A novel electroless plating of Ni-P-Al-ZrO2 nanocomposite coatings and their properties

The wear performance of electroless deposited Ni-P-Al-ZrO2 nanocomposite coatings on mild steel was studied. Nanosized aluminium-zirconium composites were first prepared by mechanical alloying in a high energy planetary ball mill for different extents of time (5, 10, 20, 30, 40 and 50 h). The 50 h milled Al+ZrO2 powder was then used as the second phase (4 g/L) for the development of electroless Ni-P-Al-ZrO2 nanocomposite coatings using alkaline bath. The phases, size, morphology of 50 h milled Al+ZrO2 nanopowder and Ni-P-Al-ZrO2 nanocomposite coatings were determined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) respectively. These coatings were heat treated at 400 °C for 1 h in argon atmosphere. Wear resistance of coatings was measured by the ball on disc method at different loads (1 N, 1.5 N, 2 N) and velocities (0.1, 0.2 m/s). Microhardness, wear and friction studies of all heat-treated coatings were investigated and compared with Ni-P coatings. The results show that the Al+ZrO2 nanopowder milled for 50 h shows unevenly sphericsl shape with particle size ranges from 30 to 40 nm. The microhardness and wear resistance of the nanocomposite coatings are improved as compared to Ni-P coatings. Hardness and wear resistance of the nanocomposite coatings further enhances on heat treatment.