Fatigue life prediction model and entropy generation of 304L stainless steel fabricated by selective laser melting

Abstract Fatigue performance and reliability application have always been the key issues restricting the development of disruptive additive manufacturing technology due to intrinsic defects caused by the manufacturing process. In the present work, tensile tests and fatigue tests of 304 L stainless steel (SS) fabricated by selective laser melting (SLM) with various laser power levels were carried out with in-situ monitoring of acoustic emission (AE) and thermal imager (TI). Microstructural characterizations were performed to measure the surface roughness, porosity, and residual stress of as-built SLMed 304 L SS. A fatigue life prediction model considering surface roughness, porosity, and residual stress was established based on experimental data. In addition, direct evidence is offered to show the strong correspondence between the temperature variable of material surface induced by energy dissipation caused by entropy generation during cyclic deformation and the degradation of material properties caused by fatigue micro-damage. This work indeed provides a novel fatigue life prediction model for SLMed 304 L SS, and advances our current understanding of underlying fatigue micro-damage mechanism of additively manufactured materials.