地质工程用高性能无钴硬质合金的制备、结构及力学性能研究

发布时间：2018-04-23 02:37

  本文选题：无Co硬质合金 + 超硬颗粒　； 参考：《中国地质大学(北京)》2016年博士论文

【摘要】：由于具有高硬度、高强度和优异断裂韧性,硬质合金作为制备钻头和钎头的工具材料在地质工程领域得到广泛应用。但常用的WC-Co硬质合金抗氧化/腐蚀性较差,限制其在海底、盐碱地及其它高氧化/腐蚀环境下的使用,且钻头和钎头在工程应用中消耗巨大,而Co价格昂贵,如能减少Co的使用,对降低钻头价格,减少作业成本具有重要意义。所以本论文主要集中于制备适合地质工程用高性能无Co硬质合金。本论文以超细WC-Ni和无金属相硬质合金为主要研究对象,采用放电等离子或热压烧结技术,通过将合金与超硬颗粒、高强晶须/纤维或纳米陶瓷颗粒进行复合来提高无Co硬质合金的力学性能和耐磨性能。通过对所制备样品烧结行为、微观结构、力学性能和磨损行为进行分析,结果表明:(1)超硬颗粒表面镀Ti或镀Cu可减少其在与WC-Ni硬质合金复合时发生的石墨化或相转变,当分别添加6 wt.%DiamondTi、8 wt.%DiamondCu或15 vol.%cBNTi时,合金的硬度达到最大值,分别约为2000、2000和1820 HV10;当分别添加2 wt.%DiamondTi、2 wt.%DiamondCu或5 vol.%cBNTi时,合金的抗弯强度达到最大值,约为960、950或1500 MPa。超硬颗粒添加量较少时,合金的磨损机制主要为粘结相的去除、WC晶粒的破碎拔出和超硬颗粒的磨损,但当超硬颗粒添加量过多时,切削棱断裂和超硬颗粒剥落变得严重。(2)添加约0.53 wt.%SiCw可提高WC-Ni硬质合金的强度和韧性,但当SiCw添加过多时,晶须团聚严重;添加预氧化聚丙烯腈纤维(PANf)可原位生成碳纤维增韧WC-Ni硬质合金,当添加10 vol.%PANf、烧结温度为1300℃时,所制备合金具有最高的硬度和强度,当添加20 vol.%PANf时,合金的断裂韧性最高,合金的磨损机制主要为粘结相去除和WC晶粒拔出。(3)添加约3-5 wt.%纳米ZrC颗粒可提高WC-Ni硬质合金的致密性、硬度、强度和断裂韧性,且此时合金磨削花岗岩时的磨损率最小,但是当其添加量高于7 wt.%时,富Zr颗粒团聚严重,合金的致密性、硬度、强度和韧性均有所降低,合金的磨损率增加,主要磨损机制为粘结相去除和WC晶粒拔出。(4)添加适量纳米AlN、La2O3或ZrC(低于5 wt.%)可提高无金属相硬质合金的致密性,抑制WC晶粒的粗化,提高合金的硬度和抗弯强度,但当其添加量高于5 wt.%时,纳米颗粒团聚严重,合金的致密性降低,硬度和强度下降;随着纳米AlN和La2O3添加的增多,合金的断裂韧性逐渐降低,但随着纳米ZrC添加的增多,合金的断裂韧性先增大后减小。所制备合金的磨损率随纳米颗粒添加量的增加先减小后增加,当合金强度较高时(约高于1000 MPa),磨损机制主要为WC晶粒断裂和拔出,但当其强度较低时(约低于1000 MPa),磨损机制主要为切削棱断裂和合金成块剥落。
[Abstract]:Because of its high hardness, high strength and excellent fracture toughness, cemented carbide has been widely used in geological engineering as a tool material for the preparation of bit and bit. However, the commonly used WC-Co cemented carbides have poor oxidation resistance / corrosion, which limits their use in seabed, saline-alkali soil and other high oxidation / corrosion environments. Moreover, bits and drill bits are consumed heavily in engineering applications, while Co is expensive. If the use of Co can be reduced, it is of great significance to reduce the price of drill bit and reduce the cost of operation. Therefore, this paper mainly focuses on the preparation of high performance Co-free cemented carbides for geological engineering. In this paper, superfine WC-Ni and metal-free cemented carbides were used as the main research objects, and the alloy and superhard particles were prepared by spark plasma or hot pressing sintering. The mechanical properties and wear resistance of Co-free cemented carbides were improved by composite of high strength whisker / fiber or nano ceramic particles. The sintering behavior, microstructure, mechanical properties and wear behavior of the prepared samples were analyzed. The results show that Ti or Cu plating on the surface of the superhard particles can reduce the graphitization or phase transition of the samples when they are compounded with WC-Ni cemented carbides. The hardness of the alloy reached the maximum value of about 2000.2000 and 1820 HV10when the alloy was added for 6 wt.DiamondTiO8 wt.%DiamondCu or 15 vol.NTi, respectively, and the flexural strength of the alloy reached the maximum value of 960950 or 1500 MPa when the alloy was added with 2 wt.DiamondTiO2 wt.%DiamondCu or 5 vol.NTi, respectively. When the content of superhard particles is small, the wear mechanism of the alloy mainly consists of the removal of bonding phase and the crushing and pull-out of WC grains and the wear of superhard particles, but when the amount of superhard particles is too much, The strength and toughness of WC-Ni cemented carbides can be improved by adding about 0.53 wt.%SiCw to the cutting edge fracture and the spalling of superhard particles, but the agglomeration of whiskers is serious when the addition of SiCw is too much. The WC-Ni cemented carbide toughened by carbon fiber can be in-situ formed by adding preoxidized polyacrylonitrile fiber (PANF). The highest hardness and strength of the alloy are obtained when the sintering temperature is 1300 鈩，

本文编号：1790098