Papers by Author: Maksim Antonov

Abstract: The present study deals with the tribological behavior of nanocrystalline diamond (NCD) coatings at high temperature sliding conditions. The NCD coatings were grown by plasma enhanced chemical vapor deposition (PECVD) method on the hard metal (WC-Co) substrates. The friction and wear tests were performed on ball-on-disc tribometer using a high-temperature chamber with rotary drive. The tests were carried out at room temperature, 300, 450 and 600 °C. The scanning electron microscopy (SEM), optical microscopy, mechanical profilometry and Raman spectrometry were used for investigation of the morphology and chemical composition of the wear scars and pristine surface. The depth and width of the wear scars measured after the high temperature sliding tests are larger in comparison with room temperature tests. It was observed that the coefficient of friction (COF) increased with increasing temperature. The wear rate of NCD coatings tested at 300-450° C was about 10 times higher than that at room temperature. The mechanisms involved for these variations are discussed.

Abstract: TiCN and TiAlN gradient coatings were deposited on the AISI 316L stainless steel substrates by lateral rotating cathode arc (LARC) physical vapour deposition (PVD) technology. Corrosion and tribocorrosion behaviour was studied in 3.5 wt. % NaCl solution. The thickness of coatings was about 3 μm. For both coatings the corrosion potential shifted to more positive values as compared to the uncoated substrate. The corrosion current density decreased for TiCN and TiAlN coatings indicating up to 40 folds higher polarization resistance. The coefficient of friction value of TiCN coating is three times lower and durability is six times higher than that of TiAlN coating under the same tribocorrosion conditions.

Abstract: The erosive wear resistance of manual arc welded hardfacings with low-carbon or stainless steel matrix, varied WC grain size (0.23-0.61 mm) and varied WC content (max. 40 wt. %) was studied. Electrodes were produced by JSC “Anykščių varis“ company (Lithuania). Testing was performed according to GOST 23.201-78 standard using the Centrifugal Accelerator of Kleis (CAK). Test parameters were as following: room temperature; silica sand with particles size 0-0.6 mm; particle impact velocity – 10, 30, 50 and 80 ms-1; impact angles – 30° and 90°.It was found that there is only minor (usually not more than 2 times) effect of WC grain size and content on erosive wear of studied hardfacings. There is strong effect of velocity on wear rate. The graph showing the effect of abrasive particle‘s kinetic energy on wear rate is provided. It was found that the wear rate increases 2.8 times faster than kinetic energy of abrasive particles. The wear resistance of coatings could be improved by addition of WC when hardfacing is tested with impact angle of 30°. However, for impact angle of 90° the addition of WC into hardfacing has no effect or is even detrimental (leading to the increase in wear rate). The hardfacings with WC grain size in the range from 0.14 to 0.27 mm have the lowest wear rates during testing with impact angle of 30°. A discussion of the wear mechanisms for the hardfacings is provided, based on data and observations obtained by using scanning electron microscopy.

Abstract: In this study, the tribological characteristics of plasma thermal spray coatings are studied with particular interest on formation and performance of Cr, Ti and Zr oxides under dry sliding at 500 °С with Pin-On-Disc configuration against NiAl. Plain Cr₂O₃, TiO₂ and ZrO₂ coatings were tested to trace the difference between performance of original and in-situ formed oxides. Friction surfaces were examined using SEM and X-ray spectral analyses. The highest wear resistance of NiAl-CrB₂ composite coatings can be related to the formation of Cr₂O₃ during the tribosynthesis process.

Abstract: This paper addresses an innovative syntactic foam produced out of metal powder (Fe), fly ash cenospheres (CS) and clay ceramic syntactic foams composite material (CM). Due to the low density of CS (bulk density - 0.38 g/cm³), the average density of these foams is about 2.6-2.9 g/cm³. It was found that CS undergoes phase transformation during thermal treatment at a temperature of 1200°C. Microstructural observations reveal a uniform distribution of CS and Fe particles in the composite. Compressive strength, and friction coefficient of obtained Fe/CS CM are in the range between 149 - 344 MPa and 0.15 - 1.1, respectively. Dependence of compressive strength on firing temperature is demonstrated exhibiting the maximum at 344 MPa; however, dependence of coefficient of friction on a material properties, obtained at different firing temperature exhibits the minimum value of 0.15 at the firing temperature of 1150 °C. The obtained syntactic form was shown to be a candidate for wear resistant applications.

Abstract: Basalt reinforced composites are quite recently (during last 20 years) developed materials having low density, high specific strength, good frictional, heat and chemical resistance. Natural mineral based fibres are potential alternatives to glass fibres for their strength and to carbon fibres for their lower cost. In order to use basalt reinforced composites for lightweight applications, it is necessary to perform wear characterisation. Basalt fibre, powder and scales reinforced, unsaturated polyester and epoxy resin composites were fabricated with various ratios of basalt and polymeric matrixes. The tribological behaviour of basalt reinforced composites was determined according to the ASTM G132 standard test method for pin abrasion testing. Results showed that type and content of reinforcement have a significant influence on the mechanical and tribological properties of the composites. Scanning electron microscope images are given to illustrate the wear mechanism of composites.

Abstract: Current paper concentrates on the wear resistance of a particle reinforced polymer matrix composite material. The composite material consists of unsaturated polyester resin that is filled with aluminum hydroxide. Aluminum hydroxide acts as hard phase and polyester as binding agent. The aim of the work was to understand the influence of particle size and filler material mass fraction to the wear resistance of the composite. The wear properties were determined according to standard test method using rubber wheel and silica.

Abstract: The main goal of this work is to study dry sliding wear behavior of NiCrSiB-TiB₂ plasma sprayed coating against NiCrSiB coating. NiCrSiB-based powders with 10, 20, 40 wt.% TiB₂ particles content were deposited on steel substrates by plasma spraying. The structure of NiCrSiB-TiB₂ coatings consists of Ni-based matrix and TiB₂ and CrB grains. Among the coatings studied, the NiCrSiB-20wt.%TiB₂ shows excellent wear-resistance. The worn surfaces were observed using scanning electron microscopy and Auger electron spectroscopy to determine the wear mechanisms.

Abstract: In the present article, the laser hardening of the carbon steel C45, previously coated by the physical vapour deposition (PVD) process, is studied. The (Al,Ti)N-G and nACo® (nc-Al_xTi_1-xN/α-Si₃N₄) coatings were applied. Nd:YAG laser with the laser beam power density of 1945 W/cm² and scan speed of 300 mm/min was used for hardening process. Laser hardening lead to the formation of hardened layer under both coatings, consisting of austenite and ferrite. The approximate depth of the hardened layer and maximal microhardness was approximately 0.2 mm and 955 HV0.05 and 0.1 mm and 520 HV0.05 in the case of the (Al,Ti)N-G and the nACo® coating, respectively. After laser hardening the sliding wear of the (Al,Ti)N-G coating decreased by 1.25 times and of the nACo® coating by 1.05 times.

Abstract: In the present study the high temperature impact/abrasion resistance of several boiler steels which are used in Estonian power plants were determined experimentally using the High Temperature Cyclic Impact Abrasion Test (HT-CIAT) at 500 and 600°C. Results indicate a strong dependence of the wear resistance on the materials microstructure and formation of the mechanically mixed layer with incorporated abrasive particles.