Study On Preparation Vitrified Bond Diamond Grinding Wheel By Sol-gel Method

Diamond is the highest hardness of the material, so it has important applicationvalue in the industry. To exert the diamond grinding performance, it is usuallyconsolidated by the bond or other auxiliary materials to manufacture a certainspecification, property and usage of grinding tool.Because vitrified bond diamond grinding tool is good heat resistance, waterresistance, oil resistance, acid/alkali resistance, shape stability and preferablegrinding efficiency, it has important application value in grinding the functionalceramics, hard alloy, refractory materials and stone. However, during the grindingwheel manufacture, for one thing, the synthetic diamond’s oxidation temperature isusually lower than the sintering temperature, making the the diamond’s intensityreduced. For another thing, the diamond is not easy to be wetted by the fused vitrifiedbond, leading to the weak bonding force between them, so the performance ofgrinding tool is not strong. For solving these problems, it often uses the specialdiamond that is coated with silicate coating or metal coating to improve the diamondoxidation resistance and the bonding strength with vitrified bond.Considering the characteristics of the sol-gel method in material preparation, inthis study, the diamond coated with the TiO₂/Al₂O₃film and theNa₂O-B₂O₃-Al₂O₃-SiO₂system vitrified bond was prepared by sol-gel method. Thenthe grinding wheel that was prepared by the vitrified bond and the coated diamondwas applied to grind the hard alloy bearing inner round. Last the vitrified bonddiamond fine powder grinding wheel was prepared by the sol spray drying method andused to accurately grind the hard alloy bearing inner round.The main research resultswere as follows:（1）Based on the sol-gel method, the parameter influences in the performance ofvitrified bond were discussed and the mole ratio of bond components wasselected（Na₂O:B₂O₃:Al₂O₃:SiO₂=7.0:13.5:9.5:70.0）.The analysis results showed thatthe vitrified bond glass structure could be changed with the rising of temperature andthe SiO₂crystal could be crystallized in the vitrified bond at800℃. The sinteringactivation energy of vitrified bond prepared by the sol-gel method was99.991kJ/mol,less than that of the vitrified bond prepared by the glass melting and mineral mixingmethod. With the increasing amount of Li₂O or K₂O, the refractoriness and the glass transition temperature of the vitrified bond was decreasing, but the liquidity andcoefficient of thermal expansion was increasing. When the additive amount of Li₂O orK₂O was2mol%, the bending strength of the vitrified bond had a small increase andthe crystallization of vitrified bond was enhanced with the Li₂O amount increasing.（2）It was systematically studied that the diamond was coated with the TiO₂/Al₂O₃film by sol-gel method and discussed the effects of TiO₂/Al₂O₃film on the diamondperformance improvement. The results were shown that the crystal phases of theTiO₂/Al₂O₃film were anatase, rutile, Al₂TiO₅and γ-Al₂O₃. The chemical bondbetween the diamond and the TiO₂/Al₂O₃film was Ti-O-C and the chemical bondbetween the TiO₂and Al₂O₃film was Ti-O-Al. After coating TiO₂/Al₂O₃film, thediamond oxidation temperature was increased, the diamond’s compressive strengthand shock strength had maintained better than that of uncoated diamond at hightemperature. The TiO₂/Al₂O₃film could improve the hydrophilicity of diamond andalso markedly improve the wettability of fused vitrified bond on diamond surface. TheTiO₂/Al₂O₃film was fused into the vitrified bond through the diffusion effect insintering process. With the method of surface tension calculation, it was showed thatthe value ofγ_slbetween the vitrified bond and diamond was reducing from65.7mJ·m^-2to44.2mJ·m^-2.（3）The grinding wheel was prepared by the Li₂O-Na₂O-B₂O₃-Al₂O₃-SiO₂vitrifiedbond and RVD140/170#diamond. Under the same percent of vitrified bond, thebending strength and hardness of the grinding wheel prepared by the diamond coatingTiO₂/Al₂O₃film was better than that of the grinding wheel prepared by the uncoateddiamond. In grinding hard alloy bearing inner round, the qualified rate of theworkpiece processed by the coated diamond grinding wheel was better than that ofuncoated diamond grinding wheel. Compared with the plating diamond grindingwheel, the machining accuracy of the bearing inner round grinded by the platingdiamond grinding wheel was slightly better than that of vitrified bond diamondgrinding wheel, but in the grinding numbers and economic benefit, the vitrified bonddiamond grinding wheel was better than the plating diamond grinding wheel.（4）It was compared the distinction of the grinding wheel prepared by thetraditional preparation method and sol spray drying method. The test was shown that,under the same percent vitrified bond, the bending strength and hardness of thegrinding wheel with the sol spray drying process was better than that of the traditionalpreparation method. In the test of grinding bearing inner round, it was confirmed thatthe grinding surface roughness of the bearing inner round processed by the grinding wheel with the sol spray drying method was lower than that of the traditionalpreparation method.Compared with the green silicon carbide powder vitrified bondgrinding wheel, in the field of grinding efficiency and surface roughness of workpiece,the diamond grinding wheel with sol spray drying method was better than that of thegreen silicon carbide grinding wheel.