Electroless nickel plating process and properties of alumina ceramics

The work aims to study the effects of plating time on surface morphology, microstructure, microhardness, surface roughness and adhesion of electroless nickel plating on alumina. Plating bath composition and process parameters were as follows: NiSO4-6H2O 25 g/L, NaH2PO2H2O 22 g/L, Na3C6H5O7 · 2H2O 64 g/L, (NH4)SO4 62 g/L, pH=5.0~6.0, heating in water bath to 90 °C and plating time 1-4 h. Surface morphology of the coatings was observed by using NovaNanoSEM50 field emission scanning electron microscopy (SEM), hardness by TH765 automatic microhardness tester, surface roughness by OLS4000 3D measurement instrument and adhesion strength by thermal shock test and in indentation method. Provided with plating time of 1-4 h, the coatings exhibited good metallic glossiness and looked silvery white after 1 h, the coating was more delicate after 4 h, but the surface gloss was poor. As the deposition time prolonged, the smoother surface of nickel plating on A1203 was, the higher its microhardness would be; the electroless coatings were free from blistering, flaking or with separation from alumina matrix. Provided with the plating time of 1~4 h, unchanged temperature and pH, as the plating time prolongs, the thickness of coatings changes slightly, the coating grains are finer, microhardness increases obviously and surface roughness reduces. Also, the coating exhibits good adhesion to substrate. © 2017, Chongqing Wujiu Periodicals Press. All right reserved.