Abstract: A spindle bearing of a numerical control machine tool appeared abnormal vibration after running for 613 h, and obvious damage marks were found on the surface of some steel balls of the failure bearing. Those damage marks were studied by means of macro and micro observation, chemical composition analysis, energy spectrum analysis. The results show that metal foreign particles enter the bearing raceway, resulting in adhesive wear occur between foreign matters and steel balls and form a “white layer” on the surface of the steel ball. Along with the adhesive wear effect aggravates, contact fatigue cracks generate inside the “white layer”, and the fatigue cracks propagation causes spalling of the steel ball surface, forms a peeling pit, causing the bearing failure. The hardness difference of each part of the failure bearing exceeds the standard, which accelerates the failure of bearing. Therefore, it is suggested that a dust cover or sealing ring should be added to the bearing, the cleanliness of lubricating grease should be improved to avoid the failure caused by metal foreign particles entered the bearing and the quality control of bearing materials should be strengthened in actual production.

Key words: rolling bearing of machine tool, adhesive wear, white layer, contact fatigue, failure analysis