Tribological behaviour of Al18B4O33-whisker-reinforced hypoeutectic Al-Si-Mg-matrix composites under dry sliding conditions

Steady-state friction and wear behaviour of as-cast and T6-treated hypoeutectic Al-Si-Mg-matrix composites reinforced with 19.5 vol.% of Al18B4O33 whiskers dry sliding against 5CrNiMo steel counterface have been investigated as a function of applied load and sliding speed. Owing to the severe interfacial cracking and fracture of whiskers which occurs under higher applied load conditions, the composites exhibited a transition from mild wear to severe wear over the applied load range from 45 to 230 N. By comparison with the as-cast composite, the T6-treated composite, with reduced whisker strength and weak whisker/matrix interface, had relatively low wear resistance. Under low applied loads, increasing sliding speed caused deep surface damage, thus inducing an increase in wear rate and coefficient of friction. As the sliding speed further increased, the formation of a mainly Al2O3 transfer layer on the worn surface and the strain-hardening of the subsurface layer contributed to decreases in wear rate and coefficient of friction of the composites. (C) 2000 Elsevier Science Ltd. All rights reserved.