Study On The Frictional And Wear Properties Of Electroless Ni-P Coating And Ni-P/PTFE Composite Coating

This paper expounds the reaction mechanisms of Ni-P alloy and Ni-P-PTFE composite electroless plating, and the reaction thermodynamics and dynamics are analyzed. The technology of Ni-P, Ni-P-PTFE electroless plating is discussed and optimized. In the electroless solution, the composite complexing agent, stabilizer and accelerant are applied, and the high-P amorphous Ni-P coating is gained; in Ni-P-PTFE composite electroless plating, proper amount of PTFE dispersion and composite surfactant are employed, and stable suspension system and excellent friction alleviation composite coating are gained.The composition, microstructure, microhardness, adhesive strength, porosity and corrosion-resistant property of Ni-P, Ni-P-PTFE composite electroless plating are studied with the help of modern analytical instrument, such as the scan electron microscope, the photo electron spectroscopy, and so on. By taking advantage of ball-on-disk friction and wear testing equipment, the friction and wear of Ni-P coating and Ni-P-PTFE coating are studied primarily, including friction coefficient, wear rate as well as factors which affect them, and abrade mechanism is searched preliminary.The results show that, proper confection of electroless solution composition and proper choice of technical parameters have a direct influence on the stability of plating solution and coating properties. Adding certain cationic and non-ionic combined surfactant in solution can help gain better self-lubricity composite coating. The wear resistance of Ni-P alloy coating and Ni-P-PTFE composite coating is superior to that of hardened and tempered 45# steel. The low friction coefficient makes Ni-P-PTFE a superb friction alleviation coating. The key factors that influence friction and wear of coating are heat treatment temperature, PTFE content in coating, load and sliding velocity, etc. The best heat treatment temperature of high-P amorphous Ni-P coating is 500℃1h while that of composite coating is 300℃1h+400℃15min. Ni-P-PTFE composite coating obtains better wear resistance when PTFE content reaches about 25vol%, and only under low velocity and load its wear resistance is superior to Ni-P alloy coating. Abrade mechanisms of Ni-P alloy coating are mainly adhesive wear, abrasive wear, fatigue wear and oxidative wear,while those of Ni-P-PTFE composite coating are mainly abrasive wear and fatigue wear, not including adhesive wear. Abrade mechanisms differ from one another under different velocity and load.