Coarsening of grain boundary carbides in a nickel-based ternary alloy during creep

Abstract Stress enhanced coarsening of grain boundary carbides resulting from creep loading is analyzed. Grain boundary carbide distribution measurements from material before and after creep testing begins the analysis. The extent of stress enhancement is determined by comparison of measurements from creep tested material with those from stress-free aged material. These measurements are analyzed with respect to existing coarsening theories. A new relationship for coarsening kinetics is presented to properly reflect the combined effects of matrix and grain boundary diffusion control and is correlated with the experimental data. This relationship is given as follows: t= 1 3K V r 3 − 3K GB 2K V r 2 +3 K GB K V 2 r−3 K GB K V 3 ln (K V r+K GB ) r 0 r where KV is a coarsening constant for volume diffusion, KGB is a coarsening constant for grain boundary diffusion, r is the carbide radius, and t is time.