Rolling contact silicon nitride bearing technology: a review of recent research

Limits, Modeling and Design of High-Speed Permanent Magnet Machines

“…Particular problem with high-speed rotation is centrifugal loading which rises with square of the speed and lowers load capacity of the bearings [141]. In order to mitigate this problem, rotor balancing is often required.…”

“…Today, specially-designed ball bearings can be found for rotational speeds up to 100.000 rpm and values of the DN number as high as 1.5 million [141].…”

“…Very small wear in these bearings is result of the fact that "silicon nitride rubbing on M-50 steel offers friction and wear characteristics as good as those of silicon nitride rubbing on itself" [150], which results in a very long bearing life. Due to the comparably low density of ceramics, silicon-nitride balls reduce centrifugal loading on the outer, steel, raceway of the bearings [141]. Ceramics, in general, are also less sensitive to lubricant type and lubricant contamination [141].…”

“…Due to the comparably low density of ceramics, silicon-nitride balls reduce centrifugal loading on the outer, steel, raceway of the bearings [141]. Ceramics, in general, are also less sensitive to lubricant type and lubricant contamination [141]. Authors of [141] report hybrid silicon nitride bearings with DN values up to 4 millions.…”

“…Standard ball bearings have the DN number below 500.000 [24]. On the other hand, DN values that are currently needed in certain high-tech applications such as turbines for aircraft or high-speed spindles amount to a few millions [141]. Under such conditions mechanical bearings are subjected to great centrifugal loading and high temperatures which both reduce bearings load capacity and life-time [141].…”