Multi-functionality of copper (Cu) in friction materials renders its replacement extremely difficult. However, rising ecological concerns and the imminent ban on its usage make it mandatory to look ...for an efficient substitute. The present paper explores a possibility to replace particulate Cu filler by stainless steel swarf (SSS) in the brake-pads. A series of five realistic multi-ingredient brake-pads containing SSS as a focussed ingredient was developed by increasing its amount from 0 to 20 wt% in the step of 5%. In another set of pads 10% of SSS was replaced by 10 wt% Cu n particulate form keeping all ingredients same to compare the performance of two fillers. These pads were characterized for their physical, mechanical and tribological properties. Tribo-performance using realistic test parameters was evaluated on the brake inertia dynamometer as per JASO C 406 standard. It was observed that with an increase in the amount of SSS, almost all the properties of brakes pads, including wear resistance improved significantly. Nonetheless, Cu- containing pad proved slightly better in recovery ratio and wear performance by 10%, but inferior in the case of fade µ (µ-coefficient of friction) and recovery µ. Worn surface analysis with scanning electron microscope (SEM) confirmed that SSS had poor interfacial adhesion with the matrix which led to a higher wear of SSS filled pads as compared to the Cu filled pads.
•Maiden effort for developing Cu-free brake-pads using Stainless-steel swarf (SSS).•Barring wear, SSS proved equally good or better in all performance properties.•Poor adhesion of SSS with resin was responsible for higher wear than Cu-filled pads.•Higher the amount of SSS, better was the performance, in general.
As one of the most important components in high-speed trains, demands are improved on the mechanical and tribological properties of materials for brake pads. In this study, a newly developed copper ...metal matrix composite (Cu-MMC) for the aforementioned brake pads was fabricated by powder metallurgy route. The microstructure and mechanical properties of Cu-MMC were investigated. Cu-MMC was tribo-evaluated by a full-scale dynamometer, and special attention was paid on the braking performances during emergency stop-braking at initial speeds from 300 to 380 km/h. Examination and analysis of the worn surface and subsurface corroborated the wear mechanism. The results indicate that Cu-MMC exhibits excellent properties and can meet the technical requirements, so it holds great promise for applications in high-speed trains.
•A newly developed copper metal matrix composite for high-speed trains was fabricated by powder metallurgy route.•The braking tests were conducted on a full-scale dynamometer designed to simulate brake characteristics of high-speed trains.•Compared with materials in service, Cu-MMC exhibited superior mechanical and tribological properties.•The worn surface and subsurface were characterised by SEM and EDS.
The composition of friction materials is being revolutionised to exclude contentious components. This work comparatively used palm kernel shells, maize husks, cocoa bean shells and melon shells ...separately with seven other component materials to achieve novel friction materials. Friction and wear of the friction materials were measured using the test rig designed and constructed in-house for this research. Results showed that the maize husk-based friction material performed greatest in terms of thermal stability, wear, porosity and water absorption. Their thermal stability level indicates suitability for use in low-speed passenger cars and other allied braking applications. Using the selected agricultural residues in place of the contentious components in traditional friction materials would potentially solve health and environmental safety challenges.
In this study, the powder metallurgy process was used to prepare friction materials. Fe and graphite powders were added to the friction materials at different proportions. The friction and wear ...properties of the materials were evaluated by the MM3000 friction and wear tester. Combined with scanning electron microscope and physical and mechanical properties testing, the influence of the synergistic effect of Fe powder and graphite on the properties of the friction materials was studied. The results showed that the total content of Fe and graphite has not changed. Moreover, the hardness and strength of the material increased by increasing the iron content. The average friction coefficient first increased and then decreased. Furthermore, the instantaneous friction coefficient stability decreased, and the wear extent first slightly decreased and then increased. The comprehensive properties of the material were optimal when the Fe content and graphite powder were 14 % and 20 %, respectively.
Paper‐based friction materials with phenolic resin as the matrix are prone to thermal damage under harsh working conditions easily leading to materials failure. To satisfy the requirements of high ...speed and heavy load service situations, paper‐based friction materials with different polyimide resin content were prepared by wet forming technology to reveal the effect of polyimide resin on the properties of composites. And a paper‐based composite with phenolic resin was used for comparison. Results show that compared with the phenolic composite, tensile strength, and shear strength of the polyimide composite were increased by 50.5% and 36.4%, respectively. Due to the strong hydrogen bond in the imide ring of polyimide, the temperature of the polyimide composite at 2% weight loss was 292.7°C, which was 106.3°C higher than that of the phenolic composite. Moreover, the wear rate was reduced by 30.3% because the friction transfer film was produced during friction. To sum up, polyimide resin has the potential to replace phenolic resin under the condition of high speed and heavy load. Besides, the composite with polyimide resin content of 40.0 wt% demonstrated the best wear resistance and considerable strength attributed to the best interface combination. This research lays a theoretical foundation for the application of polyimide resin to paper‐based friction materials.
Effect of polyimide resin content on the structure and tribological properties of paper‐based friction materials.
This article aims to describe the sequence of events (cause-effect) that lead to the transition in wear regime from moderate to severe for brake friction materials (BFM). Tribofilm, contact plateaus ...and wear debris are characterized in both regimes through different techniques. It was concluded that there is a critical tensile strength which leads to the destruction of the contact plateaus (the secondary type), resulting in a direct contact between the metallic fibers of the BFM and the tribofilm deposited on the disc’s surface. Then, the tribofilm is gradually removed over the braking applications, increasing the wear rate of the tribopair.
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•A sequence of events (cause-effect) for the transition in wear regime is presented.•A critical tensile strength results in the destruction of the secondary plateaus.•Absence of secondary plateaus leads to a direct contact between fibers and tribofilm.•Direct contact of the fibers removes the tribofilm over braking applications.•Contact between fibers and disc (without tribofilm) increases wear rate of tribopair.
The tribological behavior of new green friction materials with rice husk (RH) and rice husk ash (RHA) is discussed in the current paper. Two formulations developed, one with 6% RH and one with 6% ...RHA, were compared with a reference formulation with alumina under the AK Master test, through a braking tribometer. Formulation with RHA showed tribological performance equal to or better than the reference material, especially in high temperature applications where the RHA particles assisted in the building of the contact plateaus. Adding RH reduced the abrasive action of the composite, allowing the formation of a more homogeneous tribofilm on the disc than in the other formulations.
•An eco-friendly brake friction material with rice husk ash was developed.•Rice husk ash led to a high percentage of contact plateaus in high temperature.•Rice husk ash had similar wear and friction performance as the reference material.•Rice husk had lower friction and promoted a more homogeneous tribofilm.•Rice husk ash showed great potential as reinforcement in brake materials.
•Interaction of mixing the steel and mullite fibers can improve the mechanical properties.•Mixing the steel and mullite fibers can also improve friction stability.•Friction coefficient increases with ...increasing additional mullite fiber content.•Ceramic-matrix friction material shows sever fade due to mullite fibers agglomerated.
The purpose of the present work was to investigate and compare the mechanical and tribological behaviors of ceramic-matrix friction material (CMFM) with steel fiber (SF), mullite fiber (MF), and mixing SF and MF. The CMFM was prepared by hot-pressing sintering, and the tribological behaviors were determined using a constant speed friction tester. The worn surfaces and wear debris were observed by a scanning electron microscopy (SEM). Experiment results show that the combination of SF and MF can improve the mechanical properties that each single fiber does not have. The sever fade for the specimen reinforced by single MF during the whole friction testing can be attributed to the poor interface cohesive strength between MF and matrix. Mixing the SF and MF can improve the friction stability, and the friction coefficients for friction material with a mixture of the SF and MF increases with increasing MF content. For all specimens, increasing in the friction temperatures result in the increase of wear rates.
