A Comparative Study of Different Plasma Sprayed Coatings Applied to Railway Disc Brakes

摘要

In the railway context, the increasing number of trains into service lies in the development of new equipments. This objective requires increased peak speeds at the expense of stronger motorizations. The axle loads are thus heavier, in particular for the new double-deck trains. These parameters have significant effects on the brake system in terms of size, non-suspended masses and therefore energies to be dissipated as well. The constituent materials of the friction brakes of some railway equipment (full non-ventilated steel alloy discs for the TGV for example) have thus reached their technological limits in term of energy to be dissipated for fixed masses and size. It is thus necessary to find more powerful braking devices using new materials. The LAMIH has therefore decided to focus its research towards high energy full discs. This approach consists in coating the steel discs with low thermal diffusivity friction materials that have very high and stable mechanical and tribological characteristics at a high temperature. Using blown thermal plasma, the LAMIH has already tested reduced scale C38 discs coated with NiCr-Cr_3C_2 cermet facing on an Al_2TiO_5 pad. Henceforth, studies relate to cobalt or nickel based superalloys obtained by transferred plasma process with a view to making a reliable coating / substrate bond. Performances have been evaluated in terms of friction factor, wear, contact temperature and reliability.