Experimental investigations on the multi-layered SS316L wall fabricated by CMT-based WAAM: Mechanical and microstructural studies

Abstract

In this research work, the cold metal transfer (CMT)-based wire-arc additive manufacturing (WAAM) process was used to fabricate a multi-layered wall using SS316L wire electrode. The wall was built with optimised CMT-WAAM parameters derived from a multi-variable regression analysis. The mechanical and microstructural characteristics of the multilayered wall were studied at the bottom, middle, and top regions. The macrostructure in all three regions of the wall indicates that the layers have completely fused together. The optical micrograph displays fine equi-axed dendrites in the bottom region, columnar grains with residual δ-ferrite in the middle region, and columnar dendritic structure in the top region. The tensile and impact test values of the bottom, middle, and top regions of the wall show that the values are comparable to their wrought counterparts. It was observed that the hardness value decreased with an increase in the build height. Scanning electron microscopy (SEM) analysis of the fractured surfaces of the tensile and impact test specimens showed dimples, indicating high ductility of the as-built wall and successful fabrication.