Papers by Author: Yong Xiu Wang

Abstract: Ni-diamond composite coatings are conducted by electrodepositon. The crystal structure and surface morphology of the composite coatings were examined with X-ray diffraction (XRD) and scanning electron microscopy (SEM) and the mechanism of Ni-diamond co-deposition is conducted by catholic polarization and cyclic voltammetry method. The result reveals that diamond particles are successfully embed in Ni matrix and the coatings have an amorphous structure. Cyclic voltammetry indicate that nickel deposition process is an irreversible electrode reaction and cathode polarization curve shift towards positive with the increase of scan rates. Cathodic polarization curve shows that reduction potential of nickel to shift to more negatives with the addition of complexing agent and the slope of the polarization curve is decrease; The addition of brightener and dispersant hinder the deposition of Ni2+ and promote the growth of crystal nucleus; The join of wetting agents and diamond particles have no big influence on the deposition of nickel.

Abstract: Cr-α-Al₂O₃ composite coatings were prepared by direct current deposition experiments from Cr(Ⅲ) plating bath and the thickness of composite coatings could be up to 14 μm. The obtained Cr-α-Al₂O₃ coatings and Cr coatings were characterized by means of EDS, SEM and microhardness measurement. Results revealed that Cr-α-Al₂O₃ coatings exhibit fine-grained structure with uniform surface and the highest microhardness values(692 HV) when the α-Al₂O₃ content of coatings was 15g/L, although some pores and defects are still present in the coatings. Analysis of Tafel curves indicated that the presence of α-Al₂O₃ in the Cr coatings show better features in the corrosion resistance both in H₂SO₄ and NaOH solution than those prepared from the bath without α-Al₂O₃.

Abstract: Ni-graphite composites were prepared using co-electrodeposited technique in sulfamate bath. To obtain an optimum combination of nickel and graphite in the composites with excellent performance such as wear resistance, corrosion resistance and microhardness and so on, effects of complex agents on the performances of composites were investigated in this work. The obtained Ni-graphite coatings were characterized by means of SEM, EDS and the microhardness measurement, it was revealed that Ni-graphite coating exhibit fine-grained structure with uniform surface and high microhardness values, although some pores and defects were still present in the coating. In addition, the co-electrodeposited Ni-12.16vol% graphite coatings showed considerably better performance, analysis of Tafel curves demonstrated that corrosion resistance of the coating prepared from bath containing complex agents were better than those prepared from bath without complex agents in the NaCl and HCl solution, but worse in the NaOH solution.