The Engineering and Research Centre of the SKF Group (SKF ERC) is involved in the development and evaluation of materials for bearings.
Physical metallurgy activities include advanced electron microscopy studies, in particular, relating microstructures to bearing functional properties. The microstructure is affected to a great extent by the composition, prior processing, and applied heat treatment and some of these relationships are described in the paper.
Fatigue investigations involve the definition of the fatigue process in bearing materials. The major discoveries on fatigue processes in steels, in recent years, have been made by the use of X-ray diffraction techniques. By the application of a “pole figure” measurement program it has been quantitatively established that significant texture develops during contact fatigue, resulting in the characteristic contact fatigue spall shapes related to the application conditions.
Ceramic powder processes are of interest for bearing products and silicon nitride has the best combination of mechanical and physical properties of the current engineering ceramics. At SKF ERC the necessary specifications and quality assurance procedures have been developed in order to select and approve specific types and grades of material for ceramic bearing manufacture.
Bearings are sometimes used in situations that are incompatible with the properties of the commonly used bearing steel grades. In such cases, coating processes may be used to tailor the surface properties of bearing components to specific application conditions. The development or evaluation, or both, of such processes takes place at SKF ERC which is equipped with various surface treatment facilities and test equipment for such coatings. Examples of coated bearing products are described in the paper.