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Nitriding technology was determined to significantly enhance the performance of steel bearing rings coupled with silicon nitride balls. NBD-200 silicon nitride was tested in two different sized full scale bearing tests with two nitrided steel ring materials, M50 and M50 NiL. Test bearing sizes were 35mm bore radial bearings and 40mm bore thrust bearings. Results showed truly superior rolling contact fatigue life under conditions of thin film and contaminated lubricant. Satisfactory results were obtained under full film lubrication conditions. Several silicon nitride ball failures were experienced during the high stress, full film lubrication test which prevented demonstrating truly superior fatigue life over all steel bearings under full film lubrication conditions. Three-ball-on-rod rolling contact fatigue tests were used to screen nitriding cycles before bearing raceways were nitrided.