【作者】 胡伟达；

【导师】 万隆；

【作者基本信息】 湖南大学 ， 材料科学与工程， 2013， 博士

【摘要】 金刚石是目前已知硬度最高的物质，要发挥金刚石的磨削性能，通常需借助结合剂和其他辅助材料将其制备成具有一定规格、性能和用途的磨具。陶瓷结合剂金刚石磨具由于具有良好的耐热、耐水、耐油、耐酸碱以及磨具形状保持性好、磨削效率高等优点，在机械加工领域有重要的应用价值和广阔的应用前景。但在磨具制备过程中，一方面由于人造金刚石磨料抗氧化温度相对较低，陶瓷结合剂磨具烧结时易引起金刚石强度的下降；另一方面则是共价键形态的金刚石磨料表面不易被熔融态的陶瓷结合剂所润湿，造成两者间的结合力较弱，上述两方面原因都对磨具整体性能产生不利影响。针对此问题，目前常采用金刚石磨料表面涂覆硅酸盐涂层或镀覆金属的方法，来提高金刚石磨料的抗氧化性能以及与陶瓷结合剂的结合强度。鉴于溶胶凝胶法在材料制备方面所展示的特点，本研究工作采用该方法制备低熔、高强和流动性较好的Na₂O-B₂O₃-Al₂O₃-SiO₂系陶瓷结合剂以及对金刚石磨料表面涂覆TiO₂/Al₂O₃薄膜，并将所制结合剂和经表面涂膜改性的金刚石磨料混合后制备成砂轮用于硬质合金（YG8）轴承内圆的磨削；最后采用溶胶喷雾干燥工艺制备轴承内圆抛光磨削用的陶瓷结合剂金刚石微粉砂轮。主要研究结果如下所示：（1）基于溶胶凝胶法，制备组分摩尔比Na₂O:B₂O₃:Al₂O₃:SiO₂=7.0:13.5:9.5:70.0的陶瓷结合剂，探讨了制备工艺参数对结合剂性能的影响。分析检测表明：结合剂的玻璃结构随温度的升高发生改变，在800℃时，结合剂玻璃相中有SiO₂晶体析出；计算求得溶胶凝胶法所制结合剂烧结激活能为99.991kJ/mol，小于玻璃熔炼法以及矿物混合法所制结合剂的激活能；结合剂的耐火度、玻璃转化温度等随Li₂O和K₂O量的增加而降低，流动性和热膨胀系数则增大；当Li₂O和K₂O添加量分别为2mol%时，结合剂抗弯强度较初始结合剂有小幅提高，并且结合剂随Li₂O量的增多析晶能力增强。（2）研究了采用溶胶凝胶法在金刚石表面涂覆TiO₂/Al₂O₃薄膜的方法，分析了TiO₂/Al₂O₃薄膜对金刚石性能改善的影响。结果表明：TiO₂/Al₂O₃薄膜晶相组成主要为锐钛矿、金红石、Al₂TiO₅及γ-Al₂O₃；推断出金刚石与TiO₂/Al₂O₃薄膜间以Ti-O-C化学键连接，TiO₂与Al₂O₃薄膜间则以Ti-O-Al化学键连接；涂膜后金刚石抗氧化温度较未涂膜金刚石有所提高，且涂膜金刚石经高温热处理后抗压强度和抗冲击强度仍保持较好；TiO₂/Al₂O₃薄膜改善了金刚石的亲水性以及高温条件下与陶瓷结合剂的润湿性，通过表面张力计算求得金刚石涂膜后烧结过程中陶瓷结合剂与金刚石固液界面张力γ_sl从65.7mJ·m^-2降低到44.2mJ·m^-2；能谱分析说明TiO₂/Al₂O₃薄膜在烧结过程中通过扩散作用与陶瓷结合剂达到相互熔合。（3）采用溶胶凝胶法所制Li₂O-Na₂O-B₂O₃-Al₂O₃-SiO₂陶瓷结合剂与金刚石磨料（RVD140/170#）混合后制备成砂轮，并对硬质合金轴承内圆进行磨削。结果表明，在结合剂相同含量的条件下，涂覆TiO₂/Al₂O₃薄膜金刚石磨料所制砂轮的抗弯强度和硬度均高于未涂膜金刚石磨料砂轮；实际生产中使用的电镀金刚石砂轮在磨削轴承内圆的圆度、粗糙度以及磨削效率等方面要略好于本研究所制备的陶瓷结合剂金刚石砂轮；但在磨削工件数以及经济效益等方面，则陶瓷结合剂金刚石砂轮要优于电镀金刚石砂轮。（4）分析了常规制备方法和溶胶喷雾干燥方法对金刚石微粉与陶瓷结合剂的混合物料及所制砂轮组织结构的区别，检测结果表明，在相同结合剂含量条件下，溶胶喷雾干燥方法所制砂轮的抗弯强度和硬度都高于常规方法所制砂轮。通过对硬质合金轴承内圆的磨削实验，结果表明，溶胶喷雾干燥方法所制砂轮较常规方法所制砂轮磨削表面粗糙度低；与工厂实际使用的陶瓷结合剂绿碳化硅微粉砂轮相比，溶胶喷雾干燥方法所制金刚石微粉砂轮在磨削效率以及工件表面粗糙度等指标上都优于绿碳化硅砂轮。更多还原

【Abstract】 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.更多还原