Matrix-Diffusion-Controlled Coarsening of the γ′ Phase in Waspaloy

This paper discussed the coarsening behavior of the γ′ phase in Waspaloy during heat treatment at different aging times under the temperatures of 960 °C and 1000 °C. The morphology of γ′ phase is obtained by scanning electron microscopy and it is measured by the software Image Pro Plus 6.0 in a variety of aging conditions. The volume fraction of the γ′ phase is decreasing with the increase of the temperature. The radius of the γ′ phase is subject to involve the coarsening process during aging treatment, and the coarsening rate decreases with the extension of the aging time at certain temperature. Besides, the coarsening kinetics of γ′ phase in Waspaloy is adequately characterized by the Lifshitz–Slyozov–Wagner (LSW) theory model as the particle size distribution and coarsening behavior show excellent agreement with the LSW model. According to the experimental results and LSW model, the coarsening rate coefficients were determined to be 27.23 nm³/s and 58.67 nm³/s under the aging temperature of 960 °C and 1000 °C respectively. Meanwhile, on the basis of the experimental statistics analysis and the LSW model, the mathematical model of the coarsening behavior of the γ′ phase in Waspaloy was developed. Mathematical model developed in this paper can be used to evaluate the coarsening process of the γ′ phase during thermal exposure. The interfacial energy between the γ′ phase and the γ matrix was determined to be 56.04 mJ/m² and 44.27 mJ/m² at the temperature of 960 °C and 1000 °C respectively.