Ceramic hybrid bearings are ideally suited for use in refrigerant compressors. Ceramic hybrid bearings do not require any lubrication to run and can be lubricated directly by the refrigerant instead of oil. A recent study found that all-steel bearings started to show inadequate lubrication signs at levels of 20% to 30% dilution of refrigerant to oil. Tests were done with ceramic hybrid bearings in pure refrigerant and the bearings were in as new condition at the end of the test. This was the test that proved refrigerant can be used as a lubricant for hybrid bearings because the refrigerant forms an elasto-hydrodynamic lubricant film.
Typically, ceramic rolling elements are 60% less dense, have a modulus of elasticity 50% higher, expand only 30% as much as an all-steel bearing and have a coefficient of friction in the order of 20% of that of all-steel types. The low density of ceramic rolling elements significantly reduces the centrifugal force acting on the rolling elements in operation. This reduces internal bearing loads and facilitates better internal load distribution. The higher modulus of elasticity reduces friction and makes the bearing stiffness higher. Low friction and high stiffness allow for high operating speeds. The combination of ceramic rolling elements and hardened steel rings is a material combination that prevents galling.