The effect of heat treatment on the homogenization of CMSX-4 Single-Crystal Ni-Based Superalloy

Two solution heat treatments were used for the homogenization of as-cast CMSX-4 single crystal Ni-based superalloy and their effects were investigated. The heat treatment temperatures were established using thermodynamic calculations based on the CALPHAD method. The effect of heat treatment on the homogenization degree was evaluated quantitatively using the local chemical composition and partition coefficients, and qualitatively using element distribution maps and backscattered electron images after each cycle of the heat treatments. The evolution of porosity and dissolution of the γ/γ' eutectic pools and coarse γ' fractions were investigated using the quantitative image analysis. The experimental results showed that the strongly segregated microstructure of the as-cast superalloy homogenize with different rates as a function of temperature. In both cases a low residual level of microsegregation still maintain even after long term exposure at high temperatures. Long holding time at both temperatures generates a notable increase of porosity levels being more accentuated with the increase in temperature.