UDC 620.22:621.921
V. I. Kushch
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
vkushch56@gmail.com
Study of the thermodynamic and elastic properties of nanosized diamond single crystals by the method of classical molecular dynamics (pp. 3-15)
The results of the study of the thermodynamic and elastic properties of nanosized diamond single crystals by the method of classical molecular dynamics are presented. A number of structural models are considered, the choice of the empirical potential of interatomic interaction is justified, schemes for calculating cohesive and surface energy and elastic moduli at the macro- and nano-levels are presented. A parametric analysis of the models in the static approximation is carried out, regularities of the influence of the size and shape of the diamond nanocrystal on its thermodynamic and elastic properties are established, and a comparison is made with the available literature data.
Keywords: diamond, nanocrystal, thermodynamics, elasticity, molecular dynamics.
UDC 620.22-621.921.34
B. T. Ratov1, V. A. Mechnyk2, *, M. O. Bondarenko2, V. M. Kolodnitsky2, **
1NAO “Kazakh National Research Technical University named after K. I. Satpayev”, Almaty, Kazakhstan
2Institute of Superhard Materials named after V. M. Bakul, NAS of Ukraine, Almaty Kyiv, Ukraine
*vlad.me4nik@ukr.net
**vasylkolod56@gmail.com
Physical and mechanical properties of WC‒Co‒CrB2 matrices of composite diamond-bearing materials sintered by vacuum hot pressing for drilling tools (pp. 16-30)
The dependence of the physical and mechanical properties (hardness H, modulus of elasticity E, resistance to elastic deformation H/E and resistance to plastic deformation H3/E2) of samples of matrices made of hard alloy 94WC‒6Co (in % (by mass)) with different (from 0 to 10 % (by mass)) chromium diboride content of composite diamond-bearing materials formed by cold pressing with subsequent vacuum hot pressing was studied using nanoindentation. It is shown that the addition of CrB2 micropowder to the 94WC‒6Co composite allows the formation of a finer-grained structure, the parameters of which can be purposefully controlled by changing its concentration. At the same time, composites containing the CrB2 additive have a more uniform phase distribution and are characterized by greater solubility of components and the absence of pores at the interphase boundaries. It was found that the P–h load curves for composites of the WC–Co–CrB2 system are able to maintain their integrity compared to WC–Co composites. It was found that the introduction of CrB2 additive (in the range from 0 to 10% (by weight)) into the 94WC‒6Co composite causes a decrease in hardness H from 34.2 to 28.4 GPa and elastic modulus E from 800.4 to 510.2 GPa, but provides a more significant increase in elastic deformation resistance H/E from 0.043 to 0.056 and plastic deformation resistance H3/E2 from 0.062 to 0.088 MPa. The development of composite diamond-containing materials based on a WC‒Co‒CrB2 hard alloy matrix with increased parameters H/E and H3/E2 is important for optimizing drilling tool designs, increasing its reliability and wear resistance.
Keywords: composite, tungsten carbide, cobalt, chromium diboride, composition, concentration, vacuum hot pressing, structure, properties.
UDC 661.657.5
Peicheng Mo1, 2, 3, *, Jiarong Chen1, 2, 3, Chao Chen1, 2, 3, Yanjun Zhang1, 2, 3, Ying Luo1, 2, 3, Wenlong Wang1, 2, 3, Xiaoyi Pan1, 2, 3, Zhe Zhang1, 2, 3
1Guilin Tebon Superhard Material Co., Ltd, Guilin, Guangxi, P.R. China
2Guangxi Key Laboratory of Superhard Material, China Nonferrous Metal (Guilin) Geology And Mining Co., Ltd., Guilin, Guangxi, P.R. China
3National Engineering Research Center for Special Mineral Material, China Nonferrous Metal (Guilin) Geology And Mining Co., Ltd., Guilin, Guangxi, P.R. China
*2393707540@qq.com
Synthesis and Characterization of Polycrystalline Cubic Boron Nitride Using a Binder Based on the WC–B4C–Al2O3 System (pp. 31-39)
Using WC–B4C–Al2O3 as a binder, polycrystalline cubic boron nitride (PCBN) composite materials were synthesized under high temperature and ultrahigh pressure conditions. X-ray diffraction and scanning electron microscopy were used to analyze the phase composition and microstructure of the composite material, while its porosity, microhardness, flexural strength and abrasion coefficient were determined. The research results show that under ultra-high pressure (6 GPa) and temperature from 1250 to 1550 °C, the phase components in PCBN are mainly composed of BN, WB2, WB and Al2O3. During low-temperature sintering, the internal structure of the sample is loose, with holes and gaps, which leads to poor density, low flexural strength and low microhardness. With increasing temperature, the density, flexural strength and microhardness of PCBN increase. When the sintering temperature is 1550 °C, the comprehensive mechanical properties of PCBN are the best: microhardness is 38.6 GPa, flexural strength is 789.6 MPa, abrasion coefficient is 9371.
Keywords: PCBN, WB2, high temperature and ultra-high pressure, bonding agent.
UDC 669.018.25 M. M. Prokopiv
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv Kyiv, Ukraine
mprokopiv70@gmail.com
Formation of elongated inclusions of a new phase W2,3TiC2,6 in the structure of a hard alloy of the W–(Ti,Ta,W)–Co group after its solid-state annealing (pp. 40-48)
It was found that in the coarse-grained structure of the hard alloy WС–(Ti,Ta,W)С–10Со with a total content of TiС and TaС of 10% (by mass) and their ratio of 4:1 after sintering using a new technology and additional annealing at a temperature of 1200 °C for 7 h, in addition to carbide grains of the faceted form of WC, globular grains of the (Ti,Ta,W)С phase and layers of the Co-based phase, stochastically distributed elongated inclusions without a regular length-to-thickness ratio are present. The main chemical elements of these inclusions are W, Ti and C with the ratio described by the formula W2.3TiC2.6. The content of Co and Ta in it is at the level of statistical error (0.3%). The new chemical compound has a hexagonal crystal cell of the GaSe phase (type H) with parameters a = 15.95 nm and c = 3.75 nm. Structural inclusions of various shapes with sizes in the range of 10‒80 μm were found near individual parts of the surfaces of the new phase, in which the content and sizes of the Co-based phase exceed its similar characteristics in the main structure by 1.5‒4.0 and 6 times, respectively.
Keywords: carbides, hard alloy, structure, grains, new phase, elongated inclusions.
UDC 666.792: 621.793
I. V. Andreev, O. O. Matviychuk, N. V. Lytoshenko*, I. O. Gnatenko, O. V. Evdokimova
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
*lytnatvol@gmail.com
Microstructure and properties of porous skeletal composites based on ultra-coarse-grained tungsten carbide with a metal coating (pp. 49-61)
The influence of 0.6 μm thick coatings of ductile metals (Co, Ni, Cu) on the breaking load during compression of WC carbide particles with a size of 80/40 μm was studied. It was found that WC(Co) powder is 30% stronger than WC, and the breaking load of WC(Ni), WC(Cu), WC particles differs statistically insignificantly. For porous structures sintered with WC(Co), with an increase in pressing pressure from 30 to 200 MPa, the compressive strength increases by ~ 1.5 times and depends little on the sintering temperature. To study the dependence of the compressive strength of porous skeletal structures obtained on the basis of ultra-coarse-grained WC(Co) powders on the microstructure parameters, the method of mathematical modeling using the proposed analytical algorithm was applied. It was established that a decrease in porosity from 30 to 20% increases the strength of the material by two times. Comparison with experimental data indicates good predictive capabilities of the applied model.
Keywords: ultra-coarse-grained WC carbide, plastic coating, porous skeletal structures, compressive strength, mathematical modeling.
UDC 621.623
Yu. D. Filatov1, *, V. I. Sidorko1, A. Yu. Boyaryntsev2, S. V. Kovalev1, V. A. Kovalev1
1V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
2Institute of Scintillation Materials, NAS of Ukraine, Kharkiv, Ukraine
*filatov2045@gmail.com
The influence of dielectric constants of the processed material, polishing powder and dispersed system on the energy of their interaction during polishing of optical surfaces (pp. 62-72)
As a result of the study of the patterns of the influence of dielectric constants of the material, polishing powder and dispersed system on the energy of their interaction, it was found that the Lifshitz constants and the interaction potential of the polishing powder particle with the processed surface decrease linearly with a decrease in the dielectric permittivity function, which leads to an increase in polishing performance and a deterioration in the roughness of polished surfaces. It is shown that the efficiency of resonant energy transfer from particles of the dispersed phase of the polishing dispersed system to the treated surface is significantly affected by the separation between the processed material, the polishing powder and the dispersed system in terms of their dielectric permittivities. It is established that the dielectric permittivity functions characteristic of the polishing of optical surfaces using dispersed systems of micro- and nanopowders change in proportion to the separation in terms of dielectric permittivities, which is determined by the ratios of their static values for the processed material, the polishing powder and the dispersed system.
Keywords: polishing, dielectric permittivity, polishing productivity, surface roughness.
UDC 621.93.026.23
V. I. Lavrinenko
V. M. Bakul Institute of Superhard Materials, NAS of Ukraine, Kyiv, Ukraine
*lavrinen52@gmail.com
To the analysis of the assessment of energy costs during diamond-abrasive processing with wheels made of superhard materials (pp. 73-81)
An analysis of the assessment of energy costs in the process of diamond-abrasive processing with wheels made of superhard materials has been made and the agreed data of these indicators have been determined. It has been shown that when the known literature data for grinding processes are reduced to one dimension (kJ/cm3), they almost coincide. At the same time, such data on the specific energy intensity of grinding significantly exceed the specific heat capacity of melting of the processed material. To resolve the existing contradiction, it is proposed to introduce a calculation of the specific energy intensity of grinding for processing with wheels made of superhard materials, taking into account the volume consumed during processing of the abrasive layer of the wheel, and a formula for calculating the specific energy intensity is proposed. It is shown that the calculation according to this formula allows for an adequate assessment of the energy intensity and it corresponds to the data on the specific heat capacity of melting for such processed tool materials as high-speed steels and oxide-carbide ceramics for diamond processing processes, as well as processing with cubic boron nitride wheels.
Keywords: diamond-abrasive processing, specific energy intensity of grinding, specific heat capacity of melting, abrasive layer of the wheel.
UDC 666.762.5:621.914.1
Jinyang Xu*, Linfeng Li, Min Ji, Ming Chen
State Key Laboratory of Mechanical System and Vibration, School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai, P.R. China
*xujinyang@sjtu.edu.cn
A Study on PCD Tool Wear in Hard Milling of Fully Sintered 3Y-TZP Ceramics (pp. 82-93)
The wear behavior and mechanisms of polycrystalline diamond tools in hard milling of 3Y-TZP ceramics were examined. The workpiece samples were fabricated at full sintering temperature to fully enamel the zirconia substrate, and a PCD straight edge was brazed onto the tungsten carbide tool body along its axis direction to ensure successful orthogonal milling of the workpiece sample. A series of experiments were conducted on hard milling of samples by varying the spindle speed on a five-axis CNC machining center. The morphology of the wear of PCA edges was investigated using a scanning electron microscope to determine the dominant wear modes and fracture patterns governing hard milling of 3Y-TZP ceramics. The effect of spindle speed on the wear pattern of PCA was investigated. Based on the results, technical recommendations for hard milling of fully sintered 3Y-TZP ceramics were provided.
Keywords: zirconia ceramics, hard milling, polycrystalline diamond tools, tool wear.