Kinetic Analysis for High-Temperature Coarsening of γ Phase in Ni-Based Superalloy GH4169

The growth of precipitates in Ni-based superalloy GH4169 is critical as it controls the mechanical properties and long-term stability of the alloy. In this paper, the coarsening behavior of the main strengthening phase gamma '' in the temperature range from 800 degrees C to 900 degrees C is investigated. Two heat treatment steps, i.e., pre-precipitation of gamma '' phase and coarsening of precipitates at high temperatures, were performed on the GH4169 alloy. It was found that there were three morphological forms of gamma '' phase in chronological order: lip-shape, disc-shape, and irregular rectangle-shape with larger size. The coarsening kinetics of gamma '' phase followed the Lifshitz-Slyozov-Wagner (LSW) time-law for diffusion-controlled growth, and the activation energies of gamma '' phase before and after losing the coherent relationship with matrix were 261 kJ mol(-1) and 271 kJ mol(-1), respectively.