Study on creep deformation behaviour of various zones of 304HCu SS weld joint using impression creep tests

The present study investigated the creep behavior of different microstructural zones—base metal (BM), weld metal (WM), and heat-affected zone (HAZ)—in a multi-pass GTAW welded 304HCu stainless steel (SS) tube joint , fabricated using ER304HCu filler wire having higher wt% of Ni and Mn. Impression creep tests were conducted at 873–973 K under stresses ranging from 525 to 730 MPa. The BM and WM exhibited a true stress exponent of ∼5, indicating dislocation climb as the dominant creep mechanism, whereas HAZ showed a stress exponent of ∼3, suggesting dislocation glide as operating creep mechanism. Among the three zones, WM demonstrated superior creep resistance, with the BM exhibiting approximately 17.5 times higher creep velocity than WM at 923 K. The enhanced creep resistance of WM is attributed to its higher nickel content, which influences the activation energy for lattice self-diffusion. HAZ exhibited intermediate creep resistance between BM and WM. Finite element analysis of impression creep in BM revealed that plastic deformation primarily occurs in the early stages of creep. • Dislocation climb is identified as the dominant creep mechanism in both base metal and weld metal, where are dislocation glide is the creep mechanism in the HAZ. • Weld metal exhibits superior creep resistance compared to the base metal, attributed to its higher nickel content, which influences the activation energy for dislocation climb. • The FE analysis of Impression creep has shown that creep deformation occurred in two stages i.e transient and steady state creep