Characterization of ultrafine particles from hardfacing coated brake rotors

Abstract

Automotive brake rotors are commonly made from gray cast iron (GCI). During usage, brake rotors are gradually worn off and periodically replaced. Currently, replaced brake rotors are mostly remelted to produce brand-new cast iron products, resulting in a relatively high energy consumption and carbon footprint into the environment. In addition, automotive brakes emit airborne particles. Some of the emitted particles are categorized as ultrafine, which are sized below 100 nm, leading to a series of health and environmental impacts. In this study, two surface treatment techniques are applied, i.e., high-velocity oxygen fuel (HVOF) and laser cladding (LC), to overlay wear-resistant coatings on conventional GCI brake rotors in order to refurbish the replaced GCI brake rotor and to avoid the remelting procedure. The two coating materials are evaluated in terms of their coefficient of friction (CoF), wear, and ultrafine particle emissions, by comparing them with a typical GCI brake rotor. The results show that the CoF of the HVOF disc is higher than those of the GCI and LC discs. Meanwhile, HVOF disc has the lowest wear rate but results in the highest wear rate on the mating brake pad material. The LC disc yields a similar wear rate as the GCI disc. The ultrafine particles from the GCI and LC discs appeared primarily in round, chunky, and flake shapes. The HVOF disc emits unique needle-shaped particles. In the ultrafine particle range, the GCI and HVOF discs generate particles that are primarily below 100 nm in the running-in period and 200 nm in the steady state. Meanwhile, the LC disc emitted particles that are primarily ∼200 nm in the entire test run.

Comprehensive Analysis of Current Primary Measures to Mitigate Brake Wear Particle Emissions from Light-Duty Vehicles

“…The simulation of the PHEV results in a PN saving Despite its wear resistance, the weight analysis showed that the brake disc was subject to a loss of mass. Studies have shown that coating debris enters the environment as wear products [10,44]. The coating wear products may possess a number of hazards to human health [45].…”

Ultrafine particle emissions from dry clutches: number concentration, size distribution and chemical composition

“…Just like brakes, [22][23][24][25][26] the clutch in these experiments exhibits a run-in and a steady state phase. However, contrary to brakes where ultrane particles are predominately generated during the run-in phase, 27 the clutch emits ultrane particles both during run-in and in the steady state, as seen in Fig. 7.…”