Wetting of molten Sn-3.5Ag-0.5Cu on Ni-P(-SiC) coatings deposited on high volume faction SiC/Al composite

The wetting of molten Sn-3.5Ag-0.5Cu alloy on the Ni-P(-SiC)coated SiCp/Al substrates was investigated by electroless Ni plating process,and the microstructures of the coating and the interfacial behavior of wetting systems were analyzed.The SiC particles are evenly distributed in the coating and enveloped with Ni.No reaction layer is observed at the coating/SiCp/Al composite interfaces.The contact angle increases from^19°with the Ni-P coating to 29°,43°and 113°with the corresponding Ni-P-3SiC,Ni-P-6SiC and Ni-P-9SiC coatings,respectively.An interaction layer containing Cu,Ni,Sn and P forms at the Sn-Ag-Cu/Ni-P-(0,3,6)SiC coated SiCp/Al interfaces,and the Cu-Ni-Sn and Ni-Sn-P phases are detected in the interaction layer.Moreover,the molten Sn-Ag-Cu can penetrate into the Ni-P(-SiC)coatings through the Ni-P/SiC interface and dissolve them to contact the SiCp/Al substrate.

Microstructure,mechanical and thermal properties of Ni-P(-SiC)coating on high volume fraction SiC_(p)/Al composite

Ni-P(-SiC)composite coatings were successfully deposited on 70 vol%SiC_(p)/Al composite by electroless plating.The surface microstructures and the phase structures of the Ni-P(-SiC)coatings were examined and analyzed by scanning electron microscopy(SEM)and X-ray diffraction(XRD)before and after heat-treatment at200-400℃for 2 h.The thermal diffusivity of the deposited samples and the interface adhesion between the coating and the substrate were investigated.The experimental results show that SiC content in the coatings increases obviously and XRD peaks are enhanced with SiC content in the bath increasing from 3 to 9 g·L^(-1).After heat-treatment,the surface of the coating becomes smoother and no diffusion layer is produced at the interface.A new phase Ni3P forms in the coating during heat-treatment at 400℃.The critical load(L_(c))of Ni-P-SiC composite coating on SiC_(p)/Al composite reaches the maximum value of 84.9 N with SiC content of 3 g·L^(-1)after heat-treatment at 200℃and more or less decreases with the increase in SiC content and heat-treatment temperature.The thermal diffusivity of deposited samples gradually increases as the temperature increases;however,it reduces firstly and then climbs with the increase in SiC content.