EVALUATION OF NANO-COMPOSITE COATINGS NI–P–TIO2 SYNTHESIZED BY COMBINED ELECTROLESS/SOL-GEL PROCESS

In the present study, a new process for the production of nano-structured composite coating of metal oxide has been presented. Novel electroless composite combines sol-gel and electroless plating process 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 AZ31 substrate. The coating was found to have a crystalline structure. The nano-sized TiO2 particles (∼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 micro-hardness of the composite coatings were significantly increased to∼1025 HV200 compared to∼710 HV200 of the conventional electroless coatings produced with solid particle mixing methods.