Process and Property of TiO₂ Coating cBN Composite Powder Prepared by Sol-Gel Method

A layer of TiO₂ was coated on the surface of cubic boron nitride (cBN) particles by sol-gel method with anhydrous ethanol and water as dispersion medium and with tetrabutyl titanate as titanium source, and then cBN-TiO₂ composite powders were obtained. The effects of the molar ratio of anhydrous ethanol to butyl titanate and the molar ratio of cBN to butyl titanate on the coating effect were investigated. The preparation process was optimized. The oxidation resistance of cBN-TiO₂ composite powder under optimal process was studied. The results show that the surface of cBN particles was coated with a layer of dense TiO₂ uniformly when the molar ratio of anhydrous ethanol to butyl titanate was 10∶1 and the molar ratio of cubic boron nitride to butyl titanate was 1∶1, indicating the best coating effect. The initial oxidation temperature of cBN-TiO composite powder prepared under optimal process was 900 ℃, and was 220 ℃ higher than that of cBN micro powder before coating with TiO₂.