Interface characteristics and mechanical properties of wire-arc depositing Inconel 625 superalloy on ductile cast iron

To improve the surface properties of ductile cast iron, nickel-based superalloy was deposited on QT500–7 ductile iron by cold metal transition welding process. Effects of heat input on microstructure and interfacial characteristics of Inconel 625 deposit layers were investigated. Results showed that a good metallurgical bonding between Inconel 625 deposit layer and ductile iron could be achieved. Crystalline morphology of the deposited layer from fusion line to upper was cellular crystal, columnar dendrite, and equiaxed crystal in sequence. As dilution rate increased, carbon content of deposited layers was significantly higher than that of Inconel 625 alloy, and large amount of (Mo, Nb)-rich carbides embedded in Ni-rich solid solution dendrites. Graphite in the fusion zone was completely dissolved, and its microstructure was mainly γ-(Fe, Ni) and net carbides, while partial melted zone (PMZ) was ledeburite, martensite and incompletely dissolved graphite. Microhardness of deposited layer was higher than that of ductile iron. The shearing specimen were all fractured in the PMZ, and the interfacial bonding strength was higher than 400 MPa with a brittle-ductile mixed rupture.