Interface Bonding Between Ti-Coated CBN and Vitrified Bond

The metallization of cubic nitride boron (cBN) surface can improve the bonding between cBN and other substrates. An effective way of metallization is to coat cBN with the metal titanium. The homogeneous titanium coating on cBN surface was obtained through vacuum slow vapor deposition (VSVD) technique in this present work. X-ray diffraction (XRD) was carried out to analyze the interface structure of Ti-coated cBN deposited at the different temperatures. Ti-coated cBN composites bonded with SiO2-R2O-B2O3 vitrified bond were prepared by hot-press sintering method. The composition was investigated by the mean of electron dispersive spectrum (EDS) and the bending strengths were measured using three-point bending experiment. The results showed that the reaction between the metal Ti and cBN occurred at the deposition temperatures of 600-950DGC during depositing process. The resultant was TiN which grew on cBN surface below 800DGC but borides of titanium including TiB and TiB2 formed at above 800DGC. The coating consisting of these compounds not only protected cBN from corrosion during sintering process, but also realized the strong bonding between the cBN grit and the bond. The latter was confirmed by the result that the bending strength of Ti-coated cBN composite increased evidently in comparison with that of uncoated cBN. The theoretic calculation according to composite materials strength model showed that the interface bonding strength between cBN and the vitrified bond increased by 20 MPa owing to the coating at the deposition temperature of 800DGC.