DTA research of a third generation Ni-based single crystal superalloy

The effect of the melt overheating temperature on solidification characteristics and microstructure of a third generation Ni-based single crystal superalloy was studied by the Differencial Thermal Analysis (DTA) and the melt superheating treatment. The results show that as the melt overheating temperature increases from 1450 to 1500°C, the nucleation supercooling and solidification interval change a little, the nucleation and growth of γ phase are in a wide range of temperature. When the melt overheating temperature is above 1580°C, the nucleation supercooling increases sharply and the solidification interval decreases obviously. At the same time, the temperature range of nucleation and growth of γ phase is reduced, the precipitation of γ/γ' eutectic is decreased, and the precipitation temperature of γ' phase is elevated by 9°C compared with the one overheated to 1450°C. When the melt overheating temperature rises to 1650°C, the nucleation supercooling decreases, and the solidification interval increases appreciably. As the melt superheating temperature increases from 1500 to 1580°C, the dendrite structure is refined significantly, but then coarsened slightly when the melt superheating temperature rises to 1650°C. The results are primarily attributed to the melt structure change caused by the melt overheating temperature, and the solidification characteristics and microstructure of alloy are affected finally.