The developing of large size superalloy vacuum induction melting (VIM) ingots is limited owing to hot cracking. The hot cracking behavior of the large size GH4742 superalloy VIM ingot was investigated via experiment and simulation. The microstructure was examined by optical microscopy, and element segregation was investigated by electron probe microanalysis. The solidification temperature range and yield strength at high temperature (YSHT) were calculated by JMatPro software. The results show that the variations of microstructure and element segregation in different locations are caused by different cooling rates. Moreover, the larger secondary dendrite arm spacing and serious element segregation of Nb accelerate hot cracking of the VIM ingot. In addition, the solidification temperature range is wider, and YSHT is lower in center than at edge of the ingot. Therefore, the hot cracking susceptibility is the highest in the center of the GH4742 superalloy VIM ingot. The critical criterion of element segregation for hot cracking is that the partition coefficient of Nb should be larger than 0.5.

由于热裂，大尺寸高温合金真空感应熔炼（VIM）锭的发展受到限制。通过实验和模拟研究了大尺寸GH4742高温合金VIM锭的热裂行为。通过光学显微镜检查微观结构，并通过电子探针显微分析研究元素偏析。采用JMatPro软件计算凝固温度范围和高温屈服强度（YSHT）。结果表明，不同位置的显微组织和元素偏析的变化是由不同的冷却速度引起的。此外，较大的二次枝晶臂间距和Nb的严重元素偏析加速了VIM铸锭的热裂。另外，凝固温度范围更广，并且 YSHT 的中心低于铸锭的边缘。因此，GH4742高温合金VIM锭中心的热裂敏感性最高。热裂元素偏析的关键标准是Nb的分配系数应大于0.5。