Effects of rare earth addition and service mode on surface integrity evolution of high-end machine tool spindle bearings under service

Machine tool spindle bearings used as supporting rotator parts play a very important role in machining industry. Keeping a good surface integrity is crucial to the long-time and high-efficiency work of the bearings. To find out the crucial factors for bearing failure, surface integrity evolutions on machine tool spindle bearings made from a normal bearing steel and a newly developed rare-earth-addition bearing steel were compared after benchtop tests in this work. Furthermore, surface integrity evolutions on bearings were analyzed under field service with more complex service conditions. The results show that the surface integrity changes under both benchtop testing and filed service, while the surface damages and changes in surface integrity on the inner rings are more significant than those on the outer rings. Meanwhile, the surface damage modes are mainly scratches and impressions on the benchtop bearings, while surface rolling contact fatigue predominates the damages on the field bearings. Furthermore, the addition of rare earth elements in bearing steels transfers the crack initiation mode from inclusion initiated to martensite initiated under service, possibly resulting in a higher stability of accuracy and longer life for bearings.