Silicon Nitride Rolling Bearings for Extreme Operating Conditions

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Abstract
The high hardness and excellent high-temperature performance of ceramics are attractive for critical rolling-bearing applications, such as in high-thermal-efficiency engines. In addition, the lower density of ceramics permits lower centrifugal loads, less skidding at high speeds, and, consequently, results in longer bearing component life than conventional bearing steels or alternative super-alloys or cermets. Silicon nitride has the lowest friction and elastic modulus of the available ceramics, which reduce bearing contact stresses. This paper reviews the merits and demerits of silicon nitride as a bearing material, its processing, and different mechanisms for solid-lubricant replenishment in severe environments. Test data and application design guidelines accumulated to dale are also provided.