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 island, 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 smallscale 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 datahighlighted 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.