Sliding wear resistance enhancement by controlling W2C precipitation in HVOF sprayed WC-based cermet coating

Abstract

A unique method based on reactions between WC and Co-W-C phases was developed for controllable precipitation of W2C/W in thermal sprayed WC-Co coatings. With the increase in amount of the ultrafine precipitates, it is surprising to find that the wear rate of the prepared WC-based coatings drastically decreased by nearly 6 times before an obvious rise, and the wear mechanism gradually changes from abrasive wear in a ploughing mode to brittle fracture at surface microcracks because of the reduction in plasticity and fracture toughness. FEM modeling results indicate that inhomogeneous W2C distribution is more likely to cause localized stress concentration of coating, especially at the Co binder around which there are few W2C particles. Instead, an appropriate amount of evenly dispersed W2C can act as transitional sites to reduce the shear stress gradient between WC and Co binder, thus decreasing the plastic deformation, fatigue fracture and ploughing wear of the cermet coating.