G. D. Il’nitskaya

Studies of the oxidation stability, mechanical characteristics of materials based on max phases of the Ti-Al-(C, N) systems, and of the possibility of their use as tool bonds and materials for polishing

Thermogravimetry and differential thermal analysis have been used to study the resistance to the air oxidation of high-density samples of Ti3AlC2, Ti2AlC and Ti2Al(C1−xNx) solid solutions. It has been shown that the Ti3AlC2 samples are more stable than Ti2AlC and Ti2Al(C1−xNx) solid solutions and as the nitrogen content of the solid solution increases to x = 0.75, the oxidation resistance decreases. The following characteristics have been exhibited by the material containing 89 wt % Ti3AlC2 (the rest being Al2O3 and TiC) having density 99% of theoretical: bending strength Rbm = 500 MPa, compressive strength Rcm = 700 MPa, fracture toughness KIc = 10.2 MPa·m0.5, hardness HRA = 70 GPa, HV = 4.6 GPa, Young modulus = 149.4 ± 28.7 GPa. After sintering with diamonds or cBN (50 wt %) at 5.5–7.7 GPa and 1350–1960°C for 0.07–1.0 h the Ti3AlC2 MAX phase decomposes to form TiC and TiAl or TiB2 and a thin layer of Al4C3 forms at the interface with diamond. The Al4C3 decomposition in a composite material due to the interaction with the air moisture results in the crack initiation along the diamond perimeter, which brings about the material fracture in 1–2 weeks. It has been found that the Ti3AlC2 powder is efficient for polishing natural and synthetic jewelry crystals and competitive in polishing efficiency and quality with ACM 2/1 grade diamond.

The influence of strength characteristics of diamond grits on drilling tool performance

The paper presents the results of investigation of the effect of strength characteristics (strength, strength uniformity, thermal stability) of diamond grits on wear of impregnated drill bits and expenditure of energy for rock destruction by such tools. The influence of strength characteristics of diamond grits on the drilling tool performance has been verified experimentally. The field tests have demonstrated that the better the strength characteristics of the grits the larger the average meterage drilled per bit and the rate of penetration.

Effect of High-Voltage Electrical Discharge Treatment of Diamond Powders on Their Mechanical Characteristics

The effect of pulsed high-voltage electrical discharge (HVED) treatment on the morphometrical, structural adsorption, and mechanical properties of diamond micropowders and abrasive powders is examined. These properties largely determine the performance and wear resistance of abrasive tools for machining process. It is shown that pulsed HVED treatment is efficient in the production of diamond micropowders and abrasive powders with low impurity content and high abrasive ability.

The influence of physical-mechanical characteristics of AS6 synthetic diamond powders on wear resistance of grinding tools

The paper addresses physical-mechanical characteristics of AS6 diamond grits synthesized in the Ni-Mn-C and Fe-Si-C systems. These diamonds vary in magnetic properties, mechanical characteristics, amount of impurities and intracrystalline inclusions. The authors demonstrate a potential of using the results of investigation of morphometric characteristics of dimond powders for their efficient application in grinding tools. A relationship has been established between these characteristics and the tool wear resistance in diamond grinding.

Improving wear resistance of drilling tools fitted with synthetic diamond

The paper summarizes the findings of investigation of the influence of physicochemical and physical-mechanical properties of synthetic diamond grits on the drilling tool performance. Wear resistance of drilling tools is demonstrated to increase when they are fitted with synthetic diamond grits that are highly uniform in strength. The use of diamond grits with a better developed surface is found to provide a stronger grit retention in the bond and reduced drilling tool wear.

Magnetic methods of purification control of nanodiamond powders

Magnetic methods of quantitative determination of impurities in nanodiamond powders (NDPs) are discussed. For two types of NDPs, it is shown that the magnetic susceptibility depends on their treatment.

Effect of Physicochemical Characteristics of Diamond Micropowders on the Effectiveness of Their Separation in Magnetic Field

The paper examines the effect of chemical and pulsed high-voltage electric discharge treatment of synthetic diamond micropowders on their mechanical and physicochemical properties, magnetic fraction composition, and separation characteristic, as well as effectiveness of their distribution in the magnetic field. It is shown that treatment with molten sodium hydroxide slightly decreases the specific surface area of the powder, and pulsed high-voltage electric discharge treatment increases its specific surface area and activates its energy state, improving the effectiveness of powder distribution in the magnetic field.

Production of coarse-grained high-strength microgrits to be used in drilling tools

The technology of growing large single-crystal synthetic diamonds having high strength, strength uniformity, and thermal stability has been studied and the crystals have been produced. A design of a drill bit equipped with these single-crystal synthetic diamonds has been developed. The results of the field tests of pilot drill bits have been discussed.

Effect of impurities on the electric conductivity and magnetoresistance in carbon nanotubes

Temperature and magnetic field dependences of electric resistivity of carbon nanotubes both of the as-received material and of material chemically cleaned of impurities have been investigated. It has been shown that the temperature dependence of the electric resistivity of the studied powders of carbon nanotubes may be well described in the framework of 3D hopping conductivity with a variable hop length in a wide temperature range (5–250 K for the as-received nanotubes and 5–189 K for nanotubes after chemical treatment). Magnetoresistance of the as-received and chemically treated carbon nanotubes at temperatures of 5, 77, and 250 K has been shown to decrease with increasing magnetic field intensity.

The influence of uniformity of synthetic diamond grits on the drilling tool performance

For diamond powders with magnetic properties, which were prepared from diamond grains synthesized in the presence of ferrocobalt, a method is put forward that involves the grading of diamond grits by the degree of imperfection and additional classification to separate narrow 400/355 and 250/220 size ranges. This method is shown to provide elite diamond powders AS160-E through AS65-E that feature a great uniformity of strength and geometrical characteristics. The use of such powders in drilling bits improves the tool performance in hard rock drilling. The drill bit wear intensity is demonstrated to decrease with increasing strength and strength uniformity of AS160-E-AS65-E powders in combination with their improved linear-dimension uniformity.