Synthesis And Mechanical Properties Of Ni-P Nano-composite Coatings Reinforced By Small Al₂O₃ Nano-Particles

With the debelopment of the electroless plating technology, to make the equipments meet the severe service requirement, the eletroless plating has been developed from the single coating, to the composite coating, and to the nano-particle composite coating. The nano-particle composite plating technology is used for preparing the composite coating with the distinctive anti-wear performance.The Ni-P/α-Al₂O₃ and Ni-P/γ-Al₂O₃ nanocomposite coatings were prepared by electroless deposition with embedded nanometer-sizedα-Al₂O₃ andγ-Al₂O₃ particles, and then heat treated in vacuum. The phase structure, surface morphology and element distribution of nano-coatings were examined by means of XRD, SEM, EPMA. The micro-hardness, tribological properties and corrosion resistance were investigated and compared with Ni-P coating.In comparison to the conventional Ni-P coating, the co-deposited nano-coatings are still amorphous, and possess higher micro-hardness. Because of the steady chemical properties of the (α-Al₂O₃ particles, and the flocculent structure of theγ-Al₂O₃ particles which can be dissolved in acid and alkali, (α-Al₂O₃ make the coatings have a higher wear-resisting property and corrosion resistance whileγ-Al₂O₃ particles make them lower. All of these three coatings are heat treated at 200℃, 400℃and 600℃for 1 hour in vacuum. After that, the three coatings crystallization obviously, Ni₃P appeared. The heat treated improves the micro-hardness and tribological properties of the Ni-P/α-Al₂O₃ coatings., 200℃the coatings catch the best properties. While the heat treatment cannot better the wear resistance of Ni-P/γ-Al₂O₃ nanocomposite.