Investigation on the Effect of Post Weld Heat Treatment Temperature on Stress Corrosion Resistance of Inconel 625 Cladded on AISI 4130 Steel Using Hot Wire GTAW

In this research the effect of heat treatment offer welding (PWHT) in 650,750 and 8500C for two hours on Sulfide stress corrosion cracking resistance (SSC), welding metal Inconel 625 to low alloy steel 4130 was analyzed that was welded using Automatic TIG welding process then the mechanical properties of the joint was observed using micro hardness measure experiment (weld metal, base metal and the welding heat-affected zone) and welding metal structure using light microscopy, electron SEM(EDX), also XRD. The comparison of the microstructure in different temperatures show the least effect on microstructure in 6500C. In micro hardness measure test after post-weld heat treatment (PWHT) with increasing temperature we observed decreasing hardness of base metal and heat-effected zon and alsoincreasing weld metal micro hardness. when the temperature of post-weld heat treatment reached to 8500C phase γ" changed quickly to delta phase δ.when temperature reached to 8500C secondary phases changed to needle form. After stress testing in Sulfide environment magnetic particles (MT) was done on the samples and results showed that in the post-weld heat treatment sample 8500C tension crack is made. Pictures of stress testing(SSC) SEM sample shows that tension cracks mode is base metal cracks along the grain boundaries and it also extends the base metal to weld metal.