Microstructure-Toughness relationships in 316L stainless steel produced by laser powder bed fusion

The impact toughness and fracture toughness properties at room temperature of 316L austenitic stainless steel manufactured by laser powder bed fusion were determined and compared. The effect of the grain size and morphology, of the dislocation structures and of the oxide nanoparticles on the toughness behavior was systematically investigated. In all cases, ductile fracture resulted from decohesion at the matrix/oxide interfaces. After a stress-relief heat treatment, Charpy absorbed energy and fracture toughness at crack initiation were 170-250 J/cm2 and 350-550 kJ/m2, respectively. Dislocation recovery has no significant influence on the toughness properties. Recrystallization decreased the impact toughness and fracture toughness by up to 25% and 50% respectively, due to synergistic effects between recrystallization and oxide particle coarsening, resulting in coarse oxides located along recrystallized grain boundaries that facilitated ductile cracking. Whatever the asbuilt microstructure and the heat treatment, fracture and impact toughness obeyed a linear correlation with an accuracy of & PLUSMN;20%. They were also linearly correlated for each of the crack initiation and crack propagation stages.

Automated summary

The impact toughness and fracture toughness properties of 316L austenitic stainless steel manufactured by laser powder bed fusion were investigated. The effects of grain size, morphology, dislocation structures, and oxide nanoparticles on toughness behavior were analyzed. Ductile fracture resulted from decohesion at the matrix/oxide interfaces. Recrystallization decreased the toughness due to synergistic effects between recrystallization and oxide particle coarsening.