asacoating material. The impact of the process parameters on the acoustic emission<br />

spectrum was studied. Acoustic emission analysis enables toobtain global and integral information onthe formed<br />

cracks. The coating morphology as well as coating defects were inspected using light microscopy on<br />

metallographic cross-sections. Additionally, the resulting crack patterns were imaged in3Dbymeans ofX-ray<br />

micro-tomography.<br />

Ceramic Coatings<br />

Epitaxial growth during the rapid solidification of plasma-sprayed molten TiO2 splat<br />

S. Yao, C. Li, G.Yang and C. Li, Xi’an/CN<br />

Epitaxial grain growth during the rapid solidification of molten TiO2 in plasma spraying was studied. The<br />

crystallographic structure of the TiO2 splats deposited on rutile and α-Al2O3 substrates at150, 300 and 500 °C was<br />

characterized by high resolution transmission electron microscopy and electron back scattering diffraction. The<br />

results reveal that homo-epitaxial and hetero-epitaxial TiO2 splats can be formed atthe deposition temperature of<br />

500 °C. Epitaxial growth is significantly influenced by the crystal orientation. Itiseasier toform an epitaxial TiO2<br />

splat with a orientation inthe direction perpendicular tothe substrate surface. Inorder toexplain the<br />

formation of epitaxial splat during plasma spraying, acompetition mechanism between heterogeneous nucleation<br />

and epitaxial growth was proposed. It was indicated that the face (001) of rutile crystal exhibits the largest growth<br />

velocity, which isconducive to form an epitaxial splat for the melt with alargest undercooling degree. In addition,<br />

the effect of deposition temperature and crystalline orientation on the epitaxy was simulated. The simulation results<br />

are in agreement with the experimental observations.<br />

DVS <strong>336</strong> 5

Cold Gas Spraying I<br />

Broken characteristics of the oxide film in cold spray<br />

Y. Xie, C.Chen, M.Planche, R.Raoelison, C. Verdy and H. Liao, Belfort/FR<br />

In cold spraying, oxide-free interface is an important factor for fresh metal bonding between particles and substrate,<br />

which determines the bonding strength and final coating quality. In this study, awell-designed experiment was<br />

performed toexamine the deformation behaviour of the oxide film on copper alloy particle surface after deposition.<br />

The experiment results show that partial oxide film could bedisrupted during the high-speed impact. However,<br />

most of the oxide films were found to remain intact after particle deposition, which limited the exposure ofoxide<br />

free interface. The presence of oxide film atthe interfaces between deposited particles and substrate seriously<br />

affected the metallurgical bonding. Besides, substrate material is found to have a strong influence on the<br />

deformation behaviour and final state of the oxide film. The study also demonstrated that the bonding mode<br />

between deposited particle and substrate strongly depends onthe type of substrate.<br />

Essential factors influencing the bonding strength of cold sprayed aluminum coatings on<br />

ceramic substrates<br />

R. Drehmann, T. Grund, T. Lampke, B. Wielage, Chemnitz/DE, C. Wüstefeld, M.Motylenko and D. Rafaja,<br />

Freiberg/DE<br />

The present work summarizes the most important results of aresearch project dealing with the comprehensive<br />

investigation of the bonding mechanisms between cold sprayed Al coatings and various poly- and monocrystalline<br />

ceramic substrates (Al2O3, AlN, Si3N4, SiC, MgF2). Due to their exceptional combination of properties, metallized<br />

ceramics are gaining more and more importance for a wide variety of applications, especially in electronic<br />

engineering. Cold spraying provides aquick, flexible and cost-effective one-step process to apply metallic coatings<br />

on ceramic surfaces. However, since most of the existing cold spray-related publications focus on metallic<br />

substrates, only very little is known about the bonding mechanisms acting between cold sprayed metals and<br />

ceramic substrates. In this paper, the essential factors influencing the bonding strength insuch composites are<br />

identified. Besides mechanical tensile strength testing, athorough analysis of the coatings and especially the<br />

metal/ceramic interfaces was conducted by means of HRTEM, FFT, STEM, EDX, EELS, XRD and EBSD. The<br />

influence of substrate material, substrate temperature and particle size isevaluated with regard to the observed<br />

bonding behavior. The results suggest that, apart from mechanical interlocking, the adhesion ofcold sprayed<br />

metallic coatings onceramics is based on acomplex interplay of different mechanisms such as quasi-adiabatic<br />

shearing, static recrystallization as well as heteroepitaxial growth.<br />

Metallization of various polymers bycold spray<br />

H. Che, P. Vo and S.Yue, Montreal/CA<br />

Previous results at McGill University have shown that metallic coatings can be successfully cold sprayed onto<br />

polymeric substrates. This paper studies the cold sprayability ofvarious metal powders on different polymeric<br />

substrates. Five different substrates were used, including carbon fibre reinforced polymer (CFRP), acrylonitrile<br />

butadiene styrene (ABS), polyether ether ketone (PEEK), polyethylenimine (PEI); mild steel was also used as a<br />

bench mark substrate. The CFRP used inthis work has athermosetting matrix, and the ABS, PEEK, and PEI are<br />

all thermoplastic polymers, with different glass transition temperatures aswell as anumber ofdistinct mechanical<br />

properties. Three metal powders, tin, copper and iron, were cold sprayed with both alow-pressure system and a<br />

high-pressure system atvarious conditions. Ingeneral, cold spray on the thermoplastic polymers rendered more<br />

positive results than the thermosetting polymers, due to the local thermal softening mechanism in the<br />

thermoplastics. Thick copper coatings were successfully deposited on PEEK and PEI.<br />

6 DVS <strong>336</strong>

Maritim Industry &Off-Shore Technologies<br />

Acase study of repair work on ship engine valve stems<br />

P. T. Nielsen, D. B. Bangsgaard, K. G. Soerensen, Brøndby/DK, and P. Pallesen, Hirtshals/DK<br />

The degradation mechanisms of machine parts are well-known facts, usually resulting in replacement of<br />

components. However, in some cases, for instance, parts for large ship engines, repair will often seem more<br />

attractive. Time-wise, the vessel’s down-time will be reduced and the investment will be lower. This paper<br />

describes repair work performed onvalve stems from a52-year-old ship engine. Due to this long time in operation,<br />

the stems were damaged by wear and were no longer functional. The requirements for the stems were scarcely<br />

documented stating only afew specific requirements; therefore ashort study of the possibilities concerning rebuild<br />

material and application method was initiated. This paper illuminates the manufacturing process used; twin wire arc<br />

spraying with Monel asthe rebuild material. Monel ischosen to meet the requirements for hardness and the<br />

subsequent high precision machining. In addition, the mechanical and metallurgical properties of the rebuild<br />

coating are examined in regard to adhesion, microstructure and hardness to interpret and support the functionality.<br />

Partial repair of thermally sprayed and sealed corrosion protection – Organic coating<br />

material or thermal spraying?<br />

T. Wilhelm, C. Klesen and T. Maghet, Duisburg/DE<br />

For many decades thermally sprayed corrosion protection systems onthe basis ofZnAl orAlcarry out their service<br />

for structures in coastal areas, the offshore sector, as CUI (Corrosion Protection under insulation) oranywhere<br />

where the properties ofthermally sprayed corrosion protection systems bring important advantages interms of<br />

durability. Athermally sprayed corrosion protection system is about to protect the structure 25 to 30 years against<br />

corrosion. During this time it may be damaged due to factors like construction work, improper handling or simple<br />

aging. There are many standards and regulations, which describe the initial design of thermal spray systems,<br />

however they remain silent regarding repair. In particular, amending of partial regions is hardly described. Specific<br />

repair instructions are rare and if present, they differ from one another. Overall there isalack of knowledge of the<br />

proper procedures for partially repairing thermal spray coating systems. This project was concerned with tangible<br />

corrosion-technical issues of the coating repairs: How does the critical overlap area perform? Have organic<br />

coatings benefits? To what extent does arenewed damage affect the lifetime? The aim of the study was to develop<br />

practice-relevant instructions for the repair of thermally sprayed duplex systems.<br />

Improvements of coating properties and residual stress states in arc sprayed aluminium<br />

bronze coatings by using an alternative gas mixture<br />

M. Hauer, Rostock/DE, S. Krebs, Hamburg/DE, W.Krömmer, Unterschleißheim/DE, and K.-M. Henkel,<br />

Rostock/DE<br />

The highly cavitation erosion resistant propeller alloys CuAl9Ni5Fe4Mn and CuMn13Al8Fe3Ni2 were arc sprayed<br />

with different traverse speeds by using amixture of nitrogen and 2%ofhydrogen as atomising gas. Residual<br />

stresses were measured by the modified hole-drilling method using ESPI. Microstructural, chemical and<br />

mechanical analyses were realised to examine adhesive and cohesive properties. Additionally, the cavitation<br />

erosion behaviour was investigated. Incomparison to coatings sprayed with pressurised air, the results ofthe<br />

study show superior coating qualities with regard tomicrostructure, cavitation erosion resistance and residual<br />

stresses.<br />

DVS <strong>336</strong> 7

Power Generation – Fuel Cell<br />

Experimental and numerical study ofthe effect of gas-shrouded plasma spraying on<br />

cathode coating ofalkaline electrolysis cells<br />

T. Liu and A. Ansar, Düsseldorf/DE<br />

Dual layer electrode coating for alkaline water electrolysis was prepared byplasma spraying. For improving<br />

performance this work aims at reducing the oxide inelectrode coating. Regarding the necessity of obtaining high<br />

specific area, atmospheric plasma spray was employed under protection ofargon which was used as shrouding<br />

gas. Composite cathode was established on Ni-coated perforated steel sheet with crushed and gas atomized<br />

Nickel-based alloy powders. The dual-layer structure was acomposite of5layers ofNiAl atthe bottom and 10<br />

layers of NiAlMo as the top layer. Microstructure and morphology were studied byscanning electron microscope<br />

(SEM). Element content was estimated by energy dispersive spectrometer (EDS). Enthalpy probe was introduced<br />

for measuring plasma temperature and velocity as well as gas composition. Numerical calculation was carried out<br />

with same condition for better understanding the shrouding effect. The results showed moderate protection by<br />

using of arranged gas shrouding. Overall the dual layer region, Oxygen was decreased by 0.3% from 3.46% to<br />

3.15%. With gas shrouding coating exhibited similar element contents as coating sprayed by VPS. However, no<br />

obvious difference was observed in microstructure and morphology with or without gas shrouding.<br />

Thermally sprayed porous copper coatings for capillary transport ofliquids<br />

C. Feng, S. Yugeswaran and S. Chandra, Toronto/CA<br />

Porous copper coatings, which act as wicks for liquid transport, were fabricated using aflame spraying process.<br />

Copper and aluminum powders were fed independently into the spray torch and deposited oncopper substrates to<br />

form acomposite coating. The aluminum was subsequently removed using chemical leaching leaving aporous<br />

copper coating behind. Varying the feed rate ofaluminum powder allowed the coating porosity tobecontrolled.<br />

Channels to enhance liquid flow were made insome of the porous copper coatings byplacing pieces ofaluminum<br />

wire mesh onthe copper substrate before spraying. During spraying the sprayed powders passed through the<br />

mesh opening and created pyramid shaped arrays on the substrates. The groove width was controlled byusing<br />

different wire mesh sizes. Coatings were made with porosity varying from 2to44%,and groove width ranging from<br />

0.16 to 0.53 mm. The capillary performance of the coatings was evaluated experimentally by measuring the rateof-rise<br />

of ethanol in the coatings. The rate of rise increased with coating porosity, and decreased with groove width.<br />

Anew technology for spraying advanced low-temperature (300 ~600 °C) solid oxide fuel<br />

cells<br />

K. Yuan, Y. Yu, X. Lu, X. Ji, Beijing/CN, and B. Zhu, Stockholm/SE<br />

Solid oxide fuel cell (SOFC) has been developed for ahundred year and met agreat challenge on material design<br />

and marketing. In recent years, new SOFC materials are dug uptoachieve high energy-output performance at<br />

lower working temperature (300~600 °C), namely low-temperature SOFC (LTSOFC). In this study, Ni-Co-Al-Li<br />

oxide (NCAL) was used for making dense, thin and uniform coatings ongrooved bipolar electrode substrate for<br />

LTSOFC. Low-pressure plasma spray (LPPS) technology was applied tomanufacture the NCAL coatings. The<br />

performance of afuel cell package using the coated bipolars was tested between 350 and 600 °C, showing 6~8 W<br />

power output with 4single fuel cells (active area of 25 cm2). The LPPS technology is believed to be one ofthe<br />

ultimate ways for manufacturing the thin film/coatings for SOFC applications in future.<br />

8 DVS <strong>336</strong>

Medical Industry II<br />

Microstructure and mechanical properties of cold sprayed titanium coatings<br />

W. Żórawski, Kielce/PL, J. Madry, Mielec/PL, J. Sienicki, Mielec/PL, M. Makrenek, Kielce/PL, A. Góral, Cracow/PL,<br />

and S. Kowalski, Kielce/PL<br />

The work concerns astudy of the properties ofcold sprayed Ti coatings. This material is anattractive choice for<br />

many applications because itexhibits high strength-to-weight ratios, very good oxidation resistance, corrosion<br />

resistance and biocompatibility. Cold spraying is applied to deposit Ti coatings and elements as additive<br />

manufacturing process, however it needs higher critical velocity for deposition than other, more ductile metals.<br />

Nowadays nitrogen as cheap gas is used as working gas in cold spray process, however application helium as<br />

accelerating gas allows to obtain elements with higher strength. Itallows to understand the mechanism of cohesion<br />

between sprayed particles. In carried out experiment Ti powder with angular shape was applied in the cold<br />

spraying process. The coatings were sprayed by means of Impact Innovations 5/8 system with nitrogen and<br />

addition of helium onto 7075 Al alloy. The investigations revealed that the cold sprayed Ti coatings with addition of<br />

helium as working gas exhibit better mechanical properties, lower porosity and roughness.<br />

The influence of spray parameters onthe characteristics ofhydroxyapatite in-flight<br />

particles, splats and coatings during micro-plasma spraying<br />

X. Liu, Y. Wang, Z.Zhou, G.Wang, Z. Tan and D. He, Beijing/CN<br />

Phase composition and microstructure of hydroxyapatite (HA) significantly affects the biological and mechanical<br />

properties offinal hydroxyapatite (HA) coating. In the present study, HA coatings were deposited on Ti-6Al-4V by<br />

micro-plasma spraying (MPS) using different spray parameters. The influence of spray parameters on the<br />

composition and microstructure of the coatings were investigated. To understand the formation mechanism ofHA<br />

coatings, the in-flight particles and splats were examined as well. The morphologies of coatings surface, crosssections,<br />

initial powder, in-flight particles and splats were characterized byscanning electron microscopy (SEM). X-<br />

ray diffraction (XRD) was employed to analyze the phase composition. Three typical HA coatings were fabricated.<br />

The results indicated that the coating composition and microstructure were tightly related tothe melting state of inflight<br />

particles. And this was influenced bythe spraying parameters. The formation mechanisms ofthese coatings<br />

were discussed.<br />

Wear Protection I<br />

The protection against spray wear using pseudoalloys applied with the method of<br />

spraying<br />

R. Winkelmann, Senftenberg/DE, and H. Pokhmurska, Chemnitz/DE<br />

An important parameter that affects the protection from wear and tear, isthe geometric structure ofthe abrasive<br />

causing the destruction. The equivalent diameter of the particles of the primary influence on protection from wear<br />

and tear must be greater than the width of the particle of the crushed abrasive. Here also belongs the requirement<br />

for the distribution of the particles inside the matrix was more uniform and dense. The use of solid materials gives<br />

this possibility only in the certain circumstances, therefore, itisnecessary to use pseudoalloys. Pseudoalloys can<br />

be obtained by means ofthermomechanical processing of the conventional layers deposited bymeans of spraying.<br />

The particles of the solid material charged with kinetic energy are applied to the heated layers, and they penetrate<br />

into inside. Under the influence of the heat energy inside the layers suitable for this, the additional reaction<br />

between the substrate and the layer takes place, thus improving the adhesion of the layers. The appropriate<br />

regulations were developed, and the reproducible stratification appeared caused by spraying, that ispseudoalloys.<br />

Apositive consequence ofthe inclusion of the particles of asolid ceramic material into the spayed layer is the<br />

emergence of the current when compressed. The result of the research of the parameters are the optimal<br />

DVS <strong>336</strong> 9

performance indexes, optimization criterion served as an indicator of the intensity of the wear. Manufactured<br />

pseudoalloys underwent checking in terms of spray wear. The study of spray wear was carried out at the<br />

temperatures upto750 ° Cand speed load amounted to 37.5 m/s. The silica sand fractions +150-212 μm was<br />

used asanabrasive. Asthe covering material the alloys based onaluminum were used. In the places of transition<br />

to the substrate the multiphase alloys of the system Fe-Al are formed. It is advisable touse layers with ahigh iron<br />

content toprevent the loose and destruction.<br />

Cavitation erosion characteristics ofHVOF thermal sprayed WC-cermet coatings<br />

A. Kanno and K.Takagi, Akashi/JP, and M. Arai, Tokyo/JP<br />

Cavitation erosion (CE) damage, which occurs in the main parts (made of high chromium cast steel) of<br />

hydroelectric power generation machine, is one of the serious problems. Itisexpected that life time ofthose parts<br />

would be prolonged if the suitable CE-resistant coating is applied onthe surface of the cast steel. In this study,<br />

WC-cermet coatings (WC-CoCr and WC-Cr3C2-Ni), which were fabricated by high-velocity oxygen-fuel (HVOF)<br />

thermal spraying process, was interested in protecting CE attack to the cast steel. To clarify CE property of the<br />

WC-cermet coatings, the ultrasonic vibration tests were conducted, and the amount of volume loss characterized<br />

as CE damage was measured. The microstructure and the fracture toughness, which was evaluated by the<br />

indentation test method, of the coatings were related with the CE damage. As the results obtained in this study, the<br />

fragment which was spalled from the surface after CEtest was almost flake-like shape, and its size was from 2μm<br />

to 50μm. SEM observation indicated that this fragment included both WC particle and metal binder, which means<br />

that WCparticle and metal binder was still strongly bonded together. It was also confirmed that the amount of<br />

volume loss could relate directly with the fracture toughness KIC rather than Vickers hardness. Itwas considered<br />

that CEdamage was progressed into the depth by throwing out the fragment originated from micro crack initiation.<br />

Thus, it was required that the CE resistance of the developed coatings could belabelled through the fracture<br />

toughness.<br />

Suspension Spraying I<br />

SPS coating microstructure controlled by the surface topography using laser texturing<br />

R. Kromer, Belfort/FR, P. Sokołowski, Limoges/FR and Wroclaw/PL, R. T. Candidato, Limoges/FR, S. Costil,<br />

Belfort/FR, and L. Pawłowski, Limoges/FR<br />

Thermal barrier coatings (TBC’s) being produced at present either by atmospheric plasma spraying (APS) or<br />

electron beam physical vapor deposition (EB PVD) are widely used in the hot-temperature sections of turbines to<br />

provide thermal and corrosion protections. An emerging technology of suspension plasma spraying has become<br />

interesting for the manufacturing of thermal barrier coatings thanks to the useful microstructure including columns<br />

similarly tothe EB-PVD deposits associated with considerably lower price ofproduction. Anarrow window of<br />

optimal suspension plasma spraying (SPS) parameters remain an outstanding problem in creating the favorable<br />

microstructure. The recent studies demonstrated that the substrate roughness may play an important role in<br />

reaching columnar growth of the coatings. This study presents a follow up by showing how the substrate<br />

topography obtained by laser surface texturing may becontrolled tocreate regular columnar structure thanks to.<br />

The laser generated peaks disposed regularly on the surface can promote columnar structure growth. The<br />

formulated suspensions were sprayed onto superalloy substrates coated with powder plasma sprayed bond coats.<br />

Optimized previously, plasma spray parameters were selected to generate columnar structures and tofind out the<br />

influence of the suspension behavior on coating microstructures. The results indicate that columnar SPS coating<br />

microstructure can be controlled byoptimizing the laser treatment parameters. The control of surface topography<br />

may be an important factor toimprove the performances of TBC-SPS coatings.<br />

10 DVS <strong>336</strong>

Characteristics of dense AI2O3coating prepared by suspension plasma spraying<br />

H. Ibe, T. Masuda, K.Sato and N. Kato, Gifu/JP<br />

Sintering ceramics have been widely used in industries which require electrical and mechanical properties.<br />

Thermal sprayed ceramics coatings are also applied for the industries, however the coating which has micron size<br />

pores are limited their applications due toinferior electrical and mechanical properties compared with sintering<br />

bulk. To expand thermal sprayed ceramics coating applications, dense coatings prepared bysuspension plasma<br />

spraying are widely studied. Dense Al2O3 coatings are applicable to fabricating equipment for electronics devices,<br />

such as ESC. There are no reports regarding electric properties ofplasma sprayed dense Al2O3 coating with<br />

different spray conditions. Inthis study toachieve aelectric properties of dense Al2O3 coating, spray parameters<br />

such as plasma power, gas flow rate and spray distance are investigated. Suspension materials prepared with<br />

three microns Al2O3 powder are sprayed by high power suspension plasma spraying system. Spray conditions,<br />

plasma power, gas flow rate and stand off affect the coating density, christal phase, mechanical and electric<br />

properties. Mechanism of coating formation by plasma spraying with fine powder suspensions will bediscussed<br />

based onthe findings. Al2O3 coatings obtained bythe plasma spraying is applied for application to application<br />

utilizing the electrical insulation properties of such electronics devise manufacturing equipment components is<br />

proceeding.<br />

Equipment /Consumables &Powders, Wires, Suspensions I<br />

Influence of feedstock powder modification by heat treatments on the properties of APSsprayed<br />

Al2O3-40%TiO2 coatings<br />

L.-M. Berger, Dresden/DE, R. Vaßen and Y.J. Sohn, Jülich/DE<br />

Aluminum titanate (Al2TiO5) is a congruently melting compound in the binary Al2O3-TiO2 system, which<br />

decomposes below 1200 °C. Its properties (e.g. thermal conductivity, CTE) differ significantly from those of Al2O3<br />

and TiO2. Thus itisofspecial interest tostudy the stability ofAl2TiO5 in the spray process and its influence on the<br />

coating properties. A commercial fused and crushed Al2O3-40%TiO2 powder, which was found to be<br />

substoichiometric, was selected as the feedstock material for the experimental work, asthe composition is close to<br />

stoichiometric Al2TiO5. Part of that powder was heat-treated inair at 1150° and 1500°C inorder to vary the phase<br />

composition, while not influencing the particle size distribution and processability. The powders were analyzed by<br />

thermal analysis, XRD and FESEM including metallographically prepared cross sections. Apowder having Al2TiO5<br />

as the main phase was not possible to be prepared due to inhomogeneous distribution of Al and Ti in the original<br />

powder. Plasma spraying was performed with aTriplexPro-210 (Oerlikon Metco) using Ar-H2 and Ar-He plasma<br />

gas mixtures with 41 and 48 kW plasma power. Coatings were studied by XRD, SEM of metallographically<br />

prepared cross sections, and microhardness HV1. Moreover, the results show aclear influence of the Al2TiO5<br />

content in the feedstock powder on the phase composition of the coatings.<br />

Dry-sliding wear of laser clad nickel aluminide /chromium carbide coatings against cast<br />

iron<br />

S. Bengtsson, S.Dizdar, Höganäs/SE, and K. Gong, Göteborg/SE<br />

The wear of piston rings inlarge marine two-stroke diesel engines isamajor maintenance cost. Applying coatings<br />

with good oxidation, corrosion resistance and high temperature strength, can lower the total maintenance cost. In<br />

the past nickel aluminide with chromium carbide have been applied to pistons by thermal spraying. Using laser<br />

cladding asuitable microstructure can be formed while atthe same time avoiding cracks and bonding issues. In<br />

this report powders and coatings were manufactured in order to be able to investigate the dry-sliding wear<br />

behavior. Material with three levels of carbides was atomized. Wear test samples were manufactured bylaser<br />

cladding. The dry sliding wear-mechanism maps are generated by using block onring test setup where coated<br />

blocks slide against cast iron rings. All alloys exhibited regions ofplasticity-dominated wear and oxidational wear<br />

with atransition region in-between. The carbide-containing alloys showed lower friction and wear in comparison to<br />

the carbide free nickel aluminide alloy.<br />

DVS <strong>336</strong> 11

Session Young Professionals<br />

Twin wire arc torch with optimized flow parameters<br />

A. Farrokhpanah, L.Pershin and J. Mostaghimi, Toronto/CA<br />

Wire arc is an effective and affordable type of coating process. Detailed understanding ofithelps improving design<br />

and optimization of currently available guns. In wire arc process, an arc forming between two charged wires<br />

generates enough heat to melt the metallic wires. Blow of air athigh velocity over this bath ofmolten metal leads to<br />

atomization. The formed droplets are then accelerated towards the substrate where they impact and solidify during<br />

the coating process. The current work isafollow uptoour earlier numerical study [1] where numerical simulation of<br />

wire arc spraying using ANSYS ® FLUENT ® revealed flow circulations inside the gun can affect flow pattern and<br />

contribute toenergy dissipation. Inthis study, anattempt has been made to validate and measure this matter using<br />

experimental procedures and to seek potential ways of improvement.<br />

Lamellar bonding enhanced NiCr-Mo coating with comparable erosion resistance to<br />

similar bulk by plasma-spraying shell-core-structured powders<br />

J. Tian, Y.Wang, C.Li, G. Yang and C.Li, Xi'an/CN<br />

NiCr-Mo composite coating was prepared by plasma spraying of shell-core-structured NiCr-Mo powders. The<br />

morphologies of the NiCr-Mo powders and microstructure of the corresponding NiCr-Mo coating were<br />

characterized by SEM. Furthermore, the erosion behavior of the NiCr-Mo coating at impact angles of both 30o and<br />

90o was investigated, and was further compared with that ofthe Ni20Cr coating and the In-738 alloy bulk. Results<br />

showed that fully-dense and homogenous NiCr-Mo coating with excellent interface bonding and no pure Mo<br />

inclusions was obtained. Furthermore, the erosion test results showed that the erosion rate of the optimized NiCr-<br />

Mo coating is lower than that ofNiCr coating at both impact angles. Moreover, the NiCr-Mo coating presented<br />

excellent erosion resistance which was comparable as that of In-738 alloy bulk, attributing tothe fully-dense<br />

microstructure and metallurgical interface bonding within coating.<br />

Development ofwear-resistant high-entropy alloy coatings produced bythermal spray<br />

technology<br />

M. Löbel, T. Lindner, T. Lampke, Chemnitz/DE, and C. Kohrt, Rheinberg/DE<br />

The alloying concept of High-Entropy Alloys (HEA) has attracted much scientific interest due to an interesting<br />

combination of properties. Previous investigations have shown that high hardness and strength, comparable to<br />

bulk metallic glasses, can be achieved. Furthermore, HEAs show distinct ductility and good high-temperature<br />

resistance. First investigations on tribological properties are indicating high wear resistance. Previous<br />

investigations ofthe alloy system AlCoCrFeNiTi in bulk state have shown promising properties. Therefore, the alloy<br />

AlCoCrFeNiTi with equimolar composition was selected for transferring bulk properties to thermally sprayed<br />

coatings. The focus of this contribution is on studying tribological properties of thermally sprayed HEA coatings to<br />

enlarge the field of possible applications. Feedstock material production was carried out by high-energy ball milling<br />

(HEM) and inert gas atomization. Subsequently, coatings were deposited by Atmospheric Plasma Spray (APS).<br />

Tribological properties of the coatings under different wear regimes were investigated inball-on-disk wear tests,<br />

oscillating wear tests and scratch tests. The tribological properties are compared with aconventional hard chrome<br />

plating and correlated with microstructure.<br />

12 DVS <strong>336</strong>

Thermal spraying of thin metallic coatings<br />

F. Trenkle, R.Koehler, M. Winkelmann, F. Wuest, J.Luth and S. Hartmann, Bad Krozingen/DE<br />

Metallic coatings can be produced with thermal and cold gas spraying processes very easy. But are required, for<br />

economical or technological reasons, coating thicknesses below 50µmthe tasks become more challenging for<br />

those well established spray processes. obz innovation has developed specific spray processes, which even<br />

allows producing metallic coatings below 20 µm. Such coatings are very interesting for example for cold gas<br />

sprayed silver coatings, which have ahigh purity and agood electrical conductivity. Thinner coatings with such<br />

valuable materials directly gain economical advantages, often also compared with commonly used thin film<br />

processes.<br />

Cold gas spraying of lead-free bearing bronzes<br />

S. Theimer, P. Brethack, F. Gärtner and T. Klassen, Hamburg/DE<br />

In current process techniques tomanufacture sliding bearings, bronze components are soldered to the respective<br />

parts, which is cost and energy intensive. Apart from that, so far most bearing materials still contain lead, which in<br />

new applications is omitted by EU law to avoid associated health risks. The present study aims to offer solutions for<br />

both by using cold gas spraying as additive manufacturing technique for processing bearings directly onto steel<br />

parts and by applying that to new lead-free bronze alloys. Alead-free bronze alloy was processed as powders by<br />

gas atomization and classified to optimum sizes for cold spraying. During cold spraying, the process gas pressures<br />

and temperatures aswell asthe substrate temperature were varied with the aim to study influences by impact<br />

conditions and effective surface temperature on particle deformation and bonding. Respective coatings show low<br />

porosity, high hardness and high electrical conductivities. With properties similar to that ofbulk cast material<br />

respectively manufactured parts should meet the requirements for new bearing applications.<br />

Nozzle-internal particle velocity measurements and loading effect onparticle<br />

acceleration inside acold spray nozzle<br />

M. Meyer, F.Caruso and R. Lupoi, Dublin/IE<br />

The advantages of the solid state deposition process Cold Spray (CS) over conventional spray technologies go<br />

hand in hand with the requirement of high and well-predictable particle velocities. The acceleration of particles<br />

primarily takes place within the CS-nozzle while measurements of their velocity are conducted downstream of its<br />

exit. Despite their essential value, these observations are limited, inthat only the result of the acceleration can be<br />

evaluated, not the actual driving mechanisms themselves. Previous work has indicated that there is no conclusive<br />

understanding of these mechanisms, especially in cases of increasing particle loading. This study therefore<br />

presents atransparent rectangular CS-nozzle design (made out of quartz) for alow stagnation pressure regime. A<br />

novelty tothe field of thermal spray is the first report of particle in-flight measurements within the CS-nozzle using<br />

Particle Tracking Velocimetry (PTV) at varying particle loadings and pressure levels. It is found that particle<br />

velocities in the jet decrease with increasing particulate loading as the momentum exchange of the gas is<br />

enhanced, while in the subsonic flow region, the average velocity level increases due to particle-particle<br />

interactions with shallower axial velocity profiles. This effect is aggravated for higher working pressures, as<br />

energetic collisions cause increasing losses, depending on the number density of particles. This study forms the<br />

basis for acomprehensive nozzle-internal analysis.<br />

DVS <strong>336</strong> 13

Automotive Industry<br />

New mechanical roughening processes as surface preparation of engine cylinder bores<br />

before thermal spraying<br />

A. Roffe, M.Morgan-Hague, Belton/UK, M. Waiblinger, Ostfildern/DE, G. Sanuk, M.Joschko, Albstadt/DE,<br />

M. Kesting, Salching/DE, T. Birkner, Eislingen/DE, K.Over, M. Silk, C. Verpoort, Aachen/DE, and R. Wilton,<br />

Köln/DE<br />

Several surface preparation techniques are being used like grit blasting, HP water jet roughening as well as<br />

mechanical roughening for the preparation of Aluminum cylinder bore surfaces before athermal spray coating can<br />

be applied. However, incase of spray-repaired CI cast iron engine blocks the conventional mechanical roughening<br />

processes - using cutting inserts with small dovetail-undercut geometry – are not applicable due to the high<br />

hardness and high material toughness. Therefore such CI engine blocks are bored oversize in order to remove the<br />

bore wear damage and subsequently this rough-machined surface is coated by aNiAl-bond coating material in<br />

order toprovide sufficient bond strength for the functional top coating material. Inthis paper it will be demonstrated<br />

that the 2-step spray-repair process can be replaced by asingle-step process byusing anew diamond-rollroughening<br />

method. This process leads to significant higher bond strength values than the conventional process,<br />

including the bond coating material. PAT Adhesion test results as well as microstructural cross sections of coated<br />

cylinder bores will bepresented. The principle ofthe roll-roughening process isoutlined. In addition it will be shown<br />

that different mechanical roughening methods can be combined to obtain high bond strength values for sprayrepaired<br />

aluminum blocks which require ahigher coating thickness to compensate for the depth of the original<br />

mechanical bore activation.<br />

Development ofnovel fe-based coating systems for internal combustion engines<br />

K. Bobzin, M.Öte, T. Königstein, Aachen/DE, K. Dröder, H.W.Hoffmeister, G. Mahlfeld, Braunschweig/DE, and<br />

T. Schläfer, Luckenbach/DE<br />

Nowadays combustion engines are the most common way to impel vehicles. Thereby losses occur, due to cooling,<br />

exhaust gas and friction. Modern engines roughly dissipate 8% of the chemical energy stored in the fuel because<br />

of friction in different tribological systems. The highest potentials for optimisation can be found in the tribological<br />

system ofinner surface of combustion chamber and piston ring. Besides friction, corrosive stress of inner surface<br />

of combustion chamber increases e.g. due to the utilization of auxiliary systems such as Exhaust-Gas-Recovery. In<br />

order to save energy, reduce emissions and enhance the lifetime of combustion engines innovative coating<br />

material systems need to be developed, especially for inner surface of combustion chamber. This study focuses on<br />

the development of innovative iron based materials for combustion chamber application using Plasma Transferred<br />

Wire Arc (PTWA) and Rotating Single Wire Arc (RSW) technologies. In order toimprove the wear and corrosion<br />

resistance boron and chromium are added into the feedstock material. After deposition, different honing<br />

topographies are manufactured in order to evaluate their influence on the tribological behavior. Furthermore,<br />

electro-chemical corrosion tests are conducted by using an electrolyte simulating the exhaust gas concentrate. In<br />

conclusion an optimised coating material deposited byPTWA and RSW and improved surface topographies can<br />

be combined.<br />

Effects ofcarbon contents and gas type onhardness and wear resistance of ferrous<br />

coating fabricated by twin wire arc spray process<br />

J. Lee, J. Kim and C. Lee, Seoul/KR<br />

In automotive industry, thermal spray process isused to reduce engine weight by replacing cast iron liners inserted<br />

in cylinder bores. Especially, twin wire arc spray isone of widely used thermal spray processes with inexpensive<br />

cost and high deposition rate. Inthis study, two kinds ofwire materials, low carbon steel (0.07 wt.%C) and high<br />

carbon steel (0.80 wt.%C) were deposited bytwin wire arc spray process using two kinds ofprocess gas (i.e.,<br />

compressed air and nitrogen) in order to elucidate effects ofcarbon contents of ferrous coating and process gas<br />

type on the hardness and wear resistance ofcoating. Incase of hardness, low carbon steel coatings had higher<br />

14 DVS <strong>336</strong>

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