Effects of segment-structured DLC film on the fretting wear of railway axle journal bearings

Abstract

Fretting wear is surface damage caused by repeated slight relative slips between two contact surfaces. In railway applications, fretting wear can occur between the inner ring and the backing ring of an axle journal tapered roller bearing. The authors supposed that the fretting wear of the backing ring can be prevented by means of hard-film coatings if hard films can follow the deformation of the backing ring. A segment-structured diamond-like carbon (S-DLC) film has been proposed to solve this problem. In this work, the authors investigated the effect of S-DLC film on the fretting wear through rotation tests of full-scale railway axle bearings with the backing ring side face coated with S-DLC film or conventional continuous diamond-like carbon (C-DLC) film. As the result, the S-DLC film coated backing ring demonstrated less wear compared to the C-DLC film coated backing ring. In addition, the iron content of the grease in the bearing with the S-DLC film coated backing ring was lower than that of the grease in the bearing with the C-DLC film coated backing ring. It is conceivable that the relative sliding motion in the radial direction between them may be restrained by the latticed pattern of the S-DLC film being pressed into the inner ring large side face. It is concluded that the S-DLC film is effective in suppressing the fretting wear generated on the contact surfaces between them of the axle bearings.

Keywords

• bearing
• fretting
• wear
• diamond-like carbon
• segment-structure