Characteristics of electro-co-deposited Ni-Al2O3 nano-particle reinforced metal matrix composite (MMC) coatings

In the present work, Ni/Al2O3 metal matrix composite (MMC) coatings were prepared from a modified Watt's type electrolyte containing nano-alpha-Al2O3 particles by direct current (DC) plating method to increase the surface hardness and wear resistance of the electrode posited Ni. For these purposes, particle concentration in electrolyte, the effect of surfactant concentration, current density, and bath pH, etc. were investigated for optimization to obtain high quality coatings. Al2O3 nano-powders with average particle size of 80 nm were co-deposited with nickel matrix on the steel substrates. The depositions were controlled to obtain specific thickness (between 50 and 200 mu m) and particle volume fraction in the matrix (between 0.03 and 0.12). The characterization of the coatings was investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) facilities. The hardness of the resultant coatings was also measured and found to be 280-641 Hv depending on the particle volume in the Ni matrix. The effects of the surfactant on the zeta potential, co-deposition, and distribution of Al2O3 particles in nickel matrix, and tribological properties of composite coatings were investigated. The results showed that the wear resistance of the nano-composites was approximately 2-3.5 times increased compared with unreinforced Ni deposited material. (C) 2009 Elsevier B.V. All rights reserved.