Session: 13-11-03: Friction, Fracture, and Damage III

Paper Number: 165370

Impact of Ferritic Nitrocarburizing Treatment on GCI Rotors: Brake Wear Particle Emissions Compliance for Euro 7 Hybrid Vehicles 

The upcoming Euro 7 standards represent a major step forward in addressing the environmental impact of vehicle emissions by extending regulation beyond traditional exhaust gases. These standards will impose stringent limits on particulate emissions from brakes and tires, recognizing their significant contribution to airborne pollution. This regulation introduces stricter limits for particle emissions produced by electric vehicles during the process of braking within specific parameters.

Grey cast iron (GCI) employed in friction disc brakes is the most widely used material for brake rotors due to its mechanical and thermal properties. However, its susceptibility to corrosion and wear can impact the performance of brake systems; this kind of material also faces major challenges when trying to comply with the requirement of low emissions. Since GCI friction brakes are used intermittently in EVs, they experience performance problems and are also prone to deterioration caused by high corrosion and wear. Additionally, the emission of particulates tends to increase in these devices.  This subject becomes more severe when the brakes are left stationary for long periods of time or used extensively in humid conditions. Brake corrosion increases the quantity and mass of non-exhaust particles emission and decreases effectiveness.

Today, hybrid vehicles and electric vehicles incorporate advanced design features and technologies focused on energy efficiency, reduction of emissions, regenerative braking and much quieter operation than vehicles powered with internal combustion engines. One example of these technologies is the Ferritic Nitrocarburizing (FNC) treatment on GCI brake discs to meet Euro 7 particulate emission standards. Controlled wear-resistant nitrocarburized layers on cast iron surfaces are formed through an in-situ post-oxidation process by incorporating additional metals into the oxide layer to enhance corrosion resistance and fortify the surface against damage and potential failures. Despite the increased cost, compared to conventional coating, the benefits of FNC treatment justify the investment.

An adequate FNC treatment process will enhance wear resistance of GCI brake discs, resulting in less material loss and a slower rate of thickness variation over time. Corrosion resistance and brake wear emissions of FNC disc brakes are better when compared to grey cast iron disc that are tested according to the research presented by authors.

The present article review examines the effectiveness of FNC treatment on brake discs in comparison to the untreated gray cast iron discs. The authors focus on assessing brake wear emissions, disc thickness variation and corrosion resistance. It is estimated that this evaluation can facilitate a deeper understanding of brake performance in electric vehicles and could considerably help to comply with Euro 7 Brake emissions.

Presenting Author: Axel Reyes Rojas Facultad de Ingeniería, UNAM

Presenting Author Biography: Axel Reyes Rojas is a Master's student in Mechanical Engineering at the Faculty of Engineering, Autonomous University of Mexico. She currently works as a Chassis Brakes Design & Release Engineer at Ford Motor Company. She holds a degree in Metallurgy and Materials Engineering and has four years of experience in the automotive industry. Her research interests include brake system design, electric vehicles, vehicle dynamics, and NVH (Noise, Vibration, and Harshness) optimization.

Authors:

Axel Reyes Rojas Facultad de Ingeniería, UNAM
Marcelo López Parra Facultad de Ingeniería, UNAM