Microstructures made of ceramics take use of the inherent covalent connection between non-metal components. This suggests that they share electrons. The collaboration of the atoms that make up a ceramic allows for the development of an exceptionally intense attractive force, giving ceramics a variety of benefits over metals.
Choosing the Materials
Materials with a high elastic, or Young’s modulus, and hardness are often those with very high atomic numbers (70–90 HRc). They are resistant to shape change under pressure and offer improved wear characteristics.
The ceramic bearings may be used without the need for lubrication. This is because ceramics can’t micro-weld as other materials can. The electric arc created when the rolling element and raceway touch might produce micro-welding if the surfaces aren’t perfectly smooth. When dealing with metals, this kind of welding is often used. The bearing’s surface gets damaged and its useful life is drastically shortened as a consequence. Ceramic materials are not affected by this issue, hence they may be utilised in many situations where lubricants are not present.
- Its consistent behaviour under extreme heat conditions is indicative of a low coefficient of thermal expansion. Bond length expansion in covalent bonds requires much more energy than ionic bond expansion in metallic compounds.
- Ceramics, unlike metals and ferrous materials, are non-metallic and non-ferrous. They don’t rust or corrode the same way metals do when exposed to water and other potentially damaging elements. They are resistant to corrosion, therefore they function effectively in wet and chemically reactive environments.
- The low density of several types of technical ceramics allows for higher bearing operating speeds. Low centripetal forces and less friction make these benefits achievable.
- Many ceramics are non-magnetic and excellent insulators because they do not have any free electrons.
There are several benefits to using ceramic bearings.
In addition to its excellent strength and creep resistance, Silicon Nitride also exhibits resistance to oxidation. It can sustain greater temperatures than most metals, and it is more resistant to thermal shock than most ceramics because of its low thermal expansion coefficient.
Silicon Nitride is a material that is chosen for usage in applications requiring vacuums and high speeds. The stuff is pitch-black in colour. As a consequence of being 58% lighter than regular steel, the rolling components experience less of a reduction in centripetal force. Hence, fatigue lifetime is significantly lengthened. Unlike other ceramics, Silicon Nitride can withstand loads as great as those experienced by bearing steel. Nevertheless, Silicon Nitride cannot be utilised for the race design in any application that includes shock loading due of its exceptional hardness.
On the left are zirconia bearings, while on the right are silicon nitride bearings.
Silicon carbide, unlike other ceramic materials, is very resistant to heat and corrosion, but it is also more difficult to manufacture and more expensive to produce from raw materials. As this is the case, it is one of the less common ceramic components. In low-load, high-corrosion environments, silicon carbide shines. The physical properties of these ceramic materials and 440C stainless steel have been summarised below in the tables to assist an apples-to-apples comparison.