The effect of laser-cladding on the wear behavior of gray cast iron brake disc

Lamellar grey cast iron (type A) with a pearlitic matrix has excellent vibration damping properties, good thermal capacity and conductivity, good castability and machinability. Such properties, together with the low cost, make this material the most used in the European market for the production of cars discs brake. Recent studies have demonstrated that a part of the total non-exhaust emission produced by a car derives directly from braking systems. During their use, wear debris in the form of solid airborne particles are created from both disc and friction pads wear. Reducing these emissions by increasing the wear resistance of braking systems would therefore contribute to both decreasing pollution and increasing brake disks life. In this research, two laser-cladding coatings were proposed to increase the wear performances of cast iron discs brake. The wear resistance was evaluated through pin-on-disc and block-on-ring laboratory tests. Commercial pads material was used as counterpart in the tribological system. Conventional grey cast iron samples were used as reference material. During the tests, the coefficient of friction with the sliding distance was continuously recorded and the wear rate for both disc and pad materials was calculated at the end of each tests. The wear mechanism of the different tested conditions was investigated by means of Scanning Electron Microscope analyses on the sample worn surfaces, and the results were related to the friction coefficient and to the wear rate. The ability of laser-cladding to reduce the consumption of disk brake materials was stated.