The pore defects and surface roughness derived from additive manufacturing restrict applications in the production of ultra-long service time parts. Due to the high sensitivity of very high cycle fatigue (VHCF) resistance to defects, smaller defects may also become potential crack initiation sites. To remove these defects and consequently improve fatigue strength, three different post-processing routes, hot isostatic pressing (HIP, 1160 °C/1500 bar/3h ± 30 min), machining, and their combinations, are employed on samples in this research. Three-dimensional X-ray tomography (3D-XRT) shows that pores larger than 25 μm in diameter are mainly located in the “macropore-rich layer” with 300 μm thickness below the surface. HIP can effectively close the pores, but this does not translate into an increase in fatigue performance, which is attributed to the increased roughness. Machining with a certain depth can significantly reduce the surface roughness and remove the “macropore-rich layer.” Therefore, it can improve fatigue resistance. The co-effect of HIP and machining is confirmed to be the most effective solution to improve fatigue resistance. Taking the depth-width ratio of the micro-depression as the characteristic size of the surface roughness, it found that the fatigue life is closely related to the characteristic size of the micro depression. For the pore-induced fatigue failure, the fatigue resistance is related to the pore size and the location. The area of the crack initiation (rough area, abbreviation as RA) is introduced and ${\sqrt{\mathit{Area}}}_{\mathit{pore}}/{\sqrt{\mathit{Area}}}_{\mathit{RA}}$ is calculated to reflect the pore characterization including the size and location, and the ratio of the pore area to the RA area is found to be have a linear relationship to the fatigue life in single logarithmic coordinates.

增材制造产生的孔隙缺陷和表面粗糙度限制了超长使用寿命零件生产中的应用。由于超高周疲劳 (VHCF) 抗性对缺陷的高度敏感性，较小的缺陷也可能成为潜在的裂纹萌生点。为了消除这些缺陷并因此提高疲劳强度，本研究中的样品采用了三种不同的后处理路线，即热等静压（HIP，1160 °C/1500 bar/3h ± 30 min）、机械加工及其组合。三维X射线断层扫描（3D-XRT）显示，直径大于25μm的孔隙主要位于地表以下300μm厚的“大孔隙富集层”。HIP 可以有效地关闭毛孔，但这并不会转化为疲劳性能的增加，这归因于增加的粗糙度。一定深度的加工可以显着降低表面粗糙度，去除“富大孔层”。因此，它可以提高抗疲劳性。经证实，HIP 和机加工的共同作用是提高抗疲劳性的最有效解决方案。以微凹陷的深宽比作为表面粗糙度的特征尺寸，发现疲劳寿命与微凹陷的特征尺寸密切相关。对于孔致疲劳失效，疲劳抗力与孔的大小和位置有关。介绍裂纹萌生区域（粗糙区域，缩写为RA）并 ”因此，它可以提高抗疲劳性。经证实，HIP 和机加工的共同作用是提高抗疲劳性的最有效解决方案。以微凹陷的深宽比作为表面粗糙度的特征尺寸，发现疲劳寿命与微凹陷的特征尺寸密切相关。对于孔致疲劳失效，疲劳抗力与孔的大小和位置有关。介绍裂纹萌生区域（粗糙区域，缩写为RA）并 ”因此，它可以提高抗疲劳性。经证实，HIP 和机加工的共同作用是提高抗疲劳性的最有效解决方案。以微凹陷的深宽比作为表面粗糙度的特征尺寸，发现疲劳寿命与微凹陷的特征尺寸密切相关。对于孔致疲劳失效，疲劳抗力与孔的大小和位置有关。介绍裂纹萌生区域（粗糙区域，缩写为RA）并 发现疲劳寿命与微凹陷的特征尺寸密切相关。对于孔致疲劳失效，疲劳抗力与孔的大小和位置有关。介绍裂纹萌生区域（粗糙区域，缩写为RA）并 发现疲劳寿命与微凹陷的特征尺寸密切相关。对于孔致疲劳失效，疲劳抗力与孔的大小和位置有关。介绍裂纹萌生区域（粗糙区域，缩写为RA）并${\sqrt{\mathit{区域}}}_{\mathit{毛孔}}/{\sqrt{\mathit{区域}}}_{\mathit{RA}}$ 计算以反映孔隙特征，包括大小和位置，发现孔隙面积与 RA 面积的比率与单对数坐标中的疲劳寿命呈线性关系。