The microstructure and three-point bending behavior of Ni-Co/WC composite cladding coating

Ni-Co/WC composite coating was fabricated on ZG45 steel substrate through vacuum sintering cladding technology. Its microstructure, composition, and three-point bending behavior were analyzed through scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and mechanical testing. Results show that the distribution of WC particles presents a 3D net-like shape. A metallurgical fusion area is observed at the interface between the composite coating and the substrate. The entire coating consists of a composite coating area, a transition area, and a diffusion fusion area. The main phases of the coating are WC, Cr7C3, Cr23C6, Ni3Si, FeNi3, and Ni-Co solid solution. Three-point bending results reveal that the softness coefficient of the whole sample when the composite coating was in a compressive stress state was larger than that when the composite coating was in a tensile stress state. The bending strength of the sample is 520 MPa when the composite coating is in a compressive stress state. This value is 66% higher than that when the composite coating is located at the bottom. The cracks simultaneously extend to the substrate and interface when the composite coating was in a compressive stress state and to the substrate when the composite coating was in a tensile stress state. The fracture of the composite area is brittle, and the substrate fracture is ductile.