Increase in Braking Efficiency of Electric Vehicles Using Atomic Forged Coating Technology

Abstract

The recent paradigm shift from conventional vehicles to hybrid and electric vehicles, led to the increase in regenerative braking and decline in usage of friction brake interactions to only approximately 5-20 % braking events, when compared to the vehicles with internal combustion engine propulsion systems [1]. Formation of rust on the rotor surface and lack of its removal due to less frequent engagements of the friction brake influences the braking performance. Previously adopted coating processes based on deposition of metal-based coats have not shown significant improvements, as these coats are typically removed in a very short initial phase of operation. This paper focuses on the impact of a newly developed patented ceramic coating [2], which leads to a considerable improvement of friction performance, including the combined effects of corrosion and wear resistance. Coated rotors by applying i) the PureForge patented technology [2] and ii) the currently frequently used Geomet compound were tested against a series of laboratory prepared non-asbestos organic (NAO) brake pads. The most severe sections of the Federal Motor Vehicle Safety Standard 135 (FMVSS 135) were adopted for the bench-top testing and the scaling philosophy based on the laws of physics was used for the design of these tests. This approach was selected after a very positive response with comparative studies including data generated in the brake dynamometers and small-scale tests with the universal mechanical tester (Bruker Tribolab) [3, 4]. The surface chemistry, topography, and morphology of the tested rotors and pads were analyzed using scanning electron microscopy (FEI Quanta FEG 450), equipped with energy dispersive x-ray microanalysis (Oxford detector, Inca Systems). Results from friction tests demonstrated that the brake systems with the Pure Forge coated rotor exhibited much more stable (during individual engagements and when testing conditions changed) and comparatively higher coefficient of friction when compared to systems with Geomet coating. The friction layer developed on the rotor surfaces of two respective coatings contained the materials originally present in the coatings mixed with the products of pad wear. Interestingly, the comparative study showed that wear of both pads and rotors are significantly lower (by approximately 30%) in brake simulations with PureForge coating than in small-scale simulations using the Geomet coatings. This is particularly encouraging when the environmental aspects are considered. Observed findings are related to the specific properties of the respectively different friction layers. Surface of rotors and pads exhibited different morphology, topography, and different chemistry of the developed friction layer, when the ?PureForge? and the ?Geomet? coated rotors, respectively, are compared. Although very promising, this is considered an initial proof of concept and further studies, including the brake dynamometer and field testing are recommended.