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 signicantly affect the densi cation 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 densi cation behavior and resultant microstructural development. It was found that using a low laser energy density below 50 J/mm 3 produced an instable melt pool that resulted in the formation of unmelted particles, pores, cracks, and balling in the as-built parts with low densi cation. In contrast, the as-built parts at a high energy density above 200 J/mm 3 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/mm 3 by eliminating obvious SLM defects, which led to near full densi cation. 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.

Optimization and comparison of porosity rate measurement methods of Selective Laser Melted metallic parts

“…Studies also show that small (< 10 μm) blowhole pores (coming from gas entrapment in powder particles and in the powder layer or from powder humidity) are formed throughout the VED range [7]. At high VED, and depending on powder material, the porosity rate may once again increase as shown by [15] and [16].…”

A Short Review on the Microstructure, Transformation Behavior and Functional Properties of NiTi Shape Memory Alloys Fabricated by Selective Laser Melting

“…The energy density (volumetric energy density, E V , and linear energy density, E L ) can be simply estimated by: E V = P /( v × h × t ) E L = P / v where, P , v , h , and t represent the laser power, scanning velocity, hatch spacing, and layer thickness, respectively. The relative density of SLM fabricated NiTi parts benefits from the increase of energy density [ 29 ], like reported in other metallic materials [ 27 , 30 , 31 , 32 , 33 , 34 , 35 ], and a minimum energy density is required to produce fully dense (relative density > 99%) parts. As discussed in the work conducted by Haberland et al [ 29 ], fully dense parts could be obtained when the energy density is higher than 200 J/mm 3 .…”

“…As discussed in the work conducted by Haberland et al [ 29 ], fully dense parts could be obtained when the energy density is higher than 200 J/mm 3 . The density of SLM produced parts will decrease slightly with an extra high energy density, due to the entrapping of gases, spatter, or improper closure of keyholes [ 33 , 36 , 37 , 38 , 39 , 40 , 41 ]. The optimization of SLM process to fabricate fully dense NiTi parts can refer to Ref.…”

Nano-mechanical Behavior of H13 Tool Steel Fabricated by a Selective Laser Melting Method

“…[5][6][7] An additive manufacturing (AM) technique, which builds parts from 3D digital models typically by a layer additive process, has been an effective method to solve these problems. [5][6][7][8][9][10][11][12][13][14] Accordingly, a selective laser melting (SLM) method, a laser powder-bed AM process, should be suitable for processing of H13 because it offers the ability to not only reduce the amount of machining and hence wastage of this expensive material but also to produce intricate molds with a nearly full density and a refined microstructure. [1][2][3]13] The mechanical behavior of the H13 prepared by the SLM process is one of the most important characteristics and has been reported recently.…”

“…The H13 cuboid specimens (10 9 10 9 10 mm) are shown in Figure 1. The detailed preparation of the SLM process of this material can also be found in References 8,11,12. The cuboid specimens prepared by SLM were mounted in epoxy resin and then cross-sectioned to allow their microstructural observations.…”