Статті КРС (ЛІ)

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Browsing Статті КРС (ЛІ) by Author "Chishkala, V. A."

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    Effect of CrB2 on the Microstructure, Properties, and Wear Resistance of Sintered Composite and the Diamond Retention in Fe–Cu–Ni–Sn Matrix
    (Allerton Press Inc., USA, 2021) Mechnik, V. A.; Bondarenko, N. A.; Kolodnitskyi, V. M.; Zakiev, V. I.; Zakiev, I. M.; Gevorkyan, E. S.; Chishkala, V. A.; Kuzin, Nickolai O.
    EN: Using the method of powder metallurgy, we studied the effect of CrB2 additives (0–8 wt %) on the formation of the structure of the diamond–matrix transition zone and the matrix material, microhardness, elastic modulus, and fixation of diamond grains in a Fe–Cu–Ni–Sn matrix and determined the wear resistance of sintered composite diamond-containing materials (DCMs). Micromechanical and tribological tests were carried out using composite samples 10 mm in diameter and 5 mm thick. The transition zone structure depends significantly on the concentration of CrB2 in the composite and has a different nature than the structure of the matrix material. The structure of the DCM transition zone based on the 51Fe–32Cu–9Ni–8Sn matrix consists of Cu, α-Fe, and Ni3Sn phases with graphite inclusions, and with the addition of CrB2, it consists of the α-Fe phase and Fe3C, Cr7C3, and Cr3C2 carbide layers without graphite inclusions. The hardness and elastic modulus of the matrix material of the sintered composites linearly increase with an increase in the concentration of CrB2 in their composition, while the wear rate decreases. The addition of 2 wt % of CrB2 to the 51Fe– 32Cu–9Ni–8Sn composite increases hardness from 4.475 to 7.896 GPa and an elastic modulus from 86.6 to 107.5 GPa and decreases the wear rate from 21.61 × 10–6 to 10.04 × 10–6 mm3 N–1 m–1. The mechanism for improving the mechanical properties and decreasing the wear resistance of DCM samples containing CrB2 additive consists in grain refining of the matrix phases of iron and copper from 5–40 to 2–10 μm and in binding carbon released during graphitization of diamond grains into nanosized carbides Fe3C, Cr7C3, and Cr3C2. This, in turn, increases the ability of the matrix material to keep diamond grains from falling out during the operation of DCMs. The coarse-grained structure and the formation of graphite inclusions in the diamond–matrix transition zone explain poor mechanical and tribological properties of the initial (51Fe–32Cu–9Ni–8Sn) composite, causing its premature destruction and falling out of diamond grains from the DCM matrix.
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    Effect of Vanadium Nitride Additive on the Structure and Strength Characteristics of Diamond-Containing Composites Based on the Fe–Cu–Ni–Sn Matrix, Formed by Cold Pressing Followed by Vacuum Hot Pressing
    (Springer Link, 2021) Ratov, B. T.; Mechnik, V. A.; Bondarenko, N. A.; Kolodnitskyi, V. M.; Kuzin, Nickolai O.; Gevorkyan, E. S.; Chishkala, V. A.
    ENG: We prepared samples of composite diamond-containing materials 10 mm in diameter and 8 mm in thickness, based on the 51Fe–32Cu–9Ni–8Sn matrix (wt %) with different (0–10 wt %) concentrations of vanadium nitride (VN), the physical the mechanical characteristics of which depend on the composition of the iron matrix. The optimal (cVN = 4%) concentration of vanadium nitride in the matrix of composites sintered in the temperature range of 20–1000°C at a pressure of 30 MPa for 5 min ensures the highest indices of the physicomechanical properties of the composites (Rbm = 1110 MPa and Rcm = 1410 MPa) due to the dispersion mechanism of strengthening and modification of the structure, that is, a decrease in the average grain size, the disappearance of pores, the formation of clusters of the inhibitor phase at the interphase boundaries, and the phase composition of the composites. All sintered samples containing VN powder additives in the charge are characterized by a more uniform distribution of phases and a more dispersed structure compared to a sample without VN additives. The structure of composites containing a VN additive consists of a solid solution of nitrogen and vanadium in α-iron and a mixture of Fe, Cu, Ni, and Sn phases and primary and secondary dispersed phases of vanadium nitride.