Introduction

Hybrid bearings have rings made of bearing steel and rolling elements made of bearing grade silicon nitride (Si3N4), which make the bearings electrically insulating.

Silicon nitride rolling elements can extend bearing service life by offering enhanced bearing performance, even under difficult operating conditions.

The most direct application of silicon nitride in bearings is to make hybrid bearings. The ball or roller is silicon nitride material, and the bearing with inner and outer ring made of metal is called hybrid bearing. As the ball or other roller of hybrid bearing, the application market of silicon nitride is growing. The following table lists the advantages and specific applications of silicon nitride ceramic as bearing material. When silicon nitride is worn, it shows similar characteristics to bearing steel, that is, it spalling to form pitting points, rather than being completely broken, and the friction resistance increases and the noise increases, but the bearing can still run.In poor lubrication or even dry operation, in case of sudden damage to the material, it can also operate and perform well in an emergency state.

Advantage

● Protection from electric current damage

Hybrid bearings are non-conductive and therefore suitable for applications such as AC and DC motors and generators, where electric currents are present.

● Higher speed capability

The density of a silicon nitride rolling element is 60% lower than a same-sized rolling element made of bearing steel. Lower weight and inertia translates into higher speed capability and superior behaviour during rapid starts and stops.

● Long service life

The lower frictional heat generated in hybrid bearings, especially at high speeds, contributes to extended bearing service life and extended relubrication intervals.

● High wear-resistance

Silicon nitride rolling elements have a higher degree of hardness making hybrid bearings suitable under difficult conditions and contaminated environments.

● High bearing stiffness

With a high modulus of elasticity, hybrid bearings offer increased bearing stiffness.

● Reduced risk of smearing

Even under inadequate lubrication conditions, such as high speeds and rapid accelerations, or where there is an insufficient hydrodynamic film, the risk of smearing is reduced between silicon nitride and steel surfaces.

● Reduced risk of false brinelling

When subjected to vibration, hybrid bearings are significantly less susceptible to false brinelling (formation of shallow depressions in the raceways) between the silicon nitride and steel surfaces.

● Less sensitivity to temperature gradients

Silicon nitride rolling elements have a lower coefficient of thermal expansion, which means they are more stable over temperature gradients within the bearing and provide more accurate preload/clearance control.

Application

In the mechanical industry, silicon nitride ceramics can be used as turbine blades, mechanical seal rings, high temperature bearings, high speed cutting tools, permanent molds, etc. The reliability and service life of these devices are greatly affected due to the corrosion of metals. However, silicon nitride ceramic materials have excellent wear resistance, corrosion resistance and high temperature thermal shock resistance, which can be used in the field of machinery industry instead of metal materials

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