【作者】 李延波；

【导师】 寇自力；

【作者基本信息】 四川大学 ， 原子与分子物理， 2005， 硕士

【摘要】 立方氮化硼(cBN)是硬度仅次于金刚石的超硬材料,具有很好的抗氧化性和热稳定性,并且不与铁、镍基的金属反应。适合作为刀具的材料。各工业发达国家都把它作为提高经济效益,达到节能、高效、精密、自动化等目的的重要材料加以发展,并将其发展水平视为衡量一个国家技术进步的重要标志。我国的PcBN发展速度是不理想的,与国外在产品的品种和质量方面都存在很大的差距。 本文对高性能的立方氮化硼复合片的烧结进行了研究: 采用cBN粉末作为初始材料,在WC—Co基底上进行高温高压的烧结,实验采用直热式和旁热式两种组装,在不同的实验条件下进行探索,对得到的烧结体样品进行电镜和能谱分析,并进行硬度测试。实验结果表明:(1)使用直热式组装烧结时,烧结过程在很短时间内完成(小于1分钟),增加烧结时间,硬度没有明显变化;(2)直热式组装温度不稳定,难以烧结出比较好的立方氮化硼烧结体;(3)初始立方氮化硼粉末粒度过细时(10μ),Co在烧结体中很难扩散渗透,烧结体中有金属线产生,降低了复合片的力学性能。烧结体粒度太粗时(40μ),得到的烧结体也没有达到较高的硬度;(4)使用粒度为10μ和40μcBN粉末混合作为初始材料,在温度1500℃,压力6.0GPa,的条件下烧结30分钟,得到硬度比较高的烧结体(Knoop硬度达到3134)。 结合本实验结果,对影响PcBN性能的金属线、分层现象进行了分析。Co金属线的产生是由于在高温高压下,Co连接相在PcBN表面缺陷处偏析的结果,立方氮化硼层与WC—Co层的分层主要是由于粉末表面净化程度的影响或者实更多还原

【Abstract】 Cubic Boron Nitride (cBN) is a second hardest material known ,after diamond ,and is superior to diamond in several respects :a higher oxidation resistance ,greater chemical resistance to ferrous alloys such as steels and nickel-based superalloys. Developed countries developing cBN tools as a important material, because it is economy ,energy saving , efficient and precision, And it indicate the technology of a country. But the development of cBN tool is not perfect in our country .We drop behind developed countries not only in variety ,but also in quality.The sintering of Polycrystalline Cubic Boron Nitride(PcBN) from cBN is investigate in this paper.cBN powder is sintered by infiltrated molten Co from WC-Co substrate into cBN layer during high pressure and high-temperature sintering.. Both assembly of direct heating and assembly indirect heating are used in our experiment.. The sinter of cBN power was investigated on several temperature and pressure. From the analysis of our product by SEM ,EDS and Knoop hardness tester, some conclusion can be draw : (1)The reaction of sinter are completed in a short time (less than 40 seconds) when assembly of direct heating is used,.. There is not change clearly when prolong the heating time. (2)The assembly of direct heating is not steadily. It is very difficultto gain PcBN with excellent properties. (3)It is very difficult for cobalt to substrate into cBN layer while the size of starting cBN powder less than 10(x.The cobalt line will appear on the surface of PcBN. The Co line will debase the quality of PcBN. PcBN’s hardness is low also if the size of starting is more than 40u.(4) The highest Knoop hardness of 3134 was achieved for the 50 wt.% lOucBN power- 50 wt.% 40ncBN power composition specimen sintered at. 1500°C and 6.0GPa for 30 min.Considering the result of our experiment, The factors influencing the quality stability of PcBN are analysised. We consider that the Co line appear on PcBN surface is the result that Co is concentrated among the grains of cBN and leak out on the surface of PcBN. The fact of cBN layer separating from WC-Co layer is mainly caused by the impurity of starting cBN power ,or the temperature and pressure of sintering is not enough.Studies on sintering PcBN will play an important role in both the theoretical guide and practical value for the application in industry.更多还原