Effect of cold metal transfer and gas tungsten arc welding processes on the metallurgical and mechanical properties of Inconel® 625 weldings

TLDR: Inconel® 625 weld metal has lower mechanical properties than its corresponding annealed base metal due to the precipitation of brittle phases during solidification, and a reduction in heat input and amount of iron and silicon in the weld metal and an increase in the cooling rate are proposed.

Abstract: Inconel® 625 weld metal has lower mechanical properties than its corresponding annealed base metal due to the precipitation of brittle phases during solidification. To control the precipitation of these phases, a reduction in heat input and amount of iron and silicon in the weld metal and an increase in the cooling rate are proposed. Cold metal transfer (CMT)–gas metal arc welding (GMAW) is a process that digitally controls filler metal transfer to the weld, which reduces the heat input and dilution ratio. In this work, weldments of 2-mm-thick Alloy 625 sheets were prepared using CMT and gas tungsten arc welding (GTAW) process to compare the mechanical properties (tensile and stress-controlled fatigue life tests) of the welded joints. An increment in the tensile properties and fatigue life of CMT welds was found when compared with the GTAW welds. Microstructure characterization, grain size in the heat-affected zone, phase content in the weld metal, secondary arm spacing, and Vickers hardness measurements were performed to establish the causes of the observed differences. This result was a consequence of the lower dilution of the base metal and amount of particles in the weld metal produced by a lower heat input supplied by CMT.