Improvement on mechanical properties and wear resistance of HVOF sprayed WC-12Co coatings by optimizing feedstock structure

WC-12Co powders with a bimodal size distributed WC particles were used to produce coating by high velocity oxy-fuel (HVOF) spraying (B coating), and HVOF sprayed WC-12Co coatings from microstructured, submicrostructured and nanostructured powders were also fabricated for comparison. The phase constitution, microstructure, mechanical properties and wear performance of the coatings were investigated. Decarburization occurred during coatings preparation, and the carbide retention of B coating was 0.934, higher than that of nanostructured coating. B coating exhibited typical multimodal microstructure, and had considerably high microhardness and the highest fracture toughness among the four coatings, with the values of 1291 HV0.1 and 10.76 MPa m1/2, respectively. When sliding against GCr15 ring in block-on-ring configuration, B coating exhibited the lowest wear rate and relatively lower friction coefficient compared with other coatings, with the average values of 0.94 × 10−7 mm3 N−1 m−1 and 0.63 at 245 N load, respectively, which could be attributed to the concrete-like structure.