Impact of feed rate and arc power in wire arc additive manufacturing of AISI 308L stainless steel

In this study, the process of wire arc additive manufacturing (WAAM) by cold metal transfer (CMT) operation has been investigated for AISI 308L austenitic stainless steel. The wire feeder rate (WFR) was set between 3.5 and 7.0 m/min, while the current ranged from 72 to 115 A and the voltage from 11.1 to 12.6 V, as determined by the generator. Additionally, the robot speed was maintained at 7 mm/min for all samples. Microstructural and mechanical analyses have been conducted to improve the dilution area by considering having a different range of the width of the deposited part. Optical microscopy (OM) has been used for scanning the cross-section of the fabricated parts, and scanning electron microscopy (SEM), together with electron back scatter diffraction (EBSD), for monitoring the microstructure of the substrate, heat-affected zone (HAZ), and deposited metal. Energy-dispersive X-ray (EDX) analysis was applied to reveal the dilution area. Moreover, to link the oxidation of the peak deposition to the surface roughness, a focused ion beam (FIB) was used to remove a tiny volume of the peak surface. The results indicate that increasing the voltage and current in the WAAM process directly influences both microhardness and bead width. Microhardness reached up to 310 HV in the heat-affected zone (HAZ), while the width of the deposited bead increased from 2.9 mm at 799 W to 6.2 mm at 1449 W. Additionally, surface roughness along the deposited lines decreased with a higher wire feeder rate, with the lowest roughness recorded at 20.1 µm. Finally, FIB analysis revealed that the oxide layer was approximately 1 µm thick, with chromium penetration observed within the layer.