Abstract:To study the hot cracking sensitivity of high alloying difficult-to-deform superalloy GH4975, the crack morphology and microstructure characteristics of the GH4975 ingot were observed, and the causes of hot cracking were analyzed through solidification behavior and thermodynamic calculation. The results show that cracks propagate along grain boundaries and dendrites, and the equiaxed region has a greater cracking tendency than the columnar region. Shrinkage holes are easy to appear in the center of the ingot. The formation of continuous shrinkage holes leads to insufficient overlap between dendrites, which can be easily pulled apart under stress to form a crack source. At the same time, the segregation of Al, Ti and Nb elements between dendrites is severe. Complex precipitates, especially numerous (γ+γ′) eutectic phases, promote the nucleation and propagation of cracks. JMatPro calculation shows that GH4975 alloy has a high shrinkage rate and a wide temperature range for poor feeding during solidification. It facilitates the formation of shrinkage hole that can act as a crack source. Meanwhile, the linear expansion coefficient of the alloy changes significantly in the temperature range for poor feeding, thereby promoting crack propagation.