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Metals
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New Developments in Friction Brake Materials
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New Developments in Friction Brake Materials

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 December 2022) | Viewed by 12085

Special Issue Editor

Prof. Dr. Cinzia Menapace

E-Mail Website
Guest Editor
Department of Industrial Engineering, University of Trento, Via Sommarive 9, 38123 Trento, Italy
Interests: powder metallurgy; brake materials; thermal analysis; aluminum alloys
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In an automobile, the braking system is of primary importance for the control and safety of the vehicle, as well as the safety of the people within it. The brake assembly consists of a rotating element (the disc) and a couple of stationary friction elements (the pads). In braking, the friction elements are clamped against the disc, causing the vehicle to slow and stop. The brake pad composition contains different ingredients (binder, reinforcement, filler, friction modifier, and abrasive), while brake discs are typically made of grey cast iron. Different studies have recently been focused on improving the wear characteristics of both pad and disc materials, including disc surface modification through coating or other surface treatments. The improvement of brake materials is aimed not only at the enhancement of tribological properties (friction coefficient, specific wear, noise) but also the reduction of brake system debris release, which represents a consistent part of the road transport emissions, especially in urban areas. Different efforts are furthermore made in the substitution of harmful friction material ingredients with “green” novel components.

The aim of this Special Issue is to improve the knowledge of brake materials (pads, disc) and their possible surface modifications, considering wear properties and emissions, which are very important from the environmental point of view.

Prof. Dr. Cinzia Menapace
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Brake pad
  • Brake disc
  • Friction material
  • Brake wear emissions
  • Surface modification
  • Coating

Published Papers (5 papers)

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Research

19 pages, 17458 KiB  
Article
Comparative Study on the Friction Behaviour and the Particle Formation Process between a Laser Cladded Brake Disc and a Conventional Grey Cast Iron Disc
by Christopher Hamatschek, Klaus Augsburg, David Schobel, Sebastian Gramstat, Anton Stich, Florian Gulden and David Hesse
Metals 2023, 13(2), 300; https://0-doi-org.brum.beds.ac.uk/10.3390/met13020300 - 01 Feb 2023
Cited by 6 | Viewed by 2062
Abstract
Brake-wear particle emissions are the result of the components of a friction brake being in tribological contact, and they are classified as non-exhaust emissions. Since most of the emitted particles belong to the size classes of particulate matter (≤10 μm) and differ significantly [...] Read more.
Brake-wear particle emissions are the result of the components of a friction brake being in tribological contact, and they are classified as non-exhaust emissions. Since most of the emitted particles belong to the size classes of particulate matter (≤10 μm) and differ significantly in terms of their physico-chemical properties from automotive exhaust emissions, this source is of particular relevance to human health and, therefore, the focus of scientific studies. Previous studies have shown that coated brake discs offer significant wear and emission reduction potential. Nevertheless, no studies are available that describe the specific particle formation process, the contact conditions, the structure of the friction layer and the differences compared to conventional grey cast iron discs. The aim of this study is to describe those differences. For this purpose, the tribological behaviour, the structure of the friction layer and the associated particle dynamics within the friction contact between a laser cladding coated disc and a conventional grey cast iron disc are compared. The required investigations are carried out both ex situ (stationary) and in situ (dynamic). Parallel to the tribological investigations, the particle emission behaviour is determined on an inertia dynamometer using a constant volume sampling system (CVS) and equipment for particle number and particle size distribution measurement. The results show that, for two different brake pads, the laser cladding brake disc has lower wear and less particulate emissions than the grey cast iron brake disc. The wear behaviour of the coating varies significantly for the two brake pads. By contrast, the grey cast iron brake disc shows a significantly lower influence. Full article
(This article belongs to the Special Issue New Developments in Friction Brake Materials)
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13 pages, 5360 KiB  
Article
Microstructural and Tribological Evaluation of Brake Disc Refurbishing Using Fe-Based Coating via Directed Energy Deposition
by Hossein Rajaei, Cinzia Menapace, Sasan Amirabdollahian, Matteo Perini, Giovanni Straffelini and Stefano Gialanella
Metals 2022, 12(3), 465; https://0-doi-org.brum.beds.ac.uk/10.3390/met12030465 - 10 Mar 2022
Cited by 3 | Viewed by 2542
Abstract
In this paper, the refurbishing of worn-out brake discs by coating with powder via direct energy deposition (DED) is evaluated. A medium carbon steel powder was used to coat cast-iron discs. Deposition of this steel was carried out directly on the disc surface [...] Read more.
In this paper, the refurbishing of worn-out brake discs by coating with powder via direct energy deposition (DED) is evaluated. A medium carbon steel powder was used to coat cast-iron discs. Deposition of this steel was carried out directly on the disc surface or, alternatively, after a previous deposition of a buffer layer made of stainless steel. It was seen that the use of a buffer layer ensured a good coating adhesion, despite the formation of cast microstructures at the interfaces between the disc and the two different coatings (buffer and outer layer). Coated discs were tested against two different Cu-free commercial friction materials to evaluate their tribological properties. Very similar friction coefficients, specific wear rates, and total emissions were measured for both friction materials sliding against the coated disc. These tribological data are slightly higher with respect to those obtained in the case of an uncoated disc, suggesting that improvement of the top coating composition and surface finishing is necessary in order to achieve better performances. Full article
(This article belongs to the Special Issue New Developments in Friction Brake Materials)
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15 pages, 2940 KiB  
Article
The Role of Graphitic Carbon Nitride in the Formulation of Copper-Free Friction Composites Designed for Automotive Brake Pads
by Vlastimil Matějka, Mara Leonardi, Petr Praus, Giovanni Straffelini and Stefano Gialanella
Metals 2022, 12(1), 123; https://0-doi-org.brum.beds.ac.uk/10.3390/met12010123 - 09 Jan 2022
Cited by 9 | Viewed by 1665
Abstract
In this study, graphitic carbon nitride (g-C3N4, labelled as gCN) was tested in the formulation of copper-free (Cu-free) friction mixtures, which are potentially interesting for brake pad manufacturing. Three formulations of friction composites were prepared starting from a common [...] Read more.
In this study, graphitic carbon nitride (g-C3N4, labelled as gCN) was tested in the formulation of copper-free (Cu-free) friction mixtures, which are potentially interesting for brake pad manufacturing. Three formulations of friction composites were prepared starting from a common Cu-free master batch: (i) without graphite, (ii) with graphite and (iii) with gCN. The mixtures were pressed in the form of pins by hot-press moulding. The friction-wear performance of the prepared pins was investigated using a pin-on-disc (PoD) test at room temperature (RT), high temperature (HT) (400 °C) and, again, at room temperature (H-RT). The values of the friction coefficient (µ) for the composites with gCN (or graphite) were as follows: (i) RT test, µRT = 0.52 (0.47); (ii) HT test, µHT = 0.37 (0.37); (iii) RT after the HT tests, µH-RT = 0.49 (0.39). With respect to wear resistance, the samples with graphite performed better than the samples without this solid lubricant. To the best of our knowledge, this is the first report regarding the evaluation of the role of gCN in friction composites designed for automotive brake lining applications. The results indicate the main role of gCN as a soft abrasive. Full article
(This article belongs to the Special Issue New Developments in Friction Brake Materials)
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12 pages, 2473 KiB  
Article
Tribology and Airborne Particle Emission of Laser-Cladded Fe-Based Coatings versus Non-Asbestos Organic and Low-Metallic Brake Materials
by Yezhe Lyu, Mara Leonardi, Alessandro Mancini, Jens Wahlström and Ulf Olofsson
Metals 2021, 11(11), 1703; https://0-doi-org.brum.beds.ac.uk/10.3390/met11111703 - 26 Oct 2021
Cited by 9 | Viewed by 1720
Abstract
Laser cladding is a promising surface treatment for refurbishing worn-out cast-iron brake rotors. Previous studies on laser-cladded brake rotors have demonstrated their extensively higher wear and greater airborne particle emissions, compared with traditional cast iron rotors. In order to overcome this, a commercial [...] Read more.
Laser cladding is a promising surface treatment for refurbishing worn-out cast-iron brake rotors. Previous studies on laser-cladded brake rotors have demonstrated their extensively higher wear and greater airborne particle emissions, compared with traditional cast iron rotors. In order to overcome this, a commercial non-asbestos organic (NAO) brake material is tested against Fe-based laser-cladded and traditional cast-iron brake rotors. Two low-metallic brake pad materials are also tested as references. The materials’ coefficients of friction, specific wear rates and particle number concentrations are evaluated. The results indicate that the NAO brake material showed lower wear and had fewer particle emissions than the low-metallic brake materials when deployed against both cast iron and laser-cladded brake rotors. The NAO/laser-cladding friction pairing showed wear, particle concentration and fraction of fine particles (sub 1 μm) equivalent to those of the low-metallic/cast-iron friction pairing, creating significant potential for application in refurbishing worn-out cast-iron brake rotors. Full article
(This article belongs to the Special Issue New Developments in Friction Brake Materials)
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16 pages, 6662 KiB  
Article
Role of Promaxon-D in Controlling Tribological Performance of Cu-Free Brake Pads
by Bhaskaranand Bhatt, Navnath Kalel, Ashish Darpe and Jayashree Bijwe
Metals 2021, 11(3), 441; https://0-doi-org.brum.beds.ac.uk/10.3390/met11030441 - 07 Mar 2021
Cited by 7 | Viewed by 2414
Abstract
Copper appears to be an indispensable ingredient of non-asbestos organic (NAO) brake friction materials owing to its multifunctionality. However, recent findings proved it as a threat to aquatic life and efforts were initiated worldwide over the last few years to find a substitute [...] Read more.
Copper appears to be an indispensable ingredient of non-asbestos organic (NAO) brake friction materials owing to its multifunctionality. However, recent findings proved it as a threat to aquatic life and efforts were initiated worldwide over the last few years to find a substitute for it. Recently, the authors’ group had reported on the potential of particulate Promaxon-D (hydrated calcium silicate), a porous material for enhancement of noise–vibration (NV) performance of Cu-free brake pads. It was felt necessary to investigate how Promaxon-D (PD) contributes to controlling tribo-performance of brake pads since this aspect is most important for the brake friction materials. A series of five types of brake pads was developed by keeping parent composition fixed and varying the theme ingredient PD content from 0–20 wt.%. The tribo-performance was evaluated on a full-scale brake inertia dynamometer as per the JASO C406 test standards. The increase in PD contents led to a reduction in density, hardness, and thermal conductivity while an increase in porosity and compressibility. With the increase in PD contents, almost all tribo properties such as average μ, fade ratio, and recovery ratio got enhanced, sensitivity of µ for pressure, speed, and temperature lowered but at the cost of wear resistance. Finally, the worn surfaces of pads and discs were observed under a scanning electron microscope equipped with energy dispersive X-ray (SEM-EDX) to find out the presence of various elements at the contact zone and to monitor specific topographical events responsible for wear mechanism. Full article
(This article belongs to the Special Issue New Developments in Friction Brake Materials)
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