The Effect of the Brake Disc Materials on the Particulate Matter Emission
The amount of particulate matter (PM) emission from the brake friction couple was examined by using different types of brake discs. The gray iron brake discs with small, medium, and high carbon contents and oxynitrided gray iron discs were tested to compare the amount of brake emission during the WLTC test procedure using a non-steel type brake friction material. A ceramic disc based on SiC/C was also tested with the same friction material for comparison. The emission test was carried out using a 1/5 scale dynamometer designed for the brake emission study. The concentration and size distribution of the airborne particles were measured using an electrical low-pressure impactor (ELPI+) in the aerodynamic size range of 6 nm to 10 ��m. Results showed that the gray iron discs with high carbon contents produced more PM than low carbon content gray iron discs in moderate braking conditions. At the same braking condition, the oxynitride coated gray iron and SiC/C discs showed much less emission compared to the conventional gray iron discs. However, in high-temperature braking conditions, the thermal conductivity of the brake discs played a crucial role in the brake emission, showing pronounced brake emission when the ceramic disc was used due to the high temperature on the friction material surface due to its low thermal conductivity.