Eurobrake 2023 – Technical Sessions
Rotor and pad based fundamentals
From adhesive wear to abrasive wear mechanism when switching from conventional rotors to hard coated rotors by Carlos Lorenzana – CIO rimsa
The future of Mobility is closely related to the fight against climate change, through the limitation of emissions of all kinds to conclude with the complete electrification of the mobile fleet. In the context of the Green Deal and the objectives of “carbon neutrality” and “zero pollution”, the European Commission has committed to reducing current emission limits, from all sources. Brake wear is a significant contributor to respirable particulate matter (PM10 aerodynamic diameter less than 10 µm), particularly in areas with high traffic density and frequent braking. How far emission regulation and electrification may transform the friction industry is still to see. The application of surface technology to the rotor can technically solve this problem and several technologies are being evaluated. But changes in the rotor material induce changes in the response of the friction material, and those can be different depending on the type of friction material and the coating material and technique. In this conference we will be showing some of the changes in tribochemistry and friction response related to the use of coatings, with different carbide coatings.
Tribological data have been obtained through simulated SAE standard tests by using brake pad screening tribometer, and Tribochemistry was studied by SEM-EDS. We expect to contribute with this work to further build a deep knowledge of how coating parameters may affect the friction behavior of friction materials, allowing the community to find new ways to use more sustainable materials for wear resistant coating.
In situ characterization of the oxidation mechanisms of iron based sulfides and composites by Diego Chávez – Senior R+D+I Engineer
The stabilization of coefficient of friction and reduction of the wear by sulfides are related to their contribution to modify the phenolic resin decomposition. Synthetic iron sulfide has been always seen as a low cost and stable in price alternative to other metal sulfides, but with some drawbacks in terms of high temperature behavior, due to its oxidation mechanism over 400ºC transforming into Iron Oxide and losing its catalytic effect. Previous works of Innovamat have shown how the microstructure of the sulfide can influence the tribochemistry, oxidation temperature range and oxidation products produced by a composite sulfide. This change in tribochemistry is responsible for the variation in the wear and friction behavior.
This work explores in-situ reactivity (brake pad) of the two different synthetic iron sulfide based products, and correlates those data with previous reactivity data obtained outside of the pad. This work go deeper in understanding how adjusting the oxidation mechanism of synthetic iron sulfide leads to a modification of pad tribochemistry that contributes to the reduction of the brake pad wear, and so, improving the brake emissions, while also improving one of the historical problems of iron based sulfides, the powder agglomeration and low shelf-life. The iron sulfide composite allows similar friction performance but significantly reduces the wear of the brake pad, and therefore the emissions, due to the different oxidation mechanism in comparison to the pure iron sulfide.
We will be sharing pad cross section elemental map distribution obtained by SEM-EDS, that shows the reactivity of the sulfides prior to reach the pad surface after SAE standard tests by using brake pad screening tribometer, and XRD, TG-DTA and IR data for reactivity characterization. With this work it is expected to contribute to better understanding of sulfide behavior in friction material, allowing the community to find new ways to be more sustainable, going LME independent in their current and future challenges, especially those related to emissions control, electrification and friction material commoditization.