A novel electroless plating of Ni-P-TiO2 nano-composite coatings

A new processing concept has been developed to produce nano-structured metal-matrix composite coatings. This method combines sol-gel and electroless plating techniques to prepare highly dispersive oxide nano-particle reinforced composite coatings. Transparent TiO2 sol was added into the standard electroless plated Ni-P solution at a controlled rate to produce Ni-P-TiO2 nano-composite coatings on Mg alloys. The coating was found to have a crystalline structure. The nano-sized TiO2 particles (similar to 15 nm) were well dispersed into the Ni-P coating matrix during the co-deposition process. This technique can effectively avoid the agglomeration of nano-particles in the coating matrix. As a result, the microhardness of the composite coatings were significantly increased to similar to 1025 HV200 compared to similar to 710 HV200 of the conventional composite coatings produced with solid particle mixing methods. Correspondingly, the wear resistance of the new composite coatings was also greatly improved. (C) 2010 Elsevier B.V. All rights reserved.