Investigation and prediction of fatigue performance of SLM 316 L stainless steel based on small build orientation variations and heat treatment effects reveals significant insights for the additive manufacturing industry. This study explores how differing build orientations impact mechanical properties and fatigue performance of 316 L stainless steel manufactured using Selective Laser Melting (SLM), emphasizing its utility across various industrial applications.
Traditional manufacturing techniques are often limited by material properties and geometrical constraints. Additive manufacturing, particularly via SLM, enables the creation of complex structures, which can benefit industries ranging from aerospace to biomedical. Understanding how build orientation influences mechanical properties and fatigue life is pivotal, especially under varying operational conditions, as parts made from this material often experience cyclic loading. This study is significant as it fills gaps identified in previous fatigue evaluations, particularly examining smaller incremental angles beyond the commonly analyzed 0°, 45°, and 90° orientations.
The research involved 316 L stainless steel samples produced through SLM at various orientations: 0°, 45°, 55°, 65°, 75°, 85°, and 90°. Quasi-static and cyclic tensile tests quantified the material's mechanical performance both as-built (AB) and after undergoing heat treatment (HT). Results indicated ultimate tensile strength (UTS) exhibited modest variation of 7% for the AB condition and 13% for HT samples, demonstrating more responsiveness to heating processes. Fatigue tests revealed minimal differences at low cycles but indicated marked improvements at high cycles, with heat-treated samples consistently outperforming their AB counterparts.
"Inclination angle had a greater effect on fatigue life...with horizontal part orientations outperforming vertical ones," noted the authors. The predictive model developed showed significant promise; nearly 90% of data aligned within accepted scatter factors, underscoring the reliability of this approach to forecast fatigue performance based on experimental results.
The comprehensive methodology established for this investigation entailed the use of commercially available 316 L stainless steel powder, characterized by specific particle size distributions suitable for SLM. A Renishaw AM400 SLM system fabricated the samples, developed under controlled settings to optimize results. Post-processing heat treatments included annealing, which, contrary to surface finishing processes, showed limited uniformity improvements across samples, especially influencing residual stresses seen through varied grain structures.
Data analysis after mechanical testing exhibited variations dictated by microstructural aspects resulting from differing heat treatments and build orientations. Surface roughness and other relevant metrics indicated trends toward improved fatigue performance with HT samples, which displayed lower roughness and enhanced structural integrity. "The predictive model demonstrated robustness...with nearly 90% of data within...less than three," according to the findings, highlighting the model's effectiveness.
These insights not only establish the relationship between build orientation and fatigue life but also infer potential design criteria for future additive manufacturing processes. The study’s rigorous testing methods and its resulting predictive model equip the industry with tools to optimize SLM processes according to specific application needs. Conclusively, this research sets the stage for practical applications of 316 L stainless steel and suggests avenues for deepening our fundamental understandings of fatigue behaviors influenced by additive manufacturing parameters.