The Selective Laser Melting process involves multiple factors that are detrimental to fatigue life. It is crucial to select optimal processing parameters to avoid internal porosity, source of early failure through crack initiation mechanisms. Surface condition, especially high roughness values, may also be a critical factor for crack initiation. Influence of surface condition must be studied in the industrial context, where parts may not be completely machined before implementation. This work first focused on finding optimal parameters for producing low-porosity 316 L parts by the SLM process. Once a suitable set of parameters was found, a set of samples was characterized mechanically. Fatigue samples were then produced and submitted to various surface treatments (machining, polishing, …), while some were left as-built. They were then tested in high-cycle fatigue and S-N curves produced for each sample type. This study indicates that high-cycle fatigue life of SLM 316 L is generally inferior to wrought 316 L, with as-built samples exhibiting lower fatigue limits. This was explained by surface roughness acting as crack initiation sites. Porosity was also found to be a very significant factor in fatigue life of SLM 316 L.

中文翻译：

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工艺参数对选择性激光熔炼316 L钢力学性能和疲劳性能的影响

选择性激光熔化过程涉及多个因素，这些因素不利于疲劳寿命。选择最佳的加工参数以避免内部孔隙是至关重要的，内部孔隙是通过裂纹引发机制引起的早期破坏的根源。表面状况，尤其是高粗糙度值，也可能是引发裂纹的关键因素。必须在工业环境中研究表面状况的影响，在工业环境中，在实施之前可能无法完全加工零件。这项工作首先着重于寻找通过SLM工艺生产低孔隙率316 L零件的最佳参数。一旦找到一组合适的参数，就对一组样品进行机械表征。然后产生疲劳样品，并进行各种表面处理（机械加工，抛光等），而有些则保持原样。然后对每种类型的样品进行高周疲劳和SN曲线测试。这项研究表明，SLM 316 L的高周疲劳寿命通常不如锻造316 L，其竣工样品的疲劳极限更低。这可以通过表面粗糙度作为裂纹引发部位来解释。还发现孔隙率是SLM 316 L疲劳寿命的重要因素。