Tribological Property and Wear Mechanism of NbMoZrVSi x Refractory High-Entropy Alloy Strengthened by Eutectic Structure

In recent years, refractory high-entropy alloys (RHEAs) have gained widespread attention owing to their high structural stability and excellent mechanical properties at both room and elevated temperatures. However, their wear resistance at room temperature is often poor due to their fragility. In this study, the effect of adding small amounts of silicon (Si) to NbMoZrV RHEA on its tribological properties and wear mechanism at room temperature have been studied using various techniques including tribometer, SEM, and XPS. The results showed that adding a moderate amount of Si induced the homogeneous precipitation of a eutectic structure composed of Zr-Zr3Si phase at the bcc matrix grain boundary. This eutectic structure significantly improved the hardness and wear resistance of the NbMoZrVSi0.1 RHEA. Unlike the poor tribological behavior observed in NbMoZrVSi0.05 and NbMoZrVSi0.2 RHEAs, the NbMoZrVSi0.1 RHEA exhibited stable coefficient of friction and wear rate under dry sliding wear test at room temperature with varying normal loads. The Zr-Zr3Si eutectic structure effectively inhibited the initiation and propagation of cracks and brittle spalling during the sliding wear test, resulting in only slight abrasive wear of the NbMoZrVSi0.1 RHEA. Moreover, the mechanism promoted the subsequent homogeneous oxidation of the worn surface.