Coarsening behavior of γ′ particles in a nickel-base superalloy

The coarsening behavior of gamma' particles in a nickel-base superalloy FGH95 was investigated by means of experimental observations and growth kinetics calculations. The results show that when aging at 1000, 1080 and 1140 degrees C for different times, the relation of average particle size to time obeys the cube law ((a) over bar /2)(3) = kt, where k is 15.49 x 10(3), 77.5 x 10(3) and 230.04 x 10(3) nm(3)/min, respectively. The particle size distributions are better fit to the LSW theoretical distributions when aging at 1000 degrees C within 1440 min. The activation energy for gamma' particles coarsening is determined to be 288.20+/-1.79 kJ/mol, which correlates well to the diffusion activation energies of Al, Ti, and Nb in the nickel matrix. This indicates that the coarsening of gamma' particles is controlled by the diffusion of Al, Ti, and Nb in the nickel matrix. The coarsening kinetics of gamma' particles in FGH95 is predicted as (r) over bar (3)(t) = 1.04 x 10(16) texp[-(288200+/-1790)/RT].