Enhancing the single-track deposition quality of AISI 308L wire arc additive manufacturing via process optimization and cold forging treatment

Wire arc additive manufacturing (WAAM) has been established as a promising additive manufacturing technique for fabricating and repairing medium-to-large scale metallic engineering parts. However, achieving an excellent geometrical accuracy and high mechanical properties close to the parent metal require an optimal setting of parameters for every material system and, sometimes, post-processing treatment. In this work, WAAM of 308L stainless steel was performed, using gas metal arc welding as the heat source, at varying values of wire feed rate (WFR) and traverse speed (TS) to investigate its effects on the geometry, microstructure and mechanical properties of the deposited track. Thereafter, post-cold forging treatment was performed on the track deposited at the optimum parametric setting. The track width and height decreased with increasing TS due to reduction in the wire deposition volume per unit length of track. The track height increased as the WFR increased from 61.67 to 95 mm/s, after which the process became unstable, leading to a decline in height. The microstructure of the deposited track mainly comprised delta-ferrite and austenite phases while the hardness of the track deposits (ranging between 124-172 HV) was largely influenced by the presence of carbide precipitates and equiaxed grains size which reduced as the TS and WFR increased. The post-cold forging treatment resulted in strain hardening, which resulted in significant improvement in the track hardness (up to 219 HV) but a fall in its impact strength due to loss of ductility.