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The reduction of the total life cycle cost of the whole wheelset requires an optimization of inspection intervals for axles. Such components can, in most European countries, endure more than 30 years of service life. During this time, they are subjected to frequent non-destructive testing (NDT) inspections. It is therefore important to assess the influence of design options, such as hollow versus solid axles or mild versus high strength steel, on the prospective crack propagation life of an axle. In the present paper two dedicated crack propagation algorithms (namely AFGROW and NASGRO) will be applied to the estimation of inspection intervals of railway axles by comparing the properties of two widely used steels.

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An experimental investigation was carried out to study and compare the response to cyclic loading of the high performance railway wheel steels ER8 EN13262 and SUPERLOS®. Rolling contact tests were performed with the same contact pressure, rolling speed and sliding/rolling ratio, varying the lubrication regime to simulate different climatic conditions. The samples, machined out of wheel rims at two depths within the re-profiling layer, were coupled with UIC 900A rail steel samples. The wear rates, friction coefficients and hardness were correlated with the deformation beneath the contact surface. The crack morphology was studied and the damage mechanisms were identified. The distribution of crack length and depth at the end of the dry tests was analysed to quantify the damage. The main difference between the steels lies in the response of the external samples to dry contact: SUPERLOS® is subjected to a higher wear and lower friction coefficient than ER8, this reduces the density of surface cracks that can propagate under wet contact conditions. The analysis of feedback data from in service wheels confirmed the experimental results