Enhanced wear resistance of nanotwinned austenite in higher Si nanostructured bainitic steel

The role of a highly-deformed layer and higher Si content on the impact-abrasive wear of nanostructured bainitic steel was investigated. Using an impact-abrasion testing machine, it was demonstrated that nanostructured bainitic steel containing 3 wt% Si had the best wear resistance compared with Hardox550 steel and carbidic austempered ductile iron (CADI). During the abrasion of the high-Si nanobainitic steel, a hardened layer can be created from the formation of nanoscale twinning bundle and an austenite transformation. Twinning can act as an intermediate phase preceding martensite formation under cyclic wear conditions that are dominated by plastic deformation. The formation of lamellar twinned austenite and martensite in nanobainitic steel can effectively enhance its impact-abrasive wear resistance. It was also found that micro-cracks nucleated on the bases of abrasive craters were blunted. That mechanism could be attributed to nanoscale twin formation and transformation-induced crack arrest.