Oxidation behavior and resultant deposition efficiency and material properties of laser aided additively manufactured stainless steel 316 L

Oxidation is a common issue in directed energy deposition (DED) based additive manufacturing (AM) processes. Severe oxidation is usually considered to be detrimental, which should be avoided. However, it is found that the surface oxidation of the deposited materials can also lower the laser reflectance, thereby increasing the utilization rate of laser energy and improving deposition efficiency. In this study, stainless steel 316 L (SS 316 L) was deposited using laser aided additive manufacturing (LAAM) process in the localized argon gas shielding environment and controlled argon environment, respectively, to investigate the evolution of oxidation on the surface and in the deposited material, as well as the effect of oxidation on the deposition efficiency and material properties. Results showed that severe surface oxidation of the materials deposited in the localized argon gas shielding environment effectively lowered the laser reflectance (14.5 %), which is much lower than that deposited in argon environment (71 %). Subsequently, with the same process parameters, the deposition efficiency in the localized argon gas shielding environment can be 1.57 times of that obtained in the controlled argon environment. Meanwhile, compared with the tensile properties of SS 316 L deposited in the controlled argon environment (YS 560 MPa, UTS 717 MPa, elongation 64 %), the tensile properties of SS 316 L deposited in the localized argon gas shielding environment (YS 456 MPa, UTS 631 MPa and elongation 57 %) are lower, whereas still show a good combination of strength and ductility.