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Decarburization can remain on the surfaces of rail head steels and affect their wear and damage processes. The current research explored the influence of a decarburized layer on wear resistance and damage behavior of rail materials using a rolling–sliding wear testing machine. A decarburized layer decreases the hardness and wear resistance of rail steels, and the wear rate of a decarburized rail is over twice that of the same steel without decarburization. Multi-layer peeling appears on rail rollers without decarburization, but a decarburized layer changes the damage mechanism of the rail steel. With an increase in the depth of decarburization, the damage of rail roller turns from major spalling to pitting and peeling. In addition, surface fatigue cracks become more serious as depth increases. By contrast, shallow decarburization has little effect on rolling contact fatigue (RCF) of the rail material. Only when the depth of the decarburization exceeds a certain thickness (i.e., about 0.5 mm based on the present results), RCF damage sharply worsens as decarburization depth increases. Furthermore, adhesive wear features are obvious on the rail roller only when a decarburized zone remains at the wear surface. [ABSTRACT FROM AUTHOR]

The grinding process for maintaining the railroad rails can affect their performance. A rail grinding friction testing apparatus was developed to investigate the effects of rotational speed of grinding stone on removal behavior of rail material. The rail-grinding stone contact consists of a round, flat grinding stone and two test specimens made from Mn–steel rails that are pressed against the face of the stone. The effects of grinding wheel rotational speed on the abrasive removal mechanism of rail material are explored in detail. The results indicate that as the grinding wheel rotational speed increases, the friction coefficient, the surface roughness of rail specimens and the width of the wear grooves decrease. The grinding wear volume, the microindentation hardness of the rail specimens and the surface temperature-rise all increase as the number of grinding cycles increase. Wear debris collected during the test is composed of round particles and curled cutting chips. The debris is mainly composed of Fe 3 O 4 , FeO and Fe. As grinding rotational speed increases, the content of Fe 3 O 4 and FeO increases but the width of the cutting chips decreases. [ABSTRACT FROM AUTHOR]

The objective of this study is to investigate the braking tribological characteristics of two kinds of metro brake shoe materials using a sub-scale frictional braking machine. The results indicate that the friction coefficient of braking interface has a close relationship with the velocity and pressure. The increase of velocity and pressure raises the temperature-rise of braking interface. The increasing velocity and pressure aggravate the wear of brake shoe rings. However, the wear loss of wheel rings decreases with increasing pressure. The braking surface of brake shoe rings exhibits adhesive wear and spalling, while obvious plowing and abrasive wear are dominant on the braking surface of wheel rings. According to the experimental results, it is concluded that brake shoe B material can be used to prevent and alleviate the occurrence and evolution of groove wear on wheel tread. This might be attributed to the higher percentage of FeC 3 versus FeS 2 in its composition compared with brake material A. Field testing, completed to 100,000 km thus far, has to be completed on these materials and further work should be performed for evaluating the effect of different brake shoe materials on the groove wear of wheel tread in the field. [ABSTRACT FROM AUTHOR]