6 ball bearing materials you need to know about
Ball bearing materials are are vast. It also varies depending on the ring materials. This ensures that the interplay of cage, inner ring and outer ring in the system is harmonised. But why is this important? It is essential to have the right combination of materials in the ball bearing for specific applications. Applications that involve excessive heat, applications that need to conform to specific industry standards. Ultimately, no matter what the application, the focus needs to be on ensuring that the ball bearings running properties are always cohesive.
With igus® xiros® ball bearings, we offer stainless steel and glass balls. These work in harmony with the various polymer cages and races that we manufacture, however, for other ball bearings, the options are far greater.
Below are the most common ball materials that work efficiently with various ring materials.
Balls for metal ball bearings:
Ball bearing materials – Roller bearing steel 1.3505/100Cr6
For conventional metal ball bearings, hardened steel balls are often the preferred choice. The most popular material is a chrome steel with about 1% carbon and 1.5% chrome. Martensitic chrome steel is very well-suited to ball bearing production. The properties of this material ensure stability, they are resistant and durable in continuous operation, all key elements required for these balls. This is achieved through the steel crystalline structure. Susceptibility to corrosion tends to be low and this means that cylindrical rollers and needle rollers tend to be made of this material. But lubrication is essential so there can be issues with this.
Balls for plastic ball bearings:
Stainless steel 1.4401 and 14401 (SS316L)
For ball bearings made of plastic, such as xiros® ball bearings, unhardened stainless balls are usually used. They are exceptionally corrosion-resistant and are also very resistant to saltwater and alkalis. The maximum permissible load is already restricted by the limits of the material in the plastic rings. Another reason for stainless steel balls to be used in the majority of plastic ball bearings is that they cost less than glass balls.
Glass ball bearing materials are used when a metal-free ball bearing is needed or the requirements for chemical resistance are high. Soda-lime glass is used in bottles, drinking glasses and flat glass, as well as as a ball bearing material. It has good chemical properties, therefore, making them suitable for environments that can be exposed to brief chemical stress, but not to great thermal stress.
This type of glass ball bearing materials are much more expensive than soda-lime glass. Borosilicate glass is even more chemical-resistant than soda-lime glass, which means that it is used in applications involving strong acids. This material has very good resistance to heat and to changes in temperature, mechanical stability and low coefficient of linear expansion.
Balls for ceramic ball bearings:
Aluminium oxide Al2O3
Ceramic ball bearing materials are made of aluminium oxide, also known as oxide ceramics, have a polycrystalline structure. The properties of the lightweight balls include good corrosion, abrasion and heat resistance. They are extremely resistant to corrosion, however, it is important to avoid contact with hydrofluoric acid, hydrochloric acid, warm sulphuric acid and strong alkaline solutions. They are also electrically insulating. Balls made of Al2O3 aluminium oxide are white to ivory colour and are manufactured according to ASTM F 2094 Class II/III.
Silicon nitride Si3N4
Balls made of the silicon nitride ceramic material are lightweight but durable and offer resistance to corrosion. The material has an insulating effect. The balls are also self-lubricating and have great resistance to temperature fluctuations. They are much more expensive than balls made of aluminium oxide. Balls made of Si3N4 are a black mother-of-pearl colour.
To read more about the different ball bearing and ball bearing materials visit https://blog.igus.co.uk/metal-polymer-ceramic-how-do-you-decide-which-ball-bearing-is-best-for-your-application/