The influences of microstructure and solidification parameters on the hot cracking behaviour of an additively manufactured Ni-based superalloy via selective electron beam melting (SEBM) have been investigated. Severe intergranular hot cracking is found to occur at grain boundaries (GBs) in the SEBM-built superalloy. A generalized cracking criterion that considers various process parameters along with the GB inclination is developed on the basis of a prevailing hot cracking criterion for columnar-grained microstructure. A parametric evaluation of influencing factors is quantitatively conducted to predict the optimal conditions that could prevent hot cracking while maintaining the desirable fine microstructure. With the aid of numerical simulations, it is determined that while micro-segregation occurs at all types of GBs, its occurrence at the divergent ones tend to promote cracking. Using the results of this work, hot cracking in additively manufactured Ni-based superalloy single crystals can be potentially mitigated.

研究了微观结构和凝固参数对通过选择性电子束熔化（SEBM）增材制造的镍基高温合金的热裂化行为的影响。在SEBM建造的高温合金中，在晶界（GB）处发现了严重的晶间热裂纹。基于柱状晶粒组织的现行热裂纹判据，提出了一种考虑了各种工艺参数以及GB倾角的广义裂纹判据。定量地进行影响因素的参数评估，以预测可防止热裂纹同时保持所需的精细微结构的最佳条件。借助数值模拟，可以确定，尽管在所有类型的GB上都发生了微偏析，它在发散处的出现倾向于促进裂纹。利用这项工作的结果，可以潜在地减轻增材制造的镍基高温合金单晶中的热裂纹。