DEVELOPMENT OF FRACTURE TOUGHENED CERAMICS FOR ROLLING ELEMENT BEARINGS

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 SI3N4 ROLLERS AND BALLS IS CRITICAL AND MAKES THE DIFFERENCE BETWEEN SUCCESS OR FAILUREOF THE BEARING IN FULL SCALE TESTS. ION IMPLANTATION OF THESURFACE OF SI3N4 BALLS AND ROLLERS SHOULD INCREASE THE FACTURE TOUGHNESS AND ELIMINATE MUCH OF THE HIGH COST OF EXTREMELY FINE SURFACE POLISHING. WE PROPOSE TO EXAMINE THE EFFECT OF VARIOUS TYPES OF IMPLANTED IONS ON THE MICROHARDNESS, FRACTURE TOUGHNESS AND FRICTION COEFFICIENT OF SI3N4 BEARING MATERIAL. SIMILAR STUDIES ON OTHER CERAMICS, SUCH AS AL2O3, ALTHOUGH NOT SUITED FOR BEARING APPLICATIONS, HAVE SHOWN AN AMORPHOUS TRANSITION AND INCREASES IN FRACTURE TOUGHNESS AFTER ION IMPLANTATION OF CHROMIUM. DURING PHASE I, SCIENTIFIC FEASIBILITY WILL BE SHOWN THROUGH MICROSTRUCTURAL ANALYSIS AND MACROSCOPIC FRICTION AND ROLLING CONTACT FATIGUE TESTS ON SI3N4 BEARING MATERIAL.