Characterization of Microstructure, Tensile Strength and Corrosion Behavior of Autogenous GTA Welds of Inconel X750 With and Without Activated Compound Flux

Abstract

In the present study, an attempt has been made to join 5-mm-thick plates of Inconel X750 using autogenous tungsten inert gas (TIG) welds without and with the use of activated compound flux mixture that contains 50%SiO2 + 25%TiO2 + 25%MoO3. The welded coupons were subjected to direct aging at 705 °C for 22 h. The interfacial and fusion zone microstructures were compared for both as-welded and direct aged coupons. It is assimilated that the fusion zone is enriched with Cr23C6 at the grain boundaries along with polygonal γ′ precipitates upon direct aging. Tensile studies show the fact that the fractures occur at the fusion zones of the joints both in as-welded and direct aged conditions. The joint strengths of the autogenous TIG weldments without and with flux addition were reported as 946 and 1162 MPa in the directly aged conditions, respectively. Studies also attested that there is an increase in the tensile strength by 54% of the autogenous weldment employing compound flux upon direct aging compared to as-welded conditions. Further, the fusion zones of both the conditions and the parent metal were subjected to 3.5%NaCl environment. Potentiodynamic polarization plots clearly envisaged that the fusion zone in the directly aged condition exhibits better corrosion resistance than that of the as-welded ones.