INVESTIGATION OF ROLLING-CONTACT FATIGUE IN A HEAD-HARDENED RAIL

A laboratory metallurgical analysis of head-hardened rails, removed from a heavy haul site at various stages of life, has enabled a study to be made of the incidence of rolling contact fatigue cracks and the role played by the white etching layer. It is shown that the cracks occurring down the center of the rail are associated with white etching layer formed very early on in the life of the rail. As the traffic carried accumulated, the extent of the white layer and the population of cracks were reduced as the white layer was removed by a spalling wear mechanism. Some of the cracks penetrated beyond the white layer-pearlite interface and grew to a depth that was not always removed during normal rail maintenance grinding. These observations would explain why some head-hardened rails have had to be removed from track after only 200 million gross tons of traffic as a result of severe spalling to a depth of 3 mm.