ANALYSIS OF THE POSSIBILITIES OF USING CRN+a-C:H:W COATINGS TO MITIGATE FRETTING WEAR IN PUSH FIT JOINTS OPERATING IN ROTATIONAL BENDING CONDITIONS

Abstract

In this article, the results of wear tests of a push fit joint operating in rotational bending conditions have been presented. The assumed operation conditions were similar to those for a real rail vehicle wheel set. Samples made of uncoated C45 steel and those in which shafts were covered with a CrN+a-C:H:W coating were analysed. The push fit joint was loaded with 550 N, and it completed 8x106 cycles. Following wear tests, the macroscopic and microscopic observations of the shaft top layer were conducted to determine the intensity of fretting wear development. The former demonstrated that, in the case of uncoated shafts, wear occurs on either side of the joint, in the form of a maximum 2 mm wide ring. The use of protective coatings significantly reduced damage to the shaft top layer. Traces of fretting wear occur occasionally at the shaft circumference and affect small areas. The microscopic observations and EDS analysis of the chemical composition of the areas affected by fretting demonstrated mainly wear in the form of the build-up of material originating from, first of all, the shearing of sleeve top layer micro-irregularities that underwent plastic deformation and then oxidation.