Residual Stresses Relief in Selective Laser Melting and Hot Rolled 316L Stainless Steel

Selective Laser Melting (SLM) is one of the effective and preferred Additive Manufacturing (AM) techniques due to its advantages such as design freedom and less material waste compared to the traditional manufacturing technologies. However, residual stress is induced during the printing process due to steep thermal gradient and possible mechanical impact of the particles. The main focus of this study is on effectiveness of stress relief heat treatment on reduction of built-up residual stress in SLM samples. For the reason of comparison, same study is conducted on the conventionally manufactured (hot rolled (HR) 316L SS) samples. X-ray diffraction method was used for actual measurement of the residual stress built-up in each sample. Heat treatment at 450°C was applied for 1.5 hours to all the 316L samples and resulted in approximately 30 % reduction of residual stress in SLM samples but it could have less effect on HR 316 ones. The built-up residual stress in SLM 316L SS is found to be tensile in nature whereas HR 316L SS samples exhibited more compressive residual stress. This study also applies one of the well-known developed models for calculation of residual stress in AM processed metallic materials.