Microstructural analysis and fatigue crack initiation modelling of additively manufactured 316L after different heat treatments

• Published in: Materials & design Vol. 194; p. 108962
• Main Authors: Elangeswaran, Chola, Cutolo, Antonio, Muralidharan, Gokula Krishna, Vanmeensel, Kim, Van Hooreweder, Brecht
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.09.2020; Elsevier
• Subjects: 316L stainless steel; Additive manufacturing; Crack initiation model; Fatigue behaviour; Laser powder bed fusion; Microstructure; Fatigue behaviour; Laser powder bed fusion; Additive manufacturing; 316L stainless steel; Crack initiation model; Microstructure
• ISSN: 0264-1275; 1873-4197
• DOI: 10.1016/j.matdes.2020.108962

This study investigates the fatigue behaviour of 316L stainless steel manufactured by laser powder bed fusion. More specifically, the influence of the microstructure on fatigue is analysed for four different material conditions: as-built, stress relieved, fully annealed and hot isostatic pressed. Fully reversed tension-compression fatigue results on miniaturised vertically built and machined samples indicate that as-built and stress relieved specimens exhibit superior fatigue behaviour compared to fully annealed and hot isostatic pressed ones. Fine sub-grained cellular microstructure in as-built and stress relieved samples resulted in high fatigue performance, which was decreased with microstructure coarsening from the high temperature heat treatments. Secondly, a microstructure-based fatigue crack initiation model is adapted for additively manufactured 316L and verified for different material states. The results show that the analytical model depicts a conservative prediction for crack initiation life when compared with experimental results for full fracture. This validation offers the potential to expand the model for other material and process conditions. [Display omitted] •Additively made 316L shows superior fatigue behaviour with cellular microstructure.•Microstructure coarsening from heat treatments lowers the fatigue performance.•Microstructure-based crack initiation model is adapted for additively manufactured 316L.•The model offers prediction potential for other process & post-treatment conditions.