Lubricants

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15 pages, 5443 KiB

Open AccessArticle

Carbonaceous Decomposition Products at High Temperatures and Their Interfacial Role in the Friction Behaviour of Composite Brake Material

by Piyush Chandra Verma, Pranesh Aswath, Giovanni Straffelini and Stefano Gialanella

Lubricants 2024, 12(11), 399; https://doi.org/10.3390/lubricants12110399 - 20 Nov 2024

Viewed by 525

Abstract

This study aims to investigate the outcomes of carbonaceous products, derived from the decomposition of the components of vehicular brake materials, under high-temperature wear tests. Pin-on-disc (PoD) wear tests were conducted by using cast iron discs against pins made of commercially available low-steel [...] Read more.

This study aims to investigate the outcomes of carbonaceous products, derived from the decomposition of the components of vehicular brake materials, under high-temperature wear tests. Pin-on-disc (PoD) wear tests were conducted by using cast iron discs against pins made of commercially available low-steel friction material. Tests were carried out at different temperatures: 155 °C, 200 °C, 250 °C, and 300 °C. The characterization of the sliding plateaus on worn pin surfaces was based on X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. It was noted that at temperatures above 200 °C, the thermal degradation of the inorganic resin, used as a material binder, occurs. An interesting observation was recorded at 300 °C; the brake pin material’s friction curve showed higher stability despite having an excessive wear rate. However, the brake pin’s specific wear coefficient was higher at this temperature than was observed in the other friction tests. A detailed study of the friction plateaus on the worn-out pins at 300 °C revealed that the decomposed carbon resin product, i.e., the distorted graphite, was widespread over the surface of the pin. Lubricant stabilization can be expected, as established by the observed values of the coefficient of friction (CoF), retaining values within the 0.4–0.6 range, even at high temperatures. Other friction material components may have contributed to the formation of this ubiquitous carbonaceous interface film. Full article

(This article belongs to the Special Issue Recent Advances in High Temperature Tribology)

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16 pages, 10702 KiB

Open AccessArticle

Difference in High-Temperature Tribological Performance of Oxide/Ag-MoS₂-Based Composites

by Yufei Wang, Xibo Shao, Jianyu Liu, Xinyue Hu, Xuhui He and Guanyu Deng

Lubricants 2024, 12(10), 360; https://doi.org/10.3390/lubricants12100360 - 21 Oct 2024

Viewed by 936

Abstract

MoS₂ has excellent vacuum lubricating performance. However, it is prone to be oxidized in a high-temperature atmospheric environment, leading to the deterioration of its lubricating performance and even serious space accidents. The high-temperature lubricating performance of MoS₂-based solid lubricating materials [...] Read more.

MoS₂ has excellent vacuum lubricating performance. However, it is prone to be oxidized in a high-temperature atmospheric environment, leading to the deterioration of its lubricating performance and even serious space accidents. The high-temperature lubricating performance of MoS₂-based solid lubricating materials can be improved to some extent by the co-compounding of appropriate oxides and Ag. The tribological properties of several common nano-oxides (ZnO, TiO₂, Al₂O₃, and ZrO₂) composited with metal Ag of MoS₂-based composites were compared at 450 °C. The results showed that the comprehensive tribological performance of MoS₂-TiO₂-Ag was the best, an the average friction coefficient of about 0.26, and a wear rate of about 1.2 × 10⁻⁵ mm³/Nm, which was 18% and 43% lower than that of MoS₂-Ag, respectively. The excellent tribological properties of MoS₂-TiO₂-Ag composites were attributed to three aspects: Firstly, with the help of the oxidation resistance of TiO₂ to MoS₂ to some extent and its high ionic potential, its oxidation resistance was improved and its shear strength was reduced to provide low friction. Secondly, relying on the low shear strength and good film-forming tendency of soft metal Ag on the sliding surface, a low shear tribo-film was easily formed on the friction interface, which was helpful for the synergistic lubrication of Ag, MoS₂, and TiO₂.Thirdly, through the matching of hard TiO₂ and soft Ag, the wear resistance and bearing capacity of the composites were improved to some extent. The research results can provide some reference for the selection and design of MoS₂-based high-temperature lubricating materials and the enhancement of their tribological properties. Full article

(This article belongs to the Special Issue Recent Advances in High Temperature Tribology)

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17 pages, 4963 KiB

Open AccessArticle

Predictive Model for Scuffing Temperature Field Rise of Spiral Bevel Gears under Different Machining Conditions

by Zhi-Jie Cai, Xi-Qing Zheng, Hui-Qing Lan, Liu-Na Wang, Si-Wei Yang and Rui Shen

Lubricants 2024, 12(10), 354; https://doi.org/10.3390/lubricants12100354 - 14 Oct 2024

Viewed by 649

Abstract

Spiral bevel gears are extensively employed in mechanical transmissions; however, they are prone to adhesive wear when operating under high-speed and heavy-load conditions. Research indicates that the tooth surface roughness of gears significantly influences the friction and wear of the meshing gears. The [...] Read more.

Spiral bevel gears are extensively employed in mechanical transmissions; however, they are prone to adhesive wear when operating under high-speed and heavy-load conditions. Research indicates that the tooth surface roughness of gears significantly influences the friction and wear of the meshing gears. The present study delves into the origins of tooth surface roughness through the integration of the W-M function and fractal theory. Utilizing an involute helical gear with surface roughness for tooth cutting, a three-dimensional model is established with roughened tooth surfaces. This paper introduces an approach to developing three-dimensional gear models with roughness and applies the finite element method to perform thermodynamic analysis on gears exhibiting diverse levels of surface roughness. The thermal analysis of gears with varying degrees of roughness was conducted using the finite element method. Comparative analysis of the results under specific operating conditions elucidated the impact of roughness on tooth surface temperature rise. In order to validate the simulation model, an experimental test platform for spiral bevel gears of identical size was established. This model integrates tooth surface roughness with thermodynamic analysis, allowing for the rapid assessment of tooth surface temperature rise under different machining conditions, and reducing the cost of validating predicted tooth surface load-carrying capacity. Full article

(This article belongs to the Special Issue Recent Advances in High Temperature Tribology)

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18 pages, 27252 KiB

Open AccessArticle

High-Temperature Friction and Wear Behavior of Nickel-Alloy Matrix Composites with the Addition of Molybdate

by Jinming Zhen, Congcong Zhen, Yunxiang Han, Lin Yuan, Liwei Yang, Tianqi Yang and Shuo Guo

Lubricants 2023, 11(12), 516; https://doi.org/10.3390/lubricants11120516 - 7 Dec 2023

Cited by 1 | Viewed by 1774

Abstract

To improve the tribological characteristics of materials employed in spatial mechanisms, there is a significant requirement to develop solid lubricating composites with superior performance. This study investigates the tribological characteristics of composites consisting of a nickel matrix combined with silver molybdate and barium [...] Read more.

To improve the tribological characteristics of materials employed in spatial mechanisms, there is a significant requirement to develop solid lubricating composites with superior performance. This study investigates the tribological characteristics of composites consisting of a nickel matrix combined with silver molybdate and barium molybdate. The experimental analysis focuses on evaluating the tribological behaviors of these composites from 25 °C to 800 °C. The findings indicate that the combined application of silver molybdate and barium molybdate resulted in enhanced self-lubricating properties of the composites, particularly at temperatures over 400 °C. The inclusion of both silver molybdate and barium molybdate in the composite resulted in the achievement of a low friction coefficient (0.34–0.5), as well as a wear rate ranging from 0.47 to 1.25 × 10⁻⁴ mm³ N⁻¹m⁻¹, within the temperature range of 400 to 800 °C. Furthermore, an analysis was conducted to examine the wear processes of the composites at various sliding temperatures. This analysis was based on the evaluation of the chemical composition and morphologies of the sliding surfaces, which were verified by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and Raman spectroscopy. Full article

(This article belongs to the Special Issue Recent Advances in High Temperature Tribology)

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14 pages, 7280 KiB

Open AccessArticle

Simulation Study on the Influence of a Laser Power Change on the Residual Stress of a Laser-Melting RuT300 Valve Seat

by Wendan Tan and Ming Pang

Lubricants 2023, 11(10), 435; https://doi.org/10.3390/lubricants11100435 - 9 Oct 2023

Viewed by 1295

Abstract

In order to effectively suppress the cracking induced by the excessive residual stress of a laser-melting RuT300 valve seat, the influence of a laser power change on the residual stress was studied by constructing a finite element simulation model of a new power [...] Read more.

In order to effectively suppress the cracking induced by the excessive residual stress of a laser-melting RuT300 valve seat, the influence of a laser power change on the residual stress was studied by constructing a finite element simulation model of a new power valve seat. The absorption rate of the laser energy on the surface of the material and the change in thermophysical parameters with temperature were taken into account in the model. The results show that the melting and phase-change-hardening areas can be obtained by the laser-melting process. With the increase in laser power, the peak temperature of the molten pool increased almost linearly. The melting zone area and the phase-change-hardening zone depth increased. When the laser power was increased from 2000 to 2600 W, the peak temperature of the laser-melting RuT300 valve seat increased from 2005.09 to 2641.93 °C, the maximum depth of the melting area increased from 0.55 to 0.86 mm, the maximum width of the melting area increased from 3.42 to 4.21 mm, and the maximum depth of the phase-change-hardening area increased from 0.55 to 0.64 mm. The circumferential residual tensile stress in the melting area was much higher than in the radial and axial directions. Along the laser scanning direction, the residual stress in the melting area increased as a whole, and the residual stress in the laser-scanning finishing area greatly increased. With the increase in laser power, the circumferential residual stress at the previous scanning moment decreased, and at the closing moment of the scan, the circumferential residual stress increased with the increase in laser power. Full article

(This article belongs to the Special Issue Recent Advances in High Temperature Tribology)

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14 pages, 8120 KiB

Open AccessArticle

Influence of Concentration of Sodium Metasilicate and Descaling on the High Temperature Lubricating Effects Evaluated by Hot Rolling Mill

by Hongliang Liu, Xun Wu, Jiaxuan Huang, Xibo Shao, Pei Wang, Guanyu Deng and Long Wang

Lubricants 2023, 11(8), 352; https://doi.org/10.3390/lubricants11080352 - 18 Aug 2023

Viewed by 1860

Abstract

Lubricant is vital to improve energy efficiency and workpiece durability for the moving counterpart. High-temperature lubricants are important for the hot rolling process to reduce the rolling force and protect the roller and the strips. The current paper concerns eco-friendly sodium metasilicate as [...] Read more.

Lubricant is vital to improve energy efficiency and workpiece durability for the moving counterpart. High-temperature lubricants are important for the hot rolling process to reduce the rolling force and protect the roller and the strips. The current paper concerns eco-friendly sodium metasilicate as a high-temperature lubricant. A hot rolling mill is employed to evaluate the lubrication effect of sodium metasilicate. The influence of crucial factors of concentration of lubricant and descaling is discussed; the rolled surface was analyzed by scanning electron microscopy, energy dispersive spectroscopy, and 3D profilometer. The results depict that the sodium metasilicate can reduce the rolling force by about 7.8% when the concentration of sodium metasilicate is 18% and above, and descaling of the hot stripe makes the lubrication effect more effective, which can reach a 12.7% reduction in the rolling force. This lubrication is attributed to the formed melts of the sodium silicate layer that offers an easy shearing interface. For the un-descaled samples, the lubricant will be compacted and mixed with the oxide scale, and weakens the lubrication effect. This work suggests that sodium metasilicate can be a high-temperature lubricant for hot rolling; descaling is vital, not only for the quality of the product but also for the efficiency of the lubricant. This work will also be useful for the concentration selection of glass lubricant. Full article

(This article belongs to the Special Issue Recent Advances in High Temperature Tribology)

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17 pages, 25985 KiB

Open AccessArticle

High Temperature Friction and Wear Behavior of PTFE/MoS₂ Composites

by Jinming Zhen, Yunxiang Han, Huabao Wang, Zhenguo Jiang, Li Wang, Yuqiang Huang, Zhengfeng Jia and Ran Zhang

Lubricants 2023, 11(8), 312; https://doi.org/10.3390/lubricants11080312 - 25 Jul 2023

Cited by 2 | Viewed by 2377

Abstract

High performance polymer matrix composites with low friction and wear rate are of urgent requirement in sliding bearings and gaskets. In this study, the PTFE/MoS₂ composites were prepared and the effect of testing temperature on the tribological properties were investigated. Results show [...] Read more.

High performance polymer matrix composites with low friction and wear rate are of urgent requirement in sliding bearings and gaskets. In this study, the PTFE/MoS₂ composites were prepared and the effect of testing temperature on the tribological properties were investigated. Results show that the friction coefficient and wear rate are approximately (0.14–0.19) and (4.18–13.38 × 10⁻⁴ mm³/Nm) at testing temperatures from 25 to 250 °C, respectively. At testing temperatures above 200 °C, the coefficient of friction of the composite with the addition of MoS₂ is lower than that of pure PTFE, while the wear rate of the composite material with the addition of 2 wt.% and 5 wt.% MoS₂ is lower than that of pure PTFE at temperatures above 150 °C. At low testing temperatures (25–100 °C), the main wear mechanism is that of slight abrasive wear, while from 150 °C to 250 °C, the main wear mechanism transformed to fatigue and severe abrasive wear. Full article

(This article belongs to the Special Issue Recent Advances in High Temperature Tribology)

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Review

Jump to: Research

52 pages, 18335 KiB

Open AccessReview

A Critical Review of High-Temperature Tribology and Cutting Performance of Cermet and Ceramic Tool Materials

by Ali Elgazzar, Sheng-Jian Zhou, Jia-Hu Ouyang, Zhan-Guo Liu, Yu-Jin Wang and Ya-Ming Wang

Lubricants 2023, 11(3), 122; https://doi.org/10.3390/lubricants11030122 - 9 Mar 2023

Cited by 16 | Viewed by 4527

Abstract

Cermet materials exhibit advanced mechanical and tribological properties, and are widely used for tribology, elevated temperature, and machining applications due to their unique amalgamation of hardness, strength, and toughness. This paper presents a comprehensive overview of various cermet systems and recent advances in [...] Read more.

Cermet materials exhibit advanced mechanical and tribological properties, and are widely used for tribology, elevated temperature, and machining applications due to their unique amalgamation of hardness, strength, and toughness. This paper presents a comprehensive overview of various cermet systems and recent advances in high-temperature tribology and cutting performance of cermet and ceramic tool materials. It outlines microstructural properties, such as lessening grain sizes, obtaining extended grains, lowering grain boundary phase content, amorphous grain boundary phases crystallizing, inter-granular phase strengthening, and managing crack propagation path. Additionally, surface processing or surface modifications, such as surface texturing, appropriate roughness, or coating technique, can optimize the ceramic and cermet tribological performances. The purpose of this study is to present some guidelines for the design of ceramics and cermets with reduced friction and wear and increased cutting performance. The current research progress concerning tribological properties and surface texturing of cutting tool inserts is critically identified. Lubrication techniques are required in commercial applications to increase the lifetime of cutting tools used in harsh conditions. Liquid lubricants are still commonly utilized in relative motion; however, they have the limitations of not working in extreme settings, such as high-temperature environments. As a result, global research is presently underway to produce new solid lubricants for use in a variety of such conditions. This review also provides a quick outline of current research on this topic. Full article

(This article belongs to the Special Issue Recent Advances in High Temperature Tribology)

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