Wear behaviour of A356/25SiCp aluminium matrix composites sliding against automobile friction material

In the present paper, the wear behaviour of aluminium metal matrix composite (Al MMC) sliding against automobile friction material has been compared with the conventional grey cast iron. The wear tests have been carried out on a pin on disc machine, using pin as brake shoe lining material and discs as A356/25SiC(p) Al MMC and grey cast iron materials. Pins of 10 mm diameter have been machined from a brake shoe lining of a commercial passenger car. The grey cast iron disc has been machined from a brake drum of a commercial passenger car. The Al MMC disc has been manufactured by stir casting technique using A356 aluminium alloy and 25% silicon carbide particles and machined to the required size. The friction and the wear behaviour of Al MMC, grey cast iron and the semi-metallic brake shoe lining have been investigated at different sliding velocities, loads and sliding distances. The worn surfaces and sub-surface regions of MMC, the cast iron and the lining have been analysed using optical micrographs. The present investigation shows that the MMCs have considerable higher wear resistance than conventional grey cast iron while sliding against automobile friction material under identical conditions. A gradual reduction of friction coefficient with increase of applied load is observed for both cast iron and Al MMC materials. However, in all the tests it is observed that the friction coefficient of Al MMC is 25% more than the cast iron while sliding under identical conditions. The wear of the lining material has been observed more when sliding against MMC disc because of the ploughing of the lining material by the silicon carbide particles. The wear grooves formed on the lining material while sliding against MMC and cast iron have been analysed using optical micrographs. (c) 2006 Elsevier B.V. All rights reserved.