Compared to conventional steel bearings full ceramic ball bearings have some advantages: they have, for instance, an outstanding combination of properties like low density, high stiffness, reduced friction, high hardness and strength. Because they need less lubrication than steel bearings and have high wear and corrosion resistance they are generally materials of choice for pharmaceutical and food industries.
In this work a full ceramic bearing, consisting of two ZrO2 rings and silicon nitride balls in between, that was used in a small mixer in the pharmaceutical industry is investigated. The bearing was damaged during service because of premature wear. A failure analysis is performed by fractography and Raman spectroscopy. Raman spectroscopy showed that a stress induced phase transition from the tetragonal to the monoclinic phase was the reason behind the failure of the ZrO2-rings.