Influence of Ti on microstructure and strength of c-BN/ Cu–Ni–Sn–Ti composites

Abstract The c-BN grain has been brazed with Cu–Ni–Sn–Ti filler metal in vacuum at 1373 K holding for 600 s. The microstructure of the interface between c-BN grain and Cu–Ni–Sn–Ti filler metal has been studied using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS). The composition of the interface has been analyzed by X-ray diffraction analyzer (XRD). Experimental results showed that the reaction layer appeared at the interface between the c-BN grain and the filler metal. The reaction layer mainly consisted of TiN, TiB and TiB2. And the thickness of the reaction layer increases with the increase of Ti content in the filler metal. When Ti content in the filler metal exceeds 15 wt.%, microcracks form at c-BN side of the interface because of the increase of TiN, CuTi and Cu3Ti2 brittle phases and residual stresses, leading to a decrease of the tensile strength of c-BN/Cu–Ni–Sn–Ti composites. Ti content in the filler metal had obvious influence on microstructure and strength of c-BN/ Cu–Ni–Sn–Ti composites. The maximum tensile strength reached 105.1 MPa with 10 wt.% Ti content in the filler metal.