Effect of process parameters on bead geometry and microstructure of the stainless steel fabricated by wire arc additive manufacturing

The selection of appropriate wire arc additive manufacturing (WAAM) parameters is crucial for controlling bead morphology and dimensional accuracy in multi-layer metallic structures. This study investigates cold metal transfer (CMT)-based WAAM of 316 L stainless steel with a particular focus on two key process variables—deposition current and auxiliary wire feed speed—to establish their combined influence on bead geometry and microstructure. Unlike existing AWF-CMT WAAM studies, this work first determines the maximum stable arc travel speed for both T-CMT and AWF-CMT modes , providing an essential process boundary for high-efficiency manufacturing. Single-layer tracks were fabricated using S316L wire following an orthogonal experimental design, enabling a systematic evaluation of parameter interactions. The results reveal that arc travel speed, deposition current, and auxiliary wire feed speed exert strong coupled effects on bead width and height. Furthermore, microstructural characterization using optical microscopy and electron backscatter diffraction demonstrates that auxiliary-wire-assisted CMT produces significant quantitative grain refinement , the T-CMT deposits exhibit a relatively coarser grain structure, whereas the AWF-CMT process produces a more refined and more uniform microstructure in the deposited region , reducing the average grain size from 130μm (T-CMT) to 86μm(AWF-CMT). This study therefore establishes a new process–structure relationship for AWF-CMT WAAM and demonstrates that 316 L components manufactured with this technique exhibit markedly improved microstructural quality, confirming its suitability for industrial deployment.