Close Packed Phases in Nickel-Based Superalloys - Investigation by Diffusion Multiples

Precipitation of close-packed phases is a common problem of modern nickel-based superalloys, containing refractory or higher melting point elements such as Re, Ru, Cr, Mo and W. Thus, a fundamental understanding of phase stabilities of close-packed phases governed by these elements is of high relevance regarding the improvement of databases for nickel-based superalloys and the development of next generation superalloys. Diffusion multiples have been used to investigate the ternary systems Ni-Mo-Cr, Ni-Mo-Re and Ni-Mo-Ru at 1100°C and 1250°C. A novel manufacturing technique for diffusion multiples based on a two-step casting process will be presented. EDS and EBSD measurements lead to isothermal sections of phase diagrams. Additionally investigations of certain quaternary systems will be shown. Solubility limits of sigma-, P-, delta- and hcp-phase were determined. Adaptation of the MatCalc database to the experimental results by project partners in Vienna lead to significant improvements in predictions for multicomponent alloys.