Wear Characteristics of Wire-Arc Additive Manufactured SS308L

Abstract

Wire arc additive manufacturing (WAAM) is an efficient metal additive manufacturing technology. It can be easily accomplished with a gas metal arc welding (GMAW)—cold metal transfer (CMT) machine due to low heat input and low spatter generation characteristics. Austenitic stainless steel (ASS 308L) single thin walls were fabricated using ER308L filler wire having 1.2 mm diameter. The wear summary of the WAAM-processed 308L ASS under dry sliding at severe loading conditions is presented. Wear tests were done under dry (unlubricated) conditions, using a typical high-load pin-on-disc tribometer. AM-ASS processed with a lower heat input exhibited a low coefficient of friction (COF) and wear-rate. The microhardness is observed to be reducing steadily from the bottom layer to the top layer along the building direction to roughly 11.73%, 10.09%, and 8.44% in low, medium, and high heat input, respectively. This is attributed to the thermal history experienced by the material. X-ray diffraction (XRD) analysis of wear debris reveals that martensite is the most prevalent phase. In the wear behavior of AM-ASS, austenite transforms into martensite due to the metastability of ASS during plastic deformation. At severe stresses, plastic deformation of sliding surfaces is more prevalent. Ferrite (%) concentration decreases with the increasing load due to increased plastic deformation, which converts austenite to martensite. As deformation wear debris rolls, it hardens, fractures, and becomes cylindrical, which confirms the adhesive wear mechanism.