Mechanical properties of Inconel 718 welds performed by gas tungsten arc welding

Gas tungsten arc welding (GTAW) was used to join plates of Inconel 718. The mechanical properties were determined by tensile, microhardness, and instrumented Charpy impact tests. An ERNiFeCr-2 filler metal fed by a semi-automatic mechanism was used. Partial dissolution of the strengthening phases, γ′ and γ″, induced a soft region (~ 225 HV_1.0) in the heat-affected zone (HAZ) during welding. The yield strength (371.3 MPa) of the as-welded joint is approximately 45% of the base material in aged condition (822.7 MPa). The welds were subjected to a hardening recovery post weld heat treatment (HRPWHT). Impact testing of the hardened welds revealed a reduction of 17% in energy absorbed with respect the aged base material. Hardness measurements showed an increase to ~ 410 HV_0.1 in the fusion zone; however, due to segregation of Nb and formation of carbides, the precipitation of γ″ is not fully completed, and the yield strength (719 MPa) of the heat-treated welded joint is lower than the base material in aged condition.