Effect of post-weld heat treatment (PWHT) on microstructure and corrosion behavior in ENiCrFe-7 weld overlay cladding materials

Abstract

Effect of post-weld heat treatment(as-weld, 615℃/16 h and 615℃/48 h) on microstructure and corrosion behavior in ENiCrFe-7 weld overlay cladding materials had been investigated, the results showed that the heat treatment had an obvious influence on microstructure and corrosion properties. As-weld Alloy ENiCrFe-7 exhibited to be compressive residual stress, and it had a lot of homogeneously distributed microstructure defects(e.g. composition segregation), the pits were evenly distributed on the surface of the sample after polarization, its passive current density was the least due to formation of the densest passive film. With increasing heat treatment time to 16 h, the compressive residual stress was rapidly decreased, the degree of Cr-depletion in the dendrites was obviously increased, and a large number of pits were concentrated in the Cr-depletion area. With increasing heat treatment time to 48 h, the compressive residual stress was slightly increased compared with that at heat treatment time of 16 h, both the degree of Cr-depletion in the dendrites and microstructure defects were improved, the looser passive film was formed, general corrosion was mainly performed during polarization.