Performance of a cast-iron and WC Co-free iron-based coated disc under mild and severe brake conditions

The deposition of hard coatings on the surfaces of brake discs can significantly decrease the wear and related particulate matter of brake materials. Considering that brake materials, along with low emissions, have to guarantee excellent brake performance, the present work investigates the brake performance of a Co-free WC-FeCrAlY cermet-coated disc. The coating was deposited by the High-Velocity Oxygen Fuel technology. The influence of the braking conditions was investigated with tribological tests on a sub-scale dynamometer in a wide range of contact pressure (0.7-4.8 MPa), initial sliding speed (8-21 m/s) and temperature (above 900 degrees C). Under high temperature and velocity conditions, tribo-oxidative processes were high enough to control the frictional behavior through the formation of very large glazes on the pad surfaces. However, under high temperature and low velocity, the coated disc revealed an insufficient source of iron for the formation of extended glazes, thus the interaction was highly adhesive and associated with friction instability.