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

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 t ested material with those from stress-free aged material. These measurement s are analyzed with respect to existing coarsening theories. A new relation ship for coarsening kinetics is presented to properly reflect the combined effects of matrix and grain boundary diffusion control and is correlated wi th 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) In(K (V)r + K-GB)](r0)(r) where K-V is a coarsening constant for volume diffusion, KGB is a coarsenin g constant for grain boundary diffusion, r is the carbide radius, and t is time. (C) 2000 Published hy Elsevier Science Ltd on behalf of Acta Metallur gica Inc.