Robert Clark Tucker

Development of several new nickel aluminide and chromium carbide coatings for use in high temperature nuclear reactors

Abstract Coatings based on Cr 3 C 2 plus NiCr produced with a detonation gun (D-gun) have provided very satisfactory performance in sodium-cooled reactors for some time. In an effort to provide coatings with even lower coefficients of friction, D-gun coatings based on nickel aluminide (NiAl) with either NiCr or Tribaloy 700 “binders” have been developed. The coatings are expected to yield the same low friction characteristics found with aluminide coatings produced by diffusion processes, but they can be applied to virtually any substrate without concern for composition changes due to interdiffusion effects. Substrates that have been cold worked to increase their resistance to radiation damage ( e.g. type 316 stainless steel with 20% cold work) can also be coated without significant heating of the substrate. D-gun coatings based on both Cr 23 C 6 and Cr 23 C 6 with NiCr binders have shown excellent promise in helium-cooled reactors. For higher temperature applications, a duplex coating of Cr 23 C 6 over Cr 23 C 6 plus NiCr has been developed and has to date passed all tests in helium with a low content of oxygen. However, a still better performance, balancing lower friction with thermal shock and oxidation resistance at higher temperatures, is being sought. Toward this end, new coatings based on Cr 23 C 6 with lower “binder” contents of NiCr and NiCrAlY have been developed.

Plasma and Detonation Gun Ceramic and Cermet Coatings in Gas Turbine Engines

Plasma and detonation gun coatings of ceramic and cermet materials have achieved widespread application throughout gas turbine engines, and their use continues to grow. The coatings are used in increasingly demanding environments, thus successful utilization requires a thorough understanding of their structure/property relationships and close control of the parameters of deposition. The areas of application within the engine can be roughly separated into low and high temperature regimes. At low temperature, impact/fretting wear, erosion resistance, gas path seals, and various seals and bearings are of concern. Each area requires one or more coating types to satisfy the specific requirements of a given engine. The most common coating types include tungsten carbide-cobalt, alumina, chromium carbide-nickel chromium, a new family of cobalt-base alloys with alumina or chromia dispersions, and magnesium zirconate or stabilized zirconia. The characteristics of major significance of these coatings and their applications will be discussed.Copyright