Date of Award

1-10-2024

Publication Type

Thesis

Degree Name

M.A.Sc.

Department

Mechanical, Automotive, and Materials Engineering

Keywords

brake emission, brake pad materials, coated brake rotor, Euro 7, Low-steel brake pad, PEA coating

Supervisor

Xueyuan Nie

Rights

info:eu-repo/semantics/openAccess

Creative Commons License

Creative Commons Attribution 4.0 International License
This work is licensed under a Creative Commons Attribution 4.0 International License.

Abstract

Due to new emission regulations, the automotive industry has explored various coating and surface treatment technologies like laser cladding, thermal spraying, Ferritic Nitrocarburizing (FNC), and Plasma Electrolytic Aluminating (PEA) to improve wear and corrosion resistance in brake rotors and reduce particle emissions. The PEA process, producing alumina-based ceramic coatings on cast iron brake rotors, demonstrates excellent corrosion resistance and reduced particle emissions. This study investigates the compatibility of different brake pads with alumina-coated rotors through pin-on-disc (POD) tribotests, using various brake pad formulations. The evaluation includes PEA-coated and FNC-treated brake rotors under different corrosion conditions, analyzed through wet paper towel corrosion tests, electrochemical corrosion tests, and vehicle corrosion simulation experiments. Morphological observations and chemical element distribution are examined using SEM and energy-dispersive X-ray (EDX). Results show that alumina coatings with a dimpled surface morphology facilitate the formation of transfer bedding layers (TBL), transitioning brake rotors from abrasive wear to adhesive friction. Lower surface roughness in alumina coatings improves coverage with an even transfer layer. The NAO brake pad exhibits a higher tendency to transfer friction materials, while the low-steel pad forms a thinner TBL with good coverage. Consequently, the low-steel brake pad experiences lower weight loss against alumina-coated rotor samples, regardless of coating surface roughness. In contrast, PEA-coated brake rotor samples display minimal wear or weight gains, indicating excellent wear resistance. However, the study suggests further optimization of brake pads to achieve a lower wear rate, ensuring compliance with upcoming non-exhaust emission regulations. Regarding corrosion resistance, PEA-coated brake rotors outperform FNC-treated rotors in electrochemical corrosion tests, demonstrating a protective materials transfer layer after vehicle testing. Despite a lower corrosion resistance appearance due to metallic elements from brake pads, the PEA-coated rotor proves more wear-resistant than the FNC brake rotor, presenting potential long-term usage benefits.

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