Hybrid bearings are suitable for harsh operating conditions such as poor lubrication and high levels of contamination. The ring material is bearing steel, and the rolling elements are silicon nitride ceramic. Silicon nitride has the characteristics of high hardness, high elastic modulus, high temperature resistance and chemical corrosion resistance. Hybrid bearings form effective insulation in AC/DC motors and generators. Compared to all-steel bearings, hybrid bearings perform better in harsh conditions, but with higher contact stresses. 
However, the life of hybrid bearings is in many cases longer than that of ordinary bearings. It has excellent high-speed performance and performs well in high-speed applications such as machine tool spindles and turbochargers. The quality and reliability of ceramic rolling elements have improved dramatically over the past few decades, largely due to the introduction of non-destructive testing methods and advances in silicon nitride material purification and sintering technologies.
Fatigue life tests of hybrid bearings have shown that their rolling contact fatigue resistance is comparable to that of all-steel bearings, despite the increased contact stress. This is due to the improved quality of the ceramic balls and the improvement of the hot-press sintering process in the manufacturing process. As a result, the use of hybrid bearings in modern industrial applications is increasing.
By reviewing the development history of hybrid ceramic bearings, it can be seen that the fatigue strength of bearing-grade silicon nitride materials has made great progress in the past 20 years. The improvement of rolling contact fatigue resistance, as well as the improvement of the hot-press sintering process and the continuous reduction of porosity and surface defects in the manufacturing process, have all led to the extension of the fatigue life of hybrid bearings. 
The test results show that subsurface fatigue is the main factor determining the fatigue performance of bearings under heavy load and good lubrication conditions. Hybrid bearings, although subjected to higher contact stresses, do not have a significant increase in the probability of failure over known operating hours. As a result, hybrid bearings have a longer service life.
In general, the reason why hybrid ceramic bearings can maintain a long life in the case of large contact stress is mainly due to the excellent performance of silicon nitride ceramic materials and the continuous progress of manufacturing technology. This makes hybrid bearings very promising in modern industrial applications.