Process parameter optimization and mechanical properties for additively manufactured stainless steel 316L parts by selective electron beam melting

• Main Authors: Wang, Chengcheng, Tan, Xipeng, Liu, Erjia, Tor, Shu Beng
• Other Authors: School of Mechanical and Aerospace Engineering
• Format: Article
• Language: English
• Published: 2020
• Subjects: Engineering::Mechanical engineering; Additive Manufacturing; Selective Electron Beam Melting
• Online Access: https://hdl.handle.net/10356/142421
• Institution: Nanyang Technological University

This work presents an experimental study of process optimization of the pair of critical parameters (speed function (SF) and focus offset (FO)) for stainless steel 316 L (SS316L) parts additively manufactured by selective electron beam melting (SEBM). Here, there are two sets of optimized SF-FO parameters that could build SS316L parts with high relative densities (>99%) and well-melted top build surfaces. Tensile test results show that most of the SEBM-built SS316L samples exhibit higher tensile strengths than the conventional cast and wrought counterparts, whereas their ductility is lower. In addition, strong anisotropic tensile properties are observed for the SEBM-built SS316L samples, e.g. they generally have better tensile properties when loaded parallel to the build direction as compared to the horizontal direction. However, a large number of σ phase was found to precipitate at grain boundaries in the SS316L samples fabricated under lower SF and larger FO with a higher build temperature, which evidently deteriorates their tensile properties particularly for the horizontal direction. It is suggested that SEBM process parameters for SS316L must be optimized to avoid σ phase precipitation at elevated temperatures apart from a well-melted top build surface and a high relative density.