Effect of activating fluxes on the geometry, hardness, and microstructure of 316L stainless steel in GMAW

Activating fluxes (AF) can be applied in the welding process to improve the morphology, microstructure, and mechanical properties, such as hardness, tensile strength, and yield strength. Regarding the published research on AF application in Tungsten Inert Gas (TIG) welding, there are limited studies concerning the Gas Metal Arc Welding (GMAW) process. This gap in research has prompted investigations aimed at determining the influence of AF during the GMAW process. The purpose of this paper is to apply three types of AF (SiO₂, TiO₂, and CaCO₃) in 316L stainless steel GMAW processing and analyze their influence on the weld bead geometry, hardness, and microstructure. The results showed that the highest penetration and the smallest width can be obtained using TiO₂ as AF while the highest reinforcement can be obtained by CaCO₃ as AF. This also indicated a possible significant increase in AF addition after-welding hardness, which may be caused due to the microstructure changes. The microstructure observation revealed that the welding area without AF was mainly composed of austenite and the addition of AF increased the welding temperature, which caused the martensite structure to be found in these samples. The heat treatment was introduced to reduce the hardness since large and uneven hardness would bring negative consequences such as brittleness. The after-HT analysis showed that HT can reduce the hardness effectively and improve the uniformity of the whole weld bead. Additionally, it was found that samples with AF were more sensitive to HT. This study concludes that AF can be applied in the GMAW welding process and influence the weld bead significantly.