Material Combinations for Hydrodynamic Inert Gas-Lubricated Bearings

Abstract

Four promising material combinations were evaluated for use in hydrodynamic, gas-lubricated bearing applications. Three of these combinations were hard, wear-resistant materials; the fourth was a solid lubricant film mated against hardened steel. The test configuration was a single, tilting-pad, hydrodynamic test bearing which was deadweight loaded against a test shaft. Performance was evaluated by determining changes in the hydrodynamic behavior of the bearing during the test. All of the evaluations were made in an argon environment at temperatures of 350 F and 500 F. Each combination was subjected to one thousand starts and stops, at a stress of 4 psi, to evaluate low-speed sliding behavior. High-speed rub tests were then made by shock loading the pad against the shaft at 60,000 rpm. Two combinations were particularly effective in the start-stop tests. These were: A tungsten carbide coated pad running against an Al2 O3 coated shaft, and a chrome oxide coated pad mated against a chrome oxide coated shaft. At high speed, the best combination was the self-mated chrome oxide coating. Some possible reasons for the effective performance of chrome oxide are advanced.