Ceramic Bearing Development. Silicon Nitride Bearing Balls of ImprovedReliability: Thermal Oxidation

摘要

The major objective of this work was to improve the reliability of siliconnitride bearing balls by means of an optimized thermal oxidation treatment. Previous work had shown that the thermal fracture resistance of silicon nitride bearing balls increased when the balls were heated and oxidized in air. An optimized oxidation treatment for NBD-200 silicon nitride balls was developed, using a thermal proof test matrix. This oxidation treatment increased the thermal fracture resistance of the balls. Ball-on-rod RCF testing of oxidized and non-oxidized balls was performed at 786 KSI contact stress, with nitrided M50-NIL rods. RCF testing did not produce a significant percentage of ball failures for either the oxidized or non-oxidized condition. Alternative methods, such as four ball fatigue testing, should be considered for future work. The oxidation treatment degraded ball surface and geometry, and is suspected as a contributing factor to short rod life. Oxidation treatment does not appear to be a useful technique for improving the reliability of NBD-200 bearing balls.