The influence of selected PVD coatings on fretting wear in a clamped joint based on the example of a rail vehicle wheel set

Abstract

In this article, laboratory test results concerning the influence of selected PVD coatings on the initiation and development of fretting wear in clamped joints are presented. TiN and CrN+a-C:H:W coatings were applied to shafts, and the results of wear tests compared with those for uncoated shafts. Wear tests were conducted at a test bed which simulated the operation conditions of the wheel sets of rail vehicles moving along a straight track. The sample elements for testing were assembled by forcing the sleeve onto the shaft with the tolerance of 0.02 mm. To assess fretting at shaft top layers being tested, macroscopic observations, microscopic observations with the use of a scanning microscope, x-ray microanalysis of the chemical composition by means of the EDS method and the measurement of the top layer topography in the place of wear were performed. Test results presented concern the shaft top layer because it is that layer which mainly determines the life of a clamped joint. The results of the macroscopic observations of the sleeve hub top layer were presented, too, for comparison of the image of wear between mating surfaces.The results of the observations of the various shaft top layers indicate the mitigation of the development of fretting wear in the case of shafts with coatings; CrN+a-C:H:W coatings influence the mitigation of fretting wear better indeed. The main damage comprised by fretting in all the samples being tested is material build-up occurring as a result of adhesion. That build-up undergoes oxidation during operation. Micropits and microabrasion of the top layer are observed in places.