Effect of Melt Overheating Treatment on Pure Purification Behavior and Solidification Microstructure of FGH4096 Nickel-Based Superalloy

FGH4096 alloy was treated by melt overheating process under different melt overheating temperatures (1 415,1 463,1 523 ℃) and overheating times (10, 20, 30 min). The influence of melt overheating on the purification behavior and solidification microstructure of the alloy was studied. The results show that with increasing melt overheating temperature or prolonging overheating time, the secondary dendrite spacing decreased gradually. With increasing overheating temperature, the segregation degree of the elements in the alloy decreased, but the influence of the overheating time on the segregation degree was not significant. When the overheating temperature was 1 415-1 463 ℃, carbon-oxygen reaction mainly occurred in the melt , and the nitrogen absorption reaction was weak, resulting in low oxygen and nitrogen content. When the melt overheating temperature was 1 463-1 523 ℃, MgO crucible decomposition reaction and absorbed nitrogen reaction occurred, resulting in high oxygen and nitrogen content in the alloy.