The tribological behavior of Cu-based brake materials against Cr 3 C 2 -NiCr coated steel disks with varying roughness

A high coefficient of friction (COF) and low wear rate are expected in the braking system for high-speed trains. For this purpose, we prepared coated steel disks by spraying Cr3C2-NiCr powders and slid them against Cu-based powder metallurgy pins. Pin-on-disk tests showed a significant increase in the COF with the Cr3C2-NiCr coated disk (roughness of 1.0 µm) reaching 0.514, compared to 0.366 for the uncoated steel disk. Additionally, there was a notable reduction in wear loss of the brake material, with the coated disk losing only 0.0088g, while the uncoated disk lost 0.0760g.The lower adhesion between the coating and the pin material, combined with the abrasive action of the harder coating on the disk surface, helps maintain the friction surface flat and virgin, thus avoiding the formation of thick friction films and fatigue cracks. As a result, a higher and more stable COF with lower wear was achieved when the coated disk slid against the pins.