PREPARATION AND PROPERTIES OF NANO-TiO2-Ni-P COMPOSITE COATING

Nanometer-sized TiO2 particle-reinforced nickel-phosphorus matrix composite(TiO2-Ni-P) coatings were prepared by electroless deposition.Influences of pH value and temperature on deposition rate and effects of various surfactants on hardness of the coating were investigated.Optimum formula was obtained.It is found that the hardness of the composite coatings after the plating and heat treatments at various temperatures were higher than that of the Ni-P alloy coatings.Chemical analysis showed that the content of TiO2 particles was 2.14mass%.XRD analysis showed that the structure of the composite coating changed from amorphous to crystalline,and nickel phosphide(Ni3P) precipitated after heat treatment at 400℃ for 1h.The hardness of the composite coatings after heat treatment was as high as HV1100.The open-circuit potentials of alloy coating and composite coating in 3.5% NaCl were close and higher than that of the substrate Fe.