Study On Brazing For SiCp/Al Composite After Electroless Nickel Plating

In this paper, first nickel was plated on SiCp/Al composites. Brazing technology of SiCp/Al composites were tested by using Al802 and N0927 two kinds of Zn-Al fluxcored brazing filler metals after nickel plating on SiCp/Al composite. The brazing technology parameters were optimized. Effect of parameters of brazing of SiCp/Al composites on the joint shear strength was studied. Moreover, the brazing behaviors of SiCp/Al composites surface modification were made a primary research. The microstructure and element dispersion of the coating, the microstructure, phase, microhardness of joint region, and the microstructure and composition of fracture were analyzed by using the equipment of microscope, SEM, EDS, XRD, micro-hardness and electronic universal testing machine.Through the optimized pre-treatment process and electroless nickel plating, a continuous, dense layer of electroless nickel plating layer can be obtained. The effect of nickel plating time on coating shows that the best time of nickel plating is 70 min. The study of coating performance shows that microstructure of the coating is cellular, binding of the coating and the substrate is good, the thickness of the coating is uniform. P content in the coating is 9.21%, belonging to medium phosphorous coating. Phase structure of coating is microcrystalline structure.SiCp/Al composites can be connected by using two kinds of brazing filler metals. First, the joint shear strength increases with the rising of the brazing temperature and the holding time, then reaches the maximum, afterwards, the joint shear strength decreases with the temperature and holding time continuously increase. The micro-hardness of joint is nearly to that of the matrix metal. With the brazing filler metal of Al802, the shearing strength of the brazed joint is 65.3MPa at 460? for 20 min. With the brazing filler metal of N0927, the shearing strength of the brazed joint is 80.5MPa at 450? for 25 min.The microstructure of the joint shows that the microstructure of welding seam of two kinds brazing filler metals is uniform without pore and crack phenomenon. The phase analysis of the brazing joint demonstrates that the welding seam mainly has ?(Al) and ?(Zn). The morphology of brazed joint fracture feature indicates that the joint can present the characteristic of toughness fracture.