Microstructure and mechanical properties of electroless Ni–P–Si3N4–TiN composite coatings

A high performance electroless Ni–P–Si3N4–TiN multi-nanocomposite coating was prepared on the surface of AZ31 Mg alloy. The results showed that the surface morphology of this multi-nanocomposite coating exhibits a uniform nodular structure, and the nodular size decreases clearly while increasing TiN nanoparticle concentrations to 2 g/L in the bath, resulting in the finest size of approximately 3 μm. Furthermore, the incorporation of TiN nanoparticles and Si3N4 nanowires into the Ni–P matrix can significantly enhance the microhardness and reduce the friction coefficient of the multi-nanocomposite coatings. The maximum hardness value of 921.4 HV200 and lowest friction coefficient of 0.54 as well as minimum wear weight loss of 0.7 mg can be also reached at a TiN nanoparticle concentration of 2 g/L.