Microstructure and Tribological Properties of Electroless Ni-P Alloy Coating on Phenolic Plastic Substrate

Electroless Ni-P alloy coatings are deposited on phenolic plastic substrates. The effects of reaction temperature (80~95 ℃) on the surface morphology, the microstructure and the composition of Ni-P alloy coating are studied by using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy, while their internal stress and the hardness are measured using laser bending and microindentation. Under dry condition the tribological property of Ni-P coating is investigated on a M-2000 block-on-ring wear tester, and the wear mechanism is analyzed. The results show that increasing reaction temperature decreases phosphorus content of Ni-P coating and prompts the transformation from amorphous to nanocrystalline. Additionally, the grain grows, the roughness and hardness increase with increasing temperature. The internal stress changes from compressive stress to tensile stress, and gradually increases. The wear resistance of phenolic plastic is obviously enhanced by Ni-P alloy coating. The hardness and many other factors, e.g. internal stress and microstructure, determine the wear resistance of Ni-P alloy coating. Ni-P alloy coating prepared at 92 ℃ show the highest wear resistance. The wear mechanism changes gradually from mild adhesive wear to severe adhesive wear and then to brittle pullout.