Characteristics of Silicon Nitride Ceramic Balls

Published On: January 17, 2024Categories: knowledge
Silicon Nitride Ceramic Balls

Currently, ceramic ball bearings are gaining increasing applications in various fields and scenarios due to their excellent characteristics, especially in high-end equipment such as CNC machine tools and aerospace, where their advantages are more prominent. Ceramic materials suitable for bearing production mainly include silicon nitride (Si₃N₄), zirconia (ZrO₂), alumin (Al₂O₃), and silicon carbide (CSi). Among them, silicon nitride is characterized by low density, high hardness, corrosion resistance, high-temperature resistance, and self-lubrication. With superior comprehensive performance, it is considered the best material for manufacturing high-speed and high-precision bearing rollers. The ceramic ball (roller) is a key component in ceramic ball bearings as well as one of GELILNDE’s main products.

Silicon nitride ceramic materials have the following characteristics:

  1. Low density: The low density of ceramic rollers allows them to operate at higher speeds with less heat generation.
  2. Moderate elastic modulus: The elastic modulus of ceramic rollers is higher than that of steel rollers. Higher elastic modulus improves the dynamic stiffness of the bearing, but excessively high modulus may reduce the bearing’s load-carrying capacity due to stress concentration.
  3. Low thermal expansion coefficient:A low coefficient of thermal expansion helps reduce sensitivity to temperature changes, preventing seizing. This widens the applicable operating speed range for hybrid roller bearings.
  4. High compressive strength:High compressive strength is necessary for bearings to withstand high contact stresses. (For ceramic materials, the compressive strength is usually determined by the fracture modulus measured by three-point or four-point bending tests.)
  5. High hardness and high toughness: The combination of high hardness and high toughness results in better surface roughness and prevents damage from external hard particles and impacts.
  6. Good rolling contact fatigue resistance:This is crucial for the performance of bearing rollers.
  7. Spalling failure mode: When used as rollers, silicon nitride exhibits a fatigue spalling failure mechanism similar to bearing steel. This fatigue spalling failure mode provides warning signs of accuracy degradation and noise before seizing occurs, minimizing harm. However, the spalling failure of zirconia and alumina occurs in a catastrophic mode of sudden fragmentation, which does not meet the requirements of stable operation of ceramic bearings.
  8. High thermal stability:Silicon nitride ceramics can maintain their mechanical properties stably at an ultra-high temperature up to 800℃.
  9. Corrosion resistance: The bearing should maintain oxidation resistance and corrosion stability in the oxidation and corrosion environment, especially in the contact area where the surface oil film is squeezed off by repeated rolling.

Although silicon nitride material is not the hardest nor the most ductile in industrial ceramics, it is considered to possess the best overall mechanical and physical properties for high-performance bearing applications. In some high-demand application areas, ceramic materials also exhibit some special properties. Comprehensive rolling contact spalling tests and bearing tests have demonstrated that dense and homogeneous silicon nitride materials have excellent resistance to rolling contact fatigue. Ceramic ball bearings with silicon nitride ceramic balls as rolling elements can significantly improve the contact fatigue life of bearings, greatly expanding the application scope of rolling bearings.