ICMCTF 2012! - CD-Lab Application Oriented Coating Development

forms directly below the scale. In addition, an Al depletion gradient forms
in the composite.
3:50pm A1-2-8 Microstructural damage criterion for Ni based single
crystal superalloy coated with NiAlPt, P. Sallot (pierre.sallot@minesparistech.fr),
V. Maurel, L. Rémy, Mines-ParisTech, France
Platinum-modified aluminide coatings are widely used in both aero-engines
and land-based gas turbine because they are essential to the overall life-time
of the TBC system, which is of great interest in the industry as for the last
two decades environmental and economic issues have raised over. It
prevents the superalloy from detrimental oxidation at high temperature by
forming a dense and adherent layer of alumina on its surface, and it
improves the adhesion of the Thermal Barrier in TBC systems. Coatings
investigated in this study are deposited by platinum electroplating followed
by a low activity CVD aluminizing. The coating can be described by two
layers: an outer β-NiAlPt single-phase layer approximately 50 μm thick and
an interdiffusion zone referred to as IDZ. The coating resistance is usually
assessed using standard cyclic oxidation tests with 1 hour at the maximum
temperature during which the weight of samples is recorded by
thermogravimetric methods. Net Mass Gain curves are then obtained and
give an overview of the lifetime of the coating or allow the cross
comparison of different coatings.
This paper reports upon results of an on-going investigation on degradation
mechanisms of a platinum-modified nickel aluminide coating deposited on
a Ni-base single crystal superalloy AM1 used by SNECMA for advanced
blades. More particularly, a novel approach of the lifetime of platinummodified
coatings is proposed trough the detailed study of IDZ evolution
and its correlation with Net Mass Gain curves of coatings. The effect of
different thermal transients, hold time duration, maximum temperatures as
well as thermomechanical loadings on the IDZ evolution has been studied
and a close link with the degradation of the coating has been found.
Interrupted tests were performed to assess the kinetics of the IDZ evolution
and it was monitored using cross section analyses of specimen combining
optical microscopy and electron microprobe analysis.
The interdiffusion zone shrinks while the hold time at high temperature
increases and has been modeled by simple diffusion laws. The direct
relation between IDZ evolution and the coating degradation make it simple
to deduce a promising lifetime model for the studied coating.
4:10pm A1-2-9 Compositional and Microstructural Changes in
MCrAlY Coatings due to Interdiffusion with the Base Material, D.
Naumenko (d.naumenko@fz-juelich.de), V. Shemet, A. Chyrkin, L.
Singheiser, W.J. Quadakkers, Forschungszentrum Jülich GmbH, Germany
MCrAlY (M = Ni, Co) overlay coatings are commonly used for oxidation
protection of Ni-and Co-based superalloys in stationary gas-turbines as well
as jet engines. At high exposure temperatures, i.e. above 1000°C, which is
typical for laboratory testing of coated superalloys most of the
commercially used MCrAlY-coatings possess a two-phase microstructure
consisting of gamma Ni solid solution and intermetallic beta NiAl. The
phase composition of MCrAlY-coatings is subjected to changes with
changing temperature, due to formation of the thermally grown oxide
(TGO) as well as due to interaction with the substrate material.
Using a number of examples in the present paper it is shown how the
presence of the base material influences the phase composition and
microstructure of the coatings. In particular the effects of carbon and Ti
incorporated from the superalloy substrate into the coating are elucidated.
Furthermore, it is shown that the porosity formation at the
bondcoat/superalloy interface can be in many cases attributed to
interdiffusion induced phase transformations rather than to the Kirkendall
effect, which is commonly claimed to be responsible for the observed
porosity. The analytical studies by SEM are complemented with numerical
thermodynamic calculations using the software packages Thermocalc and
Dictra.
4:30pm A1-2-10 Effects of Hf and Zr additions on the properties and
oxidation resistance of β-NiAl+Cr overlay coatings, P. Alfano, L.
Weaver (mweaver@eng.ua.edu), University of Alabama, US
Nickel-based superalloy components in the hot sections of commercial gas
turbine engines are often protected by aluminide coatings due to their ability
to function in oxidative and corrosive environments. However, the
microstructures of these coated systems are metastable and change in
service due to interactions with the environment and interdiffusion with the
underlying substrate. The extent of these changes depends critically upon
coating microstructure, chemistry, and the environment that the coated
component operates in. This presentation highlights the influences of
chemical composition, post-deposition annealing, and isothermal oxidation
at 1050°C on the microstructures and properties of NiAl-Cr-Hf and NiAl-
Cr-Zr overlay bond coatings. In particular, the results indicated that
coatings containing Hf exhibit lower oxidation mass gains for oxidation
Wednesday Afternoon, April 25, 2012 62
times of less than 100hrs as compared to the Zr containing samples, but
higher mass gains above 100hrs of oxidation. This presentation also
highlights the effect of processing parameters, such as the addition of a seed
layer, on microstructures and coating properties. The results indicate that
the addition of a Ni seed layer can improve the adhesion between the
substrate and coating.
4:50pm A1-2-11 The application of nanocrystalline NiCrAlY layer in
thermal barrier coatings for industrial gas turbines, M.S. Hussain, M.
Daroonparvar (re_dr7@yahoo.com), Universiti Teknologi, Malaysia
Thermal barrier coating systems (TBCs) are used to protect turbine blades
against high-temperature corrosion and oxidation. They consist of a metal
bond coat (MCrAlY,M= Ni, Co) and a ceramic top layer (ZrO2/Y2O3). The
life expectancy of TBCs is expected to be improved by the application of
nanostructured MCrAlY bond coat. This paper therefore, reviews the main
techniques used in the synthesis of nano-crystalline NiCrAlY powders using
a planetary ball mill and investigates the oxidation behavior of conventional
and nanostructured atmospheric plasma sprayed (APS) NiCrAlY coatings at
elevated temperatures. Conventional NiCrAlY powder was mechanically
milled and then sprayed on a nickel based supperalloy (Inconel 738) to form
a nanocrystalline bond coat in TBC. Both conventional and nanostructured
NiCrAlY coatings were tested by high temperature oxidation at 1000°C for
24hr and then allowed to form the thermally grown oxide layer onto the
bond coat. Microstructural characterization was carried out by using X-ray
diffraction (XRD); scanning electron microscopy (SEM ); field emission
scanning electron microscopy (FESEM) equipped with energy dispersive
spectroscopy (EDS ). The adhesion strength of the as-sprayed TBCs was
tested by bond strength test. The thickness of thermally grown oxide (TGO)
at the interface of bond coat/ceramic layer, its constituents and the formed
mixed oxides within the NiCrAlY bond coat were examined.
Nanostructured coating showed much improved oxidation resistance than
the conventional one. The observed improved behavior was due to the
formation of a continuous, dense, uniform and thinner Al2O3 (TGO) layer
over the nanostructured NiCrAlY coating. This layer has been able to
protect the coating from further oxidation and had reduced the formation of
mixed oxide protrusions present in the conventional coating.
Hard Coatings and Vapor Deposition Technology
Room: Royal Palm 4-6 - Session B4-3
Properties and Characterization of Hard Coatings and
Surfaces
Moderator: J. Lin, Colorado School of Mines, US, C.
Mulligan, U.S. Army ARDEC, Benet Laboratories, US, B.
Zhao, Exxon Mobile, US
1:50pm B4-3-1 Structure and composition of TiSiCN coatings
synthesized by reactive arc evaporation: implications for cutting tool
applications., E. Göthelid (emmanuelle.gothelid@sandvik.com), L.
Löwenberg, A. Genvald, B. Ericsson, M. Ahlgren, Sandvik Tooling, Sweden
Developing the ultimate all around tool has become some sort of Holly
Grail for machining industries. Such a tool should be tough, with good flank
and crater wear resistance, a combination which is not easy to achieve.
Insert performance can be dramatically improved with the help of an
appropriate coating. We present here a novel route for depositing TiSiCN
coating on WC-Co substrates. A reactive mixture of trimethyl-silane (TMS-
(CH3)3-SiH) and N2 is used as Si, C and N source while arcing Ti at
different substrate bias. Thanks to this approach, the Si to Ti and C to N
ratios may be tuned at will. The samples structure was analyzed by XRD
and SEM, their chemical composition by EDS and XPS. Hardness and E
modulus were also determined. Interesting samples were then performance
tested in a turning application. The results show that the Si content plays a
crucial role for the texture of the film and the outcoming performances. The
best variant at ca 6-10 at % Si exhibited a good combination of flank and
crater wear resistance. These results will be discussed in the light of the
physical data acquired.
2:10pm B4-3-2 Influence of Process Parameters on the Properties of
Low Temperature (Cr1-xAlx)N Coatings Deposited via Hybrid PVD DC-
MSIP/HPPMS, K. Bobzin, N. Bagcivan, M. Ewering, R.H. Brugnara
(brugnara@iot.rwth-aachen.de), Surface Engineering Institute - RWTH
Aachen University, Germany
Ternary nitrides find widespread application as hard protective coating on
cutting tools and as corrosion and wear resistant coatings on mechanical
components. Concerning to this, ternary nitride such (Cr1-xAlx)N deposited
via PVD (Physical Vapour Deposition) show outstanding tribological,