The influence of thermal exposure on the microstructure of a Ni3Al-based single crystal superalloy

The effect of thermal exposure on the microstructure of an Ni3Al-based single crystal superalloy was investigated. The Ni3Al-based single crystal superalloy used in this experiment contained a high content of molybdenum (Mo) and a low content of chromium(Cr), which had good high-temperature strength and oxidation resistance. The alloy was exposed at 1020-1200 degrees C for different time periods. The microstructure after thermal exposure was examined by scanning electron microscope (SEM) and field emission microscope (FEM). The results indicated that precipitation of needle-like topologically close-packed (TCP) phases was only observed at certain intermediate temperature intervals (1020-1080 degrees C). Moreover, once the TCP phases precipitated, they would not dissolve back even after thermal exposed for 1000 h. No precipitation phases were observed after high-temperature thermal exposure at 1100-1200 degrees C for 25 h.