Wear resistance enhancement of electroless nanocomposite coatings via incorporation of alumina nanoparticles prepared by milling

Electroless Ni–P–Al2O3 nanocomposite coatings were deposited on steel surface from a plating solution with alumina (α-Al2O3) nano-particles prepared by mechanical milling in a high energy density ceramic stirred bead mill. The size and specific surface area of the nano-sized alumina particles were determined by acoustic particle sizer and nitrogen adsorption surface area analyzer. The phase structure, morphology and elemental composition of Ni–P–Al2O3 nano-composite coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), respectively. Effect of the nanoparticle concentration in the plating bath on the micro-hardness, wear resistance and corrosion resistance of the as-deposited and the heat-treated coatings was investigated. The results show that the incorporation of alumina nanoparticles can enhance the micro-hardness and wear resistance of electroless Ni–P–Al2O3 nanocomposite coatings, but affect the corrosion resistance.