microstructural evolution during gas metal arc welding of cantor cocrfemnni high entropy alloy and 304 austenitic stainless steel

This study investigates the microstructural evolution during gas metal arc welding (gmaw) of dissimilar joints between cocrfemnni high-entropy alloy (hea) and aisi 304 stainless steel using er316l filler wire, under varying heat inputs (0.19 vs. 0.40 kj/mm). optical microscopy, fe-sem/eds, xrd, and calphad thermodynamic calculations were employed. results show that low heat input produced an asymmetric joint with incomplete penetration and a sharp, unmixed zone at the 304ss interface, yielding a fusion zone dominated by fcc austenite with minor δ-ferrite. in contrast, high heat input achieved full penetration but caused underfill on the hea side and significantly altered weld metal composition, increasing mo content from 2.37 wt.% to 20.48 wt.% due to enhanced dilution. this high-mo composition thermodynamically stabilized brittle intermetallic phases, as confirmed by xrd which identified σ-phase and an ordered co₀.₇₂fe₀.₂₈ compound alongside fcc and bcc phases in the high heat input joint. the σ-phase, measuring approximately 40.2 at.% cr, 38.3 at.% fe, and 21.5 at.% mn, formed in the haz due to slower cooling rates. it is concluded that low heat input gmaw with er316l filler suppresses detrimental phase formation, promoting a predominantly austenitic microstructure, while high heat input, though improving mixing, promotes extensive σ-phase formation that is detrimental to joint integrity.