This research investigates the improvement of wear properties of thermal sprayed WC-Co coatings, considering the revision of chemical composition of binder phase. In this regard, creating a layer of electroless Ni-P on feedstock powder particles, whose thickness varied from 2, 3 to 4 micrometers around the initial powder, was proposed. At first, the temperature and pH of the electroless bath were optimized to 82-85 °C and 4.5. Then the capacity of bath was set to 40 g/L to create a coating with a thickness of no less than 1?m on the particles. The Ni-P layers around the particles were observed using an SEM and percentage of Ni-P layer was calculated using an Image Analysis. XRD results showed that the phase alteration befor and after coating revealed a small nickel peak. After preparation of powders, they were applied to the surface of steel discs and were compared to conventioned WC-12Co coatings. The XRD results show that the decomposition of wc in modified samples were reduced drastically. The prosity percentage decreased from 2.3% to 0.3% in the sample with 4 Ni-P layer thickness which had the highest hardness among the samples. Friction coefficient of modified samples in the ambient temperature was nearly 0.4 and in the elevated temperature, 700 °C, was 0.2 and its wear loss reduced. In the wear test, the high temperature of these coatings on the surface generated an adhesive film which increased the lubricant feature of the surface. Keywords Thermal spray, Electroless Ni-P, Binder phase, Wear.
