Microcrystalline Diamond Research Articles

Thermal conductivity of nano- and micro-crystalline diamond films studied by photothermal excitation of cantilever structures

Polycrystalline diamond films have unique structural and thermal properties that make them suitable for use in extreme environments. Recently, they have been utilized in accelerator beamlines for electron stripping due to their unique combination of mechanical and thermal properties. Thermal conductivities of nanocrystalline diamond (NCD) and microcrystalline diamond (μCD) films were characterized using photothermally actuated bimaterial cantilevers. Approximately one micrometer thick NCD and μCD cantilevers were fabricated from microwave plasma enhanced chemical vapor deposition grown polycrystalline diamond (PD) films. A layer of gold was sputtered on the diamond film surfaces to make bilayer cantilevers and the thermal response time was measured by photothermally exciting the bilayer cantilevers, causing them to deflect. Finite element thermomechanical modeling of the deflection dynamics in response to photothermal actuation was performed to determine the NCD and μCD thermal diffusivities and conductivities. By fitting the simulated and experimentally observed response times, thermal conductivities of 10 and 60 W/(m-K) were extracted for the NCD and μCD samples, respectively. Expected changes in thermal conductivity of PD in higher temperature regimes are also discussed. In addition to applications of PD films as electron stripping foils, these findings also have implication in fields such as micro/nano-electromechanical systems.

Effects of carbon concentration and gas pressure with hydrogen-rich gas chemistry on synthesis and characterizations of HFCVD diamond films on WC-Co substrates

The study concentrates on systematic investigations on the effects of extremely high or low carbon concentration (2%–14%) and gas pressure (800 Pa–3200 Pa) on crystal structures, grain sizes, phase compositions, surface and cross-sectional morphologies, growth rates, surface roughness, mechanical and tribological performances of various polycrystalline diamond films synthesized on cemented carbide (WC-Co) substrates with hydrogen-rich/argon-lean gas mixture adopting hot filament chemical vapor deposition (HFCVD) method. The crystal structure, grain size and phase composition of various diamond films synthesized with different carbon concentration and gas pressure were analyzed, indicating that as-deposited diamond films cover microcrystalline diamond (MCD), submicrocrystalline diamond (SMCD), nanocrystalline diamond (NCD) and ultrananocrystalline diamond (UNCD). The surface and cross-sectional morphologies of these various polycrystalline diamond films were observed, and the growth rates of various diamond films were calculated. The three-dimensional morphologies and surface roughness were obtained. With increasing the carbon concentration and decreasing the gas pressure during the synthesis, the crystal size decreases so that diamond film with high smoothness, low surface roughness can be obtained. Subsequently, the synthesis mechanisms of MCD, SMCD, NCD and UNCD films with different carbon concentration and gas pressure under hydrogen-rich gas mixture adopting HFCVD were discussed in detail. The elastic modulus and nanohardness of different diamond films were measured quantitatively, and the film-substrate adhesion were evaluated qualitatively. Moreover, the tribological performances of various diamond films synthesized with different carbon concentration and gas pressure were studied by sliding against silicon nitride (Si3N4) ceramic balls. Results indicate that obtaining the dynamic equilibrium between sufficiently renucleation rate of diamond nuclei and effectively removal rate of non-diamond carbon phase by adjusting carbon and gas pressure under the hydrogen-rich gas chemistry can contribute to the synthesis of high-quality UNCD film.

Synthesis and evaluation of high-performance diamond films with multilayer structure on printed circuit board drills

Printed Circuit Board (PCB) filled with a large amount of Alumina ceramics has broad application prospects in the fifth-generation industry but is hard to drill. This work focuses on high-performance diamond films to improve the working life of drilling tools and holes quality of products. By utilizing hot filament chemical vapor deposition (HFCVD) methods, the monolayer microcrystalline diamond (MCD), bilayer micro-nanocrystalline diamond (MNCD), and four-layer diamond (MNMNCD) are coated on commercial PCB drills (WC-6% Co). Solid particle erosion tests are conducted to study erosive wear mechanism of diamond films impacted by ceramic powders/particles. Besides, cutting performances of diamond coated drilling tools are evaluated by performing high-speed drilling tests with PCB as workpieces. In Erosion tests, the monolayer MCD film presents intergranular fracture and shows the lowest erosive resistance. The MNCD and MNMNCD films have similar fracture forms, where curved boundaries and steps between layers indicate their discontinuous fracture, and minor deep cone holes on the surfaces demonstrate their high resistance to crack growth. Moreover, only one minor deep cone hole is observed on the four-layer film which indicates it has the best resistance to particle impinging. In drilling tests, the number of holes drilled by the diamond coated tools before failure is regarded as criteria of working life. Then surface and sectional morphologies of holes are also observed to evaluate the quality of products. The results indicate the number of holes machined by the four-layer MNMNCD coated drills reaches 10,000, while that of the monolayer and the bilayer MNCD ones are 3000– 4000 and 6000 respectively. More importantly, different from the other two types of diamond coated tools, almost no burrs with a height of over 20 μm are observed on the hole entrance using the four-layer diamond coated tools. Therefore, considering both the working life and holes quality, the MNMNCD films excel in the cutting performance of the new type of PCB drilling.

Highly uniform polycrystalline diamond coatings of three-dimensional structures

Diamond is highly desirable as a conformal thin-film coating for three-dimensional (3D) devices due to its extreme hardness, durability and biocompatibility, especially in the case of implantable medical devices and prosthetics. Recent advances in microwave plasma chemical vapour deposition (CVD) have enabled conformal coating of such 3D structures with nanodiamond films. However, these techniques have not been extended to micro-crystalline diamond, due to interactions between the 3D substrates and resonant microwave cavity. Here we demonstrate more uniform growth of CVD polycrystalline diamond (PCD) coatings on complex-shaped structures, with the use of in-cavity Faraday cages, to isolate the 3D sample from the microwave cavity. While this does disrupt the distribution of the microwave plasma, which surrounds the 3D structure, we show that growth of relatively uniform micro-crystalline and faceted PCD films is possible over the entirety of the exposed 3D sample surface. The resultant technique opens possibilities for the coating of complex 3D geometries with a wider range of diamond materials than has been possible to date.

Why Tolbachik Diamonds Cannot be Natural

AbstractTaking into account recent publications, we provide additional comprehensive evidence that type Ib cuboctahedral diamonds and some other microcrystalline diamonds from Kamchatka volcanic rocks and alluvial placers cannot be natural and undoubtedly represent synthetic materials, which appear in the natural rocks by anthropogenic contamination. The major arguments provided in favor of the natural origin of those diamonds can be easily disproved. They include the coexistence of diamond and deltalumite from Koryaksky volcano; coexistence with super-reduced corundum and moissanite, Mn-Ni silicide inclusions, F-Cl enrichment and F/Cl ratios, and carbon and nitrogen isotopes in Tolbachik diamonds, as well as microtwinning, Mn-Ni silicides, and other inclusions in microcrystalline diamond aggregates from other Kamchatka placers. We emphasize the importance of careful comparison of unusual minerals found in nature, which include type Ib cuboctahedral diamonds and super-reduced phase assemblages resembling industrial slags, with synthetic analogs. The cavitation model proposed for the origin of Tolbachik diamonds is also unreliable since cavitation has only been shown to cause the formation of nanosized diamonds only.

Stimulated Raman Scattering in Diamond Microcrystals Synthesized at High Pressures and High Temperatures

We report the stimulated Raman scattering of light in synthetic diamond microparticles of close sizes (250–300 μm) with the generation of three Stokes satellites under the excitation by ultrashort (60 ps) YAG:Nd3+ laser pulses at a wavelength of 532 nm. The studies performed open up the possibility of creating a laser frequency array with a frequency shift of 1332 cm–1 based on stimulated Raman scattering of light in synthetic microcrystalline diamond powders in a wide spectral range, including ultraviolet and infrared ranges (0.24–2.50 μm).

Tribological performance and wear mechanism of smooth ultrananocrystalline diamond films

• HFCVD is used to synthesize UD-MCD, UD-UNCD, UD-MCD/UD-UNCD, BD-MCD, BD-UNCD, BD-MCD/BD-UNCD films on WC-Co substrates. • Growth mechanism of UNCD with high carbon concentration and low gas pressure in hydrogen-rich chemistry are illustrated. • Undoped and boron doped UNCD coatings are firstly applied on WC-Co micro drills to improve the surface smoothness. • Both boron doping and middle layer MCD contribute to the strong adhesive level of UD-MCD/UD-UNCD and BD-MCD/BD-UNCD. • The UD-MCD/UD-UNCD, BD-UNCD and BD-MCD/BD-UNCD coated PCB micro drills show superior cutting performances. 5G printed circuit boards (PCBs), composed of glass fiber, epoxy resin and ceramic, are a kind of difficult-to-machine material. The manufacture of massive high-quality micro holes on 5G PCBs raise high requirements on the tool life and machining precision of PCB micro drills. Chemical vapor deposition (CVD) diamond coatings can be used as effective protective films on PCB micro drills. The surface smoothness and coating-substrate adhesion of diamond coated micro drills are two important factors affecting the drilling performances. Different from previously reported microcrystalline diamond (MCD) or nanocrystalline diamond (NCD) coating types on cutting tools, undoped (UD-) and boron doped (BD-) ultrananocrystalline diamond (UNCD) coatings with higher surface smoothness are firstly applied on PCB micro drills to reduce the friction and cutting resistance and improve the cutting performances while machining PCBs. Moreover, different from the usual argon-rich gas atmosphere for UNCD synthesis, the synthesis mechanisms of UD-UNCD and BD-UNCD with hydrogen-rich atmosphere adopting HFCVD method are clarified. Sufficiently high renucleation rate of diamond crystallites, long mean free path of reactive precursor species and high removal rate of non-diamond carbon phases lead to the successful synthesis of UNCD films. UDMCD, UD-UNCD, UD-MCD/UD-UNCD, BD-MCD, BD-UNCD, and BD-MCD/BD-UNCD, were synthesized on PCB micro drills using HFCVD. The tribological performances and wear mechanisms of these different diamond coatings were studied systematically. The dominant wear mechanism causing tool wear and fracture of diamond coated micro drills in high-speed machining PCBs is abrasive wear. The degree of abrasive wear while machining PCBs are mainly determined by the surface smoothness, surface roughness and coefficient of friction of diamond coatings. The top layer UNCD with tiny grain size leads to the improvement of surface smoothness and tribological properties, which enhance the chip evacuation capacity and reduce the tool wear. Besides, both boron doping and middle layer MCD can contribute to the strong coating-substrate adhesion. Therefore, BD-MCD/BD-UNCD coated micro drill exhibits the best cutting performances while machining PCBs.

Effects of carbide substrate properties and diamond coating morphology on drilling performance of CFRP composite

Abstract The properties of a cemented carbide tool substrate and diamond coating were studied for the precision drilling of carbon fiber-reinforced plastic (CFRP). The microstructures and mechanical properties of WC–6 wt.% Co substrates using different WC particle sizes were examined to determine correlations between the mechanical properties and the drilling performance. The results demonstrated that WC powders with an average particle size of 2.3 μm were suitable drill substrates. Coatings of either microcrystalline diamond (MCD) or gradient nanocrystalline diamond (NCD) were deposited using hot-filament chemical vapor deposition. A drilling test using T700-grade CFRP was conducted to evaluate the drilling performance, tool wear resistance, and CFRP hole quality achieved based on the diamond coating morphology. In the CFRP drilling tests, the diamond-coated drills showed superior tool lifetimes four times longer than that of the uncoated drill. The MCD-coated drill exhibited good wear resistance compared to the gradient NCD-coated drill; however, the gradient NCD-coated drill demonstrated better machining quality in terms of the delamination factor, surface roughness inside the machined hole, and accuracy of the machining dimensions. In this study, we aimed to develop the optimal tool substrate for the drilling of general-purpose CFRP and proposed directions for the development of diamond coatings to maximize drilling performance.

Optical diagnostics of microwave plasma in process of micro/nanocrystalline diamond deposition on hard alloy tools

Diamond coatings on hard alloy tools produced by chemical vapor deposition (CVD) from methane-hydrogen mixtures greatly enhance the functional properties such as wear resistance and quality of the material processing. By varying the gas composition during the diamond film growth it is possible to cyclically change the film structure between microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) to produce MCD/NCD multilayers that improves the mechanical properties of the film and reduces its stress and roughness. As the diamond growth occurs with participation of radicals generated in the plasma thermo-chemical reactions it is important to control in situ the presence of those species and gas temperature Tg. Here we used optical emission spectroscopy (OES) to monitor atomic hydrogen, CN, CH and C2 dimer radicals in course of deposition of MCD/NCD coatings by microwave plasma CVD in CH4-H2 and CH4-N2-H2 mixtures. The gas temperature has been calculated from analysis of rotational components of structure of C2(Δν = 0) emission line. We found that addition of nitrogen (4%) in CH4-H2 plasma, which is needed to form NCD, significantly, by about 500 K reduces Tg (from Tg = 3910 K to Tg = 3330 K). We developed an algorithm tolerable to small shifts of the measured spectral lines which provided fast calculation of Tg, so that the spectrum record and the automatic processing of fine structure of C2(Δν = 0) line totally take the time of about 5 min.

Temperature stabilization of WC-Co cutting inserts with feedback to IR pyrometer upon growth of multilayer diamond coatings by microwave plasma chemical vapor deposition

We produced microcrystalline diamond coatings with nanocrystalline top diamond layer on WC-Co cutting inserts in a microwave plasma (2.45 GHz) chemical vapor deposition reactor. The coatings have a high uniformity of the substrate surface owing to elimination of the plasma edge effect by application of a moveable quartz ring above the substrate holder. Computer modeling showed how the positioning of the ring changes the electromagnetic field around the substrates. A new approach was used to stabilize the temperature of the cutting inserts during the coating process, which is based on in situ control of the quartz ring position by proportional-integral-differential (PID) regulation. The coatings have been characterized with microRaman spectroscopy in a mapping mode in cross section of the samples. Depth profiles of diamond Raman peak position and width are demonstrated and the stress in the films is estimated, the minimum stress being determined for the cutting insert apex.

Determination of sp2 and sp3 phase fractions on the surface of diamond films from C1s, valence band X-ray photoelectron spectra and CKVV X-ray-excited Auger spectra

The practice of applying the methods for determining the relative contents of carbon atoms in sp2 and sp3 hybridization states from the profiles of C1s X-ray photoelectron and carbon KVV (CKVV) Auger spectra is analyzed. Difficulties in using C1s and CKVV spectra for determining the sp2/sp3 ratios are discussed. A method is proposed for evaluating the fractions of sp2 and sp3 phases based on the fitting of the valence band X-ray photoelectron spectra by superposition of valence band spectra of samples with carbon atoms in pure sp2 and sp3 states. Relative fractions of sp2 and sp3 phases on the virgin surfaces of two ultrananocrystalline diamond films, and on their surfaces subjected to friction, were determined using C1s spectra, CKVV Auger spectra, and valence band spectra. All three methods gave the results that are consistent for virgin film surfaces with accuracy of 2%, and for the surfaces of films subjected to friction, 15%. In contrast to the ultrananocrystalline films, three XPS-based methods applied to a microcrystalline diamond film yielded significantly different sp2/sp3 ratios. The reasons for this discrepancy are shown to lie in different analysis depths of these methods, and in different morphology of the film surfaces.

Deposition of diamond films on Si by microwave plasma CVD in varied CH4-H2 mixtures: Reverse nanocrystalline-to-microcrystalline structure transition at very high methane concentrations

Microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) films were synthesized on Si substrates by a microwave plasma chemical vapor deposition in methane-hydrogen gas mixtures with a wide range of methane concentrations of 0.5–40%. The samples were investigated with scanning electron microscopy, atomic force microscopy, and Raman spectroscopy. We observed an unusual transition of the produced material structure from MCD to NCD and again to MCD with the increase in CH4 content in the gas. The deposition rate, grain size, and the roughness of the films exhibited extrema in the middle of the methane concentration range ([CH4] = 20%). Further increase of CH4 percentage leads to improvement of the diamond film quality, as confirmed by Raman spectra and SEM images while keeping a high deposition rate. These results may be used for the growth of the wide range of PCD films to be used as multipurpose protective layers, hard coatings for the cutting tools, and the diamond base for composite MCD/NCD structures.

Fabrication of AlCrN coatings on WC-Co substrates with diamond films interlayer

Physical vapour deposition (PVD) AlCrN coatings were deposited on the microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) coated WC-Co substrates. The structure, morphologies and frictional characterization of as-fabricated composite coatings were investigated. The surface roughness of MCD coated specimen covering with the AlCrN coating dramatically decreased to ~239 nm. The AlCrN/diamond coatings could provide excellent antifriction properties compared to the monolayer AlCrN coating, especially the value of coefficient of friction for AlCrN/NCD coated specimen decreased to ~0.23, it was much lower than that of the AlCrN coated specimen with ~0.50. The results showed that adopting this method, smooth surfaces for MCD coated samples and high antifriction performance for AlCrN coated samples were obtained simultaneously, which provided a beneficial technology for broadening the application field of AlCrN and diamond coatings.

Enhancing surface production of negative ions using nitrogen doped diamond in a deuterium plasma

The production of negative ions is of significant interest for applications including mass spectrometry, particle acceleration, material surface processing, and neutral beam injection for magnetic confinement fusion. Methods to improve the efficiency of the surface production of negative ions, without the use of low work function metals, are of interest for mitigating the complex engineering challenges these materials introduce. In this study we investigate the production of negative ions by doping diamond with nitrogen. Negatively biased (−20 V or −130 V), nitrogen doped micro-crystalline diamond films are introduced to a low pressure deuterium plasma (helicon source operated in capacitive mode, 2 Pa, 26 W) and negative ion energy distribution functions are measured via mass spectrometry with respect to the surface temperature (30 °C to 750 °C) and dopant concentration. The results suggest that nitrogen doping has little influence on the yield when the sample is biased at −130 V, but when a relatively small bias voltage of −20 V is applied the yield is increased by a factor of 2 above that of un-doped diamond when its temperature reaches 550 °C. The doping of diamond with nitrogen is a new method for controlling the surface production of negative ions, which continues to be of significant interest for a wide variety of practical applications.

The effect of transition-metal seeding powder on deposition and growth of diamond synthesized by hot filament chemical vapor deposition processes on cemented carbide substrates and its characterization

Hot Filament Chemical Vapor Deposition is a well-established method to synthesize diamond thin films on a non-diamond substrate. Here, we have deposited microcrystalline diamond on tungsten carbide cutting tool insert by using conventional Hot Filament Chemical Vapor Deposition technique. The substrates were ultrasonically seeded with Carbon, Diamond, Iridium, Molybdenum, Palladium, Platinum, Tantalum, Tungsten and Chromium natural powders and thereafter were deposited with the same deposition parameters to observe the effects of different seeding powders on the diamond coating. The coated tools were characterized by X-ray Diffraction and the quality of diamond crystals was assessed by using micro Raman spectroscopy. The surface morphology was studied by utilizing Scanning Electron Microscope. The discrete spherical diamond crystals were formed with carbon powder seeding while very dense along with uniform coatings were deposited on the diamond powder seeded substrate. Larger diamond crystals with good density were observed on the palladium seeded substrate. The micro Raman spectroscopy showed mixed results of sp3 and sp2 bonding. But the palladium seeding showed clear sp3 bonding due to the formation of crystals with bigger size. The Vickers microhardness value for the substrate with diamond seeding was found to be much higher than other coated tools.

Study of Early Stages in the Growth of Boron‐Doped Diamond on Carbon Fibers

With the aim to improve the properties of aeronautical carbon fiber (CF)‐reinforced polymer materials, boron‐doped diamond (BDD) has been grown on commercial CFs by microwave plasma‐enhanced chemical vapor deposition. The growth of a BDD layer on CF is expected to increase the mechanical, electrical, and thermal conductivities of the composite. The present contribution reports the different growth stages and their associated nanostructures of the BDD/CF resulting system using transmission electron microscopy, scanning electron microscopy, and Raman spectroscopy. The revealed carbon nanostructure shows four steps of growth with the following characteristics: 1) transitional interlayer, 2) graphite nanowall, 3) cauliflower‐like nanocrystalline diamond, and 4) microcrystalline diamond.

Impedance spectroscopy analysis of n-type (nitrogen-doped) ultrananocrystalline diamond/p-type Si heterojunction diodes

Heterojunction diodes are constructed by growing n-type (nitrogen-doped) ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) composite films onto p-type Si substrates in nitrogen and hydrogen mixed-gases by coaxial arc plasma deposition. The fabricated heterojunctions are analyzed regarding their film morphology and electrical properties. The complex structure of UNCD/a-C:H films, which consists of nano-sized-sp3 diamond grains and sp2-grain boundaries (GBs), makes it difficult to separate their contribution to electrical conductivity of the films using conventional characterization methods. In this paper we characterize the n-type UNCD/p-type Si heterojunction diode by employing impedance spectroscopy method, which can isolate the differing components that contribute to the overall conductivity of the film. The impedance spectroscopy is measured in the frequency range of 100 Hz to 2 MHz, with AC small signal superimpose on DC bias voltage in the range of 0–1 V. The influence of the bias on UNCD grains and GBs contribution to resistance and capacitance of UNCD/a-C:H film and n-UNCD/p-Si heterojunction is investigated by equivalent circuit model using fitting of the impedance data. The results revealed that the electrical conductivity is mainly controlled by the GBs rather than the UNCD grains. Furthermore, the extracted value of dielectric constant of N-doped UNCD/a-C:H film is found to be comparable with that of microcrystalline diamond, which indicates the capacitance contribution in the device is mainly originated from the UNCD grains. This study demonstrates capability of impedance spectroscopy to provide an obvious separated contribution of sp3 and sp2 bonded carbons to the electrical conductivity in their coexistence materials.

ANTI-WEAR PERFORMANCE OF POLISHED MICROCRYSTALLINE DIAMOND FILMS SLIDING AGAINST Si3N4 UNDER WATER LUBRICATION

In this work, aiming at enhancing the tribological behavior of chemical vapor-deposited (CVD) diamond and Si3N4 tribo-pair, mechanical polishing is performed on CVD microcrystalline diamond (MCD) films. The tribological performance of as-fabricated polished MCD (MCD-p) films is investigated by ball-on-plate reciprocating friction tests with Si3N4 ceramic balls as the counterparts under water lubrication, where the as-grown MCD films, nanocrystalline diamond (NCD) films and Si3N4 ceramic plate are employed as the contrast specimens. Under a normal load of 10 N and at a reciprocating frequency of 30 Hz for 2-mm distance, the as-fabricated MCD, NCD and MCD-p films exhibit similar steady friction coefficients after run-in state, which are 0.036, 0.032 and 0.035, respectively. Nevertheless, the wear rate of Si3N4 counterparts varies. Due to the plowing effect of as-grown MCD and NCD films, severe abrasion of Si3N4 counterparts can be observed after sliding for 20[Formula: see text]min. For the MCD-p specimen, however, the Si3N4 counterpart exhibits 2–3 orders of magnitude lower wear rate than those sliding against the as-grown MCD or NCD specimen. On the other hand, due to the reciprocating motion failing to form fluid film between the contact surfaces, high friction coefficient (0.092) and rather severe abrasion are observed for the self-mated Si3N4 ceramic contact.

Flexible, diamond-based microelectrodes fabricated using the diamond growth side for neural sensing

Diamond possesses many favorable properties for biochemical sensors, including biocompatibility, chemical inertness, resistance to biofouling, an extremely wide potential window, and low double-layer capacitance. The hardness of diamond, however, has hindered its applications in neural implants due to the mechanical property mismatch between diamond and soft nervous tissues. Here, we present a flexible, diamond-based microelectrode probe consisting of multichannel boron-doped polycrystalline diamond (BDD) microelectrodes on a soft Parylene C substrate. We developed and optimized a wafer-scale fabrication approach that allows the use of the growth side of the BDD thin film as the sensing surface. Compared to the nucleation surface, the BDD growth side exhibited a rougher morphology, a higher sp3 content, a wider water potential window, and a lower background current. The dopamine (DA) sensing capability of the BDD growth surface electrodes was validated in a 1.0 mM DA solution, which shows better sensitivity and stability than the BDD nucleation surface electrodes. The results of these comparative studies suggest that using the BDD growth surface for making implantable microelectrodes has significant advantages in terms of the sensitivity, selectivity, and stability of a neural implant. Furthermore, we validated the functionality of the BDD growth side electrodes for neural recordings both in vitro and in vivo. The biocompatibility of the microcrystalline diamond film was also assessed in vitro using rat cortical neuron cultures.

Characterization of Micro-Crystalline Diamond Tools Synthesized by HFCVD Process with Different Seeding Powders

Synthesis of diamond films on carbide insert is a recent area of research in surface engineering. This research is carryout to know the effect of different seeding powders on diamond coating of WC tool by Hot Filament Chemical Vapor Deposition (HFCVD) method. Here, the formation of microcrystalline diamond (MCD) on SPUN tungsten carbide (WC-Co) cutting tool insert is carried out. Basically, before coating in HFCVD method, the substrate cobalt content should minimize by ultra-sonic etching. The uncoated tools are seeded ultrasonically by Diamond, Iridium, Platinum and Tungsten powder at the same coating condition to observe the growth of diamond crystals. X- ray diffraction gives clear results of diamond plane and adhesion of coating. The purity of diamond crystal after coating can be clear by observing the Raman shift in Raman spectroscopy (RS). The tool is seeded with diamond powder gives more nucleation density due to the presence of more sp3 bond as compared with sp2. Use of diamond and platinum powder as a seeding material gives fully developed crystal and uniform coating during diamond film deposition by HFCVD technique, rather in case of other powder coating the discrete crystals were formed.