Abstract Ultrasonic fatigue tests were performed to investigate high and very high cycle fatigue behaviors of a laser additively manufactured Inconel 718 (IN718) alloy in the as-deposited condition. The results indicate that the competition failure behavior between the surface and interior crack initiation results in the separate S-N curve. Both manufacturing defects (e.g., gas pore, lack of fusion) and columnar grains (matrix) observed in the microstructure could act as the original fatigue micro-cracks due to the effective restriction on manufacturing defects. The fatigue sensitivity levels increase successively in terms of the type, size, and location of the maximal micro-crack.

中文翻译：

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激光增材制造镍基高温合金在高周和超高周疲劳状态下的竞争裂纹萌生行为

摘要 进行超声疲劳试验以研究激光增材制造的 Inconel 718 (IN718) 合金在沉积状态下的高周和超高周疲劳行为。结果表明，表面和内部裂纹萌生之间的竞争破坏行为导致了单独的 SN 曲线。由于对制造缺陷的有效限制，在微观结构中观察到的制造缺陷（如气孔、未熔合）和柱状晶粒（基体）都可以作为原始疲劳微裂纹。疲劳敏感性水平在最大微裂纹的类型、大小和位置方面依次增加。