An effort to enhance adhesion of diamond coatings to cemented carbide substrates by introducing Si onto the interface

For diamond-coated cemented carbide cutting tools, adhesion of the coatings remains to be a problem. This problem originates from the fact that the adhesion mechanism of the coating–substrate system is mechanical in nature and hence the adhesion of the coatings is ordinarily weak. As an effort to improve adhesion of diamond coatings to the substrates, Si was introduced into the diamond chemical vapor deposition (CVD) process, in order to produce a chemically active glue interface between the diamond coatings and the substrates. Preliminary results showed that by introducing a nontoxic precursor, octamethylcyclotetrasiloxane (D₄), and under normal microwave plasma CVD conditions, Si could be made concentrating onto the interface, benefiting the improvement in adhesion of the diamond coatings.     

碳源浓度对金刚石薄膜涂层刀具性能的影响

用热丝ＣＶＤ法,以丙酮为碳源,在ＷＣ－Ｃｏ硬质合金衬底上沉积金刚石薄膜,研究了碳源浓度对金刚石薄膜涂层刀具性能的影响,结果表明,碳源浓度对金刚石涂层薄膜质量、形貌和粗糙度、薄膜与衬底间的附着力、刀具的耐用度用度发削性能有显著影响,合理控制碳源浓度对获得实用化的在硬质合金刀具基础上沉积高附着强度、低粗糙度金刚石薄膜的新技术具有重要的意义。     

等离子体技术在提高硬质合金工具上金刚石薄膜附着力方面的应用

金刚石薄膜具有优异的性能，作为切削工具表面的保护性涂层，可以大幅度提高工具的使用寿命以及加工精度。硬质合金是一种广泛使用的工具材料，在其表面沉积高附着力的金刚石薄膜时存在着困难。等离子体中离子、原子或分子具有高的反应活性，等离子体技术在金刚石薄膜的制备中有着广泛应用。利用等离子体技术可以极大的消除因金刚石薄膜与硬质合金基体之间存在热应力以及由硬质合金中的钴粘结剂在化学气相沉积金刚石薄膜过程中的促石墨化作用而产生的不利影响，提高金刚石薄膜与硬质合金基底之间附着力。本文综述了等离子体技术在提高硬质合金工具表面金刚石薄膜附着力方面的研究进展。     

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、不能完全消除钴的有害影响的缺点。     

硬质合金CVD金刚石涂层最新进展

金刚石因具有优异的物理化学性能被认为是理想的刀具材料。硬质合金基底上涂覆CVD金刚石薄膜有利于改善刀具的加工性能和寿命,但涂层和基底之间存在热膨胀系数差异以及合金中Co对沉积有不利影响,使得薄膜附着力较差。本文综述了近几年来各种提高CVD金刚石涂层刀具切屑性能的方法,从提高薄膜附着力和改善金刚石膜的质量两个方面进行了讨论。并介绍了国外较先进的CVD金刚石涂层刀具的应用,随着技术的不断成熟,CVD金刚石涂层将会有更为广泛的应用。     

Analyzing the performance of diamond-coated micro end mills

A method is presented to improve the tool life and cutting performance of 300 μm diameter tungsten carbide (WC) micro end mills by applying thin (<300 nm) fine-grained diamond (FGD) and nanocrystalline diamond (NCD) coatings using the hot-filament chemical vapor deposition (HF-CVD) process. The performance of the diamond-coated tools has been evaluated by comparing their performance in dry slot milling of 6061-T6 aluminum against uncoated WC micro end mills. Tool wear, coating integrity, and chip morphology were characterized using SEM and white light interferometry. The initial test results show a dramatic improvement in the tool integrity (i.e., corners not breaking off), a lower wear rate, no observable adhesion of aluminum to the diamond-coated tool, and a significant reduction in the cutting forces (>50%). Reduction of the cutting forces is attributed to the low friction and adhesion of the diamond coating. However, approximately 80% of the tools coated with the larger FGD coatings failed during testing due to delamination. Additional machining benefits were attained for the NCD films, which was obtained by using a higher nucleation density seeding process for diamond growth. This process allowed for thinner, smaller grained diamond coatings to be deposited on the micro end mills, and enabled continued operation of the tool even after the integrity of the diamond coating had been compromised. As opposed to the FGD-coated end mills, only 40% of the NCD-tools experienced delamination issues.     

CVD金属石薄膜及膜——基界面形态

采用直流等离子体射流ＣＶＤ法在硬质合金基体上沉积了多晶金刚石薄膜,借助ＸＲＤ,Ｒａｍａｎ,光谱、ＳＥＭ和ＥＰＭＡ等对金刚石薄膜及膜－基界面的结构、形貌和成分进行了研究,结果表明,结晶度高的刻面型金刚石薄膜质量、纯主较好,膜－基界面处较致密,机械锚固作用明显,结合性能较好,沉积前后基体表面形貌变化很大,存在数十数米厚的脱钴－等离子体刻蚀层,等离子体刻蚀导致脱钴表面更加凹凸不平,为金刚石形核提供了有利     

CVD金刚石薄膜及膜-基界面形态

采用直流等离子体财流CVD法在硬质合金基体上沉积了多晶金刚石薄膜,借助XRD、Raman光谱、SEM和EPMA等对金刚石薄膜及膜-基界面的结构、形貌和成分进行了研究.结果表明,结晶度高的刻面型金刚石薄膜质量、纯度较好,膜-基界面处较致密,机械锚固作用明显,结合性能较好沉积前后基体表面形貌变化很大,存在数十微米厚的脱钴-等离子体刻蚀层,等离子体刻蚀导致脱钻表面更加凹凸不平,为金刚石形核提供了有利条件.     

Diamond-coated cutting tools for biomedical applications

Diamond coatings are attractive for cutting processes due to their high-hardness, low-friction coefficient; excellent wear resistance, and chemical inertness. The application of diamond coatings on cemented, tungsten carbide (WC-Co) burs has been the subject of much attention in recent years as a method to improve cutting performance and tool life. WC-Co burs containing 6% Co and 94% WC substrate, with an average grain size of 1–3 μm, were used in this study. To improve the adhesion between diamond and WC substrates, it is necessary to etch away the surface Co and prepare the surface for subsequent diamond growth. Hot filament chemical vapor deposition (HFCVD), with a modified vertical filament arrangement, has been used for the deposition of diamond films. Diamond film quality and purity has been characterized using scanning electron microscopy (SEM) and micro-Raman spectroscopy. The performance of diamond-coated WC-Co burs, uncoated WC-Co burs, and diamond-embedded (sintered) burs have been compared by drilling a series of holes into various materials such as human teeth, borosilicate glass, and acrylic teeth. Flank wear has been used to assess the wear rates of the burs when machining biomedical materials such as those just described. This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September 15–17, 2003, in Indianapolis, Indiana, and appears on pp. 273–82 of the Proceedings.     

钛过渡层与硬质合金基体表面结合状况对金刚石薄膜附着力的影响

以WC-6％Co为基体,采用磁控溅射法,在原始试样、酸腐蚀试样以及酸蚀后进行氢等离子体脱碳处理的试样上制备Ti过渡层,然后碳化过渡层为TiC。在热丝化学气相沉积装置中,制备金刚石薄膜。研究三种不同试样上的金刚石薄膜与基体的附着力。结果表明,在原始试样上的金刚石薄膜在冷却过程中自动脱落;在经等离子体处理后的试样上,金刚石薄膜与基体间附着力高于在经酸蚀处理的试样上的金刚石薄膜与基体附着力。造成这种现象的主要原因可能是等离子体脱碳还原处理降低WC晶粒表面能,增强Ti与WC间的结合强度,导致TiC过渡层与WC基体结合强度增加,从而增加金刚石薄膜附着力。     

预处理对金刚石薄膜质量及结合力的影响

目的改善硬质合金表面金刚石薄膜的结合力。方法采用热丝CVD法在硬质合金基体上制备金刚石薄膜,研究对比喷砂+一步法、喷砂+两步法、Al Cr N过渡层和传统两步法这四种预处理对金刚石薄膜质量及其结合性能的影响。对预处理后硬质合金基体表面的形貌和粗糙度进行分析,并通过扫描电子显微镜、X射线衍射、拉曼光谱及洛氏硬度计表征金刚石薄膜的形貌、结构及性能。结果喷砂有利于在基体表面获得均匀分布的凹坑,提高金刚石的形核密度及均匀性,尤其改善了金刚石颗粒的团聚现象。Al Cr N过渡层虽然表面粗糙度不高,但有大量的凸起颗粒,提供了极佳的形核点,也在一定程度上优于传统两步法的表面金刚石形核密度。在金刚石薄膜沉积参数不变的前提下,传统两步法预处理获得的涂层结合力为HF4级,喷砂结合一步法和两步法获得的结合力分别达到了HF3级和HF1级,但Al Cr N过渡层的结合力表现较差。结论 Al Cr N过渡层能阻挡Co的扩散,提高了金刚石的纯度,但金刚石膜的内应力较大,结合力差。喷砂和刻蚀复合预处理不仅能提高金刚石的结晶质量和纯度,金刚石薄膜的结合力也得到改善。     

硬质合金金刚石涂层工具基体前处理有效方法探讨

利用两种溶液浸蚀硬质合金表面，分别选择性刻蚀WC和Co.这不仅强粗化了硬质合金表面，而且，还能抑制CO在金刚石沉积过程中的负作用，从,而，提高了金刚石薄膜的质量和涂层的附着力。     

微波等离子体刻恂对WC—Co硬质合金基体金刚石薄膜附着力的影响

金刚石薄膜的附着力是影响CVD金刚石涂层刀具切削性能的关键因素,本文采用EACVD法在硬质合金（YG6）基体上沉积金刚石涂层;用Ar-H2微波等离子WC－C0衬底进行刻蚀处理,以改变基体表面与金刚石涂层间的界面结构,提高金刚石涂层的附着力;采用压痕法评估涂层附着力,借助SEM等观察刻蚀预处理方法对膜基界面的影响,并对此进行分析和讨论。     

沉积温度对硬质合金金刚石涂层附着力影响的研究

采用压痕实验、扫描电镜与激光Raman光谱分析,实验研究了酸浸硬质合金基底上金刚石涂层的附着力随沉积温度的变化.结果表明,涂层质量随沉积温度降低而显著恶化,涂层应力则随沉积温度提高而上升.从提高涂层附着力的角度考虑,存在一个最佳沉积温度.在较低的沉积温度下,涂层自身的质量较低、力学性能较差,在载荷作用下易于破坏.提高沉积温度,涂层自身的质量可得到改善,但基底中的钴向基底表面扩散的倾向加大,而且热应力增大,会严重降低涂层与基底的附着力.除硬质合金基底的预处理工艺外,沉积工艺对金刚石涂层的组织、性能以及附着力均有重要影响.     

硬质合金表面渗硼处理对CVD金刚石涂层形成的影响

采用渗硼工艺对ＹＧ６硬质合金表面进行预处理,探讨了渗硼预处理对硬质合金金刚石薄膜涂层形成的影响。研究结果表明,渗硼时Ｃｏ在硬质合金表面同Ｂ形成ＣｏＢ、Ｃｏ２Ｂ化合物层。该硼化物层在金刚石沉积过程中,能有效阻挡硬质合金中粘结相Ｃｏ向表面扩散,消除了Ｃｏ对金刚石薄膜涂层形成时的不利影响,改善了薄膜涂层质量,提高了附着力。     

脉冲偏压辅助热丝法沉积金刚石膜的实验研究

本文针对金刚石涂层应用于工具、模具的需要,研究脉冲偏压在热丝法沉积金刚石工艺中促进金刚石形核、生长的作用。进行了不同脉冲电压、频率、占空比条件下制备金刚石涂层的试验,采用金相显微镜观察涂层的颗粒尺寸及均匀性、致密性,确定了优化的工艺参数。采用优化的工艺参数在硬质合金基体表面沉积金刚石涂层,观察金刚石涂层的结构并测试与基体的结合力。结果表明,生长的金刚石涂层颗粒细小、均匀,与基体的结合力良好。     

化学气相沉积过程中Si的引入对硬质合金金刚石涂层附着力的影响

利用微波等离子体化学气相沉积方法，以H2、CH4和八甲基环四硅氧烷(D4)为原料，在硬质合金基体上沉积了金刚石涂层。与一般只使用H2、CH4为原料时的情况相比，金刚石涂层与硬质合金基体间的附着力有了一定程度的提高。对涂层断面的成分分析表明，Si在涂层与基体间的界面处有富集的倾向，而这将有助于抑制Co对涂层附着力的不利影响，提高金刚石涂层的附着力。     

Preparation of cemented carbide diamond films by gaseous boronizing pretreatment combines with self-assembly seeding process

In order to enhance the adhesion of cemented carbide diamond film and improve the cutting performance of cemented carbide diamond coating tools. This paper was the first to combine gaseous boronizing pretreatment with self-assembly seeding process to prepare diamond films on cemented carbide substrate. It not only eliminated the negative influence of cobalt (Co), but also improved the nucleation density of diamond. The gaseous boronizing pretreatment completed the boronation of the cemented carbide in a short time and obtained the CoWB phase which effectively prevented the diffusion of Co. By application of a self-assembly seeding process with the help of [2-(Methacryloyloxy) ethyl] trimethylammonium chloride (TMAEMC) highly improved the colloidal stability of nanodiamond (ND) particles. When the concentration of TMAEMC was 5 × 10⁻⁶ mol/l, the nucleation density of diamond was the highest. Rockwell indentation shows that the combination of gaseous boronizing pretreatment and TMAEMC self-assembly seeding process significantly improved the film-substrate adhesion. The reciprocating friction test shows that the diamond films prepared by this method had low friction coefficient and excellent wear resistance. Therefore, gaseous boronizing pretreatment combines with self-assembly seeding process is an effective way to achieve strong adhesion and high cutting performance of industrial diamond coating tools.     

Adhesion analysis and dry machining performance of CVD diamond coatings deposited on surface modified WC-Co turning inserts

This paper investigates the effects of different surface pretreatments on the adhesion and performance of CVD diamond coated WC-Co turning inserts for the dry machining of high silicon aluminum alloys. Different interfacial characteristics between the diamond coatings and the modified WC-Co substrate were obtained by the use of two different chemical etchings and a CrN/Cr interlayer, with the aim to produce an adherent diamond coating by increasing the interlocking effect of the diamond film, and halting the catalytic effect of the cobalt present on the cemented carbide tool. A systematic study is analyzed in terms of the initial cutting tool surface modifications, the deposition and characterization of microcrystalline diamond coatings deposited by HFCVD synthesis, the estimation of the resulting diamond adhesion by Rockwell indentations and Raman spectroscopy, and finally, the evaluation of the dry machining performance of the diamond coated tools on A390 aluminum alloys. The experiments show that chemical etching methods exceed the effect of the CrN/Cr interlayer in increasing the diamond coating adhesion under dry cutting operations. This work provided new insights about optimizing the surface characteristics of cemented carbides to produce adherent diamond coatings in the dry cutting manufacturing chain of high silicon aluminum alloys.     

实验参数对金刚石薄膜内应力的影响研究

采用热丝化学气相沉积法(HFCVD)在硬质合金基体上制备金刚石薄膜涂层,采用SEM观察金刚石薄膜形貌,采用Raman光谱法分析制备的金刚石薄膜与基体的内应力。变化丝基间距、偏流、碳浓度等参数,通过测定拉曼光谱单一谱峰的位移Δω计算涂层的内应力,从而得到制备内应力较小的金刚石膜的工艺参数范围。