Abstract: For P110 oil casing, the forming good and defect-free Inconel 625 alloy cladding layer was obtained by the cold metal transition plus pulse welding process. The composition and microstructure of the cladding layer were analyzed with the Smartzoom, Metallurgical Microscope, SEM, EDS, XRD, TEM, Carbon Sulfur Analyzer, etc. The structure of the cladding layer is columnar, dendritic, and equiaxed from the fusion line to the top of the cladding layer. The matrix is a solid solution of Ni with Laves and MC carbides distributed inside it. The cladding layer contained C and Fe diffused from the base material. The double-loop electrochemical dynamic potential reactivation method was used to study the corrosion resistance of the cladding layer, which indicates that the diffusion of C and Fe will reduce the resistance to intergranular corrosion. EBSD analysis showed that the improvement of the low-angle grain boundaries (with a grain orientation of <15^o) and Σ3ⁿ boundaries in the special high-angle grain boundaries (Σ≤29), (low Σ coincidence lattice, n=1,2,3) will improve the resistance to intergranular corrosion. The results showed that the cladding of Inconel 625 alloy with suitable process parameters can obtain a cladding layer with no obvious defects, good weld formation, and good corrosion resistance.

Key words: CMT/P welding, P110, lnconel 625 cladding, microstructure, corrosion performance