Preventive measures of fretting wear in contact surfaces of inner ring and backing ring of railway axle journal bearings (Combined effect of grooving and segment‐structured DLC coating towards backing rings)

Abstract

Fretting wear is surface damage caused by repeated slight relative slips between two contact surfaces. In railway applications, fretting wear may occur between the inner ring and the backing ring of an axle journal tapered roller bearing. The authors found that a nonuniform pressure distribution between the inner ring and the backing ring deteriorates the fretting wear; a backing ring grooved on its oil seal sliding surface has been proposed to attain a uniform distribution in the radial direction. It was also shown that the fretting wear can be suppressed by coating the backing ring side face with segment‐structured diamond‐like carbon (DLC) film, which is capable to follow the deformation of the backing ring. In this work, a rotation test of a full‐scale railway axle bearing using a backing ring combined with these two approaches has been conducted to investigate the suppression effect of the fretting wear. Results indicate that the effect of the segment‐structured DLC film decreases in comparison with the case where only the film was applied. It is conceivable that the relative sliding motion in the radial direction occurred since the segment‐structured DLC film was not indented into the inner ring large side face due to the reduction in the contact pressure by the grooved backing ring. It is concluded that the combined effect of the groove and the film is not so apparent.

Keywords

• bearing
• wear
• fretting
• grooving
• contact pressure
• pressure distribution
• coating
• diamond‐like carbon
• segment‐structure