Search Results (209)

This study examines the high-temperature tribological behavior of WE54 Mg alloy under various conditions: as-cast, solution-treated (T4), age-hardened (T6), and secondary aged (S.A). Wear tests were performed using a pin-on-disc setup, applying a normal load of 10 N, with a sliding velocity of 1 m/s, a sliding distance of 1000 m, and temperatures from 25 °C to 150 °C. Responses such as the coefficient of friction and volumetric wear rate were recorded. The results indicate that heat treatment significantly influences the wear behavior of the WE54 alloy. The lowest volumetric wear rate (8.16 ± 1.47 mm³) and wear coefficient (0.112 ± 0.02) occurred in the as-cast sample at 100 °C, while the highest volumetric wear rate (14.68 ± 1.59 mm³) and wear coefficient (0.171 ± 0.02) were found in the S.A. sample at 150 °C. Surface characterization of worn samples was conducted using field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The wear mechanisms identified include abrasive wear, oxidative wear, and delamination across all conditions, regardless of temperature. The elevated volumetric wear rate at 150 °C, irrespective of the sample condition, is attributed to oxidation and thermal softening of the material. Full article

This study presents a comprehensive evaluation of the tribological behavior of cylinder liners and piston rings—key components in internal combustion engines (ICEs). Experiments were conducted using a pin-on-disc wear tester under varying loads (50–100 N) and speeds (175–350 rpm) to determine the coefficient of friction (μ) and wear rate. The selected pin and disc materials represent real engine components to ensure realistic operating conditions. Before and after each experiment, the cylinder liner-piston ring pair was cleaned with acetone to ensure accurate measurement of mass loss. Surface roughness (Ra, Rq, Rz, µm) was assessed using a Mahr M-1 profilometer, and Brinell hardness tests were carried out using a digital optical Brinell hardness testing machine to determine the mechanical properties of the contact surfaces. The results revealed that safflower oil achieved the lowest coefficient of friction at higher speeds, with an 18% reduction compared with conventional 20W-50 engine oil. Camelina oil, camelina biodiesel and safflower biodiesel each exhibited a reduction of approximately 12.5% in friction, highlighting their potential as viable alternatives to petroleum-based lubricants. Full article

This study investigates the mechanical, tribological, and electrochemical behaviour of a novel precipitation-hardenable martensitic alloy produced by selective laser melting (SLM). The alloy was specifically engineered with an optimised composition, free from cobalt and molybdenum, and featuring reduced nickel content (7 wt.%) and 8 wt.% chromium. It has been developed as a cost-effective and sustainable alternative to conventional maraging steels, while maintaining high mechanical strength and a refined microstructure tailored to the steep thermal gradients inherent to the SLM process. Several ageing heat treatments were assessed to evaluate their influence on microstructure, hardness, tensile strength, retained austenite content, dislocation density, as well as wear behaviour (pin-on-disc test) and corrosion resistance (polarisation curves in 3.5%NaCl). The results indicate that ageing at 540 °C for 2 h offers an optimal combination of hardness (550–560 HV), tensile strength (~1700 MPa), microstructural stability, and wear resistance, with a 90% improvement compared to the as-built condition. In contrast, ageing at 600 °C for 1 h enhances ductility and corrosion resistance (Rp = 462.2 kΩ; Ecorr = –111.8 mV), at the expense of a higher fraction of reverted austenite (~34%) and reduced hardness (450 HV). This study demonstrates that the mechanical, surface, and electrochemical performance of this novel SLM-produced alloy can be effectively tailored through controlled thermal treatments, offering promising opportunities for demanding applications requiring a customised balance of strength, durability, and corrosion behaviour. Full article

This study presents a U-Net-based automatic segmentation framework for quantitative analysis of surface morphology in a PEEK-based composite following tribological testing. Controlled Pin-on-Disc tests were conducted to characterize tribological performance, worn surfaces were captured by laser scanning microscopy to acquire optical images and height maps, and the model produced pixel-level segmentation masks distinguishing different regions, enabling high-throughput, objective analysis of worn surface morphology. Sixty-three manually annotated image sets—with labels for fiber, third-body patch, and matrix regions—formed the training corpus. A 70-layer U-Net architecture with four-channel input was developed and rigorously evaluated using five-fold cross-validation. To enhance performance on the challenging patch and fiber classes, the top five model instances were ensembled through Bayesian-optimized weighted voting, achieving significant improvements in class-specific F1 metrics. Segmentation outputs on unseen data confirmed the method’s robustness and generalizability across complex surface topographies. This approach establishes a scalable, accurate tool for automated morphological analysis, with potential extensions to real-time monitoring and other composite systems. Full article

This study investigates the effect of fiber weight fraction on the tribomechanical behavior of basalt fiber-reinforced polymer (BFRP) composites under dry sliding conditions. Composite specimens with 50%, 65%, and 70% basalt fiber contents were manufactured and tested through tensile, flexural, and pin-on-disc tribological evaluations. Key tribological parameters, including the coefficient of friction (COF), specific wear rate (K), and contact temperature, were measured under various applied loads and sliding speeds. Statistical analysis was performed using a generalized linear model (GLM) to identify significant factors and their interactions. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses indicated that abrasive wear, matrix cracking, and fiber–matrix interfacial failure were the dominant wear mechanisms. The experimental results revealed that the fiber weight fraction had the most significant influence on COF (42.78%), while the sliding speed had the predominant effect on the specific wear rate (77.69%) and contact temperature (32.79%). These findings highlight the potential of BFRP composites for applications requiring enhanced wear resistance and mechanical stability under varying loading conditions. Full article

Predicting real-time wear depth distribution and the coefficient of friction (COF) in tribological systems is challenging due to the dynamic and complex nature of surface interactions, particularly influenced by surface roughness. Traditional methods, relying on post-test measurements or oversimplified assumptions, fail to capture this dynamic behavior, limiting their utility for real-time monitoring. To address this, we developed a deep neural network (DNN) model by integrating experimental tribological testing and finite element method (FEM) simulations, using acoustic signals for non-invasive, real-time analysis. Experiments with brass pins (UNS C38500) of varying surface roughness (240, 800, and 1200 grit) sliding against a 304 stainless steel disc provided data to validate the FEM model and train the DNN. The DNN model predicted wear morphology with accuracy comparable to FEM simulations but at a lower computational cost, and the COF with relative errors below 10% compared to experimental measurements. This approach enables real-time monitoring of wear and friction, offering significant benefits for predictive maintenance and operational efficiency in industrial applications. Full article

The properties of composite materials depend not only on the composition but also on the distribution and orientation of the fillers, i.e., on the internal material architecture. Using the example of two differently composed PEEK-based hybrid materials, the influence of fiber orientation on the tribological behavior of these materials in sliding contact with steel was investigated. The tribological performance of these composites was assessed using a pin-on-disc (PoD) tribometer, testing in a pv range from 0.25 to 32 MPa·m/s. The findings indicate that the printed specimens exhibit a high degree of fiber orientation aligned parallel to the printing paths. Conversely, the injection-molded samples display a three-layered structure across the thickness, with fibers in the skin layers aligned parallel to the injection direction but perpendicular to it in the core. These variations in morphology are evident in both the mechanical properties and the tribological behavior. To describe the influence of the fiber orientation on tribological properties, a model is proposed that allows the prediction of tribological properties for any fiber orientation. Although fiber orientation appears to be the dominant factor in tribological behavior, there is also a clear influence of additional fillers. Full article

The properties of lubricating oils are greatly enhanced by the incorporation of additives. With technological advancements, numerous additives have been developed and proven effective for this purpose. Some additives enhance anti-wear and anti-friction characteristics, while others improve the oil’s viscosity index. It has been noted that certain additives influence more than one property of the lubricating oil. In this study, a mixture of TiO₂ at 0.2 wt.%, 0.3 wt.%, and 0.4 wt.% and CaCO₃ at 0.4 wt.%, 0.6 wt.%, and 0.8 wt.% was used as an additive in gear oil EP140 to prepare the samples. A pin-on-disc test was conducted for the tribological characterization of the various samples. A combination of 0.2 wt.% TiO₂ and 0.4 wt.% CaCO₃ particles in the gear oil resulted in a remarkable 88.23% reduction in wear compared to the base gear lubricating oil (EP140). The combination of 0.3 wt.% TiO₂ and 0.6 wt.% CaCO₃ particles in the gear oil led to a significant 36.84% reduction in the coefficient of friction. Field Emission Scanning Electron Microscopy (FESEM) revealed that the pin tested with sample S1 (gear oil containing 0.2 wt.% TiO₂ and 0.4 wt.% CaCO₃) exhibited a smoother wear surface than the base lubricating oil. Full article

Non-exhaust emissions from the wear of brakes, tyres, and roads have become an increasing concern in recent years, already surpassing exhaust emissions by mass in many countries. However, there is a lack of studies in the scientific literature on test methods that include both real tyre and road materials. This is crucial for accurately replicating the tribological mechanisms and resulting emissions that occur during real-world driving. This study therefore employs a scaled experimental approach to investigate the influence of representative urban load and sliding speed conditions on tyre and road wear particle generation using commercial tyre and road materials. Friction, wear, and emissions were analysed using a pin-on-disc tribometer within a controlled environment, enabling the measurement of both airborne and non-airborne wear particles. The results demonstrate that under moderate test conditions, airborne tyre and road wear particle concentrations remained almost zero, with reasonable coefficients of friction and estimated non-airborne emission factors. However, under harsher contact conditions, the coefficients of friction, airborne tyre and road wear concentrations and estimated emission factors increased significantly, leading to excessive material detachment from both the tyre and road surface. These extreme wear conditions are not representative of real-world tyre–road interactions, emphasising the sensitivity and necessity of using more realistic test conditions in future studies. Full article

Squeal refers to a sustained high-intensity noise resulting from friction-induced vibrations. Although it is known that it originates from mode coupling, the conditions under which it occurs are still unclear, especially regarding the contact conditions. In this paper, pin-on-disc experimental tests are conducted in order to investigate the conditions of squeal occurrence. The tests are highly instrumented: they involve in particular a detailed measurement of near-surface temperature evolution in the pin using 16 thermocouples and a discrete monitoring of the evolution of surface profiles. As expected, the squealing frequency is closely related to the temperature level. However, the mean temperature level alone is not sufficient to predict the occurrence of squeal, especially at low temperatures. The study of local temperature elevations over the pin surface coupled with surface observations allows for assessing the evolution of macroscopic contact localization during tests at low temperatures. The contact localization is shown to be related to squeal episodes: at low temperatures, the contact is localized near the corners of the pin surface, and squeal is found to occur only in situations where the contact is evenly balanced over the corners, which is highly influenced by the initial pin surface profile. This shows that the conditions of squeal occurrence are driven in a significant extent by thermomechanical processes. Full article

This paper reports on the influence of various processing parameters and different SiC_p proportions on the outcome of mechanical, tribological, microstructural, and microcompositional investigations of Al-Cu based composites used as potential brake friction materials for eco-friendly vehicle parts. The composites were obtained by powder metallurgy, and then the sintered composite was treated at 515 ± 5 °C/6 h, quenched in water, and artificially aged at different temperatures and times. The microstructural and microcompositional investigations of the composites were made using an environmental scanning electron microscopy (ESEM), energy-dispersive X-ray spectroscopy (EDS). After analyzing the microstructures in correlation with the results of the hardness tests, the optimal proportion of SiC_p and optimal heat treatment parameters were determined. The composite samples with the best properties were chosen for tribological investigation. The friction and wear tests of samples were made under dry sliding conditions using a “pin on disc” machine, at a contact pressure of 0.35 to 1.15 MPa, 2 to 4.5 m/s relative speed, and the prediction of tribological behavior was made using a linear factorial design approach. Full article

We have investigated the sealing performance of different sealants and the abrasive effect of some Martian regolith simulants (MGS-1 and JEZ-1) by pin-on-disc tests using steel and various pin material pairs. Pin materials, representing sealants, were present in the following two forms: block types, such as pure polytetrafluoroethylene (PTFE) and composite PTFE, as well as braided pins, including pure and hybrid composite PTFE. Friction resistance, wear, surface roughness, and electron microscopy analyses were used to evaluate the tribological properties. We found significant differences between the block-type and braided pin materials regarding the sealing and wear performance. The braided pins either reached stabilized coefficients of friction at a much higher level (0.55) than the block-type pins or did not stabilize at all during the longest test duration. Martian regoliths resulted in negligible wear regarding the disc, but the hybrid composite braided pins were severely worn, causing the abrasion test to be stopped before schedule. Full article

In this work, powder metallurgy was used in order to produce self-lubricating composite materials. The NiCrSiB alloy as a matrix of the sinters and 20 wt. % CaF₂ as a solid lubricant were used. The sinters were subjected to wear tests using the pin-on-disc method at four different temperatures (room temperature (RT), 200, 400, and 600 °C). The coefficients of friction of the friction pairs were determined, and research on their wear mechanism was carried out. For this purpose, research techniques such as Light Microscopy (LM), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), X-ray Diffraction (XRD), and profilometer were used. Based on the conducted tests, it was found that CaF₂ was smeared on the surfaces of the samples and counter-specimens, particularly at elevated temperatures. Moreover, it was found that micro-cutting and micro-ploughing are the major wear of the friction pairs at room temperature, while with the increasing temperature, they were dominated by the reduction of such mechanisms, which is associated with the formation of a tribofilm composed of CaF₂ and oxidation wear. Full article

Hardness and wear resistance are the requirements of nickel-based superalloys used in gas turbine blades. This study uses laser cladding technology to develop three types of wear-resistant coatings—NiCr-2%hBN, NiCr-12%cBN, and NiCr-2%hBN-12%cBN—on GTD-111 superalloy. The above coatings’ microstructure, microhardness, and tribological behavior were systematically characterized by scanning electron microscope, hardness tester, pin-on-disc wear device, and three-dimensional profiles. The hardness test results showed that the hBN coating has the lowest hardness (692 HV) due to its layered structure, and the hBN-cBN coating has the highest hardness (992 HV) due to its complex structure and the creation of inhomogeneous nucleation centers in the coating. The wear test results showed that the hBN coating has a lower coefficient of friction (COF) (0.49) than the hard cBN coating (0.53) due to its lubricating properties. Meanwhile, the wear rate of the hBN coating is lower than the wear rate of the hard cBN due to the weak forces of one in the B-N bond. However, the wear test results of hBN-cBN coating showed that the effects of hBN and the high hardness of cBN cause the formation of a coating with the lowest wear rate (0.22 × 10⁻⁶ mm³/N·m), COF (0.41), fluctuation, wear depth (17.2 µm), and wear volume loss (0.32 × 10⁵ µ³) compared to the other two coatings. In addition, in the hBN-cBN coating, due to the greater driving force for the inhomogeneous nucleation of the melt, a larger area of equiaxed grains was formed, which in turn had a significant effect on increasing the wear resistance. Full article

This research study aims to evaluate the wear and corrosive behaviour of aluminum 6061 alloy hybrid metal matrix composites after reinforcing them with graphene (0.5, 1 wt.%) and boron carbide (6 wt.%) at varying weight percentages. The hybrid composites were processed through ball milling and powder compaction, followed by a microwave sintering process, and T6 temper heat treatment was carried out to improve the properties. The properties were evaluated and analyzed using FE-SEM, Pin-on-Disc tribometer, surface roughness, salt spray test, and electrochemical tests. The results were evaluated prior to and subsequent to the T6 heat-treatment conditions. The T6 tempered sample S1 (Al6061-0.5% Gr-6% B₄C) exhibits a wear rate of 0.00107 mm³/Nm at 10 N and 0.00127 mm³/Nm at 20 N for 0.5 m/s sliding velocity. When the sliding velocity is 1 m/s, the wear rate is 0.00137 mm³/Nm at 10 N and 0.00187 mm³/Nm at 20 N load conditions. From the Tafel polarization results, the as-fabricated (F) condition demonstrates an Ecorr of −0.789 and an Icorr of 3.592 µA/cm² and a corrosion rate of 0.039 mm/year. Transitioning to the T6 condition further decreases Icorr to 2.514 µA/cm², Ecorr value of −0.814, and the corrosion rate to 0.027 mm/year. The results show that an increase in the addition of graphene wt.% from 0.5 to 1 to the Al 6061 alloy matrix deteriorated the wear and corrosive properties of the hybrid matrix composites. Full article