Static Properties and Fatigue Strength of Wire Arc Additive Manufactured 316L

Abstract

The use of direct energy deposition (DED) has become much more common recently and in the future the DED technology will be used even more widely. Wire arc additive manufacturing (WAAM) technology has become much more widespread because it can be done cost-effectively with normal cold metal transfer (CMT) welding equipment. There is still a lack of information on the fatigue strength of parts made with different welding wires. This paper focuses on the mechanical properties of AISI 316L WAAM printed parts as well as bending fatigue strength. The average microhardness values were measured along the build direction. The optical microscope and EBSD detector were used to investigate the microstructure. The tensile strength and bending fatigue strength of the WAAM printed 316L were evaluated. The EBSD investigation revealed that due to high heat input of the WAAM process, the remelting of each consecutive deposited layer caused epitaxial grain growth in the structure, leading to coarse columnar grain structure. There were no visible pores in the microstructure of the WAAM 316L. The hardness of the WAAM 316L was homogenous in the build direction. Based on tensile strength tests, the strength in the deposition direction was greater than in the build direction which is explained by the anisotropy generated in the deposition. The results revealed that the fatigue limit of the WAAM 316L is comparable to that of 316L sheet metal. The fatigue strength of the WAAM 316L was significantly higher in the high cycle fatigue regime compared to the fatigue strength of the powder bed fusion (PBF-LB) printed 316L.