Structure and Mechanical Properties of Ni-P-Nano Al2O3 Composite Coatings Synthesized by Electroless Plating

Ni-P-nano Al2O3 composite coatings were deposited by electroless plating, and their microstructures were observed by SEM (scanning electron microscope). The microhardness and the wear resistance of the Ni-P-nano Al2O3 composite coatings were measured using microhardness tester and block-on-ring tribometer, respectively, and the comparison with those of Ni-P coatings or Ni-P-micro Al2O3 coating was given. The influences of aging temperature on their hardness and wear resistance were analyzed. The results showed that the nano Al2O3 particles were distributed uniformly in the Ni-P-Al2O3 coatings. Among three kinds of Ni-P based coatings, the hardness and wear resistance of Ni-P-nano Al2O3 coatings were largest, and the maximum values could be obtained at 400 °C. This indicated that the precipitation of nano Al2O3 particles would improve the hardness and wear resistance of the Ni-P coatings.