60% lighter than steel balls
50% higher modulus of elasticity
(Resistance to denting)
Ceramic is a natural insulator, and is beneficial where electric motor design requires a high degree of electrical insulating properties between the armature and field windings. The service life of conventional steel ball bearings in electric motors is sometimes reduced, due to pitting and corrosion caused by trace discharging, between the rings and balls. Ceramic hybrids do not suffer from this, due to their natural insulating properties. Due to their inherent longer service life, it results in a more reliable, and longer lasting product.
Due to a minimum level of Adhesive Wear, bearing components and lubricants last much longer, saving you expensive service and repair time.
High Hot Strength
High compressive and flexural strength over a wide temperature range. Lends itself for use to 2200 degrees F.
Specific density of 3.2 compared to 7.8 for steel. At high bearing operating speeds, the bearing balls have a centrifugal force which may exceed the external loads on the bearing. The low density of ceramics can reduce this load considerably.
While bearing steel is in the RC 58-64 hardness range, silicon nitride has a hardness of RC 75-80 and offers excellent wear resistance.
Coefficient of Friction
Silicon nitride has a coefficient of friction which is significantly lower, especially under marginal lubrication conditions. It also exhibits better resistance to scuffing and seizing than bearing steel.
Silicon nitride is unaffected by most common corrosive agents, and is well-suited for use in hot corrosive atmospheres, or where lubricants have been known to attack conventional bearing steels.
Long Fatigue Life
Recent improvements in purity and grain structure have given silicon nitride a high stress fatigue life equal to, or better than, that of bearing steels. Some tests have shown life 3 to 5 times that of M-50 steel.
Low Coefficient of Thermal Expansion
This property has made it difficult to mount a ceramic bearing on a steel shaft (which expands 3 times faster than ceramic). The steel shaft may crack a ceramic bearing "ring", due to the thermally induced tension stresses created in the ceramic ring.
To date, the most promising use is with bearings using ceramic balls only. Mounting difficulties and manufacturing intricacies, with their associated high costs, have slowed acceptance and potential usage of the all-ceramic bearing.
Hybrid bearing applications from small high-speed turbines to larger grease lubricated machine tool spindles have achieved good results and have been very successful.
Some information courtesy of The Barden Corporation, "all rights reserved".