Single-crystal (SC) alloy derivatives of the MAR-M 247 alloy were developed for turbine airfoil applications. This development activity focused on casting process technology, SC alloy microstructure/mechanical property relationships, and coating-SC alloy interactions. Both the exothermic and withdrawal casting processes were evaluated for producing SC components and were found to produce equivalent material from a stress-rupture standpoint. Microstructural effects associated with the removal of grain boundary strengthening elements (B, C, Zr, Hf), microporosity, recrystallized grains, and mu phase precipitation are reviewed from the standpoint of mechanical properties. Coating-superalloy interactions were assessed from both mechanical and environmental standpoints. Thin coatings have not produced any reductions in SC alloy stress-rupture or high-cycle-fatigue properties. From an environmental standpoint, removal of the hafnium from the MAR-M 247 composition reduced the oxidation resistance of diffusion aluminide coatings. An overlay coating, SCC103, was consequently developed to provide significantly improved oxidation resistance and diffusional stability.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.