The structure and interdiffusional degradation of aluminide coatings on oxide-dispersion-strengthened alloys

A study of the effects of the composition and coating processing of oxide- dispersion-strengthened superalloys on the structure and diffusional stability of aluminide coatings was undertaken. Increasing the aluminum content of the substrate resulted in the formation of a more typical nickel-base superalloy aluminide coating structure that is more resistant to spallation during high temperature isothermal exposure. The coating application process also affected the coating stability; a low aluminum outward diffusion type resulted in greater apparent stability. A scanning electron microscopy deep etching and fractography examination technique was used in an attempt to establish the location and kinetics of void formation. Aluminide protective lifetimes are still found to be far short of the mechanical property capabilities of the alloy.