Short-term creep response of AISI 316L stainless steel fabricated by laser powder bed fusion: experiments and physically based modeling

The creep response of AISI 316L austenitic stainless steel produced by additive manufacturing has garnered considerable attention in recent years. This interest stems from the unique microstructure created by the exceptionally high cooling rates characteristic of this technology. Despite numerous studies addressing this issue, the constitutive analysis of the relationships between temperature, stress, and creep response has predominantly relied on traditional phenomenological models, which do not facilitate an easy quantitative correlation with microstructural features. The primary objective of this study was to bridge this knowledge gap by proposing a physically based constitutive model that elucidates the unique dependence of the minimum creep rate on applied stress and temperature in AISI 316L steels manufactured through additive processes. The short-term creep behavior of AISI 316L stainless steel fabricated by the laser powder bed fusion additive manufacturing technology was investigated at 600 and 650 °C, using constant load and variable load experiments. The microstructure was characterized by transmission electron microscopy; fracture analysis was performed on crept samples by scanning electron microscopy. Creep response was compared to literature concerning other 316L stainless steel samples fabricated by the same additive manufacturing technology and to conventional wrought steels having a similar composition. Results showed comparable time to ruptures, although the steel investigated in the present study showed much lower (one order of magnitude) minimum creep rates. The microstructural results suggested assimilating the steel to a purposedly developed simplified model-material. Combination with available constitutive models confirmed the strong relationship between creep behavior and microstructural features.