Custom bearings are often made from stainless steel in applications where corrosion resistance or nonmagnetic properties are needed. Many grades of stainless steel are available and it is important to select the grade which best meets the requirements of the application.
Most traditional bearings are made from 52100 alloy bearing steel. This is a chromium steel that can be heat treated and ground to achieve high load capacity and durability in bearings. 440C stainless steel is the most suitable grade when an application must meet the full load capacity of a standard bearing. It has higher levels of carbon than other grades of stainless steel, in order to achieve the hardness and strength of 52100. The higher level of carbon also means that this steel, while corrosion resistant, can rust. Passivation can help eliminate this rusting.
300 series stainless steels cannot be heat treated but have very high corrosion resistance properties. Bearings which have lighter load requirements such as thrust retainers or window roller bearings are commonly made from this type of stainless. Typically a bearing made from 300 series stainless steel has about half the capacity of a standard bearing.
For applications that require moderate load carrying capability and high corrosion resistance, precipitation hardenable stainless steels are an option. Grades such as 17-4 or 17-7 are specialty grades that can achieve strength greater than 300 series without the carbon content of the 400 series grades.
Many more grades of stainless can be used in bearing manufacturing in order to customize a bearing to precisely meet the requirements of an application.