Deposition effects and interface structure of HVOF-sprayed multimodal WC-CoCr coatings

The deposition behavior of WC-CoCr powder, microstructure, hardness and fracture toughness of the coating were examined. The splats and coatings were deposited on the surface of the Q235 steel by high-velocity oxygen-fuel spraying (HVOF). The multimodal WC-CoCr powders contained three sizes of WC particles of 1.5, 0.8 and 0.3 μm, with mass fractions of 15, 66 and 5%, respectively. The splats spread on the surface of substrate in wafer type and bubble-like type. The diffusion of the Fe, Cr and Co elements and depression deformation occurred near the interface between the splats and substrate. Fine grains were observed in the substrate near the interface. The main phases in the coating are WC, W 2 C and Co 3 W 3 C. In addition, the microhardness of the coating is above 1000 HV0.3. The variation in microhardness is only 215.7 HV0.3. The fracture toughness of the coating is 4.45 MPa·m 1/2 . Graphical abstract