AN INVESTIGATION ON RESIDUAL STRESS IN 316L STAINLESS STEEL BY SELECTIVE LASER MELTING

In this paper, the residual stress of 316L stainless steel obtained from selective laser melting process is measured, and the process factors that influence residual stress are analyzed. Two levels of laser power, two levels of scanning speed, and other auxiliary factors such as height of support structure are considered. For each combination of condition, the residual stress is measured at three in-depth positions, and the microstructure is also observed. The results show that the as built 316L samples have fine microstructure with no clear grain boundaries, and the residual stresses at all measuring depths are tensile for all as-built SLM specimens. Meanwhile, it is found that the higher laser power and the lower scanning speed lead to the increase of tensile residual stress. Also, the tensile residual stress tends to increase with the depth into surface. In addition, the increase in position symmetry of specimen on the build platform appears to be able to reduce the magnitude of tensile residual stress. On the other hand, the effects of specimen location with respect to powder spreading and height of support are less conclusive.