Several tests for verification of material deterioration evaluation method of rail steel using X-ray diffraction analysis

Abstract

Quantitative evaluation of rail deterioration due to rolling contact contributes to the optimization of rail maintenance such as rail grinding. A technique for evaluating rail deterioration due to rolling contact using X-ray diffraction has been reported. To use this method as a practical method for quantifying the degree of influence of rolling contact on rails, we should clarify experimentally the basic issues such as the correlation between the calculated index and the degree of rolling contact fatigue.In this study, the validity of this X-ray diffraction analysis method is verified by evaluating specimens at different loading stages via tensile and rolling tests. The results are also compared with Kernel average misorientation (KAM) values from electron back scattered diffraction. The same method was also used to evaluate rail degradation conditions for 700 million tons of passing tonnage.The following findings are identified from the above results. Dislocation density, one of the indicators obtained by X-ray diffraction, is directly related to crack initiation in rail steels. The X-ray crystallite size, which is also linked to the increase in the KAM value, makes it suitable for evaluating the degree of strain due to rolling contact.