Microstructure and properties of Inconel 625 alloy in CMT forming repaired layers on the surface of C422 steel

Objective The aim is to evaluate influence of Inconel 625 solid solution-strengthened nickel-based superalloy as a repair material on microstructure evolution, microhardness and corrosion resistance of Cr12NiWMoV (C422) steel surface repaired by cold metal transfer (CMT) forming process. Furthermore, the correlation mechanism between its microstructural characteristics and properties is revealed. Methods An Inconel 625 cladding layer was deposited onto the surface of C422 steel by CMT process. Microstructure, phase constituents, and localized electrochemical behavior of the repaired layer were systematically characterized by optical microscopy, scanning electron microscopy, and scanning vibrating electrode technique. Meanwhile, microhardness testing was performed across different regions to assess mechanical performance, and comparative corrosion resistance was evaluated between cladding layer and base material. Results The results show that there are no defects such as cracks and poor fusion in the repaired specimen. The dendrites in cladding layer are fine and typical column grains of epitaxial growth. Between γ-Ni dendrites are discrete aggregates of fine MC-type carbides and flocculent Laves phases. Diffuse distribution of MC carbides in heat-affected zone results in its hardness (340 HV0.3) being higher than that of base material and the repaired zone. Corrosion resistance of cladding layer is superior to that of base material, which improves the overall corrosion resistance of the repaired specimen. Conclusion Inconel 625 applied via CMT process enables high-quality surface repair of C422 steel, yielding a dense cladding layer with uniform hardness and superior corrosion resistance. This study provides theoretical and practical guidance for the application of Inconel 625 in the surface repair of die steels and remanufacturing of components exposed to high-temperature service environments.