Dry sliding wear of garnet reinforced zinc/aluminium metal matrix composites

The unlubricated sliding wear behavior of ZA-27 alloy composites reinforced with garnet particles of size 30-50 mum was evaluated. The content of garnet in the alloy was varied from 2 to 6% in steps of 2 wt.%. Liquid metallurgy technique was used to fabricate the composites. A pin-on-disc wear-testing machine was used to evaluate the wear rate, in which an EN24 steel disc was used as the counterface. Results indicated that the wear rates of the composites were lower than that of the matrix alloy and further decreased with the increase in garnet content. However, in both unreinforced alloy and reinforced composites, the wear rates increased with the increase in load and the sliding speed. Increase in the applied load increased the wear severity by changing the wear mechanism from abrasion to particle cracking induced delamination wear. It was found that with the increase in garnet content, the wear resistance increased monotonically. The observations have been explained using scanning electron microscopy (SEM) analysis of the worn surfaces and the subsurface of the composites. The debris size is of the order of millimeters at higher load while at the lower load, it is of the order of a few hundred micrometers. On the basis of the above experimental observation, the sequence of micromechnical events, which lead to the generation of wear debris, has been surmized. (C) 2001 Elsevier Science B.V. All rights reserved.