Graphite particles reinforced ZA-27 alloy composite materials for journal bearing applications

The bearing characteristics of cast ZA-27/graphite composite materials with graphite particle content varying from 1-5 wt.% in steps of 2% have been investigated under lubricated, semidry and dry conditions. The composite materials were fabricated employing the liquid metallurgy technique. Graphite particles of size 80-120 mu m were used to reinforce the ZA-27 alloy. The bearing tests were conducted using a computer interfaced bearing test rig. It was found that in the tests conducted, the bearing fabricated from the composite materials exhibited lower friction in comparison with the unreinforced ZA-27 alloy. In the oil-lubricated test, the composite bearings were able to run without seizure up to the regimes of boundary lubrication with less friction. The base alloy bearings could also operate in the boundary lubrication, but under higher friction. In the semidry and dry tests, the composite bearings exhibited lower friction which further reduced with increase in the graphite content, but increased with load. In the semidry and dry tests, the alloy bearings seized at much lower loads than the composite bearings. The composite as well as the alloy bearings tested under lubrication exhibited least coefficient of friction in comparison with those tested under semidry and dry tests. (C) 1998 Elsevier Science S.A. All rights reserved.