With the introduction of EURO 7 2025, technologies are needed to drastically reduce particulate emissions from vehicles. In contrast to earlier regulations, which limited emissions from internal combustion engines in particular, the focus will now be on emissions from brakes and tires. At the beginning of 2025, the automotive industry will deliver vehicles with coated brake discs that are both corrosion and wear resistant. By using high power lasers with more than 20 kW laser power, coatings of less than 20 seconds per layer are realized, opening the doors for automotive series production. The rotational speeds of the components used for this purpose can already reach speeds of up to 400m/min. Known, as well as new material systems, must be applied with minimum loss, while at the same time the material usage must be reduced to a minimum. Layer thicknesses of less than 100 µm can be applied with laser cladding, both densely and by metallurgy bonding. Matched to the high-performance process, nozzle technologies are used to melt the flying powder particles evenly and homogeneously without subjecting them to excessive thermal stress. In addition to powerful nozzles, the intensity profile of the laser beam is crucial for melting the base material uniformly, in addition to the powder. The existing different concepts for single- or double-sided simultaneous coating are analyzed and their advantages and disadvantages evaluated. New approaches can minimize or eliminate necessary preheating processes by means of induction. In addition to the pure melt-metallurgical bonding of the powder particles with the gray cast iron material, subsequent grinding processes depend on the coating being as even as possible and with low roughness. The desired evenness can already be achieved by small overlap. However, more intensive focus is placed on the distortion of the disc caused by the metal layer. Distortion can be minimized by selecting a suitable process sequence. The choice of strategy is component-specific and depends on the geometric factors of the disc. Whereas until about 4 years ago series production was hardly conceivable even at low laser powers below 10 kW, today we see series processes with powers above 20 kW. From a pure melt dynamic point of view, the limits have not been reached. Current technical limitations and their solutions are presented and open up the possibility for a further increase in productivity and efficiency. High power cladding of brake discs enables series production of both wear protection for vehicles with combustion engines and corrosion protection for electric vehicles. This is the first time that laser cladding has been used in automotive series production.
Dr.-Ing. Thomas Molitor, Manager of Sales General Manufacturing, Laserline GmbH; Dr. Sörn Ocylok, Technical Support Cladding & AM, Laserline GmbH; Mr. Christian Budde, Application Expert, Laserline GmbH; Mr. David Weber, Application Expert, Laserline GmbH