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Comparative Study of the Mechanical and Tribological Characteristics of Fe–Cu–Ni–Sn Composites with Different CrB2 Content under Dry and Wet Friction
(Springer Nature Switzerland AG, 2021) Mechnik, V. A.; Bondarenko, N. A.; Kolodnitskyi, V. M.; Zakiev, V. I.; Zakiev, I. M.; Gevorkyan, E. S.; Kuzin, Nickolai O.; Yakushenko, O. S.; Semak, I. V.
EN: The structure, phase composition, hardness, and elasticity modulus of sintered Fe–Cu–Ni–Sn–CrB2 composites and their tribological properties under dry and wet friction have been studied by X-ray diffraction, scanning electron microscopy, microindentation, and tribological testing. The obtained results have demonstrated that the microstructure and mechanical and tribological properties of these composites depend on the CrB2 additive content. The Fe–Cu–Ni–Sn–CrB2 composites incorporate the α-Fe, γ-Fe, and Cu phases and a certain fraction of the crystalline Cu9NiSn3, NiSn3, and CrB2 phases. The hardness and elasticity modulus of these composites are almost independent of the friction medium (dry or wet), and the friction force and the wear rate are variable. The Fe–Cu–Ni–Sn–CrB2 composites are superior to the Fe–Cu–Ni–Sn composites in their mechanical and tribological properties. The addition of 2 wt % of CrB2 to the 51Fe–32Cu–9Ni–8Sn composite has decreased the friction force from 220 to 170 mN and the wear rate from 7.41 × 10–2 to 3.41 × 10–2 mm3/(N m) under dry friction and, respectively, from 200 to 140 mN and from 8.19 × 10–2 to 4.10 × 10–2 mm3/(N m) under wet friction. A further growth in the CrB2 content in the composites leads to an increase in the wear rate. The mechanism of increase in the wear resistance of the composite containing 2 wt % of CrB2 as compared to the initial composite implies the formation of a more fine-grained structure with an optimal combination of the hardness and elasticity modulus. The Fe–Cu–Ni–Sn–CrB2 composites can be used as a material for the matrix of composite diamond-containing materials subjected to strong wear.
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.
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.
Influence of Diamond–Matrix Transition Zone Structure on Mechanical Properties and wear of Sintered Diamond-Containing Composites Based on Fe–Cu–Ni–Sn Matrix with Varying CrB2 Content
(Elsevier Ltd, 2021) Mechnik, V. A.; Bondarenko, N. A.; Kolodnitskyi, V. M.; Zakiev, V. I.; Zakiev, I. M.; Kuzin, Nickolai O.; Gevorkyan, E. S.
ENG: The influence of CrB2 additive (within the interval ranging from 0 to 8 wt%) on the formation of structure of the diamond–matrix transition zone and the matrix material, microhardness, elastic modulus, retention of diamond grains in Fe–Cu–Ni–Sn matrix material and wear resistance of sintered diamond-containing composites (DCCs) by the powder metallurgy method has been studied. Micro-mechanical and tribological tests were conducted using composite samples 10 mm in diameter and 5 mm thick. It has been established that the transition zone structure significantly depends on the CrB2 content in a composite and is of a different nature than that of the matrix material. The structure of DCCs transition zone based on 51Fe–32Cu–9Ni–8Sn matrix consists of Cu, α-Fe and Ni3Sn phases with graphite inclusions. The structure of DCCs transition zone based on 51Fe–32Cu–9Ni–8Sn matrix with CrB2 additives consists of the α-Fe phase and Fe3C, Cr7C3, Cr3C2 carbide layers without graphite inclusions. It has been shown that the hardness and the elastic modulus of sintered composite matrix material increase linearly as the concentration of CrB2 in their content increases while the wear rate decreases. The addition of 2 wt% of CrB2 to 51Fe–32Cu–9Ni–8Sn composite contributes to an increase in its hardness from 4.475 to 7.896 GPa and elastic modulus from 86.6 to 107.5 GPa thus reducing the wear rate from 21.61 × 10−6 to 10.04 × 10−6 mm3 N−1 m−1. The mechanism for enhancing the mechanical properties and wear resistance of DCCs samples containing CrB2 additives consists in refining of matrix phases of iron and copper from 25 μm to 10 μm and binding the carbon released during the graphitization of diamond grains to Fe3C, Cr7C3, Cr3C2 nanoscale carbides. This, in turn, increases the ability of matrix material to keep diamond grains from falling out during DCCs operation. Low values of mechanical properties and wear resistance of the initial (51Fe–32Cu–9Ni–8Sn) composite are attributed to the coarse-grained structure and formation of graphite inclusions in the diamond–matrix transition zone, causing its premature destruction and separation of diamond grains from the DCCs matrix.
Influence of the Addition of Vanadium Nitride on the Structure and Specifications of a Diamond–(Fe–Cu–Ni–Sn) Composite System
(International OCSCO World Press, Poland, 2018) Mechnik, V. A.; Bondarenko, N. A.; Kuzin, Nickolai O.; Gevorkian, E. S.
EN: This article discusses the influence of the addition of vanadium nitride on the mechanical and operational properties of diamond composite material based on metallic bond comprised of iron, copper, nickel, and tin obtained by sintering in a mold at 800°C for 1 h with subsequent hot repressing. It has been established that the addition of vanadium nitride in the amount of 2 wt % to diamond–(51Fe–32Cu–9Ni–8Sn) increases the ultimate compressive strength from 846 to 1640 MPa and bending strength from 680 to 1120 MPa, as well as decreases the wear intensity of the composite material from 0.0069 to 0.0033 g/km. The mechanism of improving the tribological properties has been revealed.
Microstructural Features and Mechanical and Tribological Properties of Fe–Cu–Ni–Sn Composites Precipitation-Hardened with CrB2 Additions. Powder Metallurgy and Metal Ceramics
(Springer, 2021) Mechnik, V. A.; Bondarenko, N. A.; Kolodnitskyi, V. M.; Zakiev, V. I.; Zakiev, I. M.; Gevorkyan, E. S.; Kuzin, Nickolai O.
ENG: The structural features, hardness, elastic modulus, and wear resistance of Fe–Cu–Ni–Sn composites with different CrB2 contents, produced by cold pressing and subsequent sintering with additional hot pressing, were studied by X-ray diffraction, scanning electron microscopy, microindentation, and tribological testing. The micromechanical and tribological tests were performed on composite samples 10 mm in diameter and 5 mm thick in dry friction conditions. The test results showed that the mechanical and tribological properties of the composites depended on the CrB2 content. The microhardness and elastic modulus of the samples varied from 1.2 to 9.2 GPa and from 110 to 245 GPa, respectively, depending on their composition, resulting from the uneven distribution of α-Fe, Cu, Cu9NiSn3, NiSn3, and CrB2 phases. The addition of 2 wt.% CrB2 to the 51Fe–32Cu–9Ni– 8Sn composite increased its hardness from 1.2–2.8 GPa to 2.0–4.5 GPa and the elastic modulus from 110–190 GPa to 130–200 GPa and decreased the wear rate from 22.93 ∙ 10–3 to 10.19 × 10–3 mm3 N–1 m–1. The mechanism of increasing the wear resistance of the composite sample containing 2 wt.% CrB2 in comparison with the starting composite was associated with the refinement of iron and copper grains from 5–40 μm to 2–10 μm and the presence of discrete areas of greater hardness and higher elastic modulus. A further increase in the CrB2 content from 2 to 8 wt.% in the composite was accompanied by a simultaneous increase in hardness from 2.0–4.5 GPa to 4.8–9.2 GPa, elastic modulus from 130–200 GPa to 150–245 GPa, and wear rate from 10.19 ×10–3 to 16.68 ∙10–3 mm3 N–1 m–1. The higher wear rate of these composites was due to excessive brittleness caused by excessive CrB2 content.
Physico-Mechanical and Tribological Properties of Fe–Cu–Ni–Sn and Fe–Cu–Ni–Sn–VN Nanocomposites Obtained by Powder Metallurgy Methods
(Faculty of Engineering, University of Kragujevac, Serbia, 2019) Mechnik, V. A.; Bondarenko, N. A.; Kolodnitskyi, V. M.; Zakiev, V. I.; Zakiev, I. M.; Dub, S. N.; Storchak, M.; Kuzin, Nickolai O.
EN: Abstract. The results of studies aimed at improving the mechanical and operational properties of the Fe–Cu–Ni–Sn and Fe–Cu–Ni–Sn–VN composite materials obtained by powder metallurgy methods are presented. A comparative analysis of mechanical and tribological characteristics, including the determination of nanohardness, elastic modulus, friction force, friction coefficient, and volume of wear groove was performed. It was shown that the use of 3 wt% nano-dispersed VN powder in the 51Fe–32Cu–9Ni–8Sn charge, in which the grain size was ~2000–5000 nm, makes it possible to increase the nanohardness from 2.68 to 5.37 GPa and reduce the elastic modulus from 199 to 125 GPa. As a result, the parameters H/E and H3/E2, which describe the resistance of the material to the elastic deformation of failure and the resistance of the material to plastic deformation, increase by 3.3 and 20 times, respectively, and the friction force and the volume of the wear groove decrease by 1.8 and 16 times, respectively. The reasons for the change in the mechanical characteristics of sintered composites during nanoindentation and the different nature of their wear are discussed. The interrelation of the microstructure with mechanical and tribological properties is established. It is shown that the parameters H/E and H3/E2 can be used to predict the wear resistance of the composites under study.
A Study of Microstructure of Fe-Cu-Ni-Sn and Fe-Cu-Ni-Sn-Vn Metal Matrix for Diamond Containing Composites
(Published by Elsevier Inc., 2018) Mechnik, V. A.; Bondarenko, N. A.; Dub, S. N.; Kolodnitskyi, V. M.; Nesterenko, Yu. V.; Kuzin, Nickolai O.; Zakiev, I. M.; Gevorkyan, E. S.
EN: To obtain bulk of 51Fe–32Cu–9Ni–8Sn and 49.47Fe–31.04Cu–8.73Ni–7.76Sn–3VN nanocomposites, a pressing method at room temperature and subsequent hot pressing in a vacuum was used. The microstructure of the sintered composites by X-ray diffraction and transmission electron microscopy was investigated. It is shown that in the 49.47Fe–31.04Cu–8.73Ni–7.76Sn–3VN composite there was a dissolution of vanadium nitride in γ‑iron and formation of a supersaturated solid solution of nitrogen and vanadium in the α‑iron. As a result, there was a substantial grinding of ferrite grains (from 5 to 50 μm to 20–400 nm) as compared to a sample without vanadium nitride (from 5 to 50 μm to 400–800 nm). Nanocomposites are considered as promising materials to create a new generation of diamond containing composites.

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