Precipitation Behavior of α-Cr Phase in High Cr Content Superalloys

The precipitation behavior of α-Cr phase during long-term exposure at high temperatures was analyzed using the microstructural analysis approaches in INCONEL718 and INCONEL625 alloys. The structure analysis and thermodynamic calculation results show that, with increasing the exposure time, α-Cr phase precipitates and grows usually clinging to δ phase in IN718 alloy, for IN625 alloy, α-Cr phase precipitates and grows usually clinging to M₆C carbide and δ phase. This precipitation behavior possibly is due to the solubility of Cr in δ and M₆C phase dramatically decreasing with decreasing the temperature.