The Influence of Annealing Treatment on the Structure, Hardness and Tribological Properties of Ni-Cr Brush Plated Nanocoatings

Electric brush plating was employed to prepare Ni-Cr nanocoatings from Ni-Cr plating solution and an annealing treatment was carried out. X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy were used to analyze the surface morphology and phase structure of the coatings after annealing treatment at different temperatures. MH-5-VM type microhardness tester and CSM friction tester were used to measure the hardness and wear properties of the coating. The grain size of the coating was ranging from 10 nm to 20 nm for all annealing temperature.. At annealing temperatures lower than 500 ℃, Ni-Cr solid solution was revealed. At annealing temperatures higher than 500 ℃, Cr precipitate was observed. The variation of the wear resistance of the coating at elevated followed almost same trend as that of the microhardness. The coating which was annealed at 400 ℃ showed the highest hardness and the best wear resistance.