陶瓷结合剂cBN磨具的微波制备及其性能研究

发布时间：2018-05-18 02:03

  本文选题：陶瓷结合剂 + cBN　； 参考：《河南工业大学》2017年硕士论文

【摘要】：陶瓷结合剂cBN磨具因为具有耐高温、自锐性好、导热性好等优良的性能而在航空航天、汽车零部件的加工等领域得到广泛应用。然而,在使用过程中它却存在很多亟待解决的关键问题,这些问题主要根源于传统烧结的温度梯度和陶瓷结合剂的脆性。本文重点从烧结方式、添加剂(纳米碳化钒、纳米碳化铬及其复合粉末)以及辅助磨料(绿碳化硅)三个方面,探讨了陶瓷结合剂cBN磨具的制备方法与性能改善途径。主要采用万能材料试验机、差热膨胀仪、扫描电子显微镜、X射线衍射仪等检测手段,以Na_2O-CaO-B2O3-Al_2O_3-SiO_2体系为陶瓷结合剂基础体系,首先较为系统的探讨了微波烧结对陶瓷结合剂及cBN磨具性能的影响,确定了微波烧结的最佳工艺参数;然后,研究了三种纳米过渡金属碳化物及其添加量对陶瓷结合剂cBN磨具的性能影响;最后,探讨了绿碳化硅作为辅助磨料对微波烧结制备陶瓷cBN磨具的作用效果。结果表明:(1)微波烧结法可以在较低的温度(800℃,比传统烧结温度低200℃左右)下实现陶瓷结合剂的烧成,此时结合剂的抗折强度为116.12MPa,相比于传统烧结试样的最大抗折强度值(102.89MPa)提高了12.9%;磨具试样的最佳微波烧成温度为850℃(比传统烧结温度低150℃),此时,其抗折强度(69.53MPa)比传统烧结法制得试样的强度值(57.21MPa)提高了21.5%;(2)在微波烧结条件下,添加1.0wt.%的纳米碳化钒后,陶瓷结合剂及cBN磨具试样的综合热力学性能达到最佳值。其中,结合剂的平均线膨胀系数从6.63×10~(-6)℃~(-1)降低到5.83×10~(-6)℃~(-1)(降低了12.1%),流动性从108.8%增大到144.0%(增大了35.2%),磨具试样的气孔率从25.53%增大到26.80%(增大了1.27%),抗折强度从69.53MPa增大到79.75MPa(增大了14.7%);(3)在微波烧结条件下,添加1.5wt.%的纳米碳化铬后,磨具试样的热力学性能达到最佳值。其中,结合剂的平均线膨胀系数从6.63×10~(-6)℃~(-1)降低到5.57×10~(-6)℃~(-1)(降低了16.0%),流动性从108.8%增大到165.2%(改善了56.4%),磨具试样的抗折强度从69.53MPa增大到96.27MPa(改善了38.5%);(4)在微波烧结条件下,添加4.0wt.%的纳米碳化钒/铬复合粉末后,磨具试样的综合性能较好。其中,陶瓷结合剂的平均线膨胀系数从6.63×10~(-6)℃~(-1)降低到4.56×10~(-6)℃~(-1)(降低了31.2%),流动性从108.8%增大到158.8%(增大了50%),抗折强度变化幅度较小(改善了4.6%)。此外,磨具试样对模具钢的磨削性能有所改善,其磨削比增大了26.0%,平均摩擦系数减小了38.4%。(5)以绿碳化硅代替白刚玉作为辅助磨料后,磨具试样的最佳烧结温度降低了50℃,抗折强度从69.53MPa提高到80.30MPa(提高了15.5%),硬度从75.5HRB增大到95.0HRB(增大了25.8%)。但是,其磨削性能却有所降低。
[Abstract]:Ceramic bond cBN abrasives have been widely used in aerospace, automobile parts processing and other fields because of their excellent properties such as high temperature resistance, good self-sharpness, good thermal conductivity and so on. However, there are many key problems to be solved in the process of application. These problems are mainly due to the traditional sintering temperature gradient and the brittleness of ceramic binders. In this paper, the preparation and performance improvement of ceramic bond cBN abrasives are discussed from three aspects: sintering method, additives (nano-vanadium carbide, nano-chromium carbide and its composite powder) and auxiliary abrasive (green silicon carbide). By means of universal material testing machine, differential thermal expansion instrument, scanning electron microscope and X-ray diffractometer, the Na_2O-CaO-B2O3-Al_2O_3-SiO_2 system is used as the base system of ceramic bond. Firstly, the effects of microwave sintering on the properties of ceramic bond and cBN abrasive are systematically discussed, and the optimum technological parameters of microwave sintering are determined. The effects of three nano-transition metal carbides and their addition on the properties of ceramic bond cBN abrasives were studied. Finally, the effect of green silicon carbide as an auxiliary abrasive on the preparation of ceramic cBN abrasives by microwave sintering was discussed. The results show that the sintering of ceramic binder can be realized by microwave sintering at lower temperature of 800 鈩，

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