Effect of surfactant on the electrodeposition and wear resistance of Ni-Al_2O_3 composite coatings

摘要

Ni-Al_2O_3 composite coatings were electrodeposited from a Watts-type bath containing particles in suspension, which were dispersed with the aid of a cationic surfactant hexadecylpyridinium bromide (HPB). The effects of the surfactant on the zeta potential, co-deposition and distribution of Al_2O_3 particles in nickel matrix, and tribological properties of composite coatings were investigated. Experimental results showed that the addition of HPB could improve the amount of co-deposited Al_2O_3 particles, reduce the agglomeration of particles and achieve a more uniform distribution of Al_2O_3 particles in the nickel matrix. The wear resistance of the composite coatings increased with increasing concentration of HPB up to a certain optimum of 150 mg l~(-1), beyond which a decreasing trend of wear resistance was observed under dry sliding and oil-lubricated conditions. This is probably due to the increased brittleness of metal matrix when the concentration of surfactant exceeded the optimum.