During the last decade several ways have been adopted to reduce or eliminate the use of copper based products in passenger car applications, like increasing the lubricant content. But still it is challenging to replace it in an economical way in some applications, like CV or railway. Furthermore, the need of emission reduction from brakes, makes even more challenging
This blog post explores the exciting advancements in replacing copper with innovative materials, particularly oxides, to create high-performance and sustainable friction materials. Friction materials are complex systems where the tribological processes that occur at the contact surface between the pad and the rotor are critical to its performance. During braking, secondary plateaus are formed, and are important in controlling friction and wear. Prefabricated iron oxide structures, designed to mimic the morphology of these secondary plateaus, may be a substitute for copper-based materials.
Replacing copper in friction materials is no easy feat. It requires finding alternative materials that can match or exceed copper’s performance in terms of:
Oxides have emerged as a promising class of materials for replacing copper in friction materials. These compounds offer a unique combination of properties that make them well-suited for this application:
RIMSA is at the forefront of developing innovative friction materials using oxide-based solutions. Our research focuses on identifying and optimizing oxide compounds that can match or exceed the performance of copper while minimizing environmental impact, also with its minimal carbon footprint.
The result is the r0-vein family. This material is composed primarily of iron oxides and is characterized by a unique morphology. Scanning electron microscopy (SEM) reveals that LS materials exhibit thin, layered, plate-like structures, closely resembling the secondary plateaus observed on worn brake pad surfaces. The hypothesis is that incorporating this material into the friction formulation will promote the formation of a stable and effective tribofilm, enhancing friction control and wear resistance.
Images on the right: r0-vein seen in the surface of the brake pad (up) and detail of the product (down)
The baseline formulation contains lead-free brass chips, a common copper-containing additive, and is replaced with r0-vein (IP01) in volume basis. The rest of the formulation was kept constant. The table on the left shows the formulation:
Friction Performance
The GSR friction profiles of the baseline (brass-containing) and the IP01 (copper-free) formulations showed a good correlation. This indicates that the replacement of brass with the Induced Plateaus material did not significantly alter the friction behavior of the brake pad.
Wear Performance
The wear levels of the two formulations were generally within the same range. Notably, the IP01 formulation exhibited lower pad wear at high temperature (350°C) compared to the baseline formulation. This suggests that the Induced Plateaus material may contribute to improved wear resistance under severe braking conditions.
A detailed presentation about the mechanism of how and why r0-vein may become a sustainable alternative to copper replacement will be presented during Eurobrake 2025
EB2025-COM-020
Tribological Surface Engineering: Inducing Prefabricated Secondary Plateaus for Copper Substitution in Friction Materials
Dr. Carlos Lorenzana, Ing., RIMSA METAL TECHNOLOGY, SL, Spain
The transition to copper-free, low carbon footprint friction materials is a crucial step towards a more sustainable automotive industry. Oxides offer a promising pathway to achieve this goal, providing a combination of high performance, environmental friendliness, and cost-effectiveness. RIMSA’s commitment to research and innovation in this field ensures that we can continue to provide our customers with cutting-edge friction solutions that meet the evolving demands of the market while meeting customers expectations in terms of cost and sustainability.
More than 37 years dedicated to the research and development of solutions for friction and discontinuous reinforcement materials that improve the performance of fibers in any context.
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