Study on performance optimization of 316L stainless steel parts by High-Efficiency Selective Laser Melting

In this study, the layer thickness in the Selective Laser Melting (SLM) process was increased to 200 mu m to solve the problem of the low build rate of SLM. And adopted the heat treatment process to improve the mechanical properties of specimens. The single-tracks and multi-layer fabrication experiments of the aerosolized 316L stainless steel powder were carried out by using 400 W laser power. The process parameters were optimized by analyzing the density, the microstructure, the tensile properties and the defect mechanism of the molded parts. The experiment results showed that when the exposure time was 120-160 mu s and the overlap rate was 30-50%, the relative densities of the samples could be higher, up to 99.99%. The un-melted defects, the balling defects, and the micropore defects were observed in the SLM process. Un-melted defects can be avoided by adjusting the distance between the points and the hatch spacing. Balling included large balling and spatter balling. The large balling can be completely avoided by adjusting the process parameters. The spatter balling was divided into droplet spatter and powder spatter, which cannot be completely eradicated but can be inhibited by decreasing the exposure time. The build rate can be enhanced to 12.4 mm(3)/s. By the heat treatment process, the yield strength, the tensile strength and the elongation of the sample can reach 665 MPa, 718 MPa, and 35%, respectively.

Automated summary

The study increased the layer thickness and utilized a heat treatment process to improve the mechanical properties of specimens in the SLM process. By optimizing process parameters, different types of defects were identified and improvement methods were proposed.