Precision dressing of diamond tools

The author of the paper proposes a dressing tool (an adhesively active roller dresser) and the related method for dressing diamond tools. Temperatures in the grinding zone are measured, and the temperature gradient in the diamond grit-workpiece contact zone is calculated.     

Abrasive wear of individual grits in diamond rollers and sticks and its relation to the overall tool wear in dressing operations

Abrasive wear of individual grits in diamond dressing tools during the dressing of abrasive wheels is studied. The wear rate is assessed analytically allowing for mechanical-statistical and temperature characteristics of the grit operation in dressing with rollers and sticks, as well as for the temperature-induced variations of the diamond hardness. A relationship is established between wear of individual grits and that of the diamond-containing layer as a whole.     

CVD金刚石材料在高性能刀具上的应用

介绍了在激发氢气和碳氢混合气体的“活化”发光状态下使金刚石沉积的CVD金刚石制造工艺原理和“厚膜”CVD金刚石的新工艺。由于CVD金刚石的聚晶结构使其具有超过天然金刚石断裂韧性的优异特点,因此可作为切削刀具材料使用。介绍了其在高性能切削刀具和修整刀具上的实际应用情况。     

On theoretical substantiation of the choice of effective grain profile shape in modeling of diamond layer in dressing tools. Part 2. Electroforming

The paper describes, from the statistical standpoint, the mechanism of formation of spherical shape of the averaged cross section of scratches produced by flat faces of diamond grains in abrasive material of grinding wheels during their dressing with diamond rolls manufactured by electroforming. The distribution of parameters of orientation of diamond grain cutting faces has been determined and a brief comparative analysis of characteristics of dressing tools manufactured by electroforming and electroplating has been performed. A notion of the reduced effective diameter has been introduced into the model representation of a diamond cutting grain; a relationship between this diameter and the tool grain size has been found, which is needed for calculating individual and total cross-sections of cuts, dressing forces, and surface roughness of workpieces ground with pre-dressed abrasive wheels.     

On theoretical substantiation of the choice of effective grain profile shape in modeling of diamond layer in dressing tools. Part 1. Electroplating

The paper gives theoretical substantiation of the phenomenon of a circular shape of a scratch cross-section averaged over a set of cuts produced by far-from-round tips of diamond grains of electroplated dressing tools that work on the abrasive material of grinding wheels. This cross-sectional shape is identified as an effective shape of the grain that produces the scratch. Information on the scratch parameters and their relationship with the diamond grain size in the tool is needed for calculating individual and total cross-sections of cuts, dressing forces, and surface roughness of workpieces upon grinding with abrasive wheels dressed by a diamond roll.     

The versatility of hot-filament activated chemical vapor deposition

In the field of activated chemical vapor deposition (CVD) of polycrystalline diamond films, hot-filament activation (HF-CVD) is widely used for applications where large deposition areas are needed or three-dimensional substrates have to be coated. We have developed processes for the deposition of conductive, boron-doped diamond films as well as for tribological crystalline diamond coatings on deposition areas up to 50 cm × 100 cm. Such multi-filament processes are used to produce diamond electrodes for advanced electrochemical processes or large batches of diamond-coated tools and parts, respectively. These processes demonstrate the high degree of uniformity and reproducibility of hot-filament CVD. The usability of hot-filament CVD for diamond deposition on three-dimensional substrates is well known for CVD diamond shaft tools. We also develop interior diamond coatings for drawing dies, nozzles, and thread guides.Hot-filament CVD also enables the deposition of diamond film modifications with tailored properties. In order to adjust the surface topography to specific applications, we apply processes for smooth, fine-grained or textured diamond films for cutting tools and tribological applications. Rough diamond is employed for grinding applications. Multilayers of fine-grained and coarse-grained diamond have been developed, showing increased shock resistance due to reduced crack propagation.Hot-filament CVD is also used for in situ deposition of carbide coatings and diamond-carbide composites, and the deposition of non-diamond, silicon-based films. These coatings are suitable as diffusion barriers and are also applied for adhesion and stress engineering and for semiconductor applications, respectively.     

加工7075航空铝合金用金刚石涂层刀具的制备及其切削性能

采用热丝化学气相沉积(HFCVD)技术在WC-Co8%硬质合金刀具表面制备金刚石涂层,调节甲烷浓度等沉积工艺制备了单层金刚石涂层刀具和微米金刚石涂层(1.2 μm)、纳米金刚石涂层(200 nm)交替多层金刚石涂层刀具。以7075航空铝合金作为切削工件,在无润滑干切条件下测试了单层金刚石涂层刀具和多层金刚石涂层刀具的切削性能。实验结果表明,切削2 h后单层金刚石涂层刀具涂层脱落宽度达到35 μm,刀刃钝化;有多层金刚石涂层刀具的刃型保持完整,涂层无脱落。对单层金刚石涂层和多层金刚石涂层平面样品进行了洛氏压痕实验。结果表明,多层金刚石涂层的脱落面积约为单层金刚石涂层脱落面积的1/5到1/10,进一步说明多层金刚石涂层有更强的抵抗裂纹产生的能力。这些结果表明,金刚石多层结构能提高涂层与基体的界面结合力,延长金刚石涂层刀具的使用寿命。     

Preparation of CVD diamond coatings on gamma titanium aluminide using MPECVD with various interlayers

CVD diamond coatings were deposited on to γ-TiAl surfaces using a microwave plasma enhanced CVD to improve wear properties and the performance of γ-TiAl. Diamond coatings were directly deposited on to γ-TiAl substrates and deposited on to TiC, Ti₅Si₃, Al₂O₃ + TiO₂, and Si interlayers prepared on γ-TiAl substrates. The diamond coatings deposited directly on γ-TiAl suffered severe delamination and cracked. Those deposited on TiC and Ti₅Si₃ interlayers partially delaminated, whereas those deposited on Al₂O₃ + TiO₂ and Si interlayers adhered well to the underlying surfaces. The diamond films obtained were characterized using scanning electron microscopy, Raman spectroscopy, and X-ray diffraction. Raman spectra showed that polycrystalline and nanocrystalline diamond films grew on γ-TiAl. Residual internal stresses of the diamond coatings deposited on interlayered-γ-TiAl were estimated experimentally from Raman spectra. The coatings prepared on Al₂O₃ + TiO₂/γ-TiAl and Si/γ-TiAl showed lower residual stresses.     

A comparative machining study of diamond-coated tools made by plasma torch,microwave, and hot filament techniques

An effective metal-cutting tool is usually a combination of a hard coating and a tough substrate. The successful deposition of diamond outside its thermodynamic stability range has stimulated the development of a new class of cutting tools: those with diamond-coated inserts of any desired style and edge geometry. The successful implementation of diamond coatings also expedited similar research in the deposition of cubic boron nitride. This paper presents superhard coating tools, with emphasis on diamond-coated WC-Co tools, the corresponding deposition of technologies and the foreseen metal-cutting applications.     

电镀金刚石工具中新型镀层的研究

提出了一种能很好地适应电镀金刚石工具要求的新型镀层即镍钴锰三元合金镀层，给出了新镀层的镀液配方，对比测量了镍钴锰镀层与目前广为采用的镍钴和镍锰镀层的硬度与韧性。结果表明，镍钴锰三元合金镀层具有比镍钴或镍锰镀层更高的综合机械性能和低得多的钴含量，更适合于制造电镀金刚石工具，是一种有发展前途的更新换代镀层。     

Main characteristics of abrasive diamond layer in dressing tools

It is demonstrated that a dressing roller or stick as a single-layer abrasive diamond tool can be characterized, like a multilayer one, by two independent parameters—grit size (it suffices to indicate the upper sieve size only) and conditional concentration. The other characteristics (surface density of a powder batch, specific number of diamond grits) are unambiguously determined from these two parameters by means of theoretically substantiated and experimentally verified relationships. The limiting values of the diamond powder quantity on the surface of single-and multilayer tools have been established which differ from the data reported elsewhere.     

激光修整金刚石砂轮研究进展

金刚石砂轮在磨削领域起着举足轻重的作用。对于失效金刚石砂轮的止损,合理地选择金刚石砂轮修整方法成为一大难题。激光修整技术集光、电、热、机械等多种方法于一体,能有效实现金刚石砂轮的修整,受到国内外学者的广泛关注。综合阐述了激光修整金刚石砂轮的基本原理,分析了激光修整技术研究现状,并展望了未来激光修整金刚石砂轮的发展前景。     

Electrodeposited diamond coating with protection by diamond micron powder in a dressing tool. Part 2. Tool performance

The paper compares the results of tool life testing of dressing rollers with conventional electrodeposited diamond coating (EDC) and with protected EDC. The protection of EDC by diamond powder is demonstrated to extend the effective tool life (for the tools manufactured by the electroforming process) by 90% and the total tool life (i.e., till eventual failure of EDC) by 125%. The time history of the diamond grain depth in the bond has been theoretically clarified and this parameter has been found to be related to wear characteristics of the bond and diamond grains.     

Time-modulated chemical vapour deposition diamonf on mould making 2738 steel

The mould making industry is known to be worldwide in rapid expansion, due to the fact that polymeric based materials are increasingly replacing conventional used ones, thus placing enormous challenges on production methods and tools.The application of chemical vapour deposition (CVD) diamond coatings onto moulds can be a promising tool to improve properties such as adhesion, reduction on abrasion and corrosive wear, filling and releasing problems or even tool thermal fatigue. Despite its potential for use in these types of applications, diamond coating on steel substrates is not problem-free and a few critical problems such as adhesion to steel, process temperatures and film property control, remain to be solved.This paper reports on experimental results obtained from an investigation focusing on the deposition of diamond coatings onto steel substrates using the new time-modulated chemical vapour deposition process. Furthermore, the technique is evaluated in order to establish its suitability for application in mould production tools.     

Tribologische Beschichtungen

Tribological Coatings Friction and wear limit the life of tribological systems and lead to damage valued in billion. In many cases tribologically stressed components or tools can only be economically operated with the use of lubricants. Tribologically effective films can replace lubricants or reduce the extent of their use. There are many ways to realise coatings with low friction but only carbon based coatings like DLC (diamond‐like carbon) and polycristalline diamond films combine low friction with a high wear resitant.     

Evolution of the working surface of diamond dressing sticks prior to its fracture

The paper addresses working surface wear of electroplated diamond dressing sticks at a stage prior to fracture during the dressing of abrasive wheels. The fracture is found to occur through drastic breakoff of diamond grits from the bond, the grit size and the nickel bond type being the main factors that dictate the fracture onset time. The authors provide a more precise definition of the relationship between the bond hydroabrasive wear parameters, kinematic characteristics of dressing, and physical-mechanical characteristics of the bond. The difference in the wear rate between diamond grits and the bond in a single-layer dressing tool is demonstrated to introduce large errors into the measurement of specific diamond consumption by weighing. A procedure is put forward which allows a variation in the mass wear ratio between diamond grits and a bond to improve the measurement accuracy.     

生长温度对CVD金刚石薄膜的影响

系统研究了ＣＶＤ金刚石薄膜成膜过程中生长温度对薄膜质量、生长率和力学性能的影响。研究结果表明：在典型沉积条件下，生长温度愈高、薄膜的晶体质量愈好；但薄膜的应力状况和附着性能变坏；在８００℃时，金刚石薄膜的生长速率最大。讨论了ＣＶＤ金刚石薄膜作为机械工具涂层的最佳生长温度。     

Fluidized bed micro-machining and HFCVD of diamond films onto Co-cemented tungsten carbide (WC-Co) hardmetal slabs

The effect of fluidized bed (FB) treatment upon hot filament chemical vapor deposition (HFCVD) of polycrystalline diamond films onto WC-Co hardmetal substrates was investigated. Several scenarios to make the substrates ready for HFCVD were, comparatively, evaluated and the resulting diamond films were examined in terms of their morphology and adhesion. The diamond grain density was measured by scanning electron microscopy. The adhesion of continuous diamond film to substrate was evaluated by the reciprocal of the slope of crack radius-indentation load functions. Surface binder dissolution followed by FB treatment (PF pretreatment) allowed very high diamond nucleation density and smaller grain size. The adhesion of films grown on PF pretreated substrates was found to be very close to that of films deposited on hardmetal slabs pretreated by Murakami's reagent followed by Co etching with Caro's acid and seeded with diamond suspension in an ultrasonic vessel (MPS pretreatment). However, diamond coatings on MPS pretreated samples exhibited a rougher surface morphology as a result of both lower diamond nucleation density and larger substrate surface roughening by Murakami's etching. Based upon experimental findings, our newly developed PF pretreatment was found to be a very promising technique in substrates conditioning as well as in promoting adherent, uniform and smooth diamond coatings onto hardmetal tools and wear parts.     

氮碳化钛涂层制备技术的研究进展

氮碳化钛涂层具有优良的力学及摩擦学性能,作为硬质耐磨涂层,已广泛用于切削刀具、钻头和模具等,具有广阔的应用前景.综述了氮碳化钛涂层主要的制备技术,分析了温度、化学组分、涂层厚度等因素对涂层性能的影响,并指出了其发展趋势.