Microstructure and Mechanical Properties of Laser Welded 316L SLM Parts

Abstract

This paper focuses on a study conducted on laser welding of printed 316L parts that were produced with a selective laser melting process. Commercial sheet material was used as a reference for the printed 316L parts. The effect of heat treatment on joint properties, and on what stage of the process it should be applied, was studied with metallography and mechanical testing. Optical microscopy was applied to analyze the microstructure of the base material and the weld seam. Tensile testing was applied for determining monotonic strength of different structures. The printed base material showed higher strength, but lower ductility in comparison to the commercial sheet material. In the welded condition, tensile properties were impaired by the welding, but for the commercial sheet material, no clear effects were seen. The difference was hypothesized to be caused by the higher strength mismatch in the printed joints. For the welded structures, the best strength-ductility combination was achieved by heat treating the parts both before and after the laser welding.

The Effect of Severe Shot Peening on Fatigue Life of Laser Powder Bed Fusion Manufactured 316L Stainless Steel

“…Currently, AM is still not a viable replacement for all manufacturing technologies but should be capitalized in the areas where its superior properties can be utilized to produce higher quality products compared to other techniques. The strength of the LPBF manufactured 316L already surpasses the sheet metal counterparts [ 6 ] without any additional post processing. However, the fatigue properties are susceptible to lower surface quality and unfavorable defect distribution of the LPBF printed material.…”

“…From a material perspective, austenitic stainless steel 316L is one of the most prominent materials currently utilized in the AM sector and the microstructure of the laser powder bed fusion (LPBF) manufactured 316L has been widely studied [ 4 , 5 ]. The results have showed that the mechanical properties of the LPBF manufactured material in terms of the strength exceed the properties of traditionally manufactured peers [ 6 ]. However, the typical trade-off between the strength and ductility must be noted.…”

Fatigue Life and Surface Quality of Laser Powder Bed Fusion Manufactured 316L Parts by Laser Heat Treatment

“…Approximately 250-300 µm wide area has changed to a structure consisting of cellular grains and columnar dendrites. The average grain size is much larger than of the printed substructure and is very similar to the structure of a laser weld in a LPBF manufactured 316L [12]. Furthermore, the near surface area has a very fine structure and grain coarsening can be evidenced when moving deeper into the material.…”

Laser welding of additively manufactured parts - A review

“…The study found that build orientation had no significant impact on joint strength and concluded that laser welding can be used to successfully join PBF-LB/M/316L components; however, the lower mechanical properties of the joints in comparison to the base metal must be considered in the final application. The effect of heat treatment on the joints of PBF-LB/M/316L to sheet metal 316L was examined by Rautio et al [27]. The stress-relieving heat treatment (600ºC followed by 2 h annealing) performed after and before welding resulted in no significant changes in the hardness of the joint between PBF-LB/M/316L and sheet metal 316L.…”