Effects of different welding modes on microstructure and mechanical properties of 316 stainless steel by wire arc additive manufacturing

This study focused on the additive manufacturing of single-pass multi-layer thin-walled samples using 316 stainless steel. It explored three welding modes: cold metal transfer (CMT), cold metal transfer-pulse (CMT-P), and direct current-pulse (DC-P), and conducted a comparative analysis of the microstructure and mechanical properties of the samples. Under the three modes of formation, the resulting components exhibited no collapse or macroscopic porosity. The solidified structure consists predominantly of columnar dendritic crystals, along with a significant presence of secondary dendrites and cellular crystals. Upon conducting metallographic observation and utilizing electron back scatter diffraction (EBSD) technology, it was determined that the structure demonstrates a pronounced <001>//z texture. The average spacing of dendrites in the steady-state zone of the component exhibits variation based on the heat input across different welding modes, with the pattern being CMT < CMT-P < DC-P. The matrix structure was identified as γ-Fe(Cr_0.19Fe_0.7Ni_0.11) using X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) analysis, while the interstitial network structure was found to be residual δ-Fe. In CMT-P mode, the component exhibits the highest strength, characterized by a yield strength of 237 MPa, a tensile strength of 555 MPa, and an average hardness value of 209 HV0.3. In the DC-P mode, the component exhibits the highest elongation at break, reaching 52%.