Effects of Implant Copper Layer on Diamond Film Deposition on Cemented Carbides

The deposition of high-quality diamond films and their adhesion on cemented carbides are strongly influenced by the catalytic effect of cobalt under typical deposition conditions. Decreasing Co content on the surface of the cemented carbide is often used for the diamond film deposition. But the leaching of Co from the WC-Co substrate leading to a mechanical weak surface often causes a poor adhesion. In this paper we adopted an implant copper layer prepared by vaporization to improve the mechanical properties of the Co-leached substrate. The diamond films were grown by microwave plasma chemical vapor deposition from CH4:H2 gas mixture. The cross section and the morphology of the diamond film were characterized by scanning electron microscopy (SEM). The non-diamond content in the film was analyzed by Raman spectroscopy. The effects of pretreatment on the concentrations of Co and Cu near the interfacial region were examined by energy dispersive spectrum (EDS) equipped with SEM. The adhesion of the diamond on the substrate was evaluated with a Rockwell-type hardness tester. The results indicate that the diamond films prepared with implant copper layer have a good adhesion to the cemented carbide substrate due to the recovery of the mechanical properties of the Co-depleted substrate after the copper implantation and the formation of less amorphous carbon between the substrate and the diamond film.

Highly (111)-textured diamond film growth with high nucleation density

In a traditional hot-filament chemical vapor deposition (HF-CVD) system, highly (111)-textured diamond film was deposited on Si (111) substrate treated by diamond powder ultrasonic scratching or other methods. The relationship between the (111)-textured diamond film growth and the nucleation density has been discussed. The morphologies and structures of the films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy.

Influence of methane on hot filament CVD diamond films deposited on high-speed steel substrates with WC-Co interlayer

Diamond films were deposited on high-speed steel substrates by hot filament chemical vapor deposition （HFCVD） method. To minimize the early formation of graphite and to enhance the diamond film adhesion, a WC-Co coating was used as an interlayer on the steel substrates by high velocity oxy-fuel spraying. The effects of methane content on nucleation, quality, residual stress and adhesion of diamond films were investigated. The results indicate that the increasing methane content leads to the increase in nucleation density, residual stress, the degradation of quality and adhesion of diamond films. Diamond films deposited on high-speed steel （HSS） substrate with a WC-Co interlayer exhibit high nucleation density and good adhesion under the condition of the methane content initially set to be a higher value （4%, volume fraction） for 30 min, and then reduced to 2% for subsequent growth at pressure of 3 kPa and substrate temperature of 800 ℃.

Mechanism and prediction of failure of diamond films deposited on various substrates by HFCVD

Diamond films were deposited on the WC-Co cemented carbide and Si3N4 ceramic cutting tool substrates by hot-filament-assisted chemical vapour deposition. The adherence property of diamond films was estimated using the critical load (Pcr) in the indentation test. The adhesive strength of diamond films is related to the intermediate layer between the film and the substrate. Poor adhesion of diamond films to polished cemented carbide substrate is owing to the formation of graphite phase in the interface. The adhesion of diamond films deposited on acid etched cemented carbide substrate is improved, and the peeling-off of the films often happens in the loosen layer of WC particles where the cobalt element is nearly removed. The diamond films' adhesion to cemented carbide substrate whose surface layer is decarbonizated is strengthened dramatically because WC phase forms by reaction between the deposited carbon and tungsten in the surface layer of substrates during the deposition of diamond, which results in chemical combination in the film-substrate interface. The adhesion of diamond films to silicon nitride substrate is the firmest due to the formation of chemical combination of the SiC intermediate layer in the interfaces. In the piston-turning application, the diamond-coated Si3N4 ceramic and the cemented carbide cutting tools usually fail in the form of collapsing of edge and cracking or flaking respectively. They have no built-up edge(BUE) as long as coating is intact.As it wears through, BUE develops and the cutting force on it increases 1 - 3 times than that prior to failure. This can predict the failure of diamond-coated cutting tools.

Study on Morphologies and Structures of Dia m ond Films Synthesized on Cemented Carbide Substrates

Morphologies and structures of diamond films synthesized on cobalt cemented tungsten carbide substrates using DC plasma jet CVD (direct current plasma jet chemical vapor deposition) method were investigated by means of SEM, XRD, TEM and Raman spectroscopy. The results show that the high thermal gradient and the high concentration gradient of chemical species within plasma jet have a larger influence on morphologies and quality of diamond films deposited. There are residual compressive stresses with GPa order of magnitude in diamond films, and micro-stresses are quite small. mosaic block sizes, being nanometer order of magnitude, decrease with the increasing of methane concentrations. Average values of dislocation density within diamond films, estimated from the magnitude of mosaic block sizes, are at least 10(10) cm(-2) order of magnitude. This result is also confirmed by calculated value from TEM observation of diamond films. It is shown that both the lattice distortion tested by XRD and FWHM value of diamond Raman peak measured from Raman spectrum have a similar trend of change with methane concentration comparing the results of XRD and Raman spectra.

硬质合金上沉积金刚石膜的基体预处理方法进展

本文重点对近年硬质合金基体表面预处理方法及其对CVD金刚石膜沉积的影响进行了综述。按其原理来分,预处理方法可分为物理预处理法、化学预处理法以及中间层法。大量实验结果表明通过适当的预处理能有效消除或抑制基体中钴黏结相的负面影响,提高金刚石的形核密度以及膜基结合力,从而获得理想的薄膜质量。

硬质合金基体腐蚀工艺对金刚石薄膜的影响

采用不同的预处理方式浸蚀YG6硬质合金基体表面,随后在热丝化学气相沉积装置上沉积了金刚石薄膜。用扫描电子显微镜、X射线衍射仪以及洛氏硬度计对样品进行了分析检测。结果表明:一步或两步浸蚀法都能抑制沉积过程中基体表面钴的不利影响。采用两步法,即Murakami剂30min腐蚀碳化钨相,再用H2SO4∶H2O2=3∶7(体积比)混合酸腐蚀30s去除钴相,基体表面粗糙,金刚石薄膜形核密度高,结晶质量较好,金刚石涂层与硬质合金基体结合良好。

化学脱钴对硬质合金沉积金刚石薄膜的影响

采用HFCVD系统,以CH4和H2为反应气体,分别在YG3、YG6、YG10、YG13硬质合金上沉积了金刚石薄膜,研究了化学脱钴处理对不同钴含量硬质合金沉积金刚石薄膜的影响。通过对105个样品的实验结果进行统计分析发现,YG3所得金刚石薄膜样品具有足够结合强度的比例为89%;而YG6、YG10和YG13所得样品的相应值分别为24%、7%和0%。相反,YG3、YG6、YG10和YG13所得金刚石薄膜严重破坏的比例分别为0%、64%、72%和79%。研究表明,化学腐蚀脱钴处理能够解决金刚石涂层形核率低的问题,但难以解决高钴硬质合金的附着性差的问题。

WC-Co硬质合金基体上高附着力金刚石薄膜的制备

采用微波等离子体化学气相沉积(CVD)法在WC-Co硬质合金基体上制备金刚石膜,研究了TiNx中间层的引入对金刚石薄膜质量及其附着性能的影响.结果表明,在酸浸蚀脱钴处理的基础上,通过预沉积氮含量呈梯度变化的TiNx中间过渡层,可在硬质合金基体上制备出高质量的金刚石薄膜;压痕法测试其临界载荷达1000N.

YG13硼化处理后沉积气压对金刚石薄膜的影响

采用超高真空热丝化学气相沉积(HFCVD)系统,以甲烷和氢气为反应气体,在YG13(WC-13%Co)硬质合金基体上沉积金刚石薄膜。用场发射扫描电子显微镜(FESEM)和X射线衍射仪(XRD)对金刚石薄膜进行检测分析,研究YG13经950℃、3h硼化预处理后沉积气压对金刚石薄膜形貌和生长织构的影响;通过压痕法比较硼化与二步法两种预处理方法对金刚石薄膜附着性能的影响。结果表明,基体经硼化预处理后表面形成CoB、CoW2B2、CoW3B3相;当沉积温度为750～800℃,碳源浓度为3.3%时,薄膜表面形貌和生长织构随着沉积气压改变有明显的变化;硼化预处理后所得样品在1500N载荷下压痕表现出良好的附着性能,较二步法预处理更加有效地改善了膜-基附着性能。

采用WC过渡层增加金刚石薄膜附着力的研究

在微波等离子体化学气相沉积装置中 ,以WC -8%Co为基体 ,采用氢等离子体脱碳、磁控溅射镀W、碳化等方法 ,制备了微晶WC过渡层。研究了金刚石薄膜与基体的附着力。结果表明 ,表面脱碳后再镀W膜 ,W填充了氢等离子体脱碳时刀具表面因钴蒸发而留下的空洞 ,形成过渡层 ,在随后的碳化中和基体WC连接较为紧密 ,能增加金刚石薄膜与基体附着力 ,克服单纯的氢等离子体脱碳还原法降低刀具基体硬度。

纳米金刚石薄膜的制备与应用

采用偏压辅助增强热丝化学气相沉积法(Chemical vapor deposition,CVD),以WC-Co硬质合金为衬底,采用控制沉积参数和添加惰性气体Ar等CVD新工艺,制备性能优良的纳米金刚石薄膜。进一步采用扫描电镜(Scanning electron microscopy,SEM)、原子力显微镜(Atomic force microscopy,AFM)、拉曼光谱(Raman spectros- copy)、X射线衍射(X-ray diffraction,XRD)和高分辨率透射电镜(High-resolution transmission electron microscopy, HR-TEM)分析了薄膜的纳米效应。研究结果表明:纳米涂层仍然是以金刚石结构为主的多晶体,它晶体颗粒较小(20～80 nm),含有较多的晶界和sp^2结构,涂层表面粗糙度R_a≤50 nm,表面平整光滑,有利于研磨抛光。在此基础上,提出纳米金刚石复合涂层制备新技术,开发研制出各种涂层拉拔模具,在实际生产线上进行了应用,取得了显著的效果。

金刚石厚膜与硬质合金的连接

采用扩散焊与钎焊相结合的方法，用Ｔｉ箔和Ａｇ－Ｃｕ箔共同做中间层材料，在一定的温度、压力和保温时间下，实现了气相沉积金刚石厚膜与硬质合金间的牢固连接。经扫描电镜和电子探针分析发现，在金刚石与中间层界面近区有Ｃ、Ｔｉ元素的相互扩散，并且观察断口发现：断裂大部分发生在中间层上，只有局部区域金刚石的表面暴露出来。这可以说明金刚石与钎料之间已形成了牢固的冶金连接。

CVD金刚石涂层硬质合金工具表面预处理新技术

研究了利用(KOH+K3(Fe(CN)6)+H2O和H2SO4+H2O2)两种溶液浸蚀硬质合金基体,分别选择性刻蚀WC和Co的表面预处理过程.在浸蚀过的硬质合金基体上,用强电流直流伸展电弧等离子体CVD法沉积金刚石薄膜涂层.结果表明,两步混合处理法不仅可以有效地去除硬质合金基体表面的钻,而且还显著粗化硬质合金基体表面,提高了金刚石薄膜的质量和涂层的附着力.

金刚石膜与硬质合金刀片间界面Co相的研究

采用SEM和TEM对CVD金刚石膜／YG8硬质合金刀片的界面结合状态、界面Co相进行了研究．结果表明CVD金刚石膜与硬质合金刀片的界面结合类型主要是机械结合；界面相除了石墨碳外，局部区域还可观察到Co粒子．Co粒子上的生长物是微晶石墨和六方金刚石的混合物，且CO粒子与其上的生长物之间存在明显的界面．

硬质合金金刚石涂层工具基体真空渗硼预处理技术研究

研究了真空渗硼预处理硬质合金基体的表面组织、形貌、粗糙度 ,并在处理过的硬质合金基体上 ,用强电流直流伸展电弧等离子体CVD法沉积金刚石薄膜涂层。结果表明 ,真空渗硼预处理不仅可以有效地消除或控制钴在金刚石沉积时的不利影响 ,而且还显著粗化硬质合金基体表面。因此 ,提高了金刚石薄膜的质量和涂层的附着力 ,其临界载荷值达到 15 0 0N。

化学气相沉积金刚石薄膜刀具膜/基附着性能研究现状

CVD金刚石薄膜涂层刀具被认为是能最早实现CVD金刚石工业化应用的领域之一。目前,限制CVD金刚石薄膜涂层刀具产品大规模产业化应用的主要原因,是金刚石薄膜与硬质合金基底之间粘附性能较差。如何提高膜/基粘附性能,确保CVD金刚石薄膜涂层刀具优异性能的发挥、涂层刀具的使用寿命和加工性能,已成为材料科学工作者迫切需要解决的问题。介绍了影响CVD金刚石薄膜硬质合金刀具膜/基附着性能的主要因素、改善金刚石薄膜与硬质合金基体之间附着力的途径以及表征膜/基附着力的测试方法等方面的研究成果,并对提高低压气相金刚石薄膜硬质合金刀具膜/基附着性能的研究现状进行了分析。

YG6硼化综合处理后基体温度对金刚石薄膜的影响

采用热丝化学气相沉积(HFCVD)方法,以甲烷和氢气为反应气体,在经950℃×6h硼化综合处理后的YG6(WC–6%Co)硬质合金基体上制备了金刚石膜。使用场发射扫描电子显微镜(FESEM)和X射线衍射仪(XRD)对金刚石薄膜进行检测分析、对比,研究了基体温度对金刚石薄膜形貌和生长织构的影响,比较了硼化综合处理与二步法处理对金刚石薄膜附着性能的影响。结果表明,当沉积气压为2.67kPa,碳源浓度为3.3%时,薄膜表面形貌和生长织构随着基体温度改变有明显的变化,硼化综合处理较二步法预处理更加有效地改善了膜–基附着性能。

金刚石薄膜涂层硬质合金刀具的界面表征

采用SEM对金刚石薄膜涂层硬质合金刀具的金刚石薄膜表面、背面及金刚石薄膜剥落后的硬质合金刀片表面的典型形貌进行了观察，并采用TEM对金刚石薄膜／硬质合金刀片横截面的微观组织进行了研究，还采用FT—Raman光谱法对金刚石薄膜表面及金刚石薄膜剥落后的硬质合金刀片表面的微观结构进行了表征．结果表明：经适当的化学侵蚀脱钻和等离子体刻蚀脱碳预处理后，金刚石薄膜涂层硬质合金刀具的界面通常存在薄的（数十um）石墨碳层；局部区域见到金刚石粒子直接生长在WC颗粒上,金刚石膜／基横截面的典型组织层次为：金刚石薄膜／薄的石墨碳层／细小的WC层／残留的脱碳层（η相＋W相）／原始的硬质合金基体．

基于Cr过渡层沉积CVD金刚石涂层的试验研究

研究了在硬质合金上基于 Cr过渡层沉积 CVD( Chemical vapor deposition)金刚石涂层的工艺 ,利用自制的 CVD金刚石沉积设备制备出晶形完整、晶粒大小均匀、分布连续的金刚石涂层。用 SEM和 Raman光谱对CVD金刚石涂层进行了分析。结果表明 ,沉积工艺对金刚石的形态和成分有显著影响 ,基体温度在 80 0℃左右时 ,可以得到晶形完整 ,非金刚石成分较少 ,与基体结合紧密的 CVD金刚石涂层。