Influence of vacuum heat treatment on wear behavior of HVAF sprayed WC-Cr3C2–Ni coatings

WC-Cr3C2–Ni coating was deposited on SK5 steel substrate by high velocity air fuel (HVAF) spraying. The effect of vacuum heat treatment temperature on the phase composition, microstructure, microhardness and wear resistance of the coating was investigated. Inspections by scanning electron microscope (SEM) and X-ray diffraction (XRD) indicated that new phases FeW3C and Fe7W6 produced by heat treatment above 550 °C due to metallurgical reaction. When the heat treatment temperature exceeded 700 °C, typical lamellar structure disappeared, and overall uniformity of the coating was improved. The microhardness of the coatings was investigated by Vickers hardness tester and disclosed that the highest value of 1486 HV was detected in coating heat treated at 700 °C, with an increase of 15% compared to as-sprayed condition. The results from ball-on-disk wear test showed that coefficient of friction and wear rate were decreased to varying degrees after heat treatment. The coating heat treated at 700 °C had optimal wear resistance, which wear rate was 1.79 × 10−10 cm3/Nm, approximately 30% lower than as-sprayed coating. Wear equation W=6×10−7×μ/H is obtained to describe the relation between wear rate, coefficient of friction and hardness of the WC-Cr3C2–Ni coating heat treated at 550–1000 °C.