Experimental investigation on the effect of bainite traces on wear and rolling contact fatigue in ER8 railway wheel steel

The effect on wear and rolling contact fatigue of dispersed bainitic islands, as a remnant of the production process of railway wheels, is still an open issue. To address this topic, an experimental campaign was carried out on an ER8 steel by means of a small-scale bi-disc machine. The specimens were extracted at different depths under the tread of a railway wheel, characterized by decreasing hardness and a bainite content. The tests were done in dry rolling-sliding condition, in some cases followed by a wet contact session. Various measurement techniques, including an innovative vision system, were employed to evaluate wear, rolling contact fatigue and surface degradation. The results showed that, in dry condition, the prevailing damage was delamination wear, whereas, in the wet phase, shelling prevailed. None of the obtained data highlighted a detrimental effect of the bainitic content, in the concentrations considered in this study. This means that a small amount of dispersed bainite can be tolerated, reducing energy consumption, material waste and cost in the production process. • Rolling contact experiments were done on ER8 steel specimens in dry and dry-wet contact. • The specimens had different hardness and content of dispersed bainite islands. • Delamination wear was the main damage in dry contact. • Rolling contact fatigue was the main damage in dry-wet contact. • No relevant role of the bainitic islands was detected.