Solidification crack sensitivity of GH2132 superalloy deposited metal

Aiming at the problem of high sensitivity of hot crack in GH2132 superalloy welding, the microstructure, solidification behavior and cracking mechanism of GTAW deposited metal were studied by new developed welding wire, welding test of deposited metal, microstructural and fracture analysis, solidification calculation. The results show that the microstructure of the deposited metal was mainly composed of columnar dendrite γ phase (NiCrFe solid solution), Ti rich in Laves phase (Cr, Fe, Ni)₂(Ti, Mo), MC carbides and eutectic structure in the interdendritic. The solidification mode of the new developing wire was L→L + γ→L + γ + MC→L + γ + MC + Laves→γ + MC + Laves. The fracture surface showed typical cobblestone eutectic pattern, and the whole fracture morphology was covered by liquid film with free surface, indicating that the crystal crack occurred in the high temperature section. The mechanism of solidification crack was L→γ + Laves eutectic reaction with low melting point occurs at the terminal stage of solidification process. Under the action of solidification shrinkage stress, the residual liquid phase was not replenished in time and formed. The formation of Laves phase was mainly related to the segregation of Ti element during solidification. The theoretical calculation results show that the SCI (Solidification Cracking Index) value of GH2132 was 1944 ℃, and the STR (Solidification Cracking Range) was 258 ℃. In the evaluation of crystal crack sensitivity, SCI index can achieve the quantitative evaluation of crystal crack sensitivity more reasonably than STR, but there are still some problems such as incomplete factors to be considered.