DEVELOPMENT OF LOW FRICTION SURFACES ON SILICON NITRIDE BEARING ELEMENTS

THE BENEFITS OF USING HIGH PERFORMANCE CERAMICS FOR ROLLER BEARING ELEMENTS HAVE BEEN RECOGNIZED AND SOUGHT AFTER FOR SOME TIME. CERAMIC ROLLING ELEMENTS WOULD MAKE POSSIBLE HIGHER TEMPERATURE, LIGHTER AND MORE WEAR-RESISTANT BEARINGS, ESPECIALLY IN A GAS TURBINE APPLICATION. PREVIOUS TESTS HAVE SHOWN THAT THE SURFACE FINISH AND SUBSURFACE DAMAGE IN SI(3)N(4) ROLLERS AND BALLS ARE CRITICAL AND MAKE THE DIFFERENCE BETWEEN SUCCESS OR FAILURE OF THE BEARING IN FULL SCALE TESTS. ION IMPLANTATION WITH CERTAIN ELEMENTS SHOULD LOWER THE SURFACE FRICTION BY FORMING A NEAR-SURFACE SOLID LUBRICANT LAYER IN ADDITION TO MAKING THE SURFACE LESS SENSITIVE TO SURFACE FLAWS. WE PROPOSE TO EXAMINE THE EFFECT OF VARIOUS TYPES OF IMPLANTED IONS ON THE MICROHARDNESS, WEAR, AND COEFFICIENT OF FRICTION OF SI(3)N(4) BEARING MATERIAL. SIMILAR STUDIES ON OTHER CERAMICS, SUCH AS AL(2)O(3), ALTHOUGH NOT SUITED FOR BEARING APPLICATIONS, HAVE SHOWN AN AMORPHOUS TRANSITION AND INCREASE IN FRACTURE TOUGHNESS AFTER ION IMPLANTATION OF CHROMIUM. DURING PHASE I, SCIENTIFIC FEASIBILITY WILL BE SHOWN THROUGH MICROSTRUCTURAL ANALYSIS AND MACROSCOPIC FRICTION AND WEAR TESTS ON SI(3)N(4) MATERIAL.