Dry Friction Conditions Research Articles

TRIBOLOGICAL PROPERTIES OF MED610 MEDICAL MATERIALUSED IN POLYJET MATRIX 3D PRINTING TECHNOLOGY

3D printing is increasingly being used in many industries and in medicine. As a result, new materials are beingsought and researched, in particular biocompatible materials. Such materials can be used for medical devices,surgical instruments, and orthopaedic devices, as well as in bone surgery, tissue engineering, prosthetics,regenerative medicine, and the creation of drug delivery systems. This paper presents an analysis of the resultsof tribological testing of a biocompatible material used in 3D printing technology. The tests were conductedon a TRB3 tribometer (Anton) in a sphere-disk association. The tests were carried out by making cylindricalspecimens with a diameter of 40 mm and a height of 6 mm from the MED610 material using photo-curing liquidpolymer resin (PJM) technology. The specimens were fabricated in High Quality mode with a layer thicknessof 0.016 mm and with different print directions in the X-Z plane: 0, 45, and 90. The analysis was carriedout under technical dry friction conditions and in the presence of saline solution (0.9% NaCl). The tests wereperformed under fixed test parameters, i.e. speed and loading of the specimens. Ball-disc tests were carried outusing balls (counter-specimen) made of different materials with a diameter of 6 mm. Studies have shown that thedirection of printing affects tribological wear, due to the anisotropic nature of the 3D printing technology. Thelowest average coefficient of friction was obtained for specimens with a print direction of 90.

Preparation and Tribological Behaviors of Antigorite and Wollastonite Mineral Dual-Phase-Reinforced Polytetrafluoroethylene Matrix Composites

Research on polymer matrix composites with excellent tribological properties has received increasing attention in recent years. In this study, antigorite and wollastonite mineral dual-phase-reinforced polytetrafluoroethylene (PTFE) matrix composites were prepared by filling PTFE with mineral powders using ball-milling, cold-pressing, and pressureless sintering methods. The phase structure, microstructure, chemical composition, Shore hardness, and tribological behavior of the composites rubbed against steel balls under dry friction conditions were investigated. The results show that the composites have a dense structure and uniform distribution of mineral phases, with a Shore hardness of 62–68.8, an increase of 18.7–23.7% compared to pure PTFE. Compared with the addition of mono antigorite or wollastonite, the composites prepared by simultaneously filling the two minerals exhibited excellent tribological properties. The average friction coefficient and wear volume of the (10Atg + 20Wl)/PTFE composites were reduced by 44.2% and 71.4%, respectively, compared to those of pure PTFE. A dense and continuous tribofilm composed mainly of SiO2, MgSiO3, Mg2SiO4, MgO, CaO, CaMg(SiO3)2, and CaF2 was formed on the worn surfaces of both the dual-phase-reinforced PTFE matrix composites and counterpart steel balls during the friction process. The reduction in friction and wear is attributed to the reinforcement effect of the minerals on the PTFE matrix as well as the complex physical and chemical reactions at the friction interface stimulated by the synergistic effects between the two minerals. The addition of wollastonite reduced the phase transition temperature of antigorite, promoting more tribochemical reaction products with good abrasion resistance and friction-reducing properties, which contributed to the excellent tribological behavior of the composites.

The Comparison of the Multi-Layer Artificial Neural Network Training Methods in Terms of the Predictive Quality of the Coefficient of Friction of 1.0338 (DC04) Steel Sheet.

Friction is one of the main phenomena accompanying sheet metal forming methods, affecting the surface quality of products and the formability of the sheet metal. The most basic and cheapest way to reduce friction is to use lubricants, which should ensure the highest lubrication efficiency and at the same time be environmentally friendly. Due to the trend towards sustainable production, vegetable oils have been used in research as an alternative to petroleum-based lubricants. The analysis of friction in sheet metal forming requires an appropriate tribotester simulating the friction conditions in a specific area of the sheet metal being formed. Research has used a special strip drawing tribometer, enabling the determination the value of the coefficient of friction in the blankholder zone in the deep drawing process. Quantitative analysis of the friction phenomenon is necessary at the stage of designing the technological process and selecting technological parameters, including blankholder pressure. This article presents the results of friction testing of 1.0338 (DC04) steel sheets using a strip drawing test. The experimental tests involved pulling a strip of sheet metal between two countersamples with a rounded surface. The tests were carried out on countersamples with different levels of roughness for the range of contact pressures occurring in the blankholder zone in the deep drawing process (1.7-5 MPa). The values of the coefficient of friction determined under dry friction conditions were compared with the results for edible (corn, sunflower and rapeseed) and non-edible (Moringa, Karanja) vegetable lubricants. The tested oils are the most commonly used vegetable-based biolubricants in metal forming operations. Multi-layer artificial neural networks were used to determine the relationship between the value of the contact pressure, the roughness of the countersamples, the oil viscosity and density, and the value of the coefficient of friction. Rapeseed oil provided the best lubrication efficiency during friction testing for all of the tested samples, with an average surface roughness of Sa 0.44-1.34 μm. At the same time, as the roughness of the countersamples increased, a decrease in lubrication efficiency was observed. The lowest root mean squared error value was observed for the MLP-4-8-1 network trained with the quasi-Newton algorithm. Most of the analysed networks with different architectures trained using the various algorithms showed that the kinematic viscosity of the oil was the most important aspect in assessing the friction of the sheets tested. The influence of kinematic viscosity on the value of the coefficient of friction is strongly dependent on the surface roughness of the countersamples.

Effect of process parameters on the growth and wear resistance of CrAlN coating on silicon nitride surface

PurposePreparing CrAlN coatings on the surface of silicon nitride bearings can improve their service life in oil-free lubrication. This paper aims to match the optimal process parameters for preparing CrAlN coatings on silicon nitride surfaces, and reveal the microscopic mechanism of process parameter influence on coating wear resistance.Design/methodology/approachThis study used molecular dynamics to analyze how process parameters affected the nucleation density, micromorphology, densification and internal stress of CrAlN coatings. An orthogonal test method was used to examine how deposition time, substrate temperature, nitrogen-argon flow rate and sputtering power impacted the wear resistance of CrAlN coatings under dry friction conditions.FindingsNucleation density, micromorphology, densification and internal stress have a significant influence on the surface morphology and wear resistance of CrAlN coatings. The process parameters for better wear resistance of the CrAlN coatings were at a deposition time of 120 min, a substrate temperature of 573 K, a nitrogen-argon flow rate of 1:1 and a sputtering power of 160 W.Originality/valueSimulation analysis and experimental results of this paper can provide data to assist in setting process parameters for applying CrAlN coatings to silicon nitride bearings.

Influence of diamond-like carbon coatings and micro-texturing on friction and wear of seal interfaces: Experiment and simulation study

For mechanical seal friction vice in dry friction conditions, due to friction wear serious failure, is the slurry pump and other instruments in the operation of the process of the urgent need to solve the problem. In this paper, in order to optimize and enhance the friction and wear problem of mechanical seal end face of slurry pump. Surface treatment of mechanical sealing rings with diamond-like carbon (DLC) coating and surface microtexturing, and at different rotational speeds and normal forces, the surface hardness, wear coefficient and dry friction coefficient of the sealing rings were analyzed by experimental comparison, and the wear morphology was collected by electron microscopy, having analyzed the results of the sets of, the end face structure of the mechanical seal was optimized. Based on Archard wear model simulation calculations, the seal ring wear depth and wear quality were obtained. The results show: under dry friction conditions, the synergistic effect of the DLC coating and the surface micro-texture (MT), the coefficient of friction is reduced by approx. 68% and the quality and depth of wear is minimized. Excessive speeds and normal forces are more prone to wear behavior caused by abrasive wear. Simulation results of surface treatment groups, DLC / MT group maximum wear depth is the smallest; wear quality test and simulation of the maximum error within 15.7%. The results of the study can provide a basis for a phosphoric acid plant slurry pump mechanical seal design.

Origin and evolution of false brinelling and fretting corrosion under rolling conditions

Rolling bearings working in oscillating applications often suffer from false brinelling and fretting corrosion that limit their service life. At present, the study of oscillation-induced failures is primarily dominated by a large number of sliding and bench tests. However, most of the previous work are not able to fully describe the two closely related but different failure mechanisms. In this study, the origin and evolution of the two failures are thoroughly investigated under strictly controlled oscillating rolling conditions. The results show that failure evolves from false brinelling to fretting corrosion under dry friction conditions regardless of the oscillation amplitude. This process is accompanied by a large area peeling and serious oxidation, and the oxygen content increases from 2.50 wt% to 21.22 wt%. Oxidation is a crucial factor in the evolution of false brinelling into fretting corrosion. However, the distribution of microwear and oxygen content depend on the oscillation amplitude. Under lubrication conditions, the friction coefficient (COF) is smaller in the initial stage and led to local slip or transient instability of rolling elements. Therefore, the size of the wear marks and COF increased and appeared to be larger than those under a dry friction condition. However, grease can separate the contact surfaces, only surface deformation owing to false brinelling and slight damage at the roughness level occurred. The evolution of false brinelling and fretting corrosion is also closely related to residual stress. False brinelling often occurrs with residual stress accomulation, meanwhile, the residual stress increases from 120 to 300 MPa. When peeling occurs, residual stress is released. The failure pattern transformed from false brinelling to fretting corrosion and is accompanied by oxidation. So far, none of investigation is able to show satisfactory evolution of oscillating-induced failures, this study may contribute to more scientific understanding of rolling bearings against long-run reciprocating oscillating wear.

Wear of the 3D Printed Polylactic Acid Elements Sliding against the Synthetic Resins at the Higher Speed Friction

Since the requirement of high dust-free levels, it is necessary to develop the technologies with anti-wear and low dust generation for drive elements that can be quickly printed. Polylactic acid and synthetic resins are often paired with each other for the 3D printed driven elements. To achieve "smooth friction", the adhesion wear under dry friction conditions should be reduced. To achieve a "high dust-free level", the anti-wear of the paired elements under higher speed friction should be improved to reduce the generation of abrasive dust. Therefore, wear of the 3D printed polylactic acid elements sliding against the synthetic resins at the high speed friction are investigated in this paper.

Electrospark alloying of 30KhGSN2A stee l with alloy based on systems of immiscible components

The studies of the influence of the parameters of the electrospark alloying mode (EIL) on the properties of steel coated on the basis of copper alloys made it possible to determine not only the change in the mechanical and fatigue properties of the material, but also to choose rational technological modes. The rational modes of electrospark coating of bronze VBr5М and BrAZhMCz10-3-1.5, as well as an alloy based on the Cu—Pb system on the surface of parts made of steel 30KhGSN2A at the installation are determined ELFA-512M in automatic processing. It is shown that in order to eliminate the burnout of phosphorus during EIL of parts with bronze grade VBr5M, it is necessary to carry out the process in an inert gas (argon). It has been established that the coating applied by the electrospark method based on bronze does not affect the strength and plastic properties of steel 30KhGSN2A. At the same time, EIL bronze leads to a decrease in the low-cycle fatigue of samples made of steel 30KhGSN2A. Based on the results of studies of the coefficient of friction and wear of samples under dry friction conditions after EIL for the manufacture of parts operating under high loads under sliding friction conditions, taking into account the data of mechanical tests, it is possible to recommend for use bronze grade BrAZhMCz10-3-1.5 and a composite material based on immiscible components of the system 64 % Cu—36 % Pb.

ТЕХНОЛОГИЧЕСКИЕ ОСОБЕННОСТИ ВОССТАНОВЛЕНИЯ ШЕЕК КОЛЕНЧАТЫХ ВАЛОВ В СВЯЗИ С ИХ СТАРЕНИЕМ В ПРОЦЕССЕ ЭКСПЛУАТАЦИИ

Numerous publications in the open press on the restoration of crankshaft necks by various methods are known. They provide recommendations for applying coatings to worn necks. However, most work lacks studies on the change in fatigue strength and wear resistance of crankshafts. (Research purpose) The research purpose is studying the technological features of recovering the crankshafts due to their aging during operation. (Materials and methods) As objects of research, crankshafts of diesel engines of various repair sizes were selected. The surface hardness of the necks was studied using portable hardometers in the zone of the greatest and least wear. The data were processed using mathematical methods and compared with allowable hardness values for new and worn necks. Fatigue tests were carried out on machines when the bending moment was loaded along a symmetrical cycle before the appearance of a fatigue crack and final destruction for various coating methods. (Results and discussion) The surface hardness of the necks of extremely worn shafts is reduced by 10 HRC compared to the hardness for new shafts. The reason for the decrease is due to the operation of the neck in dry friction conditions, which causes heating of the surface and, as a result, tempering. The limit of endurance of limit worn shafts in comparison with the limit of endurance of new crankshafts is reduced by 20-25 percent. This is due to the accumulation of fatigue failures. Laser hardening is proposed to increase life of worn-out shafts with reduced hardness. Technological features have been developed for restoring the necks of extremely worn crankshafts. (Conclusions) The aging of crankshafts occurs with a decrease in surface hardness by 10 HRC units and a decrease in the endurance limit by 20-25 persent. Invention proposes laser thermal resistance of necks with reduced hardness, which increases wear resistance by 1.9- 2.6 times.

Simultaneously enhancing tribological and mechanical properties of epoxy composites using basalt fiber/reduced graphene oxide/paraffin wax

AbstractEpoxy composites with simultaneously enhanced tribological and mechanical properties filled with basalt belt/reduced graphene oxide/paraffin wax (EP/BF/RGO/PW) have been successfully prepared. Experimental results indicated that the mechanical property of the composites was reinforced by basalt belt, and the tribological property was greatly improved by reduced graphene oxide/paraffin wax at the same time. Thanks to the synergy of PW and RGO sheets, the optimized coefficient of friction and wear rate of the composite declined by 77.5% and 14.4% than pure EP under dry friction conditions of 60 N and 0.42 m s−1. In comparison to pure EP, the tensile strength and modulus of the optimized composite increased by 75.5% and 100% on account of the robust basalt fibers. Thus, the combination of basalt fiber and reduced graphene oxide/paraffin wax can readily realize the introduction of enhancer and oil‐impregnation in EP, offering a promising approach for simultaneously improving the mechanical and tribological properties of epoxy.Highlights A novel BF/RGO/PW 3D skeleton was developed via a facile hydrothermal method. The BF/RGO/PW can enhance the mechanical and tribological properties of EP. The basalt fibers account for the improvement in mechanical property. A reduction of 77.5% in COF and a decrease of 14.4% in wear rate were realized.

Effect of applied load on tribological behaviour of Ti–48Al–2Cr–2Nb alloy under oil-lubricated condition

With their low weights and excellent mechanical properties, TiAl alloys are expected to be applied in pistons to achieve energy savings and emissions reductions in internal combustion engines. The tribological behaviours of the Ti–48Al–2Cr–2Nb alloy against the QT600-3 material at different applied loads under oil-lubricated conditions were investigated in this study. The results showed that as the load increased, the friction coefficient and wear-scar volume significantly decreased. The wear surface of the TiAl alloy was analysed using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The wear mechanism of the TiAl alloy under oil lubrication conditions was mainly the combined effect of adhesive wear and oxidation wear, different from the wear mechanism under dry-friction conditions. Furthermore, by observing the cross-sectional morphology of the TiAl alloy after focused ion beam, it was found that the QT600-3 wear debris had compacted and accumulated on the surface of the TiAl alloy, preventing further contact between the TiAl alloy and the QT600-3. This study has the potential to accelerate the application of the Ti–48Al–2Cr–2Nb alloy in lightweight pistons.

Optimal Traction Control in High-Speed Maneuvering under Dry Friction Conditions

Optimal Traction Control in High-Speed Maneuvering under Dry Friction Conditions

Prediction on the wear rate of epoxy composites reinforced micro-filler of the natural material residue using Taguchi – neural network

The abrasive wear rate of epoxy composites reinforced with fillers sourced from recycled natural waste consisting of pollen of palm (PPW) and seashells (SSW) was studied.
 Due to the importance of polymer composites used in the tribological couplings of machinery structures, as well as their possible use in brake pads as alternative materials for harmful components in environmentally polluted asbestos, the current research seeks to develop the tribological properties of composite materials reinforced with natural fillers and environmentally friendly. The research investigated the effect of two factors, the weight percentage of natural filler wt. % (0.5 %,1 %, and 1.5 %) and testing loads (1000 g, 2000 g, 3000 g) upon the wear resistance of epoxy composites. The importance of developing epoxy compounds is evident, especially since their work does not require lubricating conditions in various industrial fields, and therefore the development of their bonding properties will increase their operational life and achieve economic benefit for the industrial sector and the environment at the same time. The epoxy composites were subjected to abrasive wear tests under dry friction conditions using a pin-on-disc system. Signal-to-noise (S/N) analysis is adopted to study the influence of the two factors, wt. % and test loads, upon the tribological wear resistance of epoxy composites. A predictive model depending on the regression equation was developed to predict the wear resistance of epoxy composites. The results showed an improvement in the wear resistance of the composite material compared to the epoxy sample without filling by about 47 %. The optimum condition for wear resistance of epoxy composites has been achieved with a weight ratio of (1.5 %) and an applied load of 1000 g

Study on Microstructure and Properties of WC Particle-Reinforced FeCoCrNi-Matrix High Entropy Alloy Composites

In recent years, high entropy alloy (HEA) matrix composites have undergone rapid development. In this work, the effects of different WC contents (10 wt.%, 20 wt.%, and 30 wt.%) on the microstructure, mechanical properties, and wear resistance of FeCoCrNi HEA matrix composites prepared by spark plasma sintering (SPS) were studied. The results show that the WC–HEA composites are mainly composed of an FCC matrix phase (Ni, Fe) and carbide phases (Cr7C3, Co3W3C, WC, etc.). The hardness of the 30 WC–HEA composites was the highest at 459.2 HV, which is 71.2% higher than the 268.3 HV of the pure matrix material. Similarly, the compressive yield strength of the 30 WC–HEA composite was the largest, reaching 1315.1 MPa, which is 112.1% higher than that of the pure matrix material. However, the compression deformation rate of the 30 WC–HEA composite significantly decreased to 16.6%. Under the same dry friction conditions, the addition of an appropriate amount of WC particles can reduce the friction coefficient of the HEA matrix. The wear volume of the composites decreased rapidly with the increase of WC content. The wear volume of 30 WC–HEA was the lowest, only 3.17% of that of the pure matrix material.

WS2-Ti-based solid-liquid synergetic lubricating coating with super-high wear resistance for space application

Solid-liquid lubricating technology is a quite effective approach to achieve long life for sliding components in space. Herein, the WS2-Ti films with porous and dense structures were prepared. The tribological performances of WS2-Ti films lubricated in two kinds of space liquid lubricants (P201 and PFPE) were mainly investigated in vacuum compared to the films in dry friction condition. The dense film exhibits the low friction coefficient of 0.02 and ultra-low wear rate of 2.3 × 10−8 mm3·N−1·m−1 in the dry friction condition. The dense film/oil coatings also show a very long wear life over 4.5 × 105 r, and their wear rates obviously decrease about 79 % and 67 % under harsh test condition compared to the porous film lubricated in P201 and PFPE, respectively. The related analyses indicate that nonpolar P201 molecule is found to have far better compatibility to WS2-Ti crystal surfaces than polar PFPE molecule. It contributes to forming compact tribolayer consisting of numerous ultrathin nanosheets, significantly extending wear life of the coating. Noteworthily, for the solid-liquid coatings, there is a new find that formation of transfer film firstly underwent amorphization and then occurred recrystallization. This reveals lubricating mechanism of the WS2-Ti/oil coating.

Preparation and tribological properties of different kinds of metal foam-polytetrafluoroethylene co-continuous phase composites

Co-continuous phase composites of polytetrafluoroethylene (PTFE) interpenetrated with five kinds of open-cell metal foams, Cu, Ni, Fe, CuNi and FeNi, were prepared via emulsion impregnation, vacuum impregnation and free sintering. The microstructure, mechanical performance, thermal stability and tribological behavior characteristics of these materials were investigated. The results showed that the filling efficiency of PTFE was between 76.1% and 98.7%. The developed composites generally exhibited enhanced strength and thermal stability. In particular, their wear rate under dry friction conditions was reduced by 63–95% compared with pure PTFE resin, which was ascribed to the effective transfer of friction heat and the enhanced load bearing capacity. However, their tribological performance weakened in a simulated seawater environment because of the diffusion of seawater in the materials and corrosion of the metal skeletons.

Tribological Behavior of Cotton Fabric/Phenolic Resin Laminated Composites Reinforced with Two-Dimensional Materials.

In this study, cotton fabric-reinforced phenolic resin (CPF) composites were modified by adding four two-dimensional fillers: graphitic carbon nitride (g-C3N4), graphite (Gr), molybdenum disulfide (MoS2), and hexagonal boron nitride (h-BN). The tribological properties of these modified materials were investigated under dry friction and water lubrication conditions. The CPF/Gr composite exhibits significantly better tribological performance than the other three filler-modified CPF composites under dry friction, with a 24% reduction in friction coefficient and a 78% reduction in wear rate compared to the unmodified CPF composite. Under water lubrication conditions, all four fillers did not significantly alter the friction coefficient of the CPF composites. However, except for an excessive amount of Gr, the other three fillers can reduce the wear rate. Particularly in the case of 10% MoS2 content, the wear rate decreased by 56%. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed for the analysis of the morphology and composition of the transfer films. Additionally, molecular dynamics (MD) simulations were conducted to investigate the adsorption effects of CPF/Gr and CPF/MoS2 composites on the counterpart surface under both dry friction and water lubrication conditions. The difference in the adsorption capacity of CPF/Gr and CPF/MoS2 composites on the counterpart, as well as the resulting formation of transfer films, accounts for the variation in tribological behavior between CPF/Gr and CPF/MoS2 composites. By combining the lubrication properties of MoS2 and Gr under dry friction and water lubrication conditions and using them as co-fillers, we can achieve a synergistic lubrication effect.

Effect of Y2O3 content on the microstructure and wear performance of plasma-sprayed Cr2O3–Y2O3 composite coatings

As the inner working surface of a diesel engine, the cylinder liner is subjected to a harsh frictional wear environment, which can lead to performance degradation and ultimately affect the engine's service life. Ceramic coatings can improve the wear resistance of the cylinder liner, thereby enhancing the reliability and stability of the diesel engine. In this study, Cr2O3–Y2O3 ceramic composite coatings were deposited on the substrate of 304 stainless steel by atmospheric plasma spraying (APS). The influence of Y2O3 content on the microstructure, porosity, phase composition, microhardness and wear performance of the composite coating was investigated. The results showed that the composite coatings exhibited a typical layered structure, and Y2O3 and Cr2O3 were dispersed relatively evenly. When the Y2O3 content was 10 %, the coating had the lowest porosity rate of 5.41 % and the highest hardness of 1094.6 HV1. As the Y2O3 content increased, the coating exhibited an increase in porosity and a decrease in hardness. Under dry friction conditions, the friction coefficient curve underwent a rapid increase phase, followed by stabilizing within the range of 0.29–0.40. When the Y2O3 content is 10 %, the coating exhibits the best wear resistance, including the lowest coefficient of friction, wear rate, and scratch depth. However, the composite exhibits the worst wear resistance when the Y2O3 content reaches 50 %. The wear mechanism was altered by the addition of Y2O3. At lower Y2O3 content, the predominant wear mechanism was abrasive wear resulting from particle refinement. Conversely, at higher content, adhesive wear caused by wear transfer from the milling balls became more prominent.

Study on the preparation of CeO2-doped AlCoCrFeNiTi high entropy alloy bioinert coatings by laser cladding: The effect of CeO2 particle size on the tribological properties of the coatings

The AlCoCrFeNiTi high entropy alloy (HEA) bioinert wear-resistant coatings reinforced by doping CeO2 particles were prepared on the surface of Ti6Al4V via laser cladding technique. In order to find out the effect of CeO2 particle size on the tribological properties of AlCoCrFeNiTi HEA coatings, the coatings doped with 1 wt% nano, submicron, and micron CeO2 particles were prepared respectively. The phase composition and microstructure of the coatings were analyzed, and the fracture toughness values of the coatings were tested. Friction and wear properties of the coatings sliding against Si3N4 ceramic grinding balls were tested under dry friction and wet friction (simulated body fluid, SBF) conditions, respectively. The results showed that the CeO2 particle size had a significant impact on the wear mechanisms of the coating and thereby improved its tribological properties. Doping with submicron CeO2 particles had the most significant improvement on the tribological properties of the coatings, followed by micron CeO2 particles, and doping with nano CeO2 particles had the weakest improvement on the tribological properties of the coatings. The distribution of submicron CeO2 particles in the coating was more dispersed and uniform, which significantly reduced the crack sensitivity of the coatings, inhibited the peeling off of the oxide film on the coating surfaces, and played a lubricating role. Under dry friction and SBF conditions, the friction coefficient of the coatings doped with submicron CeO2 particles decreased by 41.81% and 27.27%, respectively, and the wear resistance increased by 55.14% and 50.69%, respectively. This study has important reference value for the development of new bioinert wear-resistant coatings.

An assessment of the reliability of CFRP composites used in nodes of friction after impact of UV-A impacts and thermal shocks

This article describes the results of tribological research into epoxy-based composites reinforced with carbon fiber. The composites were subjected to accelerated tests simulating a semi-annual influence of environmental conditions of an elevated temperature, precipitation in combination with an influence of UV-A radiation of 0.83 W/m 2 as well as cyclic thermal shocks causing a leap temperature difference of 116.5°C. The process of friction was conducted in conditions of dry friction and wet friction in the presence of water. The authors found a positive influence of a two-month impact of environmental conditions upon increasing wear resistance. They found a reduction in weight in conditions of friction with water. At the same time, a reliability analysis for the same boundary conditions showed an increased risk of critical composite damage. The article indicates areas of safe exploitation of composites and areas of the necessity of withdrawing composites from further exploitation under the assumed environmental and tribological loads.