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The deposition of diamond films on tungsten carbide-based tools can greatly improve the life and performance of cutting tools. However, the deposition of diamond coatings on cemented carbide (WC-Co) suffers from poor film-base bond strength. In this paper, diamond coatings were deposited of phytocrystalline metal micropowders (pure, Nb, Ti, Ta) pretreatment method and the properties of diamond films were analyzed by energy spectrometry (EDS), scanning electron microscopy (SEM), Raman spectroscopy and bonding strength test of diamond films. The results show that through the experiment of the pretreatment process of surface implanted crystal metal micropowder, the best implanted crystal metal micropowder was obtained, the surface quality of implanted crystal titanium (Ti) coating was improved, the diamond Raman peaks were sharp and the indentation cracks had a crack diameter of 389 $\mu$m, which is small and has the highest bond strength. The pretreatment process of phytocrystalline diamond micropowder can deposit high-performance diamond coatings and improve the bonding strength between the coating and the substrate film base.

The outstanding properties of diamond make it an ideal material for radiation detectors especially in the high temperature, high radiation and corrosion environments. For this purpose, electrical and irradiation properties of high quality CVD diamond detector were investigated at room temperature under irradiation conditions. For freestanding diamond films, dark current was in the order of 10^-10 A and photocurrent was in the order of 10^-8 A by 5.9 keV X-ray irradiation from a ⁵⁵Fe source with the applied voltage of 40 V. Pulse height spectrum acquired using a ²⁴¹Am alpha particle source show a full-energy peak at 820 channel which corresponded to an average charge collection efficiency of approximately 40.5%. However, a good signal-to-noise ratio and an energy resolution of 1.33% for alpha particles detecting were also obtained.

Diamond films are often applied in places where there is intense friction. The use of lasers to fabricate textured arrays on diamond films can effectively reduce the friction coefficient. In this paper, we use a UV nanosecond laser to produce periodic linear and pit micro-textures over the areas of $14\ast 7{\mathrm{\text{mm}}}^2$. Laser irradiation was below the single-pulse ablation threshold corresponding to the conditions of surface graphitization during the multi-pulse irradiation. Irradiated graphitization can be detected by Raman spectroscopy, and at the same time, lattice distortion and crack initiation that accompany graphitization can be obtained by XRD and SEM, respectively. The shape of the texture also has a great influence on the residual stress. Grooved texture released the residual stress, but pit texture gave rise to uneven stress, as shown in the test result. SEM was used for observing morphological change at the edge of texture and the mechanism of internal stress changes is analyzed. Detection of texture antifriction performance by reciprocating friction and wear tester. After rubbing, the layered shedding marks of the edge of the texture were observed, and the influence of the superposition of residual stress and external stress on the texture damage was proved based on this.

We have synthesized poor quality diamond films, using high methane concentretion, by plasma-assisted chemical vapor deposition on silicon substrates. The roughness and dynamic critical exponents, α and β, of these films have been measured using an atomic force microscope. We show that the morphology, the roughness and the critical exponents of the diamond films are significantly different from those obtained with a low methane concentration. Our results are compared with Kardar–Parisi–Zhang theoretical predictions.

Diamond-coated hard alloys are prospective tool materials for extreme cutting conditions. Nucleation rate is one of important factors that affect the qualities of diamond thin films on WC-Co alloys. However, theoretical reports on nucleation rate of diamond films on WC-Co alloys are scarce. Combining the unique diamond strong orientation with substrate surface properties, an improved theoretical formula on nucleation rate of diamond films on the WC-Co alloys is deduced in this paper. First, taking account of the strong texture of diamond crystal, the expression, which is closer to the practical deposition process of diamond films on WC-Co alloys, is exclusively involved in both the effects of substrate compositions and substrate surface defects on the nucleation rate. Moreover, the theoretical formula to be slightly revised could be widely used to express nucleation rates of diamond films on various substrates.

Diamond films were deposited on the WC/Co alloy substrates by a hot-filament chemical vapor deposition (HF CVD) reactor after the substrate surfaces were chemically pretreated with the two-step etching method. Some characteristics as morphology, texture, adhesion, and chemical quality of the diamond coatings on WC/Co alloy substrates were investigated by means of X-ray diffractometer (XRD), scanning electron microscope (SEM), hardness tester, and Raman spectrum. The results indicate that increasing the Co content from 0.12% to 3.22% within the etching depth of 5–10 μm caused a morphology transformation from prism diamond to spherical diamond, and a texture one from a {111} orientation to a {110} orientation. The Raman spectrum shows that the spherical diamond film contains more non-diamond phases (graphite, amorphous carbon, diamond-like carbon, etc.) and has lower chemical quality of diamond films. The diamond coated grain sizes became about four to five times smaller when the deposition temperatures on the substrate surface were reduced from 900°C to 800°C. Compared with the spherical diamond films, the prism diamond films exhibit better adhesion on the WC–Co substrates. It is also observed that the microcrystalline orientation diamond thin films with grain sizes of 1–3 μm on WC–Co substrate were formed under the circumstances of lower deposition temperature and higher gas pressure, and the microcrystalline growth mechanism of diamond thin films with a preferential orientation on WC/Co alloy is discussed.

HFCVD diamond films have been extensively applied on inner-hole surfaces of some wear resistant components as protective coatings, the mass production of which puts forward a high request to the HFCVD equipment. In this paper, adopting a typical kind of drawing die as the substrate, several different substrate configurations are proposed to expand the capacity of the equipment. Temperature distributions on inner-hole surfaces of the substrates are respectively predicted and compared by the finite volume method (FVM) simulations. In summary, for parallel configurations, proper-designed auxiliary devices (e.g. the heat-insulated plate, the water-cooled plate and the heat-insulated cushion block) can provide sufficient effects on the uniformity of the substrate temperature distribution. Moreover, without any auxiliary devices, homogeneous substrate temperature distributions can also be obtained using circular pattern configurations (radial, hexagon and triangular). Accordingly, the HFCVD equipment referring to the design concept of the triangular configuration is trial-manufactured. In the verification experiments, similar substrate temperature values are detected in three different modules, and as-deposited microcrystalline diamond (MCD) and nanocrystalline diamond (NCD) films both present uniform grain size, thickness and quality, well validating the rationality and correctness of the simulation-based optimal design.

In this study, the diamond films are deposited on tungsten carbide substrates with 10wt.% Co via hot filament chemical vapor deposition (HFCVD). Amorphous SiC (a-SiC) interlayers with various thicknesses are fabricated between the diamond films and tungsten carbide substrates via precursor pyrolysis to promote the adhesion and friction performance of diamond films. Indentation tests are performed to evaluate the adhesion of the as-fabricated diamond films, which show that the a-SiC interlayers can greatly improve the adhesive strength between diamond films and tungsten carbide substrates with 10wt.% Co. Moreover, the thickness of a-SiC interlayer is of great importance for the effectiveness on the film–substrate adhesion enhancement. The optimum thickness of a-SiC interlayer is 1$\mu$m. Afterwards, ball-on-disc experiments are chosen to check the tribological properties of the as-fabricated a-SiC interlayered diamond film specimen with the optimum interlayer thickness, which exhibits lower friction coefficient than the conventional diamond film with no interlayer.

Femtosecond (fs) laser ablation has been recognized as an effective and promising technique for high-precision processing of natural and synthesized diamond. In this work, a study of femtosecond laser polishing for nanopolycrystalline diamond (NCD) films by chemical vapor deposition (CVD) is reported. The laser irradiation is induced by 200-fs laser pulses with a repetition frequency of 50MHz, and various laser fluences are employed to investigate their polishing effectiveness. The results show that the optimal laser fluence is 0.7J/cm², at which the nanodiamond grains on top of the cauliflower-like clusters of NCD films can be ablated. With such laser fluence, the mean surface roughness of NCD films reduces from 73.84nm to 31.88nm, which presents a 57% reduction. Nevertheless, when the laser fluence rises beyond 0.7J/cm², large amount of amorphous carbon (a-C) balls and porous lava-like morphology would come into being, resulting in severe degradation of the NCD surface.

Geological drilling required high-performance diamond drill bits. In this paper, diamond films were deposited on different drill bit substrates based on the MPCVD equipment. The properties of diamond films were analyzed by scanning electron microscopy (SEM), Raman spectra, X-ray diffraction (XRD) and tribological tests. The results showed that surface morphology of the four different substrates was good and the grain size was uniform. The diamond drill bit substrates include polycrystalline diamond compact (PDC), cemented carbide (WC–Co), impregnated diamond (IPD) and diamond thick-film welded (DT) sheets. The coefficients of friction of the deposited protective films are 0.15, 0.25, 0.23 and 0.29, respectively. What is more, the wear rates of protective films are $8.676\times 10^{-8}$, $13.491\times 10^{-8}$, $4.378\times 10^{-8}$ and $3.643\times 10^{-8}$mm³/N$\cdot$m, respectively. Addition of diamond films could effectively reduce the friction coefficient on the surface and improve the service life of drill bit.