Interdendritic Mo homogenization and sub-solidus melting during solution treatment in the Mo-strengthening single crystal superalloys

The interdendritic Mo homogenization and relevant sub-solidus melting are investigated in detail during solution treatment for Mo-strengthening single crystal superalloys. During solidification, NiMo-γ eutectics and Ni2Mo phases precipitate from the residual liquid and the Mo super-saturated interdendritic γ channel, respectively. Due to such super-saturation of Mo, Mo diffuses to interdendritic Mo-rich eutectic in first 5 min of solution treatment, and hence the eutectic sharply propagates, opposite to homogenization of Mo. The excess propagated eutectic causes the occurrence of sub-solidus melting. The proposed Mo-homogenization treatment can completely eliminate such sub-solidus melting.