Effects of test conditions on the tribological behaviour of a journal bearing in molten zinc

Wear of journal bearings, consisting of cobalt-based Tribaloy T-800 bushings and carbide-coated 316L stainless steel (316L SS) sleeves, was evaluated in a molten zinc-aluminum alloy at different speeds and loads. It was found that these bearings experienced much less wear in comparison with the commonly used Stellite 6 bearings under similar conditions. There appeared to be a threshold load level of about 6.7 kN, below which both the friction and wear of the bearings were low. With the load maintained at a constant level, an increase in the test speed resulted in lower friction and lesser wear. The worn surfaces of both bushings and sleeves were relatively smooth without the appearance of wear grooves. Thorough analyses of the tested samples revealed that both materials have a lesser tendency to react with molten zinc. The binder phases of the carbide coating, however, did react with the test bath. Cracking of the test materials near the contact surfaces indicated that surface fatigue wear was the major wear mechanism affecting the journal bearing sliding in molten zinc.