REACTION DIFFUSION IN THE NICKEL-CHROMIUM ALUMINUM AND COBALT-CHROMIUM-ALUMINUM SYSTEMS

摘要

The effects of MCrAl coating-substrate interdiffusion on oxidation life and the general multi¬phase, multicomponent diffusion problem were examined. Semi-infinite diffusion couples that had sources representing coatings and sinks representing gas turbine alloys were annealed at 1000°, 1095°, 1150°, or 1205° C for as long as 500 hours. The source and sink aluminum and chromium contents and the base metal (cobalt or nickel) determined the parabolic diffusion rate constants of the couples and predicted finite coating lives. The β source strength concept pro¬vided a method (1) for correlating β recession rate constants with composition;(2) for determin¬ing reliable average total, diffusion, and constitutional activation energies;and (3) for calcu¬lating interdiffusion coefficients.