Wear Grooves Research Articles

Sintering and Tribological Properties of Ti3SiC2-TiSix Composite Sintered by High-Pressure High-Temperature Technology.

The Ti3SiC2TiSix ceramic composite was synthesized in situ from a mixture of 3Ti:1.5Si:1.2C powders under pressures ranging from 2 to 5 GPa and temperatures of 1150 °C to 1400 °C. At medium and high temperatures (4-5 GPa and 1400 °C), Ti3SiC2 dissolves into the cubic TiC phase. SEM analysis revealed that the high-pressure-produced multilayer structure of Ti3SiC2 remained intact. The friction properties of Ti3SiC2-TiSix composites combined with copper and aluminum were studied under both dry and lubricated conditions. After the break-in period, the Ti3SiC2-TiSix/Al combination exhibited the lowest friction coefficient: approximately 0.2. In dry-sliding conditions, the friction coefficient varies between 0.5 and 0.8. The wear mechanisms for Ti3SiC2-TiSix composites paired with aluminum primarily involve pear groove wear and adhesive wear during dry friction. Irregularly shaped aluminum balls accumulate in the pear grooves and adhere to each other. With increasing sintering pressure, the average friction coefficient of Ti3SiC2-TiSix composites against Cu ball pairs first increases and then decreases. The wear rate of the samples did not vary significantly as the sintering pressure increased, whereas the wear rate of Cu balls decreased with increasing sintering pressure. The adhesive wear of the Ti3SiC2-TiSix composite with its Cu counterpart is stronger than that of the Al counterpart. Abrasive chips of Cu balls appeared in flake form and adhered to the contact interface.

Effect of argon and nitrogen environments on the structure and properties of protective cermet coatings based on titanium borides obtained by electric arc surfacing

The aim of this work was to enhance the mechanical and tribological properties of an alpha titanium substrate by forming a protective cermet coating on its surface. In this study, protective cermet coatings based on titanium borides were prepared by electric arc surfacing in a protective environment. Two types of protective environment were investigated during the surfacing process: (i) inert (argon) and (ii) reactive (nitrogen). The characteristic zones of the deposited layer were established depending on the environment used, and the coating-substrate transition zone was thoroughly examined. It was demonstrated that the formation of the transition zone results from the mutual diffusion of the molten material of the electrode material and the substrate. For the first time, the formation of TiB2-TiN eutectic in the form of whiskers 4-20 μm wide and 100-300 μm long distributed in the matrix of the Ti(B,N)x solid solution was established when forming a protective cermet coating in a nitrogen environment. The presence of this TiB2-TiN eutectic led to a significant increase in the hardness of the coating, up to 4.4 times, from 350 to 1530 HV. Tribological tests of surfacing coatings were conducted, and both 2D and 3D profiles of the wear grooves are presented, providing insight into the wear mechanism. It was found that the wear resistance of the cermet coating obtained in a nitrogen environment increased by 5.2 times, while in an argon environment it increased by 3.1 times as compared to the substrate without the protective cermet coating. The results indicate the potential of the developed protective cermet coatings for use in abrasive operating conditions.

The role of manufacturing-induced texture on the tribological performance of cold work tool steels

Manufacturing operations produce surface characteristics that, although stochastic, can significantly affect functionality, especially in forming tools, impacting contact and lubrication conditions during operation. This study investigates the influence of stochastic microtextures resulting from milling on the tribological performance of cold work tool steels with two different carbon contents (0.8 and 2 wt%). Different surface textures were observed resulting from the different C contents, with 3D roughness parameters indicating rougher surfaces for the 2.0% wt. C steel. Tribological behavior was assessed using the strip drawing test to analyze friction, wear coefficients, and wear mechanisms. Surface analysis before and after testing was executed employing SEM, EDX, and CLSM, with CLSM also used to determine 3D roughness parameters of the worn tracks. Post-test macrographic analyses and 2D roughness measurements were conducted on the pulled sheets. Tribological test data revealed lower friction and wear coefficients for the 2.0 wt% C tool steel, with susceptibility to abrasion wear, while the 0.8 wt% C tool exhibited a higher tendency towards adhesion wear. Post-test analysis suggested smoother surfaces for the 2.0 wt% C steel compared to the 0.8 wt% C steel. Macrographic analysis showed no visible wear marks on sheets tested with the 2.0 wt% C steel, contrasting with wear grooves visible on sheets pulled against the 0.8 wt% C steel. Additionally, 2D roughness measurements indicated higher roughness after pulling against the 0.8 wt% C tool compared to the 2.0 wt. C tool. Overall, the study demonstrates that manufacturing-induced textures without the need of post-manufacturing texturing influence the tribological performance of the evaluated steels, opening an avenue to be explored to improve the tribological performance of forming tools.

Development of OPR1000 RCS Hot-leg surge nozzle thermal sleeve remote removal system

The OPR1000-type reactor incorporates seven thermal sleeves (T/S) within the reactor cooling system (RCS) piping line, constructed from Inconel-600 or Inconel-690 material, depending on the power plant. In instances involving T/S made of Inconel-690 material, certain issues were identified either initially or at the commencement of operations. Consequently, the T/S installed on the safety injection nozzle was promptly removed. However, the T/S affixed to the hot-leg surge nozzle remained in operation without removal. Subsequent ultrasonic testing, conducted as part of the scheduled preventive maintenance period, revealed that the T/S associated with the hot-leg surge nozzle in the RCS pipe exhibited protrusions attributable to eccentricity and groove wear. Consequently, the removal of the T/S became imperative. This study delineates the development timeline of a remote system and highlights significant milestones achieved in the removal of the hot-leg surge nozzle T/S during the planned preventive maintenance period.

Cross-linked ZnAl-LDH/PEDOT:PSS/MoS2 coating in-situ grown on aluminum alloy for excellent protection against both corrosion and wear

In this study, a new Al-LPM composite coating was in-situ deposited on the Al alloy via a facile one-pot hydrothermal method. Morphological and compositional characterizations revealed a tri-layered structure of the Al-LPM coating, namely, zinc aluminum-layered double hydroxide (ZnAl-LDH)/poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS)/MoS2. ZnAL-LDH was deposited closest to the surface of Al alloy, and the metallic ion-cross-linking of PEDOT:PSS makes the 3D coating more robust. The unique structure endows the coating with superior protective properties against both corrosion and wear. For anti-corrosion, the Al-LPM coating showed very high self-corrosion potential (-0.092 V) and small self-corrosion current density (46.0 μA cm−2) (vs. Al substrate with -1.157 V and 354.8 μA cm−2, respectively), long-lasting high corrosion resistance (>57,000 Ω cm2) during the immersion test, and the almost intact surface morphology and composition after 360 h corrosion. For anti-wear, the friction coefficient of the Al-LPM coating was determined to be < 0.2, which was much smaller than for the Al substrate (> 0.4). Also, there were no serious wear marks and grooves left after the dry-friction test.

Стендовые испытания нового уплотнения деталей цилиндропоршневой группы судового ДВС

The engine consists of a large number of parts, each of which is responsible for a specific function of its efficient operation. The reliability of a marine diesel engine is largely determined by the resource of its individual components and parts. Therefore, in order to increase the engine life, it is necessary to allocate the most responsible parts in it, which are subject to greater wear and find solutions to increase their durability. Such details include piston rings, which affect not only the technical and economic performance of the engine, but also its reliability and environmental performance. Of the entire set of sealing parts of the cylinder-piston group, the upper piston compression ring should be distinguished as the most loaded. The main function of piston rings is noted – the creation of tightness of the combustion chamber. The passage of exhaust gases is inevitable due to the presence of a “lock” in the structure, and during operation, the wear of the piston rings leads to an increase in it, which affects fuel consumption, oil, and a decrease in engine power. One of the most negative consequences of piston ring wear is the appearance of “flutter” type vibration, which leads to the destruction of not only the ring, but also the edges of the piston grooves, especially on aluminum pistons. Worn grooves are not repaired by resorting to replacing pistons. A method for extending the service life is proposed, which consists in the use of a new sealing unit for cylinder piston group parts. The new sealing unit allows you to extend the piston's operability by boring the upper piston groove of the piston until all chips are eliminated. The operability of this node and the effectiveness of the seal was confirmed by an experiment that was conducted on the stand in conditions close to real ones. A technology for restoring the operability of pistons made of aluminum alloys is proposed.

Assessment of Wear Resistance of Galvanic Coatings of Restored Parts

The article deals with the analysis of the wear resistance characteristics of composite galvanic coatings using molybdenum disulfide as a solid lubricant on restored parts of the transport vehicles and tractors on a friction path of 500 m. The experiments demonstrated that the wear products of the sample adhere to the counterbody; the size of the wear track of the sample ranges from 328.4 to 386.5 μm; the depth of the wear groove on the surface of the sample is up to 5 µm; friction coefficient of the sample surface – 0.243-1.002; the wear factor of a counterbody made of Stainless Steel AISI 420 having the value of microhardness of 8 GPa and the coating of microhardness of 4.518 GPa is 0.019 and 1.676, respectively. The conducted studies showed that the developed technology for restoring and strengthening worn parts makes it possible to ensure the necessary tribological properties of coatings and a long service life of the restored parts.

Numerical and Experimental Study on the Influence of Honeycomb Bushing Wear on the Leakage Flow Characteristics of Labyrinth Seal

Abstract Honeycomb bushing wear has a significant effect on the leakage characteristics of the labyrinth seal. In this paper, four kinds of honeycomb bushing labyrinth seals was designed and processed. The leakage characteristics of honeycomb bushing labyrinth seal were studied experimentally under different inlet and outlet pressure ratios and sealing clearance conditions. At the same time, the numerical model of honeycomb bushing labyrinth seals were established, and the influence of honeycomb bushing wear on the flow field characteristics of labyrinth seals was analyzed by numerical simulation. The existing leakage formula was modified by the correction coefficient method. The results show that with the increase in wear depth, the leakage of the honeycomb bushing labyrinth seal increases, and the maximum leakage can be increased by 59.59%. The wear groove weakens the throttling effect of the labyrinth, causing the leakage of the seal to increase. The increase of the depth of the wear groove changes the flow area and the direction of the jet so that the leakage increases slightly. The influence of the wear groove on the leakage characteristics of the honeycomb bushing labyrinth seal is gradually reduced under the condition of large clearance. The theoretical formula of leakage is corrected by the correction coefficient method. The value calculated by the corrected theoretical formula of leakage is in good agreement with the experiment, and the error is within 10%. It meets the practical application of the project.

Microstructure, mechanical and tribological properties of Mg/CoCrFeNiMoTi high entropy alloy composites produced via FSP

In this study, multi-pass friction stir processing (FSP) was used to produce magnesium (Mg) matrix composites reinforced with CoCrFeNiMoTi high entropy alloy (HEA) particles. The effect of the HEA reinforcements on microstructure evaluation, mechanical properties (hardness and tensile) and wear performance was investigated. The composites were produced with similar pass number (three passes) and tool rotation speed (1250 rpm) and different tool transverse speeds (25 and 50 mm/min) and compared with the Mg matrix without reinforcing particles. XRD results indicated no significant reaction at the interface of the HEA and the matrix during FSP. Microstructure results showed the distribution improvement of the HEA reinforcements and elimination of lamellar structure (inhomogeneous structure) with the decrease of the tool transverse speed from 50 to 25 mm/min. Microstructures of all specimens illustrated four microstructural regions including stirring zone, thermo-mechanical affected zone, heat-affected zone and base metal. The average grain size of the stir zone reduced significantly from 12 µm for the Mg-50 to 2.5 µm and 1.6 µm for the Mg/HEAs-50 and Mg/HEAs-25 composites. The hardness value was increased from 34 HV for the base alloy to 113 HV for the FSPed composite at 25 mm/min (232 % improvement). The maximum yield and tensile strengths were obtained as 86.4 MPa and 114 MPa for the FSPed composite at 25 mm/min which presented enhancement of 92 % and 43 %, respectively as compared with the FSPed Mg alloy. The wear resistance results showed the reduction of the friction coefficient and wear rate with the addition of the HEA reinforcements with a considerable decrease in wear debris, groove depth, micro-cracks and delamination. Comparative plots confirmed that the hardening and strengthening effects of the HEA reinforcements were significantly higher than other reinforcements in Mg matrix composites.

Effects of Front Total Toe-In Angle on Tire Wear and Emissions for a Light-Duty Vehicle

An experimental investigation is carried out in this study to investigate the effect of wheel alignment, particularly the front total toe-in angle, on tire wear and emissions for a light-duty vehicle. Such investigations reveal that there is a substantial correlation among rolling resistance, energy consumption, tire wear, tire travel life, and the total toe-in angle of the front wheel. It is observed that the rate of loss in tire travel life with regard to a condition without misalignment is up to 98.33% when the front total toe-in angle is out of alignment (ranging from 0.00° to 4.20°). It is found that rolling resistance increases by about 128.86%, while CO2, CO, and NOx emissions rise by nearly 36.67%, 26.83%, and 31.25%, respectively, as the front total toe-in angle increases from 0.00° to 4.20°. The experimental results also reveal that tire circumferential groove wear is observed at 0.04 mm after the vehicle’s travelling distance of 500 km, where the front total toe-in angle is 0.00°, and the tire travelling life is 92250 km. In addition, the tire circumferential groove wear is investigated as 2.40 mm after the vehicle’s travelling distance and tire travel life are recorded to be 3,500 km and 1537.50 km, respectively, due to the occurrence of misalignment (the front total toe-in angle is 4.20°). Finally, a regression model is proposed using the test data. Such a model would be useful to explain the relationship between the related factors and determine the rate of tire wear and emissions. It is noteworthy that the wheels should always remain aligned in accordance with the manufacturer’s specifications in order to ensure optimal performance and longevity of the tires

Analysis of the Geometry of Wear Tracks in Laser Deposited Stellite 6 Coatings

A model has been developed to predict the wear groove geometry resulting from wear testing of Stellite 6 coatings on ferrous and nickel-based alloys produced by laser cladding with powers of 1 kW and 1.8 kW. Although the predictions of the model are close to the observed values, they differ in ways that can be accounted for by the incorrect assumption that only abrasive wear occurs. Abrasive wear is dominant, but there is also evidence that adhesive wear and plastic deformation occur and change the geometry and macrostructures of the wear tracks, particularly for the coatings on a Ni-based superalloy substrate. Significant differences were observed in wear track geometries and macrostructures for coatings on the substrates investigated and these differences correlate well with measured differences in the wear loss of the Stellite coatings.

Experimental Investigations on the Development of Hybrid Metal Matrix Composite of Al7075 on Microstructural, Mechanical, and Dry Sliding Aspects

Abstract This research work aims to synthesize a hybrid Al7075 metal matrix composite reinforced with sustainable and synthetic reinforcement. With the employment of an ultrasonic transducer, two-stage stir casting is used to synthesize composite materials. The prepared samples were machined and polished for mechanical, tribological, and microstructural characterization. Optical microscopy and field emission scanning electron microscopy with elemental mapping were used to analyze the microstructure of the composite material. The microstructural examination revealed the homogeneous dispersion of reinforcement particles throughout the matrix. With the incorporation of reinforcement, the synthesized composite's compressive strength and micro-hardness were both increased, and the highest values were found to be 569.172 MPa and 178.86 HV, respectively, in one of the samples (B3 sample) as compared to as-cast Al7075 alloy. Tribological examination of composite samples shows that wear-rate enhances with an increase in the content of reinforcement. The wear resistance of sample B3 is highest among all prepared composite samples. Wear debris, grooves, micro-cracks, and small pits were observed on the worn-out surfaces of the samples by field emission scanning electron microscope analysis.

Results of Sn/Pb solder affected aluminum under wear study

Nanostructured Al-Sn and Al-Pb alloys are effectively used to improve their wear characteristics. Taking this into consideration, the wear properties of aluminum have been studied while affected by both elements Sn-Pb solder at a lower level to explore its reusing potentials. In this purpose a common pin-on-disk device is used in which different dry, wet and corrosive sliding environments are applied. Additionally, pure Al, Al-Sn and Al-Pb alloys are also considered for recovering the clarification and to separate elemental effects on wear properties. The worn surfaces of the samples are examined using optical and scanning electron microscopy, both before and after wear. Surface roughness also is a measure to assess the wear properties under different environments. The findings revealed that minor solder has a great impact on the wear properties of Al with Sn playing a better role than Pb. Solid solution strengthening is the main reason for improved wear behavior in terms of the low wear rate and coefficient of friction. Both Sn and Pb do not form any intermetallic with Al but with impurities it can easily occur particularly with Sn resulting in better wear properties. This phenomenon is more prominent in corrosive environment than wet due to the protective oxide layer on the surfaces. In dry sliding conditions, numerous large wear particles, oxide debris and grooves can be seen on the worn surface, but smoother wear tracks are seen in wet and corrosive environments as form oxide film and thumbs down somewhat direct contact on the moveable surfaces. SEM analysis also reveals higher abrasive wear and plastic deformation on the worn surface produced under dry sliding conditions where minor added alloys indicating that reinforcing particles effectively influence the properties.

Tribological properties and machine learning prediction of FeCoCrNiAlN high entropy coatings

High-entropy nitride ceramic coatings exhibit excellent wear resistance and are regarded as promising coatings in tools. Predicting the coefficients of friction (COF) and related microstrain under friction condition is critical for their application. In this study, nine different FeCoCrNiAlN high-entropy coatings were prepared with varying substrate bias voltage and nitrogen gas pressure using PVD CAIP (Physical Vapor Deposition-cathode arc-ion plating). The bias voltage and nitrogen pressure significantly influenced the wear resistance of the coatings. Low nitrogen gas pressure results in insufficient ceramic phase content, leading to lower hardness and the generation of more grooves. However, coatings with high hardness exhibit excellent wear resistance. Groove wear and debris wear are closely related to the surface particles and mechanical properties of the coating. Alterations in friction load and velocity were also conducted to investigate the tribological performance of various coatings. Results suggest that the COF increased with the friction load and velocity. Furthermore, 53 sets of COF data for machine learning (ML) predictions were obtained. Seven ML regression models, including Multilayer Perceptron (MLP), were employed to predict the COF using input features, including coating deposition process, microstructure features such as elemental composition, and grain size, as well as mechanical features such as nanohardness, H/E (Hardness/Young's modulus), Lc1 (Critical load). Friction conditions include friction load and velocity. Simultaneously, the significance of multiple features such as the coating preparation processes, microstructural, mechanical properties, and friction conditions in affecting the COF of the coatings, was analyzed by the feature importance model. The results indicate that the XGBoost regression algorithm exhibited the highest R2 value and the lowest RMSE, MAE, and MSE values, which were 0.8629, 0.0659, 0.0567, and 0.0047, respectively. This model demonstrated a favorable capability in predicting the COF of FeCoCrNiAlN high-entropy coatings. Furthermore, feature importance analysis revealed that the load, Lc1, velocity and Cr have the most significant impact on the COF of the coatings.

Wear mechanism analysis and its effect on the cutting process of CBN tools during laser ultrasonically assisted turning of tungsten carbide

Tungsten carbide, known for its high hardness and brittleness, presents a challenge in traditional processes due to severe tool wear and shortened tool life, impacting machining efficiency. This paper introduces a hybrid turning method – laser ultrasonically assisted turning (LUAT) – for precision and efficient machining of tungsten carbide. LUAT combines tool ultrasonic vibration with laser-induced workpiece heating to enhance the cutting performance of tungsten carbide. Thermal modeling is utilized to determine suitable LUAT parameters. Comparative experiments are conducted to assess the advantages of LUAT in enhancing tool performance and improving surface quality. Results indicate that, compared to traditional turning, ultrasonically assisted turning, and laser assisted turning, LUAT significantly reduces tool wear and enhances tool lifespan. In LUAT of tungsten carbide, the tool wear on the rake face exhibits long strips parallel to the tool edge, while the flank face presents triangular wear land, shallow pits, and grooves. Investigation into wear characteristics and mechanisms of cubic boron nitride (CBN) tools reveals that adhesion, oxidation, and diffusion are major wear factors, with chipping and tipping being abnormal wear patterns for CBN tools. Intensified tool wear elevates cutting forces and cutting temperatures, deteriorating the surface quality of tungsten carbide turning. However, LUAT mitigates these effects, resulting in lower cutting forces and temperatures within the same wear time, improving surface quality.

Effect of liquid bridge on the thickness deviation between wafers sawn by diamond wire

Diamond wire web will be rearranged due to the reduction of structural stiffness and the enhancement of capillary force in the system for sawing ultra-thin wafers with fine-diameter diamond wire, which can cause uneven thickness between the as-cut wafers and affect the subsequent processing. A model for analyzing the transverse sawing behavior of the diamond wire caused by the liquid bridge after sawing into a workpiece was developed in this study by extending the dynamical model for a double-wire system with liquid bridge action to a multi-wire system. The stable transverse sawing state of the wire was obtained by analyzing the variation of the transverse sawing force with the as-cut wafer thickness thinning. Accordingly, the wafers thickness deviation rate affected by the wire groove wear and the liquid bridge action was calculated. The effects of the wire groove wear, the initial wire web gap, and the wire length between the guide wheel and the workpiece on the thickness deviation between the wafers sawn by the diamond wire were explored. The results show that the wafers thickness deviation increases with the increased wear of the wire grooves when the initial wire web gap is smaller than the minimum gap at which spontaneous wires adhesion can occur. The increase of wire groove wear makes the double-wire sawing more likely to occur. In addition, the wafers thickness deviation increases with decreases in the initial wire web gap and increases in the wire length between the guide wheel and the workpiece. Reducing the ratio of the initial wire span to the workpiece width helps to suppress the liquid bridge action during slicing and avoid the double-wire sawing. Since the minimum gap at which spontaneous wires adhesion can occur is large for the thick-diameter diamond wire, the fine-diameter diamond wire can be a better option for sawing the ultra-thin wafer to avoid the effect of liquid bridge on the wafers thickness deviation to the greatest extent.

A comparative study on tribological behavior of Al2O3, AlN, Si3N4 and ZrO2 ceramics sliding against polycrystalline diamond ball

Studying the tribological behavior between diamond materials and ceramics is crucial for understanding the grinding mechanism of diamond wheels on ceramics. To comprehend the tribological characteristics between diamond materials and various ceramics, this paper presents a comparative study of the tribological behaviors of Al2O3, AlN, Si3N4, and ZrO2 ceramics sliding against polycrystalline diamond (PCD) balls. The dependence of the coefficient of friction (COF), wear characteristics as well as the surface morphology of different ceramics and SiC-bonded PCD balls on load, sliding stage were examined. The effect of nanofluids on the COF and wear of different ceramics was also investigated. The results showed that the tribological characteristics of ceramic materials are strongly dependent on mechanical properties. Al2O3 and AlN ceramics with lower fracture toughness exhibit a significantly higher COF and wear volume than that of Si3N4 and ZrO2 ceramics. Al2O3 presents the highest COF (0.38) and wear volume, and Si3N4 owns the lowest COF (0.08) and wear volume under the load of 9.8 N. By examining the wear grooves of different ceramics, it is found that Al2O3 and AlN ceramics own larger debris than that of Si3N4 and ZrO2, which also causes more smearing on the ceramic and adhesion of wear debris to the SiC-bonded PCD ball for Al2O3 and AlN. Under lubricants, the COFs and the adhesion of wear debris are effectively reduced, and the wear rate of the ceramic is increased. There is little difference between deionized (DI) water and nanofluids on the effect of lubricants on COF for Al2O3 and AlN. However, for ceramics with higher fracture toughness, the nanofluids can reduce the COFs of Si3N4 and ZrO2 in comparison with DI water.

Relationship between Structure and Properties of Intermetallic Materials Based on γ-TiAl Hardened In Situ with Ti3Al

In this work, intermetallic materials based on γ-TiAl in situ strengthened with the Ti3Al phase have been obtained from the initial components of titanium and aluminum under the conditions of free SHS-compression in one technological step and in ten seconds. This method combines the process of the combustion of initial components in the mode of self-propagating high-temperature synthesis (SHS) with high-temperature shear deformation of the synthesized materials. The following initial compositions have been studied (mol): Ti–Al, 1.5 Ti–Al, and 3 Ti–Al. Thermodynamic calculations have been carried out and the actual combustion temperature of the compositions under study has been measured. To increase the exothermicity of the studied compositions, a “chemical furnace” based on a mixture of Ti–C powders has been used, which allows us to increase the combustion temperature and stabilize the combustion front. It has been found that the actual combustion temperature of the selected compositions increased from 890–1120 to 1000–1350 °C. The results of X-ray powder diffraction and SEM are presented, mechanical and tribological characteristics of the obtained materials are measured, and 3D images of wear grooves are given. It has been found that a decrease in Ti molar fraction and an increase in Al molar fraction in the initial mixture lead to an increase in the mechanical (hardness up to 10.2 GPa, modulus of elasticity up to 215 GPa) and tribological characteristics (wear up to 4.5 times, coefficient of friction up to 2.4 times) of intermetallic materials.

Characterization of Microscopic Damage Evolution of Functional Groove in Cageless Bearings

Bearings with partial function grooves as cageless bearings related to magnetic floating bearing protection have characteristics, such as fast offsetting of the impact force caused by rotor fall, and they gradually become important parts of ultra clean and cryogenic transportation systems. However, the functional failure mechanism of the bearing, which is caused by functional groove wear, is not clear. Therefore, this paper establishes a force–motion intrinsic model of particles inside the functional groove, which is based on the discrete element method, which it itself combined with the functional groove damage evolution trend analysis. Then, a hyper-quadratic surface model of inter-particle contact is established to simulate the time-varying friction coefficient of the functional groove by combining particles of different sizes to form particle clusters. Additionally, as the boundary condition, EDEM is used to solve the contact motion state of rolling element rolling through the functional groove for one week to obtain the overlap between particles and contact force change law. The results show that the wide side of the functional groove wears more seriously than the narrow side, and the rolling element leaves the functional groove with more impact than when it enters the functional groove, and the functional groove wears more seriously. In this paper, through the study of local functional groove wear of cageless ball bearing, we propose to characterize the damage extension of functional groove by using the number of particle fracture and motion trend in discrete element method, and this study provides theoretical guidance for the design of cageless bearings.

Influence of oxide polluted lubricants on friction: Trapping mechanisms

In wire winding processes, the thermal pretreatments required in the wire manufacturing process pollute the wire with a lubricant and oxide mixture. This mixture disturbs the tribological conditions at the wire/tool interface during shaping and the final quality of the product to be obtained. During shaping, the lubricant and oxide mixture accumulates and creates a wear groove in the wire guide. The observation of these grooves indicates that the erosion is caused by the presence of third-body particles which initially crack the groove with a widening of the crack thereafter. The wire/tool contact is then reproduced under conditions close to industrial conditions on a pin-on-disc test. The influence of oxide pollution and lubricant quality on the conditions is measured and demonstrated.