Description:
The thick nickel-phosphorus plating is deposited on the surface of SiCp/Al composite through electroless plating. Double zincate treatment can improve the adhesion between the coating and the substrate. High thickness (178μm) coatings were obtained after 12h of plating at 88℃. SEM, EDS, XRD, XPS, DSC, TMA and princeton electrochemical workstation analyses were performed to investigate micro-structure morphology, chemical composition, initial crystallize temperature, the coefficient of thermal expansion(CTE) and the electrochemical corrosion of the amorphous Ni-P coatings. Surface analysis has shown the surface presents a typical cauliflower-like nodular structure and some larger nodules can be seen attached and is a typical amorphous structure with only a broad diffuse scattering peak. The coating has a continuous, uniform and dense structure with high phosphorus content, which exhibits higher hardness and excellent corrosion resistance than the substrate, and the initial crystallize temperature is about 322℃. The thermal expansion of substrate and coating follows a linear law under the crystallization temperature, and the linear thermal expansion coefficient of the coating in different directions has little difference at the same temperature. Apart from that, the growth mechanism of forming thick plating was also analyzed