On the low temperature tribological behaviour of brake block materials for railway applications under dry and icy conditions
Leonardo Pelcastre, Lisa-Marie Weniger, Jens Hardell
Abstract
Incidents in the Swedish railway have been observed where a significant and sudden loss of brake performance occurs in winter conditions, on trains equipped with composite tread brake blocks (CBB). There is a necessity to establish test methods that can be used for the evaluation of brake materials under well-controlled laboratory conditions, to facilitate an understanding of the friction mechanisms between brake block and steel wheel. This work sought to characterise the tribological behaviour of different CBB materials at room temperature and −15 °C, focusing on understanding the materials response with and without presence of ice in the contact, as well as the effect of temperature on the tribological behaviour. A pearlitic cast iron brake block was used as a reference and four CBB materials were investigated, two organic and two sintered. The sintered CBB showed similar friction coefficient to the reference material and higher than the organic CBB, both at room and at low temperature. This was also seen when ice was formed on the wheel steel counter surface at −15 °C. Higher wear was observed for the sintered CBB compared to the organic CBB. The results suggest that sintered CBB can provide higher friction under winter conditions compared to organic CBB.