Interface characteristics and properties of nickel-based alloy coatings on cast iron fabricated by plasma and cold metal transfer wire-arc deposition

Nickel-based alloy deposition on cast iron surfaces is beneficial to improve wear and corrosion resistance and increase service life. In this paper, Inconel 625 nickel-based alloy on gray cast iron was wire-arc deposited by cold metal transfer process (CMTP) and plasma arc welding process (PAWP). The forming characteristics, microstructure, and interface behaviors of CMT and PAW deposits are comparatively studied. The results show that dilution rate of PAW deposited layers is significantly larger than that of CMT, and the latter interface presents “diffusion-metallurgical” bonding. Microstructure of CMT deposited layer is γ-Ni dendrite with (Nb, Mo) carbides distributed at the grain boundaries, and that of PAW deposited layer is a γ-(Fe, Ni) dendrite with eutectic carbides with complex morphology. The lamellar graphite near the interface is completely dissolved, and the microstructure is mainly ledeburite. CMT-deposited specimens exhibited significant cold cracking due to the inhomogeneous distribution of brittle high-carbon martensite and lamellar graphite in the partial melting zone and heat affected zone. Microhardness of PAW deposited layer was greater than that of CMT deposits, and the shear fracture near the interface of PAW and CMT samples presented intergranular fracture.