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

Abstract

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 50h). The 50h milled Al+ZrO2 powder was then used as the second phase (4g/L) for the development of electroless Ni–P–Al–ZrO2 nanocomposite coatings using alkaline bath. The phases, size, morphology of 50h 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 1h in argon atmosphere. Wear resistance of coatings was measured by the ball on disc method at different loads (1N, 1.5N, 2N) and velocities (0.1, 0.2m/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 50h shows unevenly sphericsl shape with particle size ranges from 30 to 40nm. 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.