Abstract The structure-property of a Ni-based superalloy fabricated by selective laser melting (SLM) was investigated under very high cycle fatigue (VHCF), and the subsurface cracking with fisheye pattern becomes a remarkable failure mode. Due to the presence of subsurface failure, the descending S–N curve property is represented. Based on 2D & 3D microscopic observation, a rough region with facets and inclusions, named as “multi-inclusion assisted facetted cracking zone (MAFCZ)”, is present within the fisheye. By combining electron backscatter diffraction analysis, the subsurface failure is related to grain size & orientation, microtexture and crystal defects. The crack is nucleated from the large grain slip with the highest Schmid factor under the assistance of the inclusions. The rough surface morphology with crack deflection reveals ultra-slow crack growth behavior within MAFCZ. Combined with failure modeling and fracture mechanics analysis, the subsurface failure mechanisms of SLM Ni-based superalloy under the VHCF are elucidated.

中文翻译：

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高周疲劳下选择性激光熔化镍基高温合金的亚表面刻面裂纹行为

摘要 研究了激光选区熔化 (SLM) 制备的镍基高温合金在甚高周疲劳 (VHCF) 下的组织性能，其中鱼眼状亚表面裂纹成为一种显着的失效模式。由于地下失效的存在，下降的 S-N 曲线属性被表示。基于 2D 和 3D 显微观察，鱼眼内存在一个带有刻面和夹杂物的粗糙区域，称为“多夹杂物辅助刻面裂纹区（MAFCZ）”。通过结合电子背散射衍射分析，次表面失效与晶粒尺寸和取向、微观结构和晶体缺陷有关。裂纹是在夹杂物的帮助下，从具有最高施密特因子的大晶粒滑移中形核的。具有裂纹偏转的粗糙表面形态揭示了 MAFCZ 内的超慢裂纹扩展行为。结合失效建模和断裂力学分析，阐明了 VHCF 下 SLM 镍基高温合金的亚表面失效机制。