Abstract
The effect of post weld heat treatment (PWHT) on microstructure and mechanical properties of deposited metal using ENiCrFe-7 covered electrode was investigated. The PWHT was conducted at 615 °C for 24 h. The results showed that three types of precipitates existed in both as-welded and PWHT deposited metals, i.e., NbC carbides, Al-Ti oxides in grains, and M23C6 carbides on grain boundaries. The M23C6 carbides coarsened after PWHT. The room temperature and elevated temperature (350 °C) tensile strength decreased by about 30 MPa, and elongation increased by about 3%–4% after PWHT. The tensile specimens presented ductile fracture feature and the dimples in PWHT condition were larger than that in as-welded condition. The hardness of deposited metal in as-welded condition was higher than that of PWHT condition. The impact toughness showed no significant change after PWHT. Both as-welded and PWHT impact specimens showed a mixed fracture mode with dominant ductile fracture and cleavage fracture.
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