In this study, grey cast iron disc brake rotors are refurbished by adding a surface layer through laser cladding. Current methods to deal with replaced rotors mainly include remelting, with a minority fraction disposed in landfill. Both approaches result in a huge waste of resources and an increase in CO₂ footprint. From a sustainable point of view, this study aims to evaluate the feasibility of refurbishing brake rotors by a combined environmental and tribological performance approach. A streamlined life cycle assessment is conducted to compare the environmental impacts between producing virgin grey cast iron brake rotors and refurbishing replaced brake rotors by laser cladding. It turns out that the energy consumption and CO₂ footprint of the laser cladding refurbished brake rotors are 80% and 90% less than the virgin brake rotors. The results show that the refurbished brake rotor yields higher friction compared to the original cast iron utilizing the same pad material. The wear and particle emissions of the disc brake contact are in this study higher for the laser-cladded one compared to the original cast iron one.

The tribological behavior and the related airborne particles emission of three copper-free automotive friction materials are investigated. The tests were conducted using a pin-on-disc tribometer equipped with a specifically designed clean-enclosure chamber for the emission measurement. Particle number concentration from particle size 0.3 µm up to 10 µm and the mass of emitted particles between 1 µm to 10 µm were measured. Particular emphasis was given to the chemical composition of the bulk materials, the friction layers and the emissions, in order to explain the acting wear mechanisms, and the recorded emission of airborne particles. The results indicate that the recorded emissions do not correlate with the friction coefficient and the wear rates, since the wear mechanisms exert a different influence on the tribological and emission behavior of the materials under study.

The present work aims at investigating the sliding friction and wear behavior, and the related emission of airborne particulate matter, of Cu-free barite containing friction materials for vehicular brake pads. In particular, the effect of different concentrations of phenolic resin, used as binder, has been considered. The tribological tests were conducted using a pin-on-disc laboratory equipment. During running-in, the friction coefficient and the emission rate of airborne particles follow the same trend and both of them are influenced by the content in the phenolic resin. The friction material with an intermediate content of phenolic resin, summing up to 6.5 wt.%, showed the best behavior. This was explained considering that the phenolic resin increases the mechanical integrity of the composite friction materials, but it also increases its compliance, thus increasing the area of contact during sliding and the extension of the relevant secondary plateaus.