Densification Behavior of 316L Stainless Steel Parts Fabricated by Selective Laser Melting by Variation in Laser Energy Density

Abstract

Selective laser melting (SLM) is an attractive manufacturing technique for the production of metal parts with complex geometries and high performance. This manufacturing process is characterized by highly localized laser energy inputs during short interaction times which significantly affect the densification process. In this present work, experimental investigation of fabricating 316L stainless steel parts by SLM process was conducted to determine the effect of different laser energy densities on the densification behavior and resultant microstructural development. It was found that using a low laser energy density below 50 J/mm3 produced an instable melt pool that resulted in the formation of unmelted particles, pores, cracks, and balling in the as-built parts with low densification. In contrast, the as-built parts at a high energy density above 200 J/mm3 showed irregular scan tracks with a number of pores and metal balls that decreased part density. The optimal laser energy density range was accordingly determined to be 58–200 J/mm3 by eliminating obvious SLM defects, which led to near full densification. The SLM samples fabricated using optimal parameters allowed observation of a microhardness of 280 Hv, ultimate strength of 570 MPa, and yield strength of 530 MPa that were higher than those of the as-cast and wrought 316L stainless steel.