Influence of heat-treatment on the properties of electroless Ni-P-WC-BN composite coatings

Nickel - phosphorus coatings with Boron nitride (BN) and Tungsten Carbide (WC) were produced on low-carbon steel substrate by electroless deposition technique. The effect of heat-treatment on micro-structure of Ni-P-WC-BN composite coatings was investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It was shown that the phase transition from an amorphous Ni–P matrix (as-deposited electroless Ni-P-N-BN-WC composite coatings) to a mixture of polycrystalline Ni and Ni3P alloy occurred by performing heat treatments. Also, it was found that heat treatment improve hardness and wear resistance of the electroless Ni-P-BN-WC composite coatings which were evaluated by a micro-hardness tester and a pin on disc wear test apparatus. Auto-lab PGSTAT30 galvanostat / potentiostat system was used to characterize the corrosion behaviors of coatings in corrosive medium 3% sodium chloride electrolyte. It was shown that heat treatment significantly improved the corrosion properties of Ni-P-BN-WC coating