Microstructure and properties of Ni + B4C/Ti coatings by high-frequency induction cladding

Abstract

To improve the microhardness and wear resistance of sucker rod steel, in situ titanium carbide (TiC)-reinforced nickel (Ni)-based alloy coatings were prepared by high-frequency induction cladding on the surface of 35CrMo steel. The surface morphologies, phase identification, microhardness, wear resistance and wear mechanism of the composite coatings were systematically analyzed. The results reveal that the in situ titanium carbide/titanium diboride (TiB2)-reinforced nickel-based composite coatings are metallurgically bonded to the substrate and the microstructures are compact and uniform without defects. The composite coatings were mainly composed of γ-nickel solid solution, Ni3Si + Ni3B dendritic eutectic structure, chromium carbides and borides. As the boron carbide + titanium powder increases, the microhardness of the composite coatings increases. The average microhardness of the nickel + 40% boron carbide/titanium composite coating is 866·7 HV, which is about 2·7 times that of 35CrMo steel. Under the same wear test conditions, the friction coefficients of the composite coatings decrease with boron carbide + titanium powder increase. Under a load of 100 N, the wear mechanisms of the composite coatings are mainly adhesive wear and abrasive wear. Under a high load of 200 N, the wear mechanisms change to brittle fracture wear, combining with abrasive and adhesive wear.