A few notes on why hybrid ceramic bearings are used for model turbines :
These are angular contact ball bearings that have precision ceramic balls fitted into a precision steel race. This arrangement offers several distinct advantages over bearing-steel balls. Ceramic balls have 60% less mass than steel balls. This is significant because as a ball bearing is operating, particularly at high rotational speeds, centrifugal forces push the balls to the outer race, and even begin to deform the shape of the ball. The deformation leads to rapid wear and bearing deterioration. A ceramic ball, with less mass, will not be affected as much at the same speed. The result is that much higher rotational speeds are possible. Acceleration and deceleration times are reduced as well. Ceramic balls do not react with the steel raceways. One of the modes of bearing failures is surface wear created by microscopic cold welding of ball material to the raceway. The cold welds actually break as the bearing rotated, creating surface roughness the leads to heat generation and bearing failure. Ceramic balls drastically reduces this mechanism, resulting in longer bearing life. Due to the nearly perfect roundness of the ceramic balls they generate much less heat as they rotate, which results in longer bearing life. Also, vibration levels are lower when compared to steels balls. Less lubrication is required. Hybrid ceramic bearings are more tolerant to lack of lubrication.