Surface Alloying Characteristics of Inconel 625 Coatings Deposited on Ductile Cast Iron by Plasma Wire-Arc Welding

Inconel 625 superalloy was deposited on the cast iron surface by plasma wire-arc welding (PWAW). The effects of the dilution rate on microstructure and interface behavior of Inconel 625 deposited coatings were investigated. The results show that the dilution rate of the deposited coatings increases from 18.55 to 67.85% with the increase of heat inputs. Good metallurgical bonding and spreading of the deposited coating interfaces could be achieved at different dilution rates. At dilution rates below 20%, the microstructure of the deposited coatings is typical of γ-Ni dendrites with (Nb, Mo)-rich carbides at grain boundaries. However, the deposited coatings are γ-(Fe, Ni) dendrites at a dilution rate exceeding 40%, and the interdendritic phase is composed of FeNiCr eutectic structure and a small amount of carbide. A partially melted zone (PMZ) mainly consists of ledeburite, martensite and unfused graphite. The microhardness of the deposited coatings increases with increasing dilution rate. The shear strength of the deposited coatings at high dilution rates is significantly larger than that at low dilution rates, and the fracture shows a brittle–ductile mixed form of rupture.