Tribology and corrosion behavior of gray cast iron brake discs coated with Inconel 718 by direct energy deposition

Abstract

Gray cast iron (GCI) is a conventional material used in industrial applications and it is well known for its usage in brake disc fabrication. In the case of vehicles that serve passenger transport, one of the solutions to prolong the lifetimes of brake discs can be to laser clad their surface with harder and corrosion-resistant materials. This research aims to improve the mechanical properties of the brake discs using Inconel 718 (IN718) metallic powder to laser cladding the parts’ surfaces by a direct energy deposition (DED) method. By using the proper process parameters, the interface between the substrate and the deposited material was uniform and adherent and forming a compact bonding of the two materials, without pores or cracks. It was found that the average hardness of the IN718 deposited material was twice higher than the one of the GCI substrates. By comparing the friction coefficient (CoF) of the IN718 coatings with that of the brake discs, a difference of 0.12 in favor of IN718 was assessed. The depth of the wear track was analyzed for both materials and showed that the pin trace on the GCI (−150 µm) surface was 3 times deeper than the trace produced on the surface coated with IN718 (−50 µm). The corrosion resistance of the IN718 coating was superior by four orders of magnitude to that of GCI substrate in 3.5 wt.% NaCl aqueous solution.