This study demonstrates the improvement in the fatigue strength of additive manufacturing (AM) metals such as laser-based powder bed fusion of metals by post-processing. Titanium alloy samples manufactured by powder bed fused (PBF) Ti6Al4V produced through laser sintering (LS), treated by submerged laser peening (SLP), cavitation peening (CP), and shot peening accelerated via a water jet (SPwj), were subjected to torsional fatigue testing and compared with the as-built specimen. At SLP, the samples were treated by laser ablation (LA) and laser cavitation (LC) which was developed following LA. A cavitating jet was used for CP. For comparison, conventional post-processing using SPwj was also performed. To characterize the microstructural modification caused by the three post-processing methods, the cross-section of the treated surface was observed by electron backscatter diffraction. The fatigue strengths at 10 cycles were found to be 217, 361, 313, and 285 MPa for the as-built, SLP, CP, and SPwj specimens, respectively. The primary factors contributing to fatigue strength improvement by post-processing were surface smoothing and the introduction of compressive residual stress. The experimental observations were used to derive correlation formulas to estimate the fatigue life improvement due to post-processing as the function of the surface roughness and surface residual stress.

中文翻译：

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浸没式激光喷丸、空化喷丸和喷丸对提高激光烧结粉床电熔Ti6Al4V扭转疲劳强度的影响

这项研究证明了增材制造 (AM) 金属的疲劳强度可以通过后处理得到改善，例如基于激光的粉末床金属熔合。采用激光烧结 (LS) 生产的粉末床熔凝 (PBF) Ti6Al4V 制造的钛合金样品，经过浸入式激光喷丸 (SLP)、空化喷丸 (CP) 和水射流加速喷丸 (SPwj) 处理，扭转疲劳试验并与竣工试件进行比较。在 SLP 中，样品经过激光烧蚀 (LA) 和继 LA 之后开发的激光空化 (LC) 处理。 CP 使用空化射流。为了进行比较，还进行了使用 SPwj 的传统后处理。为了表征三种后处理方法引起的微观结构变化，通过电子背散射衍射观察了处理表面的横截面。对于竣工、SLP、CP 和 SPwj 样本，10 个周期的疲劳强度分别为 217、361、313 和 285 MPa。通过后处理提高疲劳强度的主要因素是表面平滑和残余压缩应力的引入。实验观察结果被用来推导相关公式来估计由于后处理而导致的疲劳寿命改善，作为表面粗糙度和表面残余应力的函数。