IMPROVING THE MECHANICAL CHARACTERISTICS OF 316L STAINLESS STEEL PRODUCED BY SELECTIVE LASER MELTING AND STUDYING THE EFFECT OF POROSITY ON STRENGTH

Abstract

The results of experiments on the study of the physical and mechanical properties and microstructure of 316L stainless steel produced by additive technology selective laser melting are obtained. The dependences of the physical and mechanical properties (density, tensile strength, yield strength, elongation to failure, Young's modulus, nano hardness) of 316L steel on the main parameters of the selective laser melting (laser power, scanning speed) are obtained. 316L steel produced by selective laser melting has high mechanical characteristics: tensile strength – 710 MPa; yield strength – 610 MPa; elongation to failure – 48%; relative density – 99.5%, which is comparable to the values obtained for 316L steel produced by traditional methods. These characteristics were obtained using the optimal parameters of selective laser melting: laser power 100 W, scanning speed 200 mm/s, layer thickness 50 ?m, the distance between the scanning tracks is 80 ?m. It is shown that the use of the “volumetric energy density” parameter is usefully for carrying out a primary assessment of technological modes and solving the problem of optimizing the parameters of selective laser melting to obtain a material with high physical and mechanical properties. The nonlinear dependence of the mechanical properties of 316L steel on the main technological parameters can be explained by the influence of porosity arising at non-optimal modes. It is shown that selective laser melting allows controlling the porosity of 316L steel by varying the parameters of the technological mode. Thus selective laser melting makes it possible to produce both a material with a high density close to theoretical values and a material with controlled porosity.