Application of Plasma Spraying as a Precursor in the Synthesis of Oxidation-Resistant Coatings
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JTTEE5 22:992–1001 DOI: 10.1007/s11666-013-9947-2 1059-9630/$19.00 ASM International
Application of Plasma Spraying as a Precursor in the Synthesis of Oxidation-Resistant Coatings P. Ritt, O. Lu-Steffes, R. Sakidja, J. H. Perepezko, W. Lenling, D. Crawmer, and J. Beske (Submitted January 11, 2013; in revised form May 7, 2013)
Thermal spray methods offer a versatile and flexible approach to the manufacture of coatings as a final product. A novel application of thermal spray coating is demonstrated by incorporating a plasma-sprayed Mo layer coating as a precursor step within an integrated costing design. The effectiveness of the twostep design is illustrated for aluminoborosilica coatings on SiC/C composites and W substrates based on the plasma-sprayed Mo precursor and subsequent codeposition of Si and B by a pack cementation method. Even with incomplete precursor coverage, an aluminoborosilica coating is developed because of the high initial fluidity of the as-pack coating. An effective oxidation resistance is observed following exposure at elevated temperatures (1373-1673 K) in ambient air and during torch testing at 1773 K, providing clear evidence that the plasma spraying of Mo is a viable precursor step in the formation of the oxidation-resistant Mo-Si-B-based coating.
Keywords
aerospace, aircraft, high-temperature application
1. Introduction In order to increase the efficiency of jet turbine engines, higher operating temperatures which exceed the melting point of nickel-based superalloys are needed (Ref 1). It is clear that alternative materials must possess several exceptional properties such as a high melting point and sufficient mechanical properties at high temperatures to be effective in extreme environments. Furthermore, the material must be able to resist catastrophic oxidation while in service at elevated temperatures. Due to these rigid criteria, there are few materials that are available for being used effectively in jet turbine engines and hypersonic flight applications. Alternative materials such as refractory metal alloys and ceramic matrix composites, among others, are being considering for future aerospace needs. In order to provide oxidation protection for these materials over a wide range of temperatures, external coatings are required. The Mo-Si-B alloy system has been utilized to design a multilayer coating that has the ability P. Ritt, O. Lu-Steffes, R. Sakidja, and J.H. Perepezko, Department of Materials Science and Engineering, University of WisconsinMadison, 1500 University Avenue, Madison, WI 53706; R. Sakidja, Department of Physics and Astronomy, University of Missouri-Kansas City, 257 Flarsheim Hall, 5110 Rockhill Road, Kansas City, MO 64110; and W. Lenling, D. Crawmer, and J. Beske, Thermal Spray Technologies, Inc., Sun Prairie, WI 53590. Contact e-mail: [email protected].
992—Volume 22(6) August 2013
to protect at both low- and high-temperature regimes. During the application of the Mo-Si-B-based coating by codeposition of silicon and boron in an alumina filler through pack cem
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