Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

New Fraunhofer coating process provides effective protection for brake discs

03.09.2019

More than many other auto parts, brake discs are subject to repeated mechanical loads. As a result of this continual abrasion, they produce fine particulate matter, which pose a substantial environmental burden. Now, however, a new coating process developed by the Fraunhofer Institute for Laser Technology ILT and RWTH Aachen University can significantly reduce this impact. By using “Extreme High-speed Laser Material Deposition”, known by its German acronym EHLA, it has proved possible to provide brake discs with an effective protection against wear and corrosion in a procedure that is both fast and economic.

Traditional brake discs are made of grey cast iron containing lamellar graphite phases. The virtue of this material lies in its good thermal conductivity and high thermal capacity, all for a relatively low price. The downside is a strong propensity to corrode coupled with high material wear during service, which generates substantial emissions of fine particulate matter.


Coating a brake disc with the EHLA process.

© Fraunhofer ILT, Aachen, Germany / Volker Lannert

To date, it has proved difficult to provide adequate protection for brake discs by means of conventional coating processes such as electroplating or thermal spraying. The problem with such processes is that they do not produce a metallurgical bond between the cast iron and the protective coating; moreover, they are expensive and use a lot of materials.

Economic and technical advantages

Now, however, a new process avoids these drawbacks. Developed by Fraunhofer ILT in Aachen, together with the Chair for Digital Additive Production DAP at RWTH Aachen University, it is known as Extreme High-speed Laser Material Deposition (EHLA).

“The EHLA process is ideal for use in the automotive industry, especially for coating brake discs,” explains Thomas Schopphoven, research fellow and team leader of Productivity and System Technology within the Laser Material Deposition group at Fraunhofer ILT.

“Conventionally, it’s very difficult to coat brake discs, because they have to withstand high loads, and there are also economic and environmental considerations. But with EHLA, it’s now possible to apply coatings that from a metallurgical bond with the base material of the disc and therefore adhere very strongly. Unlike conventional coatings, these do not flake and chip.”

Advance on conventional processes

Coatings produced with conventional processes have pores and cracks. With the EHLA process, the coating remains intact and therefore provides longer and more effective protection for the component. This increases service life and prevents early failure as a result of damage to the surface of the brake disc. Moreover, the process is suitable for a wide range of materials. Therefore, it is possible to select an environmentally friendly coating for each specific application.

The EHLA process is a new process variant on the well-known laser material deposition, which has proved highly successful in areas such as the repair of turbine blades. EHLA does, however, have a number of decisive advantages.

High process speed reduces heat input

With the EHLA process, the powder particles of the coating material are melted directly in the laser beam, rather than in a melt pool on the surface of the component. Since the melt pool now is fed by liquid drops of material rather than solid particles of powder, the coating process is much faster, rising from the 0.5–2 meters per minute with conventional laser material deposition to as much as 500 meters per minute.

This also substantially reduces the exposure to heat of the material being coated. Unlike conventional laser material deposition, where the heat affected zone can have a depth of one or more millimeters, thermal exposure with the EHLA process remains in the micrometer range. This enables the use of entirely new material combinations such as coatings for aluminum or – as with the brake discs – cast-iron alloys.

The low heat input prevents the carbon to dissolve from the brake disc into the melt, otherwise resulting in brittle phases, pores, joining defects and cracks in the coating and bonding zone. In other words, it is now possible for the first time ever to provide brake discs made of gray cast iron with an effective coating that is firmly bonded with the base material.

Reliable and resource-efficient process delivering high quality

With laser material deposition, the coating produced is usually at least half a millimeter in thickness. This consumes a lot of material and also makes finishing substantially more complicated. By contrast, the EHLA process produces very thin layers of between 25 and 250 micrometers. As a result, the coating is both purer and smoother, with roughness reduced to around one-tenth of its previous value.

Moreover, the EHLA process uses as much as 90 percent of the fed powder material. It is therefore extremely resource-efficient and more economic. The basic requirements for the use in an industrial, mass-production setting are at reach.

Indeed, industrial application could soon be a reality. Initial investigations have demonstrated that the EHLA process is capable of reliably producing coatings – with different material combinations – for conventional brake discs made of gray cast iron. A system that is ready for use in mass production, including a modified grinding process for finishing the components, is currently under construction at the Aachen-based company HPL Technologies.

Multiple awards for EHLA

Meanwhile, the virtues of this new process have persuaded the juries from a total of three different prizes for innovation: the Joseph von Fraunhofer Prize in 2017; the Berthold Leibinger Innovationspreis in 2018; and, in the same year, second place in the Stahl-Innovationspreis, in the category “Steel in Research and Development”, as an environmentally friendly laser-based alternative to chrome (VI) coatings.

Fraunhofer at the IAA 2019

Details on the EHLA process and other current trends from research and development will be presented, from September 10–13, at the joint Fraunhofer booth (C12, in Hall 4.1) at this year’s IAA international motor show in Frankfurt.

Wissenschaftliche Ansprechpartner:

Dipl.-Ing. Thomas Schopphoven
Group Laser Material Deposition
Telephone +49 241 8906-8107
thomas.schopphoven@ilt.fraunhofer.de

Dr.-Ing. Andres Gasser
Group Manager Laser Material Deposition
Telephone +49 241 8906-209
andres.gasser@ilt.fraunhofer.de

Weitere Informationen:

https://www.ilt.fraunhofer.de/en.html

Petra Nolis M.A. | Fraunhofer-Institut für Lasertechnik ILT

Further reports about: IAA ILT Laser Lasertechnik coating conventional processes cracks discs environmentally friendly

More articles from Trade Fair News:

nachricht Modular OLED light strips
17.09.2019 | Fraunhofer-Institut für Organische Elektronik, Elektronenstrahl- und Plasmatechnik FEP

nachricht Deburring EXPO: Finishing sheet edges and functional surfaces with the laser
12.09.2019 | Fraunhofer-Institut für Lasertechnik ILT

All articles from Trade Fair News >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Stevens team closes in on 'holy grail' of room temperature quantum computing chips

Photons interact on chip-based system with unprecedented efficiency

To process information, photons must interact. However, these tiny packets of light want nothing to do with each other, each passing by without altering the...

Im Focus: Happy hour for time-resolved crystallography

Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Hamburg and the European Molecular Biology Laboratory (EMBL) outstation in the city have developed a new method to watch biomolecules at work. This method dramatically simplifies starting enzymatic reactions by mixing a cocktail of small amounts of liquids with protein crystals. Determination of the protein structures at different times after mixing can be assembled into a time-lapse sequence that shows the molecular foundations of biology.

The functions of biomolecules are determined by their motions and structural changes. Yet it is a formidable challenge to understand these dynamic motions.

Im Focus: Modular OLED light strips

At the International Symposium on Automotive Lighting 2019 (ISAL) in Darmstadt from September 23 to 25, 2019, the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, a provider of research and development services in the field of organic electronics, will present OLED light strips of any length with additional functionalities for the first time at booth no. 37.

Almost everyone is familiar with light strips for interior design. LED strips are available by the metre in DIY stores around the corner and are just as often...

Im Focus: Tomorrow´s coolants of choice

Scientists assess the potential of magnetic-cooling materials

Later during this century, around 2060, a paradigm shift in global energy consumption is expected: we will spend more energy for cooling than for heating....

Im Focus: The working of a molecular string phone

Researchers from the Department of Atomically Resolved Dynamics of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg, the University of Potsdam (both in Germany) and the University of Toronto (Canada) have pieced together a detailed time-lapse movie revealing all the major steps during the catalytic cycle of an enzyme. Surprisingly, the communication between the protein units is accomplished via a water-network akin to a string telephone. This communication is aligned with a ‘breathing’ motion, that is the expansion and contraction of the protein.

This time-lapse sequence of structures reveals dynamic motions as a fundamental element in the molecular foundations of biology.

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Society 5.0: putting humans at the heart of digitalisation

10.09.2019 | Event News

Interspeech 2019 conference: Alexa and Siri in Graz

04.09.2019 | Event News

AI for Laser Technology Conference: optimizing the use of lasers with artificial intelligence

29.08.2019 | Event News

 
Latest News

UMD-led study captures six galaxies undergoing sudden, dramatic transitions

19.09.2019 | Physics and Astronomy

Study points to new drug target in fight against cancer

19.09.2019 | Health and Medicine

New tool improves beekeepers' overwintering odds and bottom line

19.09.2019 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>