V. G. Gargin

Novel hybrid ultrahard material

A novel hybrid ultrahard polycrystalline composite material has been produced by the reinforcement of the polycrystalline diamond composite thermostable material with a CVD grown polycrystalline diamond. It has been found that a thermal treatment of a polycrystalline diamond grown at high pressure ensures an increase of the CVD diamond hardness from 77 to 140 GPa. Tests of drilling tools have shown that in turning granite of the XI drillability index the wear intensity of rock destruction elements of the hybrid ultrahard material is lower than that of rock destruction elements of polycrystalline diamond composite thermostable material by a factor of 14.

Structure and physico-mechanical properties of CVD diamonds of various crystalline perfections in the hybridite material

A comparison study has been conducted of the substructure of samples of CVD diamonds of various crystalline perfections in the hybridite material produced at high pressures and temperatures. The material thermostability and hardness variation as a result of the formation of a polycrystalline shell of diamond thermostable composite material around a CVD diamond at high pressure and temperature have been examined. Based on the data obtained on the efficiency of tools from hybridite with CVD diamonds of various structural perfections, the most efficient applications of tools have been recommended.

Structure and hardness of octahedral natural diamond single crystals depending on the HPHT treatment conditions

The structure evolution of octahedral natural diamond single crystals has been studied depending on the HPHT treatment using Raman scattering and infrared spectroscopy. It has been found that the formation of a polycrystalline diamond capsule around a single crystal at p = 8 GPa and T = 1500°C gives rise to a combined structural-stressed state in the single crystal due to its plastic strain. This state has been manifested by a significantly (more than double) broadening of the characteristic line of diamond (1332 cm−1) in the Raman spectrum and the increase of a single crystal hardness from 105 to 120 GPa.

New superhard material for drilling tools

The authors discuss physical-mechanical properties of a new thermostable polycrystalline diamond composite material and its potential use in rock-destruction tools for drilling wells in hard rock. The paper presents the results of investigation aimed at clarifying the effect of dimensions of inserts made of this new material on the drilling tool performance. An optimal size of inserts to be set in the bit face has been established which improves hard rock drilling efficiency in comparison to conventional tools.

Diamond polycrystalline composite material and its properties

The results of experimental studies on the development of a diamond polycrystalline material to equip drill bits have been considered. Angles of wetting graphite by sintering aids Ni, Co, and alloy of them have been defined. Among the composites, which have been tested, the longest durability and the highest strength have been exhibited by the composite of the Cd-Co-34Ni formulation.

Comparative physico-mechanical characteristics of micron powders of synthetic and natural diamonds and polycrystalline composite materials based on them

Physico-mechanical characteristics of micron powders of synthetic (SD 40/28) and natural (ND 40/28) diamonds and of polycrystalline composite materials based on them have been studied. Both the powders have been shown to meet the requirements of DSTU 3292-95 (State Standard of Ukraine). At the same time the abrasiveness of natural diamond is higher than that of synthetic diamond, while the grain density and specific surface is lower than that of synthetic diamond grains. The elastic characteristics of sintered polycrystalline composite materials (the Young modulus, shear modulus, bulk modulus, Poisson ratio, and wear resistance in stone working by friction) of a composite sintered from the natural diamond micron powder are higher, while the life at cyclic compression is somewhat lower as compared to a composite sintered from the synthetic diamond micron powder.

Diamond polycrystalline composite material with dispersion-hardened nickel-based additive

A diamond polycrystalline composite material with improved physico-mechanical characteristics has been obtained at high pressure and temperature using nickel and cobalt powders and tungsten carbide nanopowder as sintering aids. Samples of this material reinforced with CVD polycrystalline diamond at high pressure and temperature have been manufactured.

Influence of High Pressure and Temperature on the Structure and Properties of the WC–6Co Hard Alloy

The results are presented of the barothermal treatment studies of a WC–6Co hard alloy at high pressure (7 GPa). It is shown that such a treatment of hard alloy leads to the deterioration of the basic physico-mechanical characteristics, specifically the strength at the contact, and the coercive force, which is stipulated by the increase of the defects amount in the structure of the carbide phase of the hard alloy.

Phase transformations of n-layer graphenes into diamond at high pressures and temperatures

The effect of high pressure (7.7 GPa) and temperature (1700°C) on the phase transformations of both graphene plates with a high degree of crystallinity having less than four layers and thickness not exceeding 5 nm and powders of multilayer graphenes (of 10–20 monolayers) and 8–12 nm in thickness was experimentally studied in the presence of carbon solvents (Ni–Mn alloy, iron). Factors both contributing and inhibiting the diamond synthesis from graphene in the presence of the solvents for carbon are defined. It is shown that the transformation of multilayer graphenes into diamond at high pressure and temperature by a two-stage scheme of the diamond synthesis (i.e., after three-dimensional structural ordering of graphene at the first stage) is preferable.

Structure and properties of impact diamonds from the Popigai Deposit and polycrystals based on them

Properties of impact diamonds from the Popigai Deposit have been studied in a free state and in a composition of a compact. Raman spectra have been taken of the initial micron powders and polycrystals HP-HT sintered both in the presence of sintering aids and without them. Hardness, HV, of sintered polycrystals have been found, structural variations in diamond crystal lattice depending on the sintering conditions have been studied.