Carbon nanotubes-reinforced Ni foam interlayer for brazing SiO2-BN with Ti6Al4V alloy using TiZrNiCu brazing alloy

Abstract Brazing SiO2-BN with Ti6Al4V is often associated with the problems of high residual stress and excessive Ti-based compounds formed. To overcome these problems, we report a new type interlayer of carbon nanotube (CNT) reinforced Ni foam fabricated by plasma enhanced chemical vapor deposition. The in-situ grown CNT are homogenously dispersed on 3D structure Ni foam, which could effectively avoid damage and agglomeration in the brazing seam. Result shows that Ni foam could consume excessive dissolved Ti, and CNT was beneficial for restricting the growth of phase, improving joining strength and releasing residual stress rapidly. The average shear strength of the joint brazed with CNT-Ni foam is about 50 MPa, and this value is about 5 times higher than that of joints brazed with pure TiZrNiCu. Further, a new simulated experiment was carried out innovatively to solving the difficulty of investigating interfacial behavior of CNT in brazing seam. Then the results clarify that integral structure of CNT can prevent the reaction with Ti. In situ growth of CNT on Ni foam could provide a way for introducing CNT into brazing seam without damaging structure of CNT.