Experimental Investigation and Thermodynamic Assessment of Phase Equilibria in the Cr-Mo-Ru Ternary System

Phase equilibria of the Cr-Mo-Ru ternary system at 1100 °C and 1200 °C have been experimentally investigated using electron probe microanalyzer and x-ray diffraction. The σ-Cr 2 Ru forms a σ-(Mo 5 Ru 3 , Cr 2 Ru) continuous solid solution phase with the σ-Mo 5 Ru 3 phase at 1200 °C, but not at 1100 °C. The BCC (Cr, Mo) continuous solid solution phase exists at both 1100 °C and 1200 °C. Based on the measured experimental results and the thermodynamic parameters of the three binary sub-systems, a set of self-consistent parameters of the Cr-Mo-Ru system was evaluated using the CALPHAD method. Several vertical sections, isothermal sections, and liquidus surface projection of the Cr-Mo-Ru ternary system were calculated in this study. The results of phase equilibrium experiments and thermodynamic calculations show that although the solid solubility of the σ phase in the Cr-Mo and Mo-Ru binary systems is relatively small, it is exceptionally large in the Cr-Mo-Ru ternary system. The current obtained thermodynamic parameters of the Cr-Mo-Ru ternary system can provide the essential information and support for the theoretical guidance on the design of the Ni-based multi-component superalloys.