Effect of grain boundary precipitation on the mechanical integrity of EBW joints of Inconel 625

Abstract

The precipitation effects on the mechanical behavior of electron beam welded joints of Inconel 625 in the as-welded [AW] and post-weld heat treatment [PWHT] conditions have been investigated in this research study. A PWHT comprising of direct aging [DA] treatment at 700 °C for 100 h in vacuum at a pressure of 10−5 mbar was performed on the weld joints. The microstructure of the base alloy opined the precipitation of MC system carbides and γ′′ strengthening phase after subjecting to DA. Also, Nb–Mo rich precipitates and the Laves phase was noticed in the inter-dendritic arms of the fusion zone (FZ) of welded joints in the AW conditions. DA treatment has a notable effect on the weld mechanical characteristics of Inconel 625 joints. The precipitation of γ′′ strengthening phase is reasoned for the significant rise in the yield strength [YS] and tensile strength [TS] of the base alloy and EBW joints.