Coarsening kinetics of γ′ precipitates in the commercial nickel base Superalloy René 88 DT Original Research Article

René 88 DT samples were subjected to different cooling rates after a supersolvus treatment, and aged for varying periods of time from 25 to 200 h at 760 °C. Primary and secondary γ′ precipitate sizes were measured after each heat treatment. Coarsening rate constants were calculated and reported based on the measured precipitate sizes. When describing the change in radius (r) as a function of time (t), fits between the experimental results and analysis were investigated for two types of functional relationships, r3 vs. t and r2 vs. t. The experimental rate constants derived from this analysis were compared with analytical values deduced from two different models: volume diffusion and bulk diffusion through the interface. The applicability of the two mechanisms for γ′ coarsening is discussed based upon the comparison between the analytically derived and experimentally observed values of these rate constants.