Approaches to oxidation-resistant refractory metal alloys

The focus of the research reported here was on the design of high-temperature alloys which would form protective Si02 and A1203 scales on exposure to high-temperature, oxidizing environments. One way to promote the growth of such scales is to incorporate sufficient amounts of Si or A1 in the alloy substrate; typically, additions of approximately 35 to 45 weight percent (all alloy compositions are given in weight percent unless explicitly stated otherwise) of Si or Al would be required to form the respective scales, in the absence of additional protective-scale-forming elements. At such levels of alloying additions, the formation of intermetallic phases is likely, which may have undesirable features such as low melting temperatures or poor mechanical properties. The research described was an attempt to address these problems from a fundamentally different point of view, for Moand Nb-based alloys, through the use of a dispersed reservoir phase.