Enhanced quasi-static and dynamic tensile properties of stainless steel 316L produced by laser aided additive manufacturing in controlled argon environment

Abstract

In this paper, laser aided additive manufacturing (LAAM) of stainless steel 316L (SS 316L) in a controlled argon environment was investigated. The controlled argon environment can significantly reduce the oxidation and fundamentally change the process conditions. It was found that after inhibiting oxidation, the surface of the deposited SS 316L showed remarkably high reflectance (71%) to laser radiation, which minimised heat accumulation. Subsequently, stable melt pool temperature and high cooling rate (4.1 × 104 K/s) were also observed. Furthermore, nano-sized oxides were found to be nucleated owing to excessively low internal oxygen content (220 ppm). The unique process condition resulted in enhanced strengthening effect due to cellular structure refinement and dispersed nano-sized oxides. Consequently, a desirable balance of high strength and ductility was achieved for the as-deposited materials under both quasi-static tension (strain rate 10−3 s−1, yield stress 560.0 MPa, ultimate tensile strength 717.2 MPa, and elongation 64.0%) and dynamic tension (strain rate 3150 s−1, maximum flow stress 1241 MPa, and elongation 37.5%).