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% h ave been investigated under lubricated, semidry and dry conditions. Th e composite materials were fabricated employing the liquid metallurgy technique. Graphite particles of size 80-120 mu m were used to reinfor ce 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 f riction in comparison with the unreinforced ZA-27 alloy. In the oil-lu bricated test, the composite bearings were able to run without seizure up to the regimes of boundary lubrication with less friction. The bas e alloy bearings could also operate in the boundary lubrication, but u nder higher friction. In the semidry and dry tests, the composite bear ings exhibited lower friction which further reduced with increase in t he graphite content, but increased with load. In the semidry and dry t ests, the alloy bearings seized at much lower loads than the composite bearings. The composite as well as the alloy bearings tested under lu brication exhibited least coefficient of friction in comparison with t hose tested under semidry and dry tests. (C) 1998 Elsevier Science S.A . All rights reserved.