Surface Damage Assessment in Rail and Wheel Steels Using an Innovative Vision System

Rolling-sliding tests were done by a bi-disc machine on specimens realised by two different railway wheel steels (SUPERLOS® and ER8), coupled with the same rail steel (900A). Varying contact load and sliding speed were applied, up to very severe working conditions. Weight loss and coefficient of friction were monitored during the tests. At the end of the tests, the surface state was evaluated by roughness measurements obtained by an innovative laser distance sensor. Wear severity was evaluated in terms of specific T-gamma and Archard coefficients. The results showed that, with increasing load and sliding speed, there is a sudden transition from mild or severe wear to catastrophic wear. This is correlated with both parameters, but the sliding speed showed a stronger effect. The roughness at the test end is strongly correlated with the sliding speed. Among the wheel steels, the SUPERLOS® showed a better performance than the ER8, the rail steel showed better performance than the wheel steels, rarely being subjected to catastrophic wear. These tests showed the capability of the experimental set-up to simulate very severe wear regimes, whereas the innovative vision system showed its potential as a damage evaluation tool in rolling contact tests.