Brake industry targets Euro 7 compliance with new manufacturing and materials technologies
New materials, advanced coatings and innovative manufacturing techniques are helping brake suppliers reduce particulate emissions ahead of Euro 7, with potential emissions reductions of up to 90% while maintaining performance and durability
The Euro 7 regulations will soon come into play, applying to new passenger cars from November 2026 and later to heavy-duty vehicles from May 2028 and for the first time non-exhaust particulate emissions (PMs) from vehicle brakes will be under close scrutiny.
Brake and material specialists have been working to prepare for the regulations, with extensive research and development efforts resulting in new and innovative approaches to braking and friction technologies.
At EuroBrake 2026, in Mainz, Germany, brake system specialists and technical engineers presented their latest work in the field. Manufacturing techniques and material developments were at the heart of projects that aim to cut brake-related PM emissions.
Mixing materials
“We all know that environmental pollution is one of the greatest issues to public health worldwide, and that the automotive industry is one of the largest contributors,” stated Gorka Alonso, Project Manager at Azterlan – a metallurgy specialist based in Bizkaia, Spain. “There are two primary sources of particulate matter (PM) emissions: On the one side, we have the tailpipe emissions from the burning of different fossil fuels, and on the other we have the PMs emitted directly from braking. This invisible pollution must be controlled.”
Alonso explained that a number of different approaches could be taken to meet Euro 7 targets for brake-related emissions, from the introduction of surface treatments and coatings to the adoption of more costly carbon-ceramic brake discs. However, he also believes that metallurgical engineering and the modification of chemical compositions could help improve the performance of conventional cast iron brake discs.
At one of the company’s foundries, Alonso and his team manufactured ventilated brake discs using three alloy compositions. The first was a conventional grey cast iron disc with 3.7% carbon and 1.95% silicon. In the second alloy they reduced the silicon content and increased the aluminium to 4.37%, and in the third they increased both the silicon and aluminium to 3.35% and 4.37% respectively. Each alloy then underwent thermodynamic modelling, SEM/EDX Analysis (Scanning Electron Microscopy paired with Energy Dispersive X-ray Spectroscopy), mechanical testing, and PM10 measurements.
The modified alloys achieved a 40% reduction in PM emissions during brake testing when compared to the conventional cast iron disc. They also produced notable mechanical improvements, with the second alloy gaining 45% in hardness and tensile strength, and the third gaining 11% in hardness and 65% in tensile strength. Additionally, the mass of the both alloys that contain higher aluminium content was reduced by up to 22%.
“PM emissions are greatly reduced due to a combination of refining the graphite in the alloy, the increased content of aluminium, and the increased hardness and tensile strength,” Alonso noted. “There is a cohesion between all of the compounds within the microstructure, and as a result, we have proved that we can significantly improve the performance of the discs.”
Alonso suggested that further PM emissions reduction could be feasible, and hinted at achieving a 65% reduction with another alloy. However, he admitted that further testing and validation needs to be carried out before the details are made public.
Electric arc
In his presentation, Hyunwook Cho, R&D Director, SHKorea, focused on the development of cost-effective and wear-resistant coatings for brake discs using an electric arc spraying process. With support from colleagues at Hyundai, Cho and his team were able to carry out extensive research and development, examining the possibility of using six different coatings while ensuring they meet Euro 7 brake emissions requirements.
As well as reducing brake-related emissions, one of the key drivers for developing the coatings was cost. Laser metal deposition (LMD) coatings offer high durability, and are resistant to wear and corrosion. As such, they can help greatly reduce non-exhaust emissions. However, they are currently very costly due to raw material prices and the equipment investment needed for manufacturing. In comparison, Cho explained that the equipment costs for electric arc spraying are around a third of the price, and the cost of the wire feedstock is far lower than the metal powders needed for LMD.
“The best performing coating was a hybrid of commercial 97 MXC (Methoxychlor) and stainless steel 420, and its performance was compared with that of an LMD coated brake disc,” Cho explained. “The material used for LMD was stainless steel 430 containing 25% titanium carbide. The WLTP (Worldwide Harmonised Light Vehicle Test Procedure) test results showed that the LMD disc achieved PM2.5 emissions of 0.2 milligrams and PM10 emissions of 0.54. In comparison, the arc spray coating achieved 0.23 milligrams of PM2.5 emissions and 0.46 milligrams of PM10, showing a very similar performance.”
While early findings of the research show promise, Cho admitted that there is still work to be done. He suggested that electric arc spray coatings require “larger grinding allowance than LMD coatings” due to a relatively rough and uneven top surface. Reducing this could decrease machining time, energy consumption and overall production cost.
“Previously, a grinding allowance corresponding to a coating thickness of 300 micrometer was required, but under optimised conditions, the grinding allowance could be reduced to approximately 250 micrometer,” he said. “However, because the uppermost region contains only partial coating coverage and irregular peaks, the overall grinding energy and processing time may not differ significantly from those required for LMD coatings. This is an area that requires a further investigation.”
The next steps, Cho continued, would be to carry out further tests and analysis to investigate the NVH (noise, vibration and harshness) characteristics of the new coating materials, as well as further optimisation of the manufacturing process to improve performance while reducing cost. In parallel, he is aiming to collaborate on the development of friction materials specifically tailored for the electric arc spray coating system.
Crucial coatings
The solutions presented by Cho and Alonso clearly offer viable pathways for reducing PM emissions from brakes. But, as Martina Rota, Materials Development Coordinator at Brembo, pointed out, it is also important to target the used car market. She explained that Europe’s fleet is ageing, with the average vehicle age exceeding 12 years. Therefore, even if every new car comes equipped with advanced braking systems to meet Euro 7 requirements, a large proportion of brake-generated PMs will continue to come from the ageing fleet.
Rota and her colleagues began to develop new brake discs and pads with the specific purpose of retrofitting vehicles. The primary goal was to reduce non-exhaust PM emissions by 90% while also keeping the cost down.
“We developed two disks with tailored friction materials,” said Rota. “Solution number one consists of a lower brake disc coupled with a low emission friction material, while solution number two is a coated brake disc paired with dedicated low steel friction material. We also aimed for adaptability, targeting the maximum number possible of vehicles – sedans, SUVs and light commercial vehicles.”
The first solution retained a traditional cast iron disc architecture, whereas the second leveraged advanced surface engineering techniques to create a grey cast iron substrate and a ferritic bond layer containing approximately 20% carbide reinforcement. The team fitted a selection of Volkswagen models with the two brakes: the Transporter, the T-Roc and the Passat. This allowed them to determine whether or not emissions reductions are application-specific or if they are transferable across vehicle classes. A mix of tests were then carried out, from variable inertia dynamometer testing and repeated WLTP braking cycles to real driving emissions (RDE) style tests.
"The first solution with the lower brake disc and low emission friction material confirmed a significant emission reduction over a wide range of application and braking conditions,” Rota revealed. “The PM10 reduction is in the range of 73 to 78% at the WLTP condition, with a reduction of 50 to 77% when we apply more demanding braking conditions. Solution number two with the coated brake disc and dedicated low friction material showed excellent emissions reduction over a wide range of application and braking conditions. The PM10 reduction is in the range of 73 to 80%, but notably, the PM10 reduction is higher at around 84 to 87% when more demanding braking conditions are applied."
Looking ahead, Rota suggested that both solutions
could provide huge reductions in brake-related PM emissions for ageing fleets
around the world. She suggested that the second solution is likely to bring
greater benefits, but “the simple substitution of suitably tailored brake
components can easily lead to significant and effective brake emissions
reduction.”
