Tribology and corrosion behavior of Gray Cast Iron brake discs coated with Inconel 718 by Direct Energy Deposition

Abstract There has been an increased concern related to environmental pollution, caused by the emission of particles released during the braking process. In the future, environmental safety laws will be increasingly restrictive and the development of new viable alternative technologies will be inherent. Because gray cast iron (GCI) has a low cost and mechanical properties compatible with this type of application, it will be difficult to identify a similar material to replace it. In the case of vehicles that serve passenger transport, the most convenient solution is to cover the brake discs made of GCI with materials that reduce wear and corrosion, but which at the same time maintain or improve their functional performance. This research aims to improve the mechanical properties of the brake discs by laser cladding using Inconel 718 (IN718) metallic powder by Direct Energy Deposition (DED) method. The interface between substrate and the deposited material was uniform, forming a compact bonding of the two materials. The average hardness of the IN718 deposited material was twice higher than the one of the GCI substrates. The friction coefficient (CoF) of the IN718 coatings was higher by 0.12 compared with the substrate material. The depth of the wear track for the layers deposited with IN718 was -50 µm, while the depth of the wear track of the exposed substrate GCI was 3 times higher (-150 µm). The corrosion resistance of the coating was superior by four orders of magnitude to that of GCI substrate in 3.5 wt.% NaCl aqueous solution.