A new electroless nickel deposition technique to metallise SiC_p/Al composites

A new electroless nickel (EN) plating technique is described, which eliminates the conventional use of palladium catalyst. The paper has studied systematically the nickel activation technology and its effect on the deposition rate, as well as theoretical description of the activation and deposition processes for electroless Ni-P alloys. It has been found that the deposition rates increase and approach a maximum value with the increase in the immersion time, the temperature and time of the heat treatment during activation process. The optimal pretreatment conditions are obtained to deposit nickel on the surface of the SiC_p/Al composites reinforced with 70 vol.% fine particulate silicon carbide. The nickel activation and electroless nickel plating are investigated using SEM, EDAX and XPS. Also, microhardness, adhesion and porosity measurements are carried out to characterize the coatings. Electroless nickel layer adheres better to nickel-activated SiC_p/Al composites because nickel-substrate bonding takes place during activation and plating. The values of microhardness are enhanced after coating with nickel. A model is purposely introduced to describe the growth of catalytic centers in the active film and its effect on the deposited layer.