Journal of Superhard Materials最新文献

The effects of sintering parameters and liquid phase content on the properties of Fe-rich based pre-alloyed impregnated diamond bit (IDB) matrix were investigated using orthogonal experimental design. Based on the analysis of the results, it was found that sintering temperature and liquid phase content have significant effects on the bending strength, hardness, relative density, and wear rate of the matrix. For metal matrix composite (MMC), as the sintering temperature increased from 900 to 1050°C, the bending strength, hardness (HRB), and relative density of the MMC decreased first, then increased, and finally decreased again, while the wear rate increased with temperature. With increasing liquid phase content, the four properties of the MMC showed a similar trend of increasing first and then decreasing. Comparatively, the effects of holding time and sintering pressure on the properties of the matrices were smaller than those of sintering temperature and liquid phase content, but they also had significant effects on some properties of the matrices. Holding time had a more significant effect on hardness and wear resistance, while sintering pressure only had a significant effect on hardness. After adding diamonds, the bending strength of diamond matrix composite increased first and then decreased with increasing temperature, while the bending strength continued to decrease with the increase of liquid phase content. This study provides a feasible method for studying the effects of various sintering parameters and liquid phase content on the properties of Fe-rich pre-alloyed IDB matrix, which is helpful for optimizing the preparation process of drill bits.

The effect of boron oxide on the surface of grains from superhard materials on the performance characteristics of grinding tools is studied. The possibility of increasing the strength of cubic boron nitride (cBN) grains by their thermal treatment in air at a low temperature due to the filling of their defective space with a B₂O₃ film is shown. The results of tests show that the wheel containing cBN powder have higher wear resistance and lower specific grinding energy. It is demonstrated that just boron oxide on the surface of grains from superhard materials is an important factor of increasing their performance characteristics in grinding tools.

The article presents the results of a study on the thermal conductivity of ceramic cutting materials produced from exothermic mixtures of Cr₂O₃ with AlN and ZrO_2(M)–Al–C via hot pressing. The characteristics of the resulting materials were compared with those of commercial cutting ceramics Al₂O₃–TiC grade CC650 (Sandvik Coromant, Sweden).

Abstract—As a result of studying the mechanism of polishing with a disperse system from micro- and nanopowders for polystyrene scintillators, sludge nanoparticles (SP) and polishing powder wear particles (PP) were established to form due to Förster resonance energy transfer (FRET) occurring in a four-mode regime in the open microresonator formed by the surfaces of a treated material and a polishing powder particle. The disperse phase particles in the polishing disperse system were demonstrated to wear twice faster as compared to treated material removal. The total cross section of SPs scattering on PPs (31.1 Mb) during the scattering of quantum nanoparticles in the open resonator formed by the treated material and lap surfaces was shown to be much larger than the total cross section of PPs scattering on SPs to result in the absence of a deposit from polishing powder wear nanoparticles on the treated surface and the presence of a deposit from sludge nanoparticles on the lap surface. The results of calculating the material removal rate were established to agree with the data of experimental polystyrene polishing rate measurements at a deviation up to 4%, and SP deposit fragments on the lap surface were from 0.2 to 1.0 mm in size and discretely arranged within an annular zone with a radius of 24.5 mm. The polishing of polystyrene based scintillation elements with a disperse system from micro- and nanoparticles was shown to improve the pulse shape discrimination of fast neutrons and gamma quanta by high aspect ratio detectors by 14%.

We investigated the effect of steel milling on the structure of SiC–Al₂O₃ composite materials, synthesized in steel drums using steel milling bodies. The study focused on examining the physical and mechanical properties, specifically the flexural strength and hardness, of the synthesized samples. Optimal values of these characteristics were determined based on the composition of the composite and the specific processing conditions employed.

A diamond/graphene composite structure can be obtained using graphene oxide (GO) to undergo a significant thermal reduction reaction at approximately 200°C. The prepared composites were characterized via X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy. The effects of different particle sizes and diamond contents on the products’ phase composition and microstructure were studied. Results indicate that GO underwent a significant thermal reduction reaction at approximately 200°C. Most GO materials were reduced to graphene. They underwent expansion and were peeled off into an organ-like shape. A graphene coating was formed on the surface of diamond particles via a simple heat treatment from the mixtures of diamond and GO powders. The coating effect of large diamond particles was poor because of their high inertness. A quasi core–shell structure of diamond/graphene composite structure can be obtained using fine-grained diamonds.

Melting of cubic boron arsenide, BAs, has been studied at pressures up to 8 GPa using in situ electrical resistivity measurements. It was found that above 2.5 GPa BAs melts congruently, and the melting curve has a negative slope (–53 ± 5 K/GPa), indicating a higher density of the melt as compared to the solid phase. The melting point of BAs at ambient pressure has been estimated to be 2410(30) K.

The effect of wSiC and wSi₃N₄ whiskers on the ultimate dynamic tensile strength (R_{{text{m}}}^{{text{d}}}) of superhard BL group cBN composites synthesized in the cBN–NbN–Al and cBN–NbN–Al₂O₃ systems is considered. It is demonstrated that (R_{{text{m}}}^{{text{d}}}) is ranged from 182 to 333 MPa and depends on the character of a filler. It is pointed out that the addition of wSiC whiskers to the initial sintering mixture increases (R_{{text{m}}}^{{text{d}}}) of sintered ceramic averagingly by 10–15% and, at the same time, the presence of Al₂O₃ leads to a slight decrease in the material strength.

PcBN (polycrystalline cubic boron nitride) carbide insert were synthesized with cBN/Zr/Al as raw material under high temperature and pressure. The effects of synthesis pressure on the interfacial morphology, wear resistance, microhardness and flatness of PcBN carbide insert were investigated. The test results show that with the increase of synthesis pressure, the composite interfacial bond is more dense and homogeneous, and the bonding strength between the cBN layer and the alloy substrate is higher. Additionally, the density, microhardness and abrasion resistance of the PcBN carbide insert were improved. Meanwhile, under the ultra-high pressure, the thickness deviation of the PcBN carbide insert gradually decreases, the thickness distribution gradually becomes uniform, and the flatness of the samples gradually becomes better.

As a result of studying the mechanism of optical glass polishing by means of disperse systems from ceria powders, it has been established that glass is eliminated via the removal of sludge nanoparticles from the treated surface during its interaction with polishing powder particles, which occurs in an open microresonator formed by the surfaces of the treated material and polishing powder particles due to Förster resonant energy transfer between the energy levels of polishing powder and treated material particles. It has been shown that, in a bimodal system with a discrete spectrum of natural frequencies, the number of sludge nanoparticles generated in the treated surface–disperse system–lap surface grows with an increase in the bulk wear coefficient, the lifetime of the excited state of treated surface clusters, and the microresonator Q factor. A method of calculating the treated material removal rate and the roughness parameters of polished surfaces has been developed to establish that the deviation of the calculated polishing rate from experimental data is less than 2%, and the errors of calculating the arithmetic mean R_a and mean square R_q deviations of the polished surface profile attain 10%, and the calculated maximum profile height R_max is 40–50% underestimated as compared to experimental data.