Application of Segment-Structured CrN Film to Fretting Wear Prevention in Contact Surfaces of Inner Ring and Backing Ring of Railway Axle Journal Bearings

Abstract

Axle journal bearings composed of an inner ring, a backing ring, etc. are used in railway applications. The axle bearings often show fretting wear due to slight relative slip between the inner ring and the backing ring. In this work, the authors have investigated the effects of segment-structured chromium nitride (CrN) film coated on the backing ring on the fretting wear. A rotation test using a full-scale railway axle bearing with a backing ring of a side face which is coated with the segment-structured CrN was conducted. As a result, the segment-structured CrN film had little effect on fretting wear prevention. This is presumably because the CrN film was formed in the groove between the segments. Therefore, when the backing ring was deformed due to the rotary bending of the axle, some cracks and decohesion occurred in the CrN film because the CrN film formed in the groove between the segments was not able to follow the deformation. It is conceivable that the fretting wear of the axle journal bearing can be prevented if it is possible to establish a method in which the CrN film is not formed in the groove between the segments.