【作者】 张爱菊；

【导师】 李志宏；

【作者基本信息】 天津大学 ， 材料学， 2009， 博士

【摘要】 立方氮化硼基陶瓷复合材料以其特有的性能,在铁族元素及黑色金属材料的加工方面获得了愈来愈广泛的应用。本文系统研究了组成、原料及制备工艺对CBN基复合材料用结合剂性能和结构的影响,研究了表面处理状态对CBN材料本身性能的影响和对CBN复合材料结构性能的影响。并探索了用陶瓷结合剂CBN粉体制备微晶结构CBN磨料的工艺和磨料性能。研究结果表明:Li₂O对陶瓷结合剂耐火度降低的作用最强,其次是CaF₂、ZnO,MnO₂对耐火度的改变程度不大,而Fe₂O₃可以提高结合剂的耐火度。原料类型对陶瓷结合剂的性能具有明显影响。与氧化物原料相比,碳酸盐原料的添加可以降低陶瓷结合剂的耐火度;当添加原料的碳酸盐分解温度较低时,引入碳酸盐与引入氧化物的样品性能差别不大;当碳酸盐的分解温度在试样烧成温度附近时,碳酸盐原料向结合剂相引入气孔,使其性能下降;对比氢氧化物和碳酸盐原料,发现当氢氧化物的分解温度较低时,引入氢氧化物原料的样品性能较好。陶瓷结合剂制备工艺对其性能也有一定的影响。对于添加碳酸盐的陶瓷结合剂体系,预熔处理可以减少结合剂相中气孔的含量,提高试样的强度。对于添加氧化物的陶瓷结合剂体系,预熔处理是不必要的。对CBN磨料进行酸处理、碱处理及低温玻璃涂层处理。酸处理有利于提高CBN磨料的单颗粒抗压强度、冲击韧性及热稳定性,而碱处理使CBN磨料表面的缺陷暴露出来,降低CBN磨料的性能。选择已有的Ti镀层和刚玉涂层的CBN磨料与本实验中制备的涂覆玻璃相的CBN磨料进行对比,发现溶胶-凝胶法制备的低温玻璃涂层不仅提高CBN磨料的力学性能,还显著提高其耐热性,使其起始氧化的温度点提高了近100℃。同时玻璃涂层使CBN与陶瓷结合剂之间达到化学结合,显著改善了CBN基陶瓷复合材料的界面结合状态。以CBN超细粉为原料,以陶瓷结合剂为粘结相,采用无压烧结工艺制备出微晶CBN磨料。实验结果表明,试样结构致密、强度较高,其性能与单晶磨料接近。更多还原

【Abstract】 Owing to high hardness, high strength and the other unique properties, CBN matrix ceramic composite is becoming one of the most potential tools in modern engineering applications. In this article, effects of additives, raw materials and preparation process on the properties of vitrified bond were studied. Surface treatment of CBN abrasive and preparation of microcrystalline CBN abrasive were also researched.The results indicated that Li2O was the most excellent element for decreasing refractoriness, and the following were CaF2 and ZnO. No obvious decreasing of refractoriness with addition of MnO2, whereas the refractoriness was increased with import of Fe2O3. Raw materials had notable effects on the performance of glass binder for CBN matrix ceramic composite. The results showed that the element in the form of carbonate was more beneficial to the refractoriness and fluidity of glass binder than that in the form of oxide. Moreover, if decomposition temperature of carbonate was lower, the mechanical property of specimens had no obvious difference with addition of carbonate or oxide. However, if carbonate was decomposed nearby the specimens’sintering temperature, the raw materials in form of carbonate did harm to improve the mechanical property of glass binder. Comparation between hydrate and carbonate, if decomposition temperature of hydrate was lower, raw materials in form of hydrate was more favorable to improve properties of glass binder than that in form of carbonate. Preparation processing had obvious influence on the properties of vitrified bond. The results indicated that premelting treatment was necessary for the glass binder with addition of carbonate. The porosity was reduced and the strength was increased with premelting processing.CBN abrasive particles were treated with acid or alkali and coated with low temperature glass coatings. The results were shown as follows: Acid treatment was beneficial to the single particle compressive strength, impact toughness and heat resistance of CBN abrasive grains. On the contrary, alkali treatment was harmful to the properties of CBN abrasive grains. CBN abrasive particles coated with low temperature glass coatings were compared with Ti coated CBN particles and corundum coated CBN particles. The results described that the sol-gel glass coating was excellent for oxidation protection of CBN abrasives because their beginning oxidizing temperature was higher about 100oC than that of uncoated CBN grains. The mechanical property of CBN abrasive particles was significantly increased with glass coatings. For the application of glass coated CBN abrasives to vitrified grinding wheels, it was evident that the glass coating provided high bonding strength between CBN abrasive grains and vitrified bond system.Microcrystalline CBN abrasive was prepared with ultrafine CBN powder as raw material and glass vitrified bond as binder sintering at pressureless processing. The results indicated that the microcrystalline CBN abrasive had dense structure and high strength. The property of the specimens was approaching to single crystal abrasive.更多还原