Lubricants

18 pages, 4725 KiB

Open AccessArticle

Experimental Study on Thermal Elastohydrodynamic Lubrication Performance Calculation and Take-Off Speed of Thrust Bearing of Canned Motor Pump

by Yanjun Cao, Yingjie Yu, Haiming Gang, Qichen Shang, Xiaozhe Meng, Mohan Yang and Qian Jia

Lubricants 2025, 13(4), 191; https://doi.org/10.3390/lubricants13040191 - 21 Apr 2025

Abstract

In this paper, the calculation model and method of the lubrication performance of the thrust bearing, which considers the thermal bomb deformation, are constructed based on the working characteristics of the main pump thrust of the nuclear power plant. The key design parameters [...] Read more.

In this paper, the calculation model and method of the lubrication performance of the thrust bearing, which considers the thermal bomb deformation, are constructed based on the working characteristics of the main pump thrust of the nuclear power plant. The key design parameters of the tile package Angle θ are analyzed by taking the design parameters of the thrust-bearing tile as the variable. The circumferential fulcrum coefficient of tile, the influence of tile thickness B, and tile elastic modulus E on the lubrication performance of thrust bearing are analyzed to obtain improved design parameters. The lubrication performance of the thrust bearing includes the minimum oil film thickness h_min, the maximum temperature of oil film T_max, total flow Q_x, total power consumption W, maximum thermal deformation of axial bush δT_max, and the maximum elastic deformation of the axial bush δF_max. The scale test of the designed thrust bearing is carried out. The take-off speed of the bearing is tested and compared with the results of the theoretical analysis. The study results show that the influence is becoming more obvious from θo to h_min. Moreover, the impact becomes more obvious from T_max to Q_x, B to hmin, and Q_x to δT_max and δF_max. Lastly, the impact is also obvious from E to Q_x and δF_max. Full article

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20 pages, 8653 KiB

Open AccessArticle

Leakage Flow Characteristics of Novel Two-Stage Brush Seal with Pressure-Equalizing Hole

by Yu Li, Huanze Xu, Jinghan Zhang, Dan Sun and Zemin Yang

Lubricants 2025, 13(4), 190; https://doi.org/10.3390/lubricants13040190 - 19 Apr 2025

Viewed by 81

Abstract

Uneven inter-stage pressure drops of the common two-stage brush seal (CBS) lead to a problem that the second stage bristles bear excessive pressure load, and this problem leads to the premature failure of the brush seal. In this paper, a novel two-stage brush [...] Read more.

Uneven inter-stage pressure drops of the common two-stage brush seal (CBS) lead to a problem that the second stage bristles bear excessive pressure load, and this problem leads to the premature failure of the brush seal. In this paper, a novel two-stage brush seal (NBS) with the backing plate holes of the second stage was proposed, and a three-dimensional numerical model of the NBS was established. Then, the effects of the pressure-equalizing (PE) hole on the inter-stage pressure drop distribution of the NBS were numerically analyzed, and an optimal structure was obtained. Finally, the leakage flow characteristics of this optimal structure were studied. The results showed that the NBS with PE hole increased the passage area of the downstream, and so effectively improved the uneven pressure drops of the CBS, and the pressure drop balance ratio of the NBS was obviously smaller than that of the CBS. For the structural parameters studied in this paper, the pressure drop balance ratio of the NBS was improved by 45.6~67.9% compared to the CBS. Moreover, when PE holes were 0.4 mm in diameter, 5.95 mm in height, and the number of rows was 1, the NBS had the best pressure drop balance and its leakage was only 8.7% higher than that of the CBS. Full article

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16 pages, 7371 KiB

Open AccessArticle

Anisotropic Wear Resistance of Heat-Treated Selective Laser-Melted 316L Stainless Steel

by Menghui Sun, Qianqian Zhang, Jinxiu Wu, Hao Wang, Xu Wang, Hao Zhang, Yinong An, Yujie Liu and Long Ma

Lubricants 2025, 13(4), 189; https://doi.org/10.3390/lubricants13040189 - 19 Apr 2025

Viewed by 74

Abstract

Anisotropic microstructures and wear resistance are caused by large thermal gradients during selective laser melting (SLM). Investigating the wear resistance in different planes of SLM specimens is crucial. Hence, the effect of heat treatment on the anisotropy of the microstructure, density, microhardness, and [...] Read more.

Anisotropic microstructures and wear resistance are caused by large thermal gradients during selective laser melting (SLM). Investigating the wear resistance in different planes of SLM specimens is crucial. Hence, the effect of heat treatment on the anisotropy of the microstructure, density, microhardness, and wear resistance of SLM 316L stainless steel was studied. Specimens subjected to solution + aging treatment exhibited γ austenite and α ferrite phases with lower microstrain, as determined via X-ray diffraction (XRD) analysis. Microstructure observations demonstrated that SLM 316L appears as intersecting melt pools on the XOY plane and fish scale-like melt pools on the XOZ plane. After heat treatment, the melt boundaries disappeared, carbides (M₂₃C₆) precipitated at grain boundaries and within the grains, and the microstructures coarsened and became more uniform. The microhardness and wear resistance of the XOY plane were shown to be superior to those of the XOZ plane, and the microhardness decreased following heat treatment. Compared with SLM 316L, the microhardness of the XOY and XOZ planes of the specimen subjected to solution + aging treatment decreased by 5.96% and 4.98%. The friction and wear test results revealed that the specimen after solution + aging treatment had the lowest friction coefficient and the smallest wear rate. The wear rates of specimens from the XOY and XOZ planes after solution + aging treatment were 21.1% and 27.1% lower than that of SLM 316L, exhibiting the best wear resistance. Full article

(This article belongs to the Special Issue Friction and Wear of Alloys)

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20 pages, 4320 KiB

Open AccessArticle

The Impact of Oil Viscosity and Fuel Quality on Internal Combustion Engine Performance and Emissions: An Experimental Approach

by Milton Garcia Tobar, Kevin Pinta Pesantez, Pablo Jimenez Romero and Rafael Wilmer Contreras Urgiles

Lubricants 2025, 13(4), 188; https://doi.org/10.3390/lubricants13040188 - 18 Apr 2025

Viewed by 137

Abstract

The automotive industry faces increasing challenges due to fuel scarcity and pollutant emissions, necessitating the implementation of strategies that optimize engine performance while minimizing the environmental impact. This study aimed to analyze the influence of oil viscosity and fuel quality on the engine [...] Read more.

The automotive industry faces increasing challenges due to fuel scarcity and pollutant emissions, necessitating the implementation of strategies that optimize engine performance while minimizing the environmental impact. This study aimed to analyze the influence of oil viscosity and fuel quality on the engine performance and pollutant emissions in an internal combustion engine. A Response Surface Methodology (RSM)-based experimental design was employed. Three oil viscosity levels (SAE 5W-30, 10W-30, and 20W-50) and three fuel quality levels (87, 92, and 95 octane) were evaluated using a Chevrolet Grand Vitara 2.0L (General Motors, Quito, Ecuador) tested on a dynamometer. The oil grades were selected to represent a practical range of viscosities commonly used in commercial vehicles operating under local conditions. The results indicate that using lower-viscosity oil (SAE 5W-30) increased the engine power by up to 6.25% compared to when using SAE 20W-50. Additionally, using higher-octane fuel led to an average power increase of 1.49%, attributed to improved combustion stability and the ability to operate at a more advanced ignition timing without knocking. The emissions analysis revealed that high-viscosity oil at high RPMs increased CO₂ emissions to 14.4% vol, whereas low-viscosity oil at low RPMs reduced CO₂ emissions to 13.4% vol. Statistical analysis confirmed that the engine speed (RPM) was the most influential factor in emissions (F = 163.11 and p < 0.0001 for CO₂; F = 247.02 and p < 0.0001 for NOx), while fuel quality also played a significant role. These findings suggest that optimizing the oil viscosity and selecting the appropriate fuel can enhance engine efficiency and reduce emissions, thereby contributing to the development of more sustainable automotive technologies. Future research should explore the use of ultra-low-viscosity lubricants (SAE 0W-20) and assess their long-term effects on engine wear. Full article

(This article belongs to the Special Issue Advances in Hydrodynamic Friction in Combustion Engines)

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16 pages, 9284 KiB

Open AccessArticle

The Impact of Surface Roughness on the Friction and Wear Performance of GCr15 Bearing Steel

by Tiantian He, Wenbo Chen, Zeyuan Liu, Zhipeng Gong, Sanming Du and Yongzhen Zhang

Lubricants 2025, 13(4), 187; https://doi.org/10.3390/lubricants13040187 - 18 Apr 2025

Viewed by 144

Abstract

Surface roughness plays a crucial role in determining surface quality, influencing factors such as vibration, noise, assembly precision, lubrication, and wear resistance in bearings. This research examines how surface roughness (Sa) affects the friction and wear characteristics of GCr15 steel under conditions with [...] Read more.

Surface roughness plays a crucial role in determining surface quality, influencing factors such as vibration, noise, assembly precision, lubrication, and wear resistance in bearings. This research examines how surface roughness (Sa) affects the friction and wear characteristics of GCr15 steel under conditions with adequate oil lubrication while varying the applied load. The findings indicate that with an increase in Sa, the friction coefficient of GCr15 steel also increases. As the load rises from 15 N to 35 N, the friction coefficient remains relatively constant. However, higher loads lead to more severe wear of the microprotrusions on the surface of GCr15 steel. The wear area first decreases and then increases as Sa increases. The minimum wear area occurs when Sa is 0.5 μm. Additionally, a back propagation neural network (BPNN) model has been developed to predict the wear performance of GCr15 steel. Validation experiments show that the average prediction error for the BPNN model is 10.64%. Full article

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24 pages, 24408 KiB

Open AccessArticle

Pin-on-Disc Experimental Study of Thermomechanical Processes Related to Squeal Occurrence

by Quentin Caradec, Sacha Durain, Maël Thévenot, Mathis Briatte, Merten Stender, Jean-François Brunel and Philippe Dufrénoy

Lubricants 2025, 13(4), 186; https://doi.org/10.3390/lubricants13040186 - 18 Apr 2025

Viewed by 134

Abstract

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 [...] Read more.

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

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14 pages, 5772 KiB

Open AccessArticle

Study on the Tribological Behaviors of a Wave Glider’s Wing’s Rotating Shaft Using Fractal and Chaotic Analysis

by Shihui Lang, Hua Zhu and Xuehai Lian

Lubricants 2025, 13(4), 185; https://doi.org/10.3390/lubricants13040185 - 16 Apr 2025

Viewed by 137

Abstract

This paper conducts wear tests of rotating shafts and bearings, and collects the wear amount, surface morphology, and friction force signals to study its tribological behaviors using the fractal and chaotic analysis. The rotation shaft surface fractal dimension were calculated to characterize the [...] Read more.

This paper conducts wear tests of rotating shafts and bearings, and collects the wear amount, surface morphology, and friction force signals to study its tribological behaviors using the fractal and chaotic analysis. The rotation shaft surface fractal dimension were calculated to characterize the self-similarity and smoothness, the signals’ phase trajectories were constructed, and its correlation dimension and phase-point saturation were calculated to reveal the dynamic evolution of the system. The results show that the surface fractal dimension increases from low to high. The phase trajectory fluctuates and then maintains in a finite space, and the correlation dimension increases and stabilizes near the larger value while the phase-point saturation has the opposite evolution. The changes in surface fractal dimension, phase trajectories, correlation dimension, and phase-point saturation are similar to the wear rate, exhibiting a transition from instability to stability, which is more objective and sensitive than traditional representation methods. According to the fractal and chaotic characterization results of the worn surface and friction force signal, the material of CrNiMoN has better friction and wear properties than GCr15. The results reveal the tribological behaviors and wear mechanisms of the rotating shaft and provide guidance for material selection and designing, along with a basis for characterizing the wear status of the rotating shaft of wave glider wing. Full article

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17 pages, 2619 KiB

Open AccessArticle

Optimizing Hyaluronan-Based Lubricants for Treating Thoracolumbar Fascia Pathologies: Insights from Tribological and Pharmacokinetic Studies

by Alexandra Streďanská, Matěj Šimek, Jana Matonohová, David Nečas, Martin Vrbka, Jakub Suchánek, Veronika Pavliňáková, Lucy Vojtová, Martin Hartl, Ivan Křupka and Kristina Nešporová

Lubricants 2025, 13(4), 184; https://doi.org/10.3390/lubricants13040184 - 16 Apr 2025

Viewed by 124

Abstract

In a world where the incidence of non-specific lower back pain (LBP) is steadily increasing, researchers are still searching for effective solutions for patients. Hyaluronic acid (HA) viscosupplementation is commonly used to restore lubrication in osteoarthritis (OA) and other medical applications, but its [...] Read more.

In a world where the incidence of non-specific lower back pain (LBP) is steadily increasing, researchers are still searching for effective solutions for patients. Hyaluronic acid (HA) viscosupplementation is commonly used to restore lubrication in osteoarthritis (OA) and other medical applications, but its rapid metabolism limits efficacy. This study evaluates whether an HA derivative can replace native HA for the treatment of non-specific LBP while maintaining or enhancing its frictional properties and improving in vivo stability. Six HA-based lubricants, both native and derivatized, were tested in a tribological rabbit fascia model and a new synthetic model. Reduced HA derivative showed better tribological properties and longer in vivo residence time compared to native HA, as demonstrated in pharmacokinetic studies in rabbits. The 316 kDa HA and reduced HA exhibited the most stable tribological properties, which were influenced by their molecular weight and concentration. These findings suggest that both native and reduced HA are promising viscosupplements for intrafascial injection in the treatment of LBP, with reduced HA potentially enhancing effectiveness through a prolonged effect. Full article

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21 pages, 8225 KiB

Open AccessArticle

Contact Load Calculation Models for Finite Line Contact Rollers in Bearing Dynamic Simulation Under Dry and Lubricated Conditions

by Yongxu Hu, Liu He, Yan Luo, Andy Chit Tan and Cai Yi

Lubricants 2025, 13(4), 183; https://doi.org/10.3390/lubricants13040183 - 15 Apr 2025

Viewed by 204

Abstract

The key to exploring the behavior of bearings through dynamic methods lies in establishing an accurate model for calculating the contact load between the roller and the raceway. Based on the half-space theory of Boussinesq, this study developed a full-order model for calculating [...] Read more.

The key to exploring the behavior of bearings through dynamic methods lies in establishing an accurate model for calculating the contact load between the roller and the raceway. Based on the half-space theory of Boussinesq, this study developed a full-order model for calculating the contact load of the finite line contact roller. The model adopted an iterative procedure to calculate the contact load of each roller slice according to deformations. According to the comparisons between the contact loads obtained by the proposed model and those obtained by FEA, the average error for a cylindrical roller was approximately 2%, while that for a tapered roller was approximately 17%. By neglecting the influences of inter-slice contact stresses on the deformation of local roller slice, a fast-calculating method for the full-order model was developed, thereby reducing the calculation time by approximately 77%. By integrating the fast method with the Dowson–Higginson’s formula, another model was developed to calculate the contact load under lubrication conditions. The proposed models were utilized to investigate the dynamic characteristics of a double-row tapered roller bearing, and the results were validated through experiments. The proposed method could be utilized to assess dynamic performances of bearings across different operating scenarios. Full article

(This article belongs to the Special Issue Advances in Lubricated Bearings, 2nd Edition)

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25 pages, 8753 KiB

Open AccessArticle

Research on RV Reducer Shaft Bearing Force and Structural Optimization

by Xiaoxu Pang, Dingkang Zhu, Xinlong Wang, Minghao Yang, Qiaoshuo Li, Duo Liu and Hai Wu

Lubricants 2025, 13(4), 182; https://doi.org/10.3390/lubricants13040182 - 15 Apr 2025

Viewed by 147

Abstract

This paper addresses the unclear bearing force of an RV reducer shaft by establishing a transmission model and analyzing the force situation of each component. Three force models for the crank support bearing, swivel arm bearing, and main bearing are developed. The force [...] Read more.

This paper addresses the unclear bearing force of an RV reducer shaft by establishing a transmission model and analyzing the force situation of each component. Three force models for the crank support bearing, swivel arm bearing, and main bearing are developed. The force variations under different working conditions and the impact of structural parameters on shaft bearing forces are analyzed. Structural optimization is performed using Kriging-NSGA-II to minimize bearing forces. The results show similar load patterns for the bearings, with the force magnitude being ranked in the following order: rotating arm > crank support > main bearing. After optimization, the bearing forces are reduced by 8.26% for the crank support shaft, 10.35% for the rotating arm shaft, and 5.15% for the main shaft. Full article

(This article belongs to the Special Issue Advances in Lubricated Bearings, 2nd Edition)

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17 pages, 15797 KiB

Open AccessArticle

Unbalance Response of a Hydrogen Fuel Cell Vehicle Air Compressor Rotor Supported by Gas Foil Bearings: Experimental Study and Analysis

by Ming Ying and Xinghua Liu

Lubricants 2025, 13(4), 181; https://doi.org/10.3390/lubricants13040181 - 14 Apr 2025

Viewed by 161

Abstract

In rotating machinery, unbalanced mass is one of the most common causes of system vibration. This paper presents an experimental investigation of the unbalance response of a gas foil bearing-rotor system, based on a 30 kW-rated commercial hydrogen fuel cell vehicle air compressor. [...] Read more.

In rotating machinery, unbalanced mass is one of the most common causes of system vibration. This paper presents an experimental investigation of the unbalance response of a gas foil bearing-rotor system, based on a 30 kW-rated commercial hydrogen fuel cell vehicle air compressor. The study examines the response of the system to varying unbalanced masses at different rotational speeds. Experimental results show that, after adding unbalanced mass, subsynchronous vibration of the rotor is relatively slight, while synchronous vibration is the main source of vibration; when unbalanced mass is added to one side of the rotor, the synchronous vibration on that side initially decreases and then increases with speed, while synchronous vibration on the opposite side continuously increases with speed; when unbalanced mass is added to both sides, the synchronous vibration on each side increases with the phase difference of the unbalanced mass at low speed, while the opposite trend occurs at high speed. The analysis of the gas foil bearing-rotor system dynamics model established based on the dynamic coefficient of the bearing shows that the bending of the rotor offsets the displacement caused by the unbalanced mass, which is the primary reason for the nonlinear behavior of the synchronous vibration of the rotor. These findings contribute to an improved understanding of GFB-rotor interactions under unbalanced conditions and provide practical guidance for optimizing dynamic balancing strategies in hydrogen fuel cell vehicle compressors. Full article

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24 pages, 18010 KiB

Open AccessArticle

Reducing the Friction Coefficient of Heavy-Load Spherical Bearings in Bridges Using Surface Texturing—A Numerical Study

by Qian Hu, Qingxiang Pei and Pei Li

Lubricants 2025, 13(4), 180; https://doi.org/10.3390/lubricants13040180 - 13 Apr 2025

Viewed by 152

Abstract

Spherical bearings play a crucial role in maintaining the safety of bridge systems. The frequent operation and wear rate over their lifespan highlight the necessity for methods to improve their tribological performance. In this study, GQZ-60000 unidirectionally movable spherical bearings were the research [...] Read more.

Spherical bearings play a crucial role in maintaining the safety of bridge systems. The frequent operation and wear rate over their lifespan highlight the necessity for methods to improve their tribological performance. In this study, GQZ-60000 unidirectionally movable spherical bearings were the research object, and three different surface textures—spherical cap, ellipsoidal cap, and double spherical cap—were incorporated into a curved PTFE surface to enhance its tribological performance, with the major focus being on reducing the friction coefficient. The Jakobsson–Floberg–Olsson cavitation boundary condition was used to solve the Reynolds equation numerically to obtain the elastohydrodynamic lubrication pressure, and the parametric effect of the three textures on the friction coefficient were analyzed. Based on the simulation results, a rational texture with rational geometric values are recommended to obtain the minimum friction coefficient of the bearing. However, it was also found that the deformation of the lubricated surface significantly affects the lubricant film thickness, and cavitation of the lubricant film may also affect the selection of rational textures, especially when the relative sliding velocity between lubricated surfaces is high. Full article

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12 pages, 2493 KiB

Open AccessArticle

Predicting the Viscosity of Ester Biolubricants by the Functional Groups of Their Compounds Using a Sensitivity Parameter Model

by F. Javier Ramos, Juan Carlos de Haro, Juan Francisco Rodríguez, Ángel Pérez and Manuel Carmona

Lubricants 2025, 13(4), 179; https://doi.org/10.3390/lubricants13040179 - 12 Apr 2025

Viewed by 182

Abstract

Oleic-based trimethylolpropane (TMP) ester mixtures can be produced via esterification reaction between oleic acid (OA) and TMP, presenting important application as biobased lubricants. In this study, a new mathematical model that allows us to predict kinematic viscosities of such mixtures based on kinematic [...] Read more.

Oleic-based trimethylolpropane (TMP) ester mixtures can be produced via esterification reaction between oleic acid (OA) and TMP, presenting important application as biobased lubricants. In this study, a new mathematical model that allows us to predict kinematic viscosities of such mixtures based on kinematic viscosity sensitivity parameters from product functional groups was developed, and it was also checked by fitting the experimental kinematic viscosities of the biolubricant products at 40 and 100 °C. This way, it is possible to predict kinematic viscosities and the viscosity index of these biolubricant mixtures and even pure TMP-esters without the availability to measure purified compounds. Moreover, the influence on the viscosity properties of the different chemical functional groups can be assessed with this physical model. So, the deleterious or beneficial effects of intermediate products and unreacted OA on the biolubricant viscosity index (VI) were quantified, showing that Trioletate and also Dioleate TMP-ester and their mixtures meet very interesting lubricant properties (VI up to 218), whereas the Monooleate TMP-ester and the unreacted OA decrease dramatically the viscosity properties. We believe that these findings can pave the way for the improvement and development of bio-based lubricant formulations towards effective industrial development. Full article

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17 pages, 11217 KiB

Open AccessArticle

Research on Feature Extraction Method and Process Optimization of Rolling Bearing Faults Based on Electrostatic Monitoring

by Ruochen Liu, Han Yin, Jianzhong Sun and Lanchun Zhang

Lubricants 2025, 13(4), 178; https://doi.org/10.3390/lubricants13040178 - 12 Apr 2025

Viewed by 184

Abstract

Electrostatic detection is a highly accurate way to monitor system performance failures at an early stage. However, due to the weak electrostatic signal, it can be easily interfered with under complex real-world conditions, leading to a reduction in its monitoring capability. During the [...] Read more.

Electrostatic detection is a highly accurate way to monitor system performance failures at an early stage. However, due to the weak electrostatic signal, it can be easily interfered with under complex real-world conditions, leading to a reduction in its monitoring capability. During the electrostatic monitoring of rolling bearings, noise can easily drown out the effective signal, making it difficult to extract fault characteristics. In order to solve this problem, a sparse representation based on cluster-contraction stagewise orthogonal matching pursuit (CcStOMP) is proposed to extract the fault features in the electrostatic signals of rolling bearings. The method adds a clustering contraction mechanism to the stagewise orthogonal matching pursuit (StOMP) algorithm, performs secondary filtering based on atom similarity clustering on the selected atoms in the atom search process, updates the support set, and finally solves the weights and updates the residuals, so as to reconstruct the original electrostatic signals and extract the fault feature components of rolling bearings. The method maintains fast convergence while analysing the extraction effect by comparing the measured signals of rolling bearing outer ring and bearing roller faults with the traditional StOMP algorithm, and the results show that the CcStOMP algorithm has obvious advantages in accurately extracting the fault features in the electrostatic monitoring signals of rolling bearings. Full article

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14 pages, 6751 KiB

Open AccessArticle

Corrosion Resistance of SAE 5160 Steel Deposited by Duplex Simultaneous Treatment with Hastelloy Cathodic Cage

by Marcos Cristino de Sousa Brito, Juliermes Carvalho Pereira, Lauriene Gonçalves da Luz Silva, Renan Matos Monção, Ediones Maciel de Sousa, Weslley Rick Viana Sampaio, Igor Oliveira Nascimento, Anthunes Íkaro de Araújo, Michelle Cequeira Feitor, Thercio Henrique de Carvalho Costa and Rômulo Ribeiro Magalhães de Sousa

Lubricants 2025, 13(4), 177; https://doi.org/10.3390/lubricants13040177 - 12 Apr 2025

Viewed by 301

Abstract

SAE 5160 steel, classified as high-strength, low-alloy steel, is widely used in the automotive sector due to its excellent mechanical strength and ductility. However, its inherently low corrosion resistance limits its broader application. This study explores the application of the cathodic cage plasma [...] Read more.

SAE 5160 steel, classified as high-strength, low-alloy steel, is widely used in the automotive sector due to its excellent mechanical strength and ductility. However, its inherently low corrosion resistance limits its broader application. This study explores the application of the cathodic cage plasma deposition (CCPD) technique to enhance the corrosion resistance of SAE 5160 steel. The treatment was performed using a Hastelloy cathodic cage under two atmospheric conditions: hydrogen-rich (75%H₂/25%N₂) and nitrogen-rich (25%H₂/75%N₂). Comprehensive analyses revealed significant improvements in surface properties and corrosion resistance. The hydrogen-rich condition (H25N) facilitated the formation of Cr_0.4Ni_0.6 and CrN phases, associated with a nanocrystalline structure (37.6 nm) and a thicker coating (45.5 μm), resulting in polarization resistance over 290 times greater than that of untreated steel. Conversely, nitrogen-rich treatment (H75N) promoted the formation of Fe₃N and Fe₄N phases, achieving a dense but thinner layer (19.6 μm) with polarization resistance approximately 20 times higher than that of untreated steel. These findings underscore the effectiveness of CCPD as a versatile and scalable surface engineering technique capable of tailoring the properties of SAE 5160 steel for use in highly corrosive environments. This study highlights the critical role of optimizing gas compositions and treatment parameters, offering a foundation for advancing plasma-assisted technologies and alloying strategies. The results provide a valuable framework for developing next-generation corrosion-resistant materials, promoting the longevity and reliability of high-strength steels in demanding industrial applications. Full article

(This article belongs to the Special Issue Fundamentals and Applications of Tribocorrosion)

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21 pages, 6182 KiB

Open AccessArticle

Assessing the Compatibility of PAO and POE with Fluoroelastomer (FKM) for Potential EVs Application

by Bernardo Tormos, José M. Liñeira Del Río, Adbeel Balaguer and Enrique Giménez

Lubricants 2025, 13(4), 176; https://doi.org/10.3390/lubricants13040176 - 11 Apr 2025

Viewed by 244

Abstract

The accelerated growth of electric vehicle (EV) powertrains has prompted the development of specialized fluids that meet stringent thermal and electrical requirements for immersion cooling systems, including interactions with non-metallic components like fluoroelastomer (FKM). This research investigates the interactions between fluoroelastomer (FKM) and [...] Read more.

The accelerated growth of electric vehicle (EV) powertrains has prompted the development of specialized fluids that meet stringent thermal and electrical requirements for immersion cooling systems, including interactions with non-metallic components like fluoroelastomer (FKM). This research investigates the interactions between fluoroelastomer (FKM) and two potential base fluids—polyalphaolefin (PAO4) and a polyol ester (POE)—to assess their suitability for immersion cooling applications. Immersion tests, following an adapted ASTM D7216 standard, evidenced changes in FKM’s mass, Shore A hardness, and tensile strength. Furthermore, the physical, electrical, and thermal properties of the tested fluids were analyzed before and after immersion to determine whether contact with the FKM elastomer compromised their performance. The findings of this study reveal that the fluid exerts a greater influence on the elastomer than vice versa. This study bridges a knowledge gap in regards to EV fluid development and material science, contributing to the development of durable and efficient thermal management solutions. Full article

(This article belongs to the Special Issue Tribology of Electric Vehicles)

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14 pages, 3057 KiB

Open AccessArticle

Experimental Study: Bearing Degradation Caused by Electrical Currents and Voltages at Low Speeds

by Zifan Li, Ran Cai and Xueyuan Nie

Lubricants 2025, 13(4), 175; https://doi.org/10.3390/lubricants13040175 - 10 Apr 2025

Viewed by 295

Abstract

In electric vehicles (EVs), bearings in traction motors are increasingly prone to electrical damage under operational currents and voltages, leading to accelerated wear and reduced lifespan. This study examines the extent of bearing damage under low-speed, electrically charged conditions to understand wear behavior [...] Read more.

In electric vehicles (EVs), bearings in traction motors are increasingly prone to electrical damage under operational currents and voltages, leading to accelerated wear and reduced lifespan. This study examines the extent of bearing damage under low-speed, electrically charged conditions to understand wear behavior at boundary lubrication better. Bearings were driven at low speed by a motor, with inner and outer rings connected to a pulsed power supply’s positive and negative terminals, simulating real-world shaft voltage conditions. The applied electrical parameters included voltages from 5 V to 240 V and frequencies of 10 kHz, leading to voltages at the bearing peaking between 0.1 and 12 V measured by an oscilloscope and multimeter. The tested bearings were disassembled, and scanning electron microscopy (SEM) was used to assess the damage associated with varying electrical stresses. The results revealed distinct wear patterns and degradation effects when the shaft current and peak voltage reached 2.5 A and 12 V, emphasizing the critical need for protective strategies. Future work will focus on evaluating the impact of higher rotational speeds and controlled power supply conditions to analyze the effects of increased power supply settings and compare outcomes to low-speed scenarios. Full article

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18 pages, 7965 KiB

Open AccessArticle

Research on the Lubrication State of the Contact Interface Under the Tilt and Skew State of the Roller of the Aviation Bearing

by Lina Zhou, Xiaofeng Yang, Zhigang Luo, Jingjing Zhang, Zhen Li and Xiaodong Wang

Lubricants 2025, 13(4), 174; https://doi.org/10.3390/lubricants13040174 - 10 Apr 2025

Viewed by 296

Abstract

The lubrication behavior and mechanical characteristics of the main bearing area of an aero-engine main shaft bearing determine the reliability and life of the main shaft bearing. In aero-engine main shaft bearings, the lubricant not only plays the role of lubrication but also [...] Read more.

The lubrication behavior and mechanical characteristics of the main bearing area of an aero-engine main shaft bearing determine the reliability and life of the main shaft bearing. In aero-engine main shaft bearings, the lubricant not only plays the role of lubrication but also affects the dynamic characteristics of the bearing; therefore, if the lubricant drag force is insufficient, it will lead to rolling body slipping. Slipping not only affects the reliability of the bearing operation but also will make the temperature of the contact area instantaneously increase, leading to the occurrence of gluing, scraping and other lubrication failure phenomena in the main bearing area. A lubricant under the shear conditions of traction characteristics is actually the external manifestation of rheological properties. Rheological properties are one of the elastic fluid power lubrication theories and are an important part of the study. Elasto-hydrodynamic lubrication theory of the oil film pressure, film thickness and temperature and solid domains interact to form a thermal–fluid–solid coupling relationship; this coupling relationship affects the main bearing area of the lubrication behavior and mechanical properties, thus affecting the lubrication state of the bearings and dynamic characteristics. With the continuous improvement of aero-engine performance requirements for main shaft bearings, it is of great significance to carry out a coupling study of the lubrication behavior and mechanical properties of the bearing contact zone under heavy load, high speed and high temperature conditions to improve the service performance, reliability and life of the bearings. Full article

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24 pages, 12513 KiB

Open AccessArticle

Effect of Applied Current on Tribological Properties of Polyphenyl Ether

by Chencheng Wu, Renguo Lu, Hiroshi Tani, Shinji Koganezawa, Xujun Liu and Peihong Cong

Lubricants 2025, 13(4), 173; https://doi.org/10.3390/lubricants13040173 - 9 Apr 2025

Viewed by 234

Abstract

The widespread adoption of electric vehicles (EVs) has introduced new challenges in drivetrain lubrication, particularly concerning electrical corrosion, frictional wear, and hydrogen embrittlement. While polyalphaolefin (PAO)-based lubricants are commonly used, they struggle under high-speed and high-torque conditions. In contrast, polyphenyl ether (PPE)-based lubricants [...] Read more.

The widespread adoption of electric vehicles (EVs) has introduced new challenges in drivetrain lubrication, particularly concerning electrical corrosion, frictional wear, and hydrogen embrittlement. While polyalphaolefin (PAO)-based lubricants are commonly used, they struggle under high-speed and high-torque conditions. In contrast, polyphenyl ether (PPE)-based lubricants offer superior wear resistance and effectively suppress hydrogen generation, making them promising for EV applications. This study examines the effects of current direction and magnitude on tribofilm formation and frictional behavior in a PPE-lubricated environment. The results show that PPE exhibits unique tribofilm adhesion characteristics influenced by electrical conditions, unlike PAO. Surface analysis reveals that the tribofilm mainly consists of amorphous carbon, and friction under an electrical bias induces PPE oxidation, with oxidation products forming more readily at the positive electrode. Tribofilm formation correlated with increased friction and wear, particularly under currents of 10 mA or higher. Although PPE is more sensitive to electrical influences than PAO, it exhibits excellent wear resistance and maintains a low coefficient of friction even under electrification. This suggests that PPE could be suitable for lubrication in electrical environments and may serve as a promising lubricant for EV drive systems and similar applications. Full article

(This article belongs to the Special Issue Synthetic Greases and Oils)

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33 pages, 14949 KiB

Open AccessArticle

Tribological Behaviors and Statistical Experimental Design of Sintered and Age-Hardened Aluminum–Copper Based Composites

by Ileana Nicoleta Popescu, Badriyah Alhalaili, Florina Violeta Anghelina, Claudiu Nicolicescu and Ruxandra Vidu

Lubricants 2025, 13(4), 172; https://doi.org/10.3390/lubricants13040172 - 8 Apr 2025

Viewed by 239

Abstract

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 [...] Read more.

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

(This article belongs to the Special Issue Friction and Wear of Alloys)

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22 pages, 1849 KiB

Open AccessArticle

Investigating Film Thickness and Friction of an MR-Lubricated Journal Bearing

by Gerben van der Meer and Ron van Ostayen

Lubricants 2025, 13(4), 171; https://doi.org/10.3390/lubricants13040171 - 8 Apr 2025

Viewed by 272

Abstract

Magnetorheological (MR) fluids are frequently reported to have potential as lubricants for hydrodynamic bearings operating at high loads, but no comprehensive effort has been made to investigate their performance under a variety of operating conditions. This paper, therefore, presents an extensive experimental and [...] Read more.

Magnetorheological (MR) fluids are frequently reported to have potential as lubricants for hydrodynamic bearings operating at high loads, but no comprehensive effort has been made to investigate their performance under a variety of operating conditions. This paper, therefore, presents an extensive experimental and numerical investigation of an MR-lubricated hydrodynamic journal bearing subjected to different loads and magnetic fields, and compares these results to those of an oil-lubricated bearing. It is shown that by increasing the magnetic field strength, the performance characteristics of the bearing can be changed from low hydrodynamic friction and a high transition speed to high hydrodynamic friction and a low transition speed. Furthermore, it was found that the way in which these characteristics scale with increasing load differs for the MR- and oil-lubricated bearings. With MR lubrication, the relative change in characteristics with the application of a magnetic field is smaller at higher loads, due to the strong shear-thinning rheology of MR fluids. To include these effects in the model, a basic relation for the apparent MR viscosity as a function of shear rate, temperature, and magnetic field strength is introduced. Finally, the bearing was made from a polymer to improve wear resistance under MR lubrication, but a comparison with a Reynolds equation-based numerical model indicates possible performance degradation due to shape errors, which is a known issue with this bearing material. Full article

(This article belongs to the Special Issue Tribological Characteristics of Bearing System, 3rd Edition)

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24 pages, 19641 KiB

Open AccessArticle

Wear Characteristics and Optimization Measures of Disc Cutters During Large-Diameter Slurry Tunnel Boring Machine Advancing in Soil-Rock Composite Strata: A Case Study

by Yingran Fang, Xinggao Li, Yinggui Cao, Hongzhi Liu and Yidong Guo

Lubricants 2025, 13(4), 170; https://doi.org/10.3390/lubricants13040170 - 8 Apr 2025

Viewed by 224

Abstract

The large-diameter slurry tunnel boring machine (TBM) is widely used in the construction of tunnels across rivers and seas. However, cutter wear has become a critical issue that severely limits the tunnelling efficiency. Taking the Qingdao Jiaozhou Bay Second Subsea Tunnel Project as [...] Read more.

The large-diameter slurry tunnel boring machine (TBM) is widely used in the construction of tunnels across rivers and seas. However, cutter wear has become a critical issue that severely limits the tunnelling efficiency. Taking the Qingdao Jiaozhou Bay Second Subsea Tunnel Project as the background, the wear patterns of disc cutters on the atmospheric cutterhead of a large-diameter slurry TBM under complex geological conditions were analyzed. The flat wear of disc cutters induced by factors such as rock chip accumulation in front of the cutterhead, the jump trajectory when changing disc cutters, alloy-insert disc cutter mismatch, cutter barrel clogging, and severe wear of scrapers is discussed. Furthermore, the impacts of measures such as slurry circulation to remove rock chips during TBM stoppage, clay dispersant injection into the slurry chamber, cutter barrel flushing, and the wear resistance optimization of cutters and cutter barrels on reducing cutter wear were investigated. Based on numerical simulations and field data, a methodology for determining the optimal timing for cutter replacement is proposed. The results indicate the following: The circulation system effectively reduces accumulation, minimizing secondary wear of the disc cutters and lowering the risk of clogging in the cutter barrel. Adopting measures such as shield shutdown, a circulation system to carry away the slag, cutter barrel flushing, and soaking in 2% dispersant for 8 h can effectively reduce the accumulation of rock chips and mud cakes on the cutterhead, which in turn reduces the flat wear of the disc cutter. Measures such as making the cutter body and cutter ring rotate together and adding wear-resistant plates to the cutter barrel greatly improve the life of the cutter. The sharp increase in composite parameters can serve as an effective marker for assessing cutter conditions. The findings of this study can provide valuable insights into reducing cutter wear in similar projects. Full article

(This article belongs to the Special Issue Recent Advances in Tribological Properties of Machine Tools)

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17 pages, 3249 KiB

Open AccessArticle

An Integrated Methodological Approach for Interpreting Used Oil Analysis in Diesel Engines

by Reinaldo Ramirez Camba, Cristian Garcia Garcia, Milton Garcia Tobar and Jorge Fajardo Merchan

Lubricants 2025, 13(4), 169; https://doi.org/10.3390/lubricants13040169 - 8 Apr 2025

Viewed by 364

Abstract

This study develops an integrated methodological approach for interpreting used oil analysis results in diesel engines, focusing on optimizing maintenance strategies. The methodology combines a literature review with a quantitative assessment of 156 lubricant analysis reports from a fleet of diesel waste collection [...] Read more.

This study develops an integrated methodological approach for interpreting used oil analysis results in diesel engines, focusing on optimizing maintenance strategies. The methodology combines a literature review with a quantitative assessment of 156 lubricant analysis reports from a fleet of diesel waste collection trucks operating in Cuenca, Ecuador, a high-altitude city. The framework includes critical limits for key lubricant parameters, correlation analysis, and Principal Component Analysis (PCA) to identify dominant degradation mechanisms. The Binary Segmentation (BS) algorithm is also used for Change-Point Detection. The findings indicate four primary degradation pathways: thermal–chemical degradation influenced by sulfur, oxidation, and soot; metallic wear and base depletion, involving iron, chromium, and copper; external contamination linked to silica and copper; and viscosity alteration due to lubricant aging. Significant degradation shifts were identified at approximately 346 and 444 service hours, suggesting critical points for condition-based maintenance interventions. This study highlights the effectiveness of multivariate statistical tools in enhancing the interpretation of used oil analysis and optimizing predictive maintenance strategies. The integration of Change-Point Detection and multivariate analysis provides a robust framework for defining oil change intervals based on lubricant condition rather than fixed time- or mileage-based criteria. This approach offers practical benefits for fleet operations, enabling the reduction in operational costs, enhancing engine reliability, and minimizing the environmental impact of unnecessary lubricant changes. Full article

(This article belongs to the Special Issue Intelligent Algorithms for Triboinformatics)

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17 pages, 15544 KiB

Open AccessArticle

Characterisation of Tribological Properties and Morphologies of Ni-P and Ni-B Coatings

by Kristóf Bányai, Máté Czagány, Sándor Kovács and Gabriella Bognár

Lubricants 2025, 13(4), 168; https://doi.org/10.3390/lubricants13040168 - 7 Apr 2025

Viewed by 246

Abstract

The protective coatings industry is expanding, offering significant improvements in abrasion and wear resistance, which are crucial for economic sustainability. Despite the advancements, there remains a research gap in understanding the tribological properties and surface morphologies of electroless Ni-P and Ni-B coatings. This [...] Read more.

The protective coatings industry is expanding, offering significant improvements in abrasion and wear resistance, which are crucial for economic sustainability. Despite the advancements, there remains a research gap in understanding the tribological properties and surface morphologies of electroless Ni-P and Ni-B coatings. This study aims to fill this gap by characterizing the surface structures, friction coefficients, and wear properties of two types of Ni-P and one type of Ni-B coatings. Using a ceramic ball counterpart in an SRV5 tribometer, we compared the wear rates according to Archard’s and Liu’s models, adhering to the DIN 51834-1 standard. Scanning electron microscopy was employed to analyze the impact of surface structures on friction coefficients and wear factors. The results reveal significant differences in wear resistance and friction behaviour among the coatings, providing valuable insights for their application in various industries. Full article

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15 pages, 9432 KiB

Open AccessArticle

Contribution of Zn–Co Alloys Coatings Study: Electrodeposition Methodology, Micromechanical Properties, and Tribological Behavior

by Faten Nasri, Dorra Trabelsi, Mohamed Kharrat, Maher Dammak, Antonio Pereira, César Cardoso and Florence Vacandio

Lubricants 2025, 13(4), 167; https://doi.org/10.3390/lubricants13040167 - 7 Apr 2025

Viewed by 216

Abstract

: An overview of the literature reveals that electrodeposition baths significantly influence deposited coatings’ morphology and properties. The present study investigates a sulphate-based bath in terms of the additive, pH, and temperature for the electrodeposition of Zn–Co alloys onto mild steel, achieving a [...] Read more.

: An overview of the literature reveals that electrodeposition baths significantly influence deposited coatings’ morphology and properties. The present study investigates a sulphate-based bath in terms of the additive, pH, and temperature for the electrodeposition of Zn–Co alloys onto mild steel, achieving a nanocrystalline structure. The obtained results of the cyclic voltametric and SEM analyses revealed that sodium allowed the enhancement of cobalt electrocrystallisation (22.6 wt%) to homogenize further layers’ structure. However, the adjustment of pH allowed for the obtention of deposits with a refined structure containing only 5 wt% cobalt. Although an increase in room temperature resulted in deposit coatings with the same cobalt content, it notably produced a smoother structure. Subsequently, Zn–Co coatings were compared to pure zinc layers in terms of micromechanical and tribological behaviour. The morphology shifted from hexagonal platelets to nodular structures with the incorporation of cobalt, leading to an increase in microhardness. The morphology transformation, coupled with micromechanical reinforcement, contributed to the mitigation of friction and the improvement of the wear resistance of zinc layers through cobalt alloying. In fact, this improvement enhances the performance of zinc-coated applications in automotive and aerospace industries, particularly for standard assembly components that require adequate resistance to wear and abrasion during handling and tightening. Full article

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19 pages, 8971 KiB

Open AccessArticle

Synthesis of an Ionic Liquid-Based Cutting Lubricant and Its Performance Comparison with Mineral Oil in Hard Turning

by Rajashree Mallick, Ramanuj Kumar, Amlana Panda, Ashok Kumar Sahoo and Diptikanta Das

Lubricants 2025, 13(4), 166; https://doi.org/10.3390/lubricants13040166 - 6 Apr 2025

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Abstract

This study compares the hard turning performance under dual-nozzle minimum quantity lubrication (MQL) using mineral oil and 1-butyl-3-methylimidazolium chloride-based ionic fluids. Key performance indicators, including tool life (based on tool wear), surface roughness, cutting power, cutting temperature, cutting sound, carbon emission, and circularity [...] Read more.

This study compares the hard turning performance under dual-nozzle minimum quantity lubrication (MQL) using mineral oil and 1-butyl-3-methylimidazolium chloride-based ionic fluids. Key performance indicators, including tool life (based on tool wear), surface roughness, cutting power, cutting temperature, cutting sound, carbon emission, and circularity error, were evaluated to assess manufacturing sustainability. The results revealed that ionic fluid-assisted MQL significantly outperformed mineral oil, improving tool life by 28.75% and reducing surface roughness by 5.58%, attributed to the superior lubrication and cooling ability of ionic fluids. Additionally, after 85 min of machining, the power consumption and carbon emission were greatly reduced under ionic fluid conditions, indicating a lower environmental impact. For precision machining concerns, the ionic fluid proved more favorable, as circularity error under mineral oil conditions was 2.67 times higher than with ionic fluids. The weighted Pugh matrix awarded ionic fluid a higher sustainability score (+7) than mineral oil (+1), establishing it as the superior cooling option for hard turning, enhancing sustainability in machining difficult-to-cut metals. Full article

(This article belongs to the Special Issue Advances in Ionic Liquids as New Lubricant Materials)

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16 pages, 10121 KiB

Open AccessArticle

Parameter Optimization for the Improvement of Tribological Behavior of Textured Tapered Roller Bearings

by Risheng Long, Qiang Ma, Qingyu Shang, Haiming Wang, Ying Yao, Yueyong Wang and Lin Zong

Lubricants 2025, 13(4), 165; https://doi.org/10.3390/lubricants13040165 - 5 Apr 2025

Viewed by 212

Abstract

To enhance the operational stability and service life of tapered roller bearings (TRBs), this study investigates the application of surface texturing technology using laser marking to fabricate micro-dimples with controlled diameters and distributions on the TRB outer ring. An orthogonal experimental design was [...] Read more.

To enhance the operational stability and service life of tapered roller bearings (TRBs), this study investigates the application of surface texturing technology using laser marking to fabricate micro-dimples with controlled diameters and distributions on the TRB outer ring. An orthogonal experimental design was implemented to systematically evaluate the effects of three key dimple parameters—diameter, depth, and angular distribution—on the tribological performance under starved lubrication. The results demonstrate that the textured surfaces significantly improve friction-reducing performance and wear resistance. Optimal dimple parameters (diameter: 200 μm, depth: 10 μm, angular interval: 0.9°) were identified, achieving a 43.6% reduction in the average coefficient of friction (COF) and a 75.7% decrease in wear loss compared to smooth bearings. These findings would offer a practical approach to enhancing the durability and operational reliability of TRBs in industrial applications. Full article

(This article belongs to the Special Issue Recent Achievements and Future Developments in Surface Texture Control of Tribological Properties)

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23 pages, 26223 KiB

Open AccessArticle

Evolution of Microstructure, Hardness, and Wear Behavior of Medium-Entropy CuNiSiCrCoTiNbx Alloy

by Denis Ariel Avila-Salgado, Arturo Juárez-Hernández, Nelson Javier Izaguirre-Bonilla, Jonathan Muñoz Tabora and José Luis Camacho-Martínez

Lubricants 2025, 13(4), 164; https://doi.org/10.3390/lubricants13040164 - 5 Apr 2025

Viewed by 233

Abstract

Medium-entropy alloys (MEAs) allow the formation of different phases, generally in a solid-solution state, and compounds that favor obtaining alloys with properties superior to those of conventional alloys. In this study, medium-entropy CuNiSiCrCoTiNbx alloys were fabricated via melting in a vacuum induction furnace. [...] Read more.

Medium-entropy alloys (MEAs) allow the formation of different phases, generally in a solid-solution state, and compounds that favor obtaining alloys with properties superior to those of conventional alloys. In this study, medium-entropy CuNiSiCrCoTiNbx alloys were fabricated via melting in a vacuum induction furnace. The influence of the Nb addition (X = 0, 0.5 and 1 wt%) alloying elements on the microstructure, hardness, and wear resistance of the CuNiSiCrCoTiNb₀ (M1), CuNiSiCrCoTiNb_0.5 (M2), and CuNiCoCrSiTiNb₁ (M3) alloys were explored using X-ray diffraction (XRD), scanning electron microscopy (SEM), and a ball-on-disc tribometer, respectively. In general, the results indicated that the incorporation of Nb alloying element promoted the evolution of the microstructure, increased the hardness, and improvement of the wear resistance. The XRD and SEM findings demonstrate that higher Nb addition and aging heat treatment (AT) modification mainly favored the formation of dendritic regions and the precipitation of the Co₂Nb, Cr₃Si, and Ni₂Si phases, which promoted the refinement and strengthening of the microstructure. Significant increases in hardness were recorded: 11.95% increased, promoted by the addition of Nb before (E1) and after (E2, E3, and E4) the heat treatments. The maximum hardness values recorded were 92 ± 0.11 (AC) and 103 ± 0.5 HRB (AT-60 min) for the M3 alloy. The increase in hardness caused by Nb addition and aging heat treatments contributed to the dry sliding wear resistance response, decreasing material loss by 20%. This was related to the high concentration of precipitated phases rich in CoNb, CrSi, and NiSi with high hardness. Finally, the M3 alloy aged for 60 min exhibited the best specific wear rate behavior, with a material loss of 1.29

{m m}^{3}

. The commercial Cu-Be C17510 alloy experienced a maximum hardness of 83.47 Hardness Rockwell B, HRB, and a high wear rate of 3.34 mm³. Full article

(This article belongs to the Special Issue Friction and Wear of Alloys)

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22 pages, 7086 KiB

Open AccessArticle

A Non-Linear Optimization Model for Controlling the Real Area of Contact in Surface Texture Design

by Sandra D. Ekşioğlu and Min Zou

Lubricants 2025, 13(4), 163; https://doi.org/10.3390/lubricants13040163 - 3 Apr 2025

Viewed by 166

Abstract

Motivated by the potential of surface texturing to enhance the tribological performance of micro- and nano-electromechanical systems (MEMS/NEMS), this study proposes a novel non-linear optimization approach for designing textured surfaces. This model minimizes the contact area between interacting surfaces and deformation during sliding [...] Read more.

Motivated by the potential of surface texturing to enhance the tribological performance of micro- and nano-electromechanical systems (MEMS/NEMS), this study proposes a novel non-linear optimization approach for designing textured surfaces. This model minimizes the contact area between interacting surfaces and deformation during sliding under dry conditions by controlling key design parameters, such as the size and shape of the designed surface. We test the performance of the proposed model using the lotus leaf surface with dimensions of 248 × 136 micrometers. Due to the large size of the model, we propose a solution approach which consists of a data aggregation step, an optimization step, and a data disaggregation step. The optimization step decomposes the model into smaller models that are easier to solve. Via the sensitivity analysis, we highlight the trade-offs between data aggregation and model decomposition and their effect on the quality of the solutions found. In conclusion, our approach bridges the gap between fabrication capabilities and design requirements, paving the way for significant advances in tribological performance and surface engineering. Full article

(This article belongs to the Special Issue Tribology of Textured Surfaces)

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21 pages, 8648 KiB

Open AccessArticle

Study on Current-Carrying Friction Characteristics and Corrosion Resistance of Carbon Brush/Collector Ring by Copper–Graphene Electrodeposition Process

by Meiyun Zhao, Jianwen Li, Chenshi Li, Yangyang Li and Xiaolong Zhang

Lubricants 2025, 13(4), 162; https://doi.org/10.3390/lubricants13040162 - 3 Apr 2025

Viewed by 180

Abstract

The collector ring/carbon brush assembly of a hydrogenerator set is a critical component for transmitting excitation current into the self-exciting winding. Its operating environment necessitates excellent corrosion resistance and current-carrying frictional properties. The surface condition and material composition of the collector ring are [...] Read more.

The collector ring/carbon brush assembly of a hydrogenerator set is a critical component for transmitting excitation current into the self-exciting winding. Its operating environment necessitates excellent corrosion resistance and current-carrying frictional properties. The surface condition and material composition of the collector ring are key factors influencing the performance of the brush/ring interface. Coatings have proven effective in enhancing both tribological and corrosion-resistant characteristics. In this study, copper/graphene composite coatings were fabricated via electroplating, and the effects of graphene deposition rate on current-carrying friction characteristics were systematically investigated to optimize electroplating parameters. The results showed that the composite coating reduced contact resistance by 32.58% and friction coefficient by 37.59%. Electrochemical and immersion tests were conducted to evaluate the corrosion behavior under varying pressure and current density conditions. The results revealed that the optimal corrosion resistance was achieved under 1 N pressure and 12 A/cm² current density. The copper/graphene composite coating demonstrated superior corrosion resistance compared to uncoated samples. In summary, the electroplated copper/graphene composite coatings exhibit excellent current-carrying frictional performance and corrosion resistance, offering a promising solution for enhancing the durability and efficiency of hydrogenerator collector rings. Full article

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Lubricants, Volume 13, Issue 4 (April 2025) – 56 articles

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