Microstructure evolution of directionally solidified DZ125 superalloy with melt superheating treatment

The melt superheating treatment is carried out for DZ125 superalloy during directional solidification. Under the same thermal gradient and solidification velocity, the microstructure evolution of directionally solidified DZ125 superalloy is systematically investigated by changing the melt superheating temperature. The results show that the dendrite is refined with the melt superheating temperature increasing from 1500 °C to 1650 °C. However, it becomes coarse after the melt superheating treatment at 1750 °C. The dendrite segregation first reduces with the increase of melt superheating temperature between 1500 °C and 1650 °C, but becomes more severe when the superheating temperature is higher than 1650 °C. The carbide morphology presents script-like when the melt superheating temperature is below 1600 °C. Further increasing the melt superheating temperature, it is mainly blocky and nodular. Moreover, the reason of microstructure evolution with melt superheating treatment is discussed. The results are useful for promoting the development of high quality directionally solidified superalloy.