Microstructure and sulfide stress corrosion cracking of the Inconel 625/X80 weld overlay fabricated by cold metal transfer process

The use of cold metal transfer process (CMT) is an excellent alternative to depositing nickel-based alloys on oil and gas pipelines due to the relatively small dilution. However, sulfide stress corrosion cracking (SSCC) of dissimilar weld joints has proven to be an issue. Therefore, this study investigates the microstructure and SSCC behavior of an Inconel 625/X80 weld overlay fabricated CMT process focusing on the tempering effect. Four-point bending tests show a high SSCC susceptibility of the non-overlap zone due to the formation of coarse structure in the heat affected zone and narrow martensite layer along the fusion boundary. However, microstructural characterization indicates a tempering effect in the overlap zone, producing homogenized microstructure and less residual strain in the heat affected zone. Therefore, the SSCC resistance is greatly improved, especially for the fusion boundary, because reversed austenite in the martensite layer could decrease the accumulation of hydrogen at lath boundaries.