Tribological Behavior Research Articles

Investigation of Tribological Behavior of Coated and Untreated Rail Steels Under Wet Conditions

Abstract Rails are exposed to more stresses, especially in the regions of narrow radius curves and switch passages. Therefore, the tribological features of these regions are important. In this study, the effect of boronization on tribological properties was examined. For this purpose, experiments were carried out on samples boronized at 800 °C for 2 hours and 8 hours and on untreated samples. With these experiments, the friction coefficient, volume loss and surface roughness values of the samples under wet conditions were examined. In addition, the microstructures of the material after boriding were observed by SEM and EDX. The variance and regression method (ANOVA) was used for the statistical analysis of the experimental results. After SEM examinations, a coating layer of ~22 µm (FeB) and ~48 µm (FeB+Fe2B) were obtained on the surface of the rail steels boronized for 2 and 8 h, respectively. The microhardness of the rail steels, which was ~300 HV for the untreated sample, increased to ~1900 HV and ~2400 HV with the boronizing process boronized for 2 and 8 h, respectively. According to the ANOVA results, the effects of the boronizing process on the decrease of the friction coefficient and the volume loss were calculated as 42% and 46%, respectively. Finally, according to the corrosion results, the corrosion resistance of the boronized rail steels decreased with the boride layer formed.

Experiment and modelling of texture and sliding direction dependence on finger friction behavior

AbstractHumans rely on their fingers to sense and interact with external environment. Understanding the tribological behavior between finger skin and object surface is crucial for various fields, including tactile perception, product appearance design, and electronic skin research. Quantitatively describing finger frictional behavior is always challenging, given the complex structure of the finger. In this study, the texture and sliding direction dependence of finger skin friction was quantified based on explicit mathematic models. The proposed double-layer model of finger skin effectively described the nonlinear elastic response of skin and predicted the scaling-law of effective elastic modulus with contact radius. Additionally, the skin friction model on textured surface considering adhesion and deformation factors was established. It revealed that adhesive term dominated finger friction behavior in daily life, and suggested that object texture size mainly influenced friction-induced vibrations rather than the average friction force. Combined with digital image correlation (DIC) technique, the effect of sliding direction on finger friction was analyzed. It was found that the anisotropy in finger friction was governed by the finger’s ratchet pawl structure, which also contributes to enhanced stick-slip vibrations in the distal sliding direction. The proposed friction models can offer valuable insights into the underlying mechanism of skin friction under various operating conditions, and can provide quantitative guidance for effectively encoding friction into haptics.

Current-Carrying Tribological Behavior of Textured Au/MoS2 Coatings in Vacuum

Abstract Sliding electrical contact has been widely used in spacecraft such as slip ring for solar windsurfing, and its service life directly affects that of the spacecraft. Au as a sliding electrical contact material has been widely used in aerospace equipment, but poor lubricity limits its service life. To address this issue, this study introduces MoS2 into the texturing holes of the Au coating, which can improve the lubricity, and maintain the continuity of Au and thus its conductivity. Additionally, the effect of texture density on the vacuum current-carrying tribological properties of the textured Au/MoS2 coating was investigated. The results indicate that texture not only reduces the mechanical properties of the coating but also affects the amount of MoS2 that can be filled. A high texture density greatly reduced the carrying capacity, leading to serious abrasive wear. However, low texture density results in serious adhesive wear owing to insufficient lubricity. Under an appropriate texture density, excellent vacuum current-carrying tribological behaviour can be achieved depending on the formation of a transfer film of MoS2 and Au, which maintains conductivity through Au and provides lubricity through MoS2. This study is of great significance in prolonging the service life of sliding electrical contacts and provides a new idea for the design of sliding electrical contact materials.

Tribological characteristics and film behaviour of polytetrafluoroethylene in jatropha with sodium dodecyl sulphate as surfactant

In this research, a bio lubricant was developed utilising eco-friendly constituents of jatropha oil, polytetrafluoroethylene (PTFE) and sodium dodecyl benzenesulphonate (SDBS), characterised and tested with four-ball tribometer under ASTM D2783 standard. The tribological performance in terms of friction, wear, load carrying ability and evaluation of the film behaviour on stability and strength was conducted. According to Fourier transform infrared spectroscopy (FT-IR) of the study, the presence of the two additives in base jatropha oil demonstrated good functional groups desired for lubricant lubricity. In comparison to base jatropha under 40 kg and 1200 rpm, blended 1 wt-% PTFE + 0.8 wt-% SDBS additives produced an outstanding reduction in coefficient of friction (61.4%) and good load carrying strength among all the samples tested, but commercial shell oil (CSO) outperformed under wear resisting potential. Scanning electron microscopy (SEM) and a 3D surface profilometer were used to examine the rubbed surfaces. Findings indicate that the boundary film on the worn surface was made up of PTFE and SDBS nanoparticles that deposited film elements of sulphur and higher carbon content. The decrease in the percentage of iron (Fe) indicates that tribo-pairs were separated from direct contact under additives usage. According to the research, adding an anti-wear substance to the new formulation could increase wear protection, thus effectively making it comparable with CSO counterpart.

Effects of nanofillers on the physical, mechanical, and tribological behavior of carbon/kenaf fiber–reinforced phenolic composites

Abstract This research investigates the effect of kenaf/carbon fiber reinforcement with the addition of nanofillers such as multi-walled carbon nanotubes (MWCNT) and cellulose nanocrystal (CNC) in the phenolic matrix composite. Three different types of samples were made using short carbon fiber, kenaf fiber (KF), BaSO4, Cashew dust, MWCNT, and CNC. Sample 1 contains 40 wt% of carbon fiber with binders reinforced in the phenolic matrix, whereas, in sample 2, carbon fiber has been replaced with KF in the MWCNT-modified phenolic matrix. On the other hand, in sample 3, carbon fiber has been replaced with KF in a CNC-modified phenolic matrix. The physical, mechanical, and tribological properties were investigated and compared. The results showed that sample 1 exhibited higher mechanical performance compared to other samples. On the other hand, the least wear loss and a high coefficient of friction were observed for Sample 2 compared to Samples 1 and 3. Even though KF-based composites exhibited slightly lower mechanical performance, they showed excellent tribological behavior.

Experimental lap-shear tests on friction dampers with single and double slotted holes

Several experimental lap shear tests have been performed to assess the initial values of the slip resistance and their evolution during a cyclic loading history. Both friction dampers with parallel slotted holes and double slotted holes have been investigated. Friction devices with shims made of a previously tested material, called M4, have been tested and the tribological behaviour, the degradation of the friction coefficient, the influence of the bolts’ preload and the effect of Belleville washers have also been investigated. Moreover, a phenomenological model for the force-displacement response has been calibrated for the modelling of the cyclic response of the friction device. This is particularly important for the development of non-linear dynamic analyses of seismic resistant frames equipped with friction joints aiming at an accurate prediction of the structural response during a seismic event. Finally, a quality control of the friction properties of different batches of friction shims has been performed by means of the Fisher-Berens and Snedecor tests.

Influence of microtextured parameters of dry gas sealing rings on tribological performance

Purpose This study aims to research the influence mechanism of microtextured geometric parameters of dry gas seal end face on the tribological behavior under dry frictional conditions. Design/methodology/approach The microtexture was processed using laser processing, while the diamond-like carbon (DLC) film was applied through magnetron sputtering; the experimental platform of friction vibration was established, the frictional and vibrational properties of different geometric parameters were tested; the data signals of vibrational acceleration and frictional torque were collected and processed using data acquisition instrument. The entropy characteristic parameters of 3D vibrational acceleration were extracted based on wavelet packet decomposition method. The end-face topography was measured with ST400 three-dimensional noncontact surface topography instrument. Findings The geometry of pits plays a key role in influencing friction performance; the permutation entropy and fuzzy entropy of the vibration acceleration signal changed with variations in microtextured parameters. A textured surface with appropriately size parameters can trap debris, enhance the dynamic pressure effect, reduce impact between the friction interfaces and improve the frictional vibrational performance. In this research, microtextured surface with Φ150 µm-10% and Φ200 µm-5% can effectively reduce friction and vibration between the end faces of a dry gas seal. Originality/value DLC film improves the hardness of seal ring end face, and microtexture improves the dynamic effect; the tribological behavior monitoring can be realized by analyzing the characteristics of vibration acceleration sensitive parameter with friction state. The findings will provide a basis for further research in the field of tribology and the microtexture optimization of dry gas seal ring end face. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2023-0389/

Lubrication Mechanism of TC4 Titanium Alloy Against Silicon Nitride by ILs ([Li (Synthetic Esters)] NTF2)

ABSTRACTThe ILs ([Li (synthetic esters)] NTF2) were prepared by the in situ synthesis method. The tribological behaviour of the ILs to friction pairs of Ti‐6Al‐4V titanium alloy against silicon nitride was studied by SRV‐V under different concentrations and friction frequencies; the wear scar was studied by SEM, XPS and TOF‐SIMS. The results showed that the friction coefficient and wear loss decreased gradually with the increase of the LiNTF2 content; when the LiNTF2 content reached a certain value (10%), the friction coefficient and wear loss did not change much. Tribofilm composed of titanium oxide, Al2O3, TiFO2, AlOF2, Ti2O4F and Al2O3F plays a major role in lubrication and anti‐friction effect.

Tribological analysis of titanium alloy (Ti-6Al-4V) hybrid metal matrix composite through the use of Taguchi’s method and machine learning classifiers

The preparation and tribological behavior of the titanium metal matrix (Ti-6Al-4V) composite reinforced with tungsten carbide (WCp) and graphite (Grp) particles were investigated in this study. The stir casting procedure was used to fabricate the titanium metal matrix composites (TMMCs), which had 8 weight percent of WCp and Grp. The tribological studies were designed using Taguchi’s L27 orthogonal array technique and were carried out as wear tests using a pin-on-disc device. According to Taguchi’s analysis and ANOVA, the most significant factors that affect wear rate are load and distance, followed by velocity. The wear process was ascertained by scanning electron microscopy investigation of the worn surfaces of the composite specimens. Pearson’s heatmap and Feature importance (F-test) were plotted for data analysis to study the significance of input parameters on wear. Machine learning classification algorithms such as k-nearest neighbors, support vector machine, and XGBoost algorithms accurately classified the wear rate data, giving an accuracy value of 71.25%, 65%, and 56.25%, respectively.

Tribological Study of Fe–Cr Alloys for Mechanical Refinement in a Corn Stover Biomass Environment

The tribological behavior of three Fe–Cr alloys with Cr contents ranging from ~12 to 16 wt.% as well as low-alloy high-carbon 52100 steel were investigated using pin-on-disk wear testing. Wear tests were performed in both open atmospheric (dry) and biomass environments (wet). Delamination and abrasion were observed to be the dominant wear regimes following dry wear tests. For wet testing, adhesion and pitting corrosion were determined to be the primary wear mechanisms in the Fe–Cr alloys while adhesion and delamination/cracking were identified as the primary wear mechanisms in the 52100 steel. The 440C stainless steel and 52100 steel specimens exhibited the lowest wear volume following dry (7.58 ± 0.52 mm3 and 0.78 ± 0.05 mm3, respectively) and wet wear testing (0.11 ± 0.06 mm3 and 0.12 ± 0.09 mm3, respectively); however, these specimens exhibited the most significant corrosion damage. The 410 stainless steel specimen exhibited the best resistance to corrosion after wear testing in the deacetylated and disc-refined corn stover slurry and had measured wear volumes after dry and wet wear testing of 6.84 ± 0.88 mm3 and 0.33 ± 0.12 mm3, respectively. The worst wear resistance was observed by the 420 stainless steel specimen after both dry and wet wear testing.

Characterization of the friction-induced attractor trajectories during the running-in process in ball-on-disk tribosystem

PurposeThe purpose of this study is to solve the issues of time-consuming and complicated computation of traditional measures, as well as the underutilization of two-dimensional (2D) phase-trajectory projection matrix, so a new set of features were proposed based on the projection of attractors trajectory to characterize the friction-induced attractors and to reveal the tribological behavior during the running-in process.Design/methodology/approachThe frictional running-in experiments were conducted by sliding a ball against a static disk, and the friction coefficient was collected to reconstruct the friction-induced attractors. The projection of the attractors in 2D subspace was then mapped and the distribution of phase points was adapted to conduct the feature extraction.FindingsThe evolution of the proposed moment measures could be described as “initial rapid decrease/increase- midterm gradual decrease/increase- finally stable,” which could effectively reveal the convergence degree of the friction-induced attractors. Moreover, the measures could also describe the relative position of the attractors in phase–space domain, which reveal the amplitude evolution of signals to some extent.Originality/valueThe proposed measures could reveal the evolution of tribological behaviors during the running-in process and meet the more precise real-time running-in status identification.

Thickness dependent tribological and magnetic behavior of two-dimensional cobalt telluride (CoTe2)

Abstract Two-dimensional (2D) layered transition-metal based tellurides (chalcogens) are known to harness their surface atoms’ characteristics to enhance topographical activities for energy conversion, storage, and magnetic applications. The gradual stacking of each sheet alters the surface atoms’ subtle features such as lattice expansion, leading to several phenomena and rendering tunable properties. Here, we have evaluated thickness- dependent mechanical properties (nanoscale mechanics, tribology, potential surface distributions, interfacial interaction) of 2D CoTe2sheets and magnetic behavior using surface probe techniques. The experimental observations are further supported and explained with theoretical investigations: density functional theory (DFT) and molecular dynamics (MD). The variation in properties observed in theoretical investigations unleashes the crucial role of crystal planes of the CoTe2. The presented results are beneficial in expanding the use of the 2D telluride family in flexible electronics, piezo sensors, tribo-generators, and next-generation memory devices.

Optimized machine learning with hyperparameter tuning and response surface methodology for predicting tribological performance in bio‐composite materials

AbstractThis study investigates the influence of NaOH treatment on tribological behavior in hybrid fiber‐reinforced composites, specifically employing Banana fiber with Al2O3 filler in an epoxy matrix. Through design of experiments (DOE), disc speed, wear duration, and NaOH treatment are analyzed for specific wear rate (SWR) and coefficient of friction (COF). To advance the understanding of wear characteristics, the study leverages advanced machine learning, using Python‐powered artificial neural networks (ANN), is integrated with innovative ANN hyperparameter optimization. Optimized parameters (1050 rpm, 60 s, 5% treatment) significantly minimize SWR (12.38 × 10−5 mm3/Nm) and COF (0.2). Scanning electron microscopy (SEM) analysis reveals improved interfacial adhesion and identifies micro‐cracks as the primary wear mechanism. This work contributes to a profound understanding of wear in hybrid composites, offering a fine‐tuned predictive model for optimizing tribological behavior and advancing material science and engineering.Highlights Reduced SWR, COF in composites via NaOH optimization. DOE: Explored disc speed, duration, NaOH impact. Advanced machine learning techniques enhanced wear prediction. Innovative: ANN hyperparameter optimization. Optimal Parameters: 1050 rpm, 60 s, 5% treatment.

Tribological behaviour of TiAlN and AlCrN coatings on stainless steel

TiAlN and AlCrN coatings are widely used in applications that require high stress resistance. In this work, the tribological behaviour of physical vapour deposition (PVD) TiAlN and AlCrN commercial coatings deposited on AISI martensitic stainless steel is studied. Microstructure of the coatings was analysed by X-ray diffraction (XRD), optical microscopy (OM) and scanning electron microscopy (SEM) and nanohardness was measured. Pin-on-disk and abrasive wear tests were performed. Adhesion was evaluated using Rockwell C Indentation and scratch test. The thickness of both coatings was approximately 3 µm. AlCrN lost 30 and 10 times less volume than TiAlN in pin-on-disk tests, under low and high loads, respectively. The steady friction coefficient value was also lower. This indicated that the AlCrN coating had a better performance under sliding conditions. On the other hand, the mass loss was similar for both coatings under abrasive wear, even under severe conditions. In the scratch tests, TiAlN coating failed at 60 N load and AlCrN coating at 70 N, the latter showing a higher value of critical load. The deformation was similar for both coatings as it could be observed in the profiles obtained by a mechanical profilometer at 60 N, however, AlCrN did not show film delamination. This enhanced performance can be attributed to higher fracture toughness and load carrying capacity, which not only improved the mechanical properties of the coating but also its adhesion to the stainless-steel substrate.

Experimental study of frictional behaviour of powdered soaps for wire drawing

Better understanding of frictional behaviour of powdered soaps used in dry wire drawing can lead to improvements in wire quality and large savings in energy consumption. The latter is particularly significant given the colossal amounts of energy expended in wire drawing processes. However, there is currently a very limited understanding of the subject, including a lack of quantitative data on soap friction. This is at least in part likely to be due to complex tribological behaviour of the powdered soaps, which is very different from that of lubricating oils. This paper studies frictional behaviour of sodium and calcium powdered soaps, using a ball-on-disc tribometer (ETM rig) incorporating a powder ‘scoop’, and under contact conditions pertinent to die-wire contact in wire drawing. Tests employed a WC ball and C15E steel disc to mimic die and wire materials respectively. Results show that under high sliding conditions, friction coefficient with powered soaps is remarkably low, at 0.03 and 0.04 for sodium and calcium soaps respectively. Friction generally decreased with increasing contact pressure and sliding speed. Post-test analysis of ETM specimens showed the presence of thick soap layers on the rubbed surfaces. However, in ETM tests friction was observed to sharply increase leading to the onset of scuffing, soon after the supply of soap to the contact was interrupted, suggesting that any solid deposited layers are easily removed and cannot exclusively explain the low friction. The observed trends suggest that low soap friction may be due to the ability of the soaps to form low shear stress lubricating films at high contact temperatures which are associated with the harsh conditions of high-speed and high-pressure. The results provide new insights into the frictional behaviour of powdered soaps which can be used to optimise the wire drawing processes as well as a direct input to wire deformation models.

Tribological Behavior of Sulfonated Polyether Ether Ketone with Three Different Chemical Structures under Water Lubrication.

With the development of the shipbuilding industry, it is necessary to improve tribological properties of polyether ether ketone (PEEK) as a water-lubricated bearing material. In this study, the sulfonated PEEK (SPEEK) with three distinct chemical structures was synthesized through direct sulfonated polymerization, and high fault tolerance and a controllable sulfonation degree ensured the batch stability. The tribological and mechanical properties of SPEEK with varying side groups (methyl and tert-butyl) and rigid segments (biphenyl) were compared after sintering in a vacuum furnace. Compared to the as-made PEEK, as the highly electronegative sulfonic acid group enhanced the hydration lubrication, the friction coefficient and wear rate of SPEEK were significantly reduced by 30% and 50% at least without affecting the mechanical properties. And lower steric hindrance and entanglement between molecular chains were proposed to be partially responsible for the lowest friction behavior of SPEEK with methyl side groups, making it a promising and competitive option for water-lubricated bearings.

EXPERIMENTAL, TRIBOLOGICAL STUDIES ON SINTERED Al–xV2O5–2B4C COMPOSITES USING BIO-OILS

This reports the tribological behavior of sintered aluminum composite with bio-oil as lubricant. The composite is fabricated by powder metallurgy route, and the aluminum is reinforced with the particles V2O5 and B4C. The bio-lubricant oil is Pongamia, Jatropha, and blended Pongamia with Jatropha of equal volume. The wear test was carried out at the sliding speed of 3[Formula: see text]m/s and load ranging up to 180 N, and the wear behavior of Al–xV2O5–2B4C composite. Then the composite’s friction coefficient and weight loss were tested on a pin-on-disc tribometer. Further, pinworn surfaces were analyzed by Scanning Electron Microscope. The mix of Pongamia with Jatropha of equal volume resulted in a good change in specific wear rate and coefficient of friction of composites.

Effect of heat treatment on the microstructure and mechanical properties of biocompatible Ti–Ta–Nb–Zr alloys prepared by selective laser melting

Abstract In this paper, a low elastic modulus, non-cytotoxic Ti-10Ta-2Nb-2Zr titanium alloy was prepared by selective laser melting additive manufacturing. The effect of annealing and solution heat treatment on the structure, mechanical properties, and tribological behavior were investigated. The results show that the microstructure was composed of the main α′ phase and a small amount of β phase. Heat treatment improved strength and elongation. The ultimate tensile strength (UTS) and elongation of the deposited specimen were 807 ± 8.74 MPa and 6.6 ± 0.75 %, respectively. After annealing, the UTS was nearly the same, but the elongation increased to 15.3 ± 0.95 %. After solution and aging, the UTS and elongation increased to 873 ∼ 813 MPa and 9.25–11.9 %, respectively. The elastic modulus of the deposited specimen was 120 ± 6.81 GPa. The elastic moduli of heat treated specimens ranged from 74 ± 4.04 to 96 ± 5.13 GPa. The elastic moduli of heat treated specimens were close to that of β-type titanium alloys. The wear mechanism was mainly abrasive wear and oxidative wear. Compared with the deposited and annealed specimens, the solution and age treated specimens had low friction coefficients and much better wear resistance. In terms of properties and cost, the designed alloy has great potential in the medical implant field.

Tribological Behaviors and the Lubrication Mechanism of Functionalized Boron Nitride Nanosheet-Containing Fluid for Titanium Alloy Cold Rolling

Tribological Behaviors and the Lubrication Mechanism of Functionalized Boron Nitride Nanosheet-Containing Fluid for Titanium Alloy Cold Rolling

Tailoring the mechanical and high‐temperature tribological properties of Si‐DLC films by controlling the Si content

The poor high‐temperature tribological performance of diamond‐like carbon (DLC) films severely limits their applications. To address this issue, silicon (Si) doped DLC films with Si content ranging from 0 to 11.52 at.% were synthesized utilizing the plasma‐assisted reactive magnetron sputtering technique. The influence of Si incorporation on the microstructure and mechanical properties was meticulously investigated by Raman spectroscopy, scanning electron microscope (SEM), X‐ray photoelectron spectroscopy (XPS), nanoindentation, and scratch testing. To ascertain the tribological behavior of the Si‐DLC films under elevated temperature conditions, in situ high‐temperature tests were conducted, spanning temperatures from ambient to 500°C. The findings indicated that distinct lubrication mechanisms prevail for Si‐DLC films with varying Si content across different temperature domains. As the test temperature and Si content increased, the lubrication mechanism exhibited a gradual transitions from high‐temperature induced graphitization to a particle wear regime dominated by SiC and formed SiO2 abrasive phases. The comprehensive performance of the films peaked at a Si content of 4.72 at.%, suggesting an optimal composition for high‐temperature applications. It is postulated that the in‐depth investigation presented herein holds considerable value for the design and fabrication of DLC films intended for use in high‐temperature settings, potentially unlocking their full potential in such demanding environments.