【作者】 刘沙；

【导师】 易丹青；

【作者基本信息】 中南大学 ， 材料学， 2003， 博士

【摘要】 金刚石薄膜与硬质合金基体较差的粘结性能，以及金刚石薄膜本身不稳定的组织结构性能，是阻碍金刚石涂层硬质合金产品大批量生产和应用的关键问题，其研究目前仍是一个热点。解决这两个问题，必须掌握硬质合金基体上金刚石薄膜形核、生长和性能的诸多影响因素及其相互关系和变化规律。论文的主要研究内容和方法包括： 1) 研究了用Murakami剂浸蚀WC相、和各种酸及其混合液除去Co相的化学浸蚀，特别是二步法浸蚀硬质合金基体表面预处理工艺方法，以及与之相匹配的热丝法化学气相沉积(HF CVD)金刚石薄膜沉积工艺。 2) 用X射线衍射(XRD)、扫描电子显微术(SEM)、X射线电子能谱(EDXS)、拉曼(Raman)光谱仪、洛氏硬度(Rockwell Hardness)计等检测分析了硬质合金基体表面特性和金刚石薄膜的性能。 3) 在理论上较为全面地研究了影响金刚石涂层硬质合金过程的主要因素，硬质合金基体表面特性对金刚石薄膜形核的影响，以及硬质合金基体上金刚石薄膜组织结构及性能的特点和变化规律。 4) 建立了热丝法金刚石涂层硬质合金温度场模型，采用程序计算和绘制了温度场图形，并讨论了其影响因素。 5) 研究了微晶金刚石薄膜在硬质合金基体上取向生长工艺和机理。 6) 研究和探讨了硬质合金基体上磁控溅射钼中间过渡层、离子渗氮的预处理工艺方法，及其对金刚石薄膜组织结构的影响。 论文研究的主要结果有： 1) 二步浸蚀法是除去硬质合金基体表面一定深度范围内Co含量的有效方法，并对硬质合金基体表面特性有重要影响。对于不同Co含量的硬质合金基体，应采用不同的浸蚀剂和工艺方法。采用与金刚石沉积过程相匹配的工艺，可以改善硬质合金基体上金刚石薄膜的性能。 2) 硬质合金基体表面Co含量和沉积温度场是引起金刚石薄膜组织结构和性能变化的两个主要因素，而其中起主导作用的因素，将根据具体情况的变化而进行转变。随着CVD沉积温度的降低，金刚台文。沙博士学位论文摘要石薄膜的晶粒组织明显减小。在800一1000℃温度范围内，降低CVD沉积温度约100℃，可使金刚石薄膜的晶粒度减小约5倍。但沉积温度降低至约700℃时，薄膜的金刚石纯度大大降低。 3)金刚石薄膜形核率的计算，与一般的球冠状核心不同，必须考虑金刚石晶核的外表形状。当硬质合金基体表面有钻存在时，硬质合金基体上金刚石薄膜形核率的计算，应采用下列公式: dN/d‘二A’pNAn·{exp(Ed一Es一△G’/kT)一exp(一E{/kT)}丫厄不丽不当硬质合金基体表面预处理引起表面位错密度增加时，金刚石薄膜形核率的计算为: ‘N/‘t二A‘pN人n·‘e·p‘E‘一Es一△G‘/kT，·e·p(一△G’d/kT，一e·p‘一E;/kT，}厂不丽r 另外，表面预处理引起的其它表面缺陷如空位、晶界等密度的增加，同样应考虑进去，故上式还应加上两项:exp。Q/kT)和expGEh/kT)，其中Q为空位表面扩散激活能，E，、为晶界表面扩散激活能。 4)采用较低的CVD沉积温度(约为800℃)和较高的气压，在硬质合金基体上制得了结构取向为{001}面、晶粒度约为1一3林m的金刚石薄膜。其机理研究表明，硬质合金基体表面WC的取向，对金刚石薄膜生长取向有重要影响。 5)热丝法金刚石涂层硬质合金温度场的模型为日ZT日ZT日乙T.日‘T .q(r)~--，丁十一一-气犷十—a丫‘口Y‘兄=O式中，q(r)=(责)q。e一k·2，而q。=qz(，石k一，/2)。 热源参数q。和基体表面特性参数兄对金刚石涂层硬质合金温度场的影响作用几乎同等重要，而基体厚度h的影响也应该高度重视。 6)磁控溅射铝作为硬质合金基体上中间过渡层，可以抑制基体中的钻在界面的扩散，获得高纯度的金刚石薄膜。与未沉积铝过渡层的基体相比，金刚石薄膜在有铝过渡层基体上的晶体生长速度较慢，获得相同厚度金刚石薄膜的时间需延迟约1小时。 硬质合金与钢铁产品同时进行等离子渗氮后，试样沉积薄膜的组织形貌呈典型的类金刚石球形状，其金刚石的化学纯度很低，薄膜以石墨和非晶碳为主。更多还原

【Abstract】 There are two key problems that hamper the batch production and widespread applications of the diamond coated WOCo hardmetals products. One is low adhesion between the substrates and diamond films, the other is difficult to control the quality of diamond films. To solve the problems, it is necessary to find out and master the correlativity and change regularity of the influence factors on diamond nucleation, growth and properties on WOCo hardmetals, which are correlative with not only the diamond deposition process but also pretreatment process. The research contents and methods of the paper are as followings:1)The substrate surfaces were chemically pretreated with the one-step, and especially two-step etching methods, using Murakami reagent and acid solutions. Diamond films were deposited on the WOCo substrates by a hot-filament chemical vapor deposition reactor.2)The substrates surface properties and properties of the diamond coatings were characterized by means of XRD(X-ray diffraction), SEM (scanning electron microscope), EDXS (energy dispersive X-ray spectroscopy), Raman spectroscopy and so on.3)Theories were systematically and comprehensively investigated, including the main influence factors on diamond deposition process and pretreatment process, influence of WOCo substrate properties on diamond film nucleation, and the characteristics and change regularities of morphology, texture and properties of diamond films on WOCo hardmetals.4)The temperature field model of HF CVD diamond coated WOCo hardmetals was established and calculated, and the influence factors on the temperature field model were discussed.5)Orientation growth process and mechanism of microcrystalline diamond films on WOCo substrates were studied in detail.6) The substrate surface pretreatment processes were performed, including magnetron sputtering Molybdenumintermediate layer deposited on WC-Co alloy, plasma nitriding on WC-Co alloy. The pretreatment surface properties and diamond films properties were characterized, and the influence factors on their properties were discussed.Based on the research results, the following main conclusions can be drawn.l)The two-step chemical etching method was effective to removing Co contents on the substrate and prevent .the Co negative effects, the properties of diamond films on the WC-Co alloys could be improved, matched with the suitable HF CVD process.2)The two main influence factors on the transformation of morphology and texture, and properties of diamond films on WC-Co alloys are the Co contents and temperature distribution field. Which one is more important depends on the changes of the concrete conditions. The diamond film grain sizes become smaller with the decrease of the deposition temperature. Within the temperature field of 800-1000C, the diamond film grain sizes became 5 times smaller when the deposition temperature was decreased by 100C. The chemical quality of diamond coatings is very low when the deposition temperature drop to lower than temperature of 700C.3) It is different from the ball cap nucleus in shape, the diamond nucleus shape should be considered when calculating the nucleation rate of diamond films. The nucleation rate of diamond films on the WC-Co alloys is expressed asdN/dt=A*pNAns{exp(Ed -Es - G* /kT) - exp(-Es / kT)}/When the dislocation density increased by the surface pretreatment, the nucleation rate of diamond films on the WC-Co alloys is governed by the following equationBesides the dislocation density, when the defects, such as vacancies and boundaries, density increased by the surface pretreatments, two factors as exp(-Q /kT) and exp(-Eb /kT) should be added into the above equation, where Q-vacancy surface diffusion activation energy , Eb-boundary surfacediffusion activation energy.4)Under the lower deposition temperature (about 800C) and higher pressure, microcrystalline diamond films with {001} Orientation growth and 1-3 Mm sizes on WC-Co substrates were obtained. Its growth mechanism shows the substrate surface texture of W更多还原