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 hypoeute ctic Al-Si-Mg-matrix composites reinforced with 19.5 vol.% of Al18B4O33 whi skers dry sliding against 5CrNiMo steel counterface have been investigated as a function of applied load and sliding speed. Owing to the severe interf acial cracking and fracture of whiskers which occurs under higher applied l oad conditions, the composites exhibited a transition from mild wear to sev ere wear over the applied load range from 45 to 230 N. By comparison with t he as-cast composite, the T6-treated composite, with reduced whisker streng th and weak whisker/matrix interface, had relatively low wear resistance. U nder low applied loads, increasing sliding speed caused deep surface damage , thus inducing an increase in wear rate and coefficient of friction. As th e 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 c omposites. (C) 2000 Elsevier Science Ltd. All rights reserved.