Research On Rolling Spalling And Wear Characteristic Of Wheel Steel

Tread spalling has being become major failure mechanism of wheel and key cause of restrictive development in railway with the increase of the speed and the weight of motor vehicles. Understanding of the formation mechanism of wheel spalling would help to bring enormous economic benefit and develop new materials of wheel for the development of railway.Rolling wear and spalling behavior of wheel steel have been studied by using JD-1 rail-wheel tribology simulate machine and reciprocating rolling test apparatus. Various examinations have been performed by means of optical microscopy (OM), hardnesstester, laser confocal scanning microscopy (LCSM) and scanning electron microscopy (SEM). The effects of carbon content, braking force, normal load and frequency on rolling spalling have been focused on. Furthermore, the role of contact stress in the rolling spalling and wear process is described with shakedown limit theory, and the mechanism of rolling spalling is explored systematically. Main conclusions are drawn as follows:1. As the carbon content of wheel steel is increased, there doesn't appear obvious change in the rolling friction property, but a transformation from abrasion to fatigue wear is observed in the rolling wear behavior. The degree of spalling depends upon carbon content of wheel steel, and the spalling is significant at high carbon content. Furthermore, the decrease in carbon content can remarkably alleviate the spalling, but lead to the increases in wear volume of wheel steel.2. It is found that the rolling wear behavior of wheel differs significantly under various rolling-sliding conditions. The tangential friction force on the contact increasing sharply with the increase in braking moment of friction pairs, and fatigue wear and adhesion are dominated on the worn surface. At bigger tangential force, there appears distinct plastic deformation on the surface of wheel steel, which results in the occurrence of rolling spalling wear.3. It is evident that the rolling spalling is associated with fatigue wear. They are characterized by abrasive wear at low normal load and by severe spalling at high normal load. However, spalling is independent on frequency under the rolling-sliding conditions.4. Asymmetric orthogonal shearing stress plays an important role in the initiation and the expansion of microcrack in the plastic deformation region. Moreover, it is suggested that the increase in the yield strength of both wheel and rail materials as well as appropriate shape of wheel-rail contact can alleviate spalling.