Improving the Damage‐Resistance of Si3N4‐Based Ball and Roller Bearing Components and Their Non‐Destructive Evaluation

Silicon nitride (Si 3 N 4 ) is the material of choice to combine mechanical and physical properties for use in high performance bearing devices. A critical drawback, however, is its limited impact strength. During manufacturing and precision hard machining impact forces may result in damage in the form of so-called C-cracks. To reduce this effect, an improved new silicon nitride material was developed with increased impact strength. In order to test this property, special equipment was constructed based on a pendulum test It reveals significant differences between various silicon nitride grades as well as other ceramics. Based on these results, the material was also adapted to produce roller bearing components. In order to use silicon nitride balls or rollers in safety-relevant applications like aircraft engines a non-destructive evaluation is necessary to assure there are no critical defects. The appropriately required equipment was developed and improved over several years. By now, automatic apparatuses for ultrasonic testing of bearing balls and rollers are available and will be introduced, In particular a new prototype for rapid evaluation of up to 2000 balls per day allows for cost-effective large scale testing.