Characterization of airborne wear debris produced by brake pads pressed against HVOF-coated discs
A significant fraction of the non-exhaust particulate matter emissions from vehicular traffic comprises fine particles from the wear debris of brake pads and discs. Recent studies have shown that these emissions can be consistently reduced by using wear resistant disc coatings. This study thoroughly analyses the debris produced by a low-met brake pad, which is dyno-bench tested against both cast iron and WC-CoCr-coated brake discs. To achieve this, particles in the size range of 2.5 µm to 30 nm were collected and characterized. The results showed a consistent reduction in the particle emission as well as in the concentration of iron oxides, which are mainly released from the disc tribo-oxidation in the coated disc. Furthermore, a few tungsten carbides, released from the coating, were also observed in the wear fragments. The results of this study can be useful for improving the protective coating and consequently help in reducing particulate matter emission further.
Keywordswear debris characterization wear disc WC-Co coating High velocity oxygen fuel (HVOF)
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The authors would like to thank their colleague Gloria Ischia, Ph.D, for her valuable technical assistance for the TEM sample preparation and observations. Our colleague, friend, and project leader, Guido Perricone (Brembo S.p.A.) is also acknowledged for his continuous encouragement in pursuing our goals while working together within the H2020 EU Project: LOWBRASYS — a LOW environmental impact BRAke SYStem-GA: 636592. The EU Commission is acknowledged for its financial support.
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