Tribological Behavior and Material Removal Mechanisms in Sapphire Lapping Using HFCVD Diamond-Coated Tools.

Diamond-coated tools have extremely extraordinary physical and chemical properties and have become ideal tools for machining the emerging materials that are hard to machine. In mass production of diamond-coated milling tools, the homogeneity of diamond coatings has always been sought for and is highly influenced by the uniformity of temperature field near the tool substrate. In order to further improve the uniformity of the temperature field and deposit diamond coatings with uniform thickness, a novel hot filament chemical vapor deposition (HFCVD) device with separated worktables and plates for mass production of diamond-coated milling tools is proposed. First, the simulation models of previous device with integrated worktable versus new device with separated worktables are established using finite volume method. The simulation results shows that the temperature distribution is more uniform in the device with separated worktables. Second, temperature measurement experiments are conducted, which prove the correctness of simulation model. Subsequently, experiments involving the deposition of diamond coatings on milling tools are conducted using two kinds of worktables, utilizing the same parameters as in the simulation. Finally, high-speed milling experiments are conducted to test the diamond-coated milling tools. According to the results of SEM, Raman and high-speed milling experiments, it can be concluded that the homogeneity of coating thickness and cutting performance of the milling tools produced by HFCVD device with separated worktables and plates are better.

Among the unique opportunities and developments that are currently being triggered by the fourth industrial revolution, developments in cutting tools have been following the trend of an ever more holistic control of manufacturing processes. Sustainable manufacturing is at the forefront of tools development, encompassing environmental, economic, and technological goals. The integrated use of sensors, data processing, and smart algorithms for fast optimization or real time adjustment of cutting processes can lead to a significant impact on productivity and energy uptake, as well as less usage of cutting fluids. Diamond is the material of choice for machining of non-ferrous alloys, composites, and ultrahard materials. While the extreme hardness, thermal conductivity, and wear resistance of CVD diamond coatings are well-known, these also exhibit highly auspicious sensing properties through doping with boron and other elements. The present study focuses on the thermal response of boron-doped diamond (BDD) coatings. BDD coatings have been shown to have a negative temperature coefficient (NTC). Several approaches have been adopted for monitoring cutting temperature, including thin film thermocouples and infrared thermography. Although these are good solutions, they can be costly and become impractical for certain finishing cutting operations, tool geometries such as rotary tools, as well as during material removal in intricate spaces. In the scope of this study, diamond/WC-Co substrates were coated with BDD by hot filament chemical vapor deposition (HFCVD). Scanning electron microscopy, Raman spectroscopy, and the van der Pauw method were used for morphological, structural, and electrical characterization, respectively. The thermal response of the thin diamond thermistors was characterized in the temperature interval of 20–400 °C. Compared to state-of-the-art temperature monitoring solutions, this is a one-step approach that improves the wear properties and heat dissipation of carbide tools while providing real-time and in-situ temperature monitoring.

Diamond coating were deposited on serrated blade by hot filament chemical vapor deposition (HFCVD) method. The lapping experiments of sapphire wafer were carried out by using diamond coated tools. The diamond coatings and machined surface of the sapphire wafer were characterized by scanning electron microscopy (SEM), laser confocal microscope and Raman spectrum. The results show that the lapped sapphire chips are small irregular chips and long thread-like debris. During the lapping process, there is graphitization of diamond crystal. A low surface roughness can be obtained using a spherical grain diamond coated tool.

Effect of pretreatment strategy on the microstructure, mechanical properties and cutting performance of diamond coated hardmetal tools using HFCVD method

Diamond coatings were deposited on PCB (printed circuit board) carbide milling tool substrates under various schemes of acid and alkali pretreatment by hot filament chemical vapor deposition (HFCVD). Scanning electron microscopy and X-ray coating analysis were used to examine the surface morphology of the milling tools and the impact of de-cobalt from the substrate surface after pretreatment. Milling experiments were carried out to study the cutting performance of diamond-coated PCB micro-milling tools under various pretreatment processes. The results show that abrasive wear, coating flaking, and cutting-edge chipping are the main failure forms of coated PCB milling tools. The substrate pretreatment process with 20 min of alkali etching followed by 20 s of acid etching allows the diamond-coated micro-milling tools to produce the best film–substrate adhesion and substrate strength. These milling tools also have the longest service lives and are suitable for the high-speed cutting processing of PCB.

Novel conversion annealing pretreatment for improved deposition of diamond coatings onto WC-Co cemented carbide

Diamond-coated tools can greatly improve the productivity of machining highly abrasive materials such as high silicon–aluminium alloys used in the automotive industry. Cemented-carbide diamond-coated tool inserts have not become an off-the-shelf product owing to several difficulties including insufficient adhesion of diamond to the substrate and questionable reproducibilty in their machining performance in the manufacturing. In order to overcome these difficulties, a better understanding of the effects of the chemical vapour deposition (CVD) conditions such as methane concentration, reactor pressure and substrate temperature is important. In this work, cemented tungsten carbide tool inserts with 6 wt% Co (WC–Co) were coated with diamond films deposited at five different methane concentrations (1–9 vol%). Here we present preliminary results of the effect of methane concentration variation on the following physical properties of the diamond coating: surface morphology; crystal structure; chemical quality; surface roughness; residual stress. The results indicate that the best physical properties of diamond-coated tool inserts using hot-filament CVD are achieved with diamond coatings deposited at methane concentrations ranging from 1 to 3%.

Various HFCVD diamond coatings synergistically tuned using CH4 gas flow and working pressure and key merit evaluation of their coated tools

Chemical vapor deposition of diamond coatings on tungsten carbide (WC–Co) riveting inserts

Diamond coatings were prepared on alumina by hot filament chemical vapor deposition, which constituted an insulator used in a laser pump. The composition and morphologies of the diamond coatings were characterized by Raman spectra and scanning electron microscope. The effects of the pressure of the deposition chamber and the distance from the filament to the base on the composition and structure of the deposited diamond coatings were studied.

Analyzing the performance of diamond-coated micro end mills

Cutting performances of MCD, SMCD, NCD and MCD/NCD coated tools in high-speed milling of hot bending graphite molds

Performance and characterisation of CVD diamond coated, sintered diamond and WC–Co cutting tools for dental and micromachining applications

Performance and characterisation of CVD diamond coated, sintered diamond and WC–Co cutting tools for dental and micromachining applications

Cutting performance of time-modulated chemical vapour deposited diamond coated tool inserts during machining graphite