The rolling-sliding wear behavior and damage mechanism of the rail steel treated by plasma selective quenching

Abstract

Plasma selective quenching (PSQ) is a promising technique for creating discrete hardened spots (PSQ spots) in the surface layer of the rail to increase its service life. However, cracks occur at one side of the PSQ spots after long-term service, hindering the large-scale application of PSQ treated rails. To reveal the effect of PSQ on the wear behavior of rail steel and damage mechanism of PSQ spots, rail rollers with a thickness of 10 mm were firstly PSQ treated by a laminar plasma jet. Then rolling-sliding contact wear tests were conducted to explore the wear behavior and damage characteristics of the PSQ treated rail rollers. In addition, contact simulation of the contact wear tests was carried out. Results showed that the wear resistance of the PSQ treated rail rollers was improved by 1.26–1.75 times. Such improvement is a result of the increased hardness of the PSQ spots and the reduced plastic deformation of the substrate between two adjacent PSQ spots. Severe cracks and breaks were observed at the entry side of the PSQ spots while no obvious damage appeared at the exit side. The mechanism of such a special pattern of damage was that there was a strain difference at the boundary between the entry side of hardened PSQ spot and the soft substrate while no different strains were produced at the exit side. This paper clarified the damage mechanism of the PSQ spots under the rolling-sliding contact conditions, providing the basis for further improvement on the performance of the PSQ treated rail steel.