Microstructure, Mechanical Properties, and Residual Stress Distribution of AISI 316L Stainless Steel Part Fabricated by Laser Metal Deposition.

In this paper, AISI 316L stainless steel part is obtained by laser metal deposition additive manufacturing method. The microstructure of the part was observed and analyzed by an optical microscope. The tensile mechanical properties and residual stress distribution of the part were tested by tensile test and the contour method. The results show that the bulk structure is mainly columnar crystal and equiaxed crystal, and the latter layer of laser metal deposition will form a remelted zone and heat-affected zone in the former deposition zone. Tensile test results show that the tensile strength of tensile specimens parallel to laser scanning direction and perpendicular to laser scanning direction is basically the same, but the elongation of the specimens perpendicular to the laser scanning direction is relatively better. The main reason is the different distribution characteristics of columnar crystals and equiaxed crystals in the two directions. Relatively large deformation occurs on the cut surface of the specimen after low-speed wire cut. The residual stress test results indicate that tensile stress is formed in the upper part and it reaches 315 MPa at the top surface. And compressive stress is formed at the part/substrate interface and the substrate.