Grinding – good or bad for reduction of rolling contact fatigue– observations from in-service rails with white etching layer

Abstract

Rail grinding has been widely applied in railway networks worldwide to remove or prevent rolling contact fatigue (RCF) cracks. However, some concerns have arisen regarding grinding, that it may introduce initial damage to the rail and largely shorten the RCF life. This work aims to better understand the effect of grinding on the long-term degradation of in-service rails, particularly concerning White Etching Layer (WEL) and RCF cracks. Seven rail samples were selected and taken from the Belgian and Swedish railway networks, with different grinding histories, accumulated loads, and steel grades. The mechanical and microstructural properties of these samples were examined through the hardness test and optical microscopy. WEL and microcracks were observed in both ground and non-ground rails, suggesting that rail grinding does not create additional defects nor negatively impact the rail surface after long-term service. Macrocracks were observed only in rail samples that had undergone zero or a single grinding cycle, confirming the beneficial role of rail grinding in mitigating RCF cracks. Ratcheting is the dominant crack initiation mechanism under the examined conditions, while WEL may also contribute to crack formation, given that macrocracks predominantly occur at the transition between the WEL and the pearlite.