Dry sliding wear behavior of the high-strength nanostructured bainitic steel containing 3.5 wt% aluminum

Abstract

The acceptable wear behavior of nanostructured bainitic steels has enhanced their potential to be industrialized, and their applications in the automotive industry. This study focused on the wear behavior of the high-strength nanostructured bainitic steel containing 3.5 wt% aluminum (low-cost and low-density) to assess the dominant sliding wear mechanism and the correlation between the microstructure and applied load on the sliding wear resistance. A pin-on-disk tribometer was used to evaluate dry sliding wear behavior, and the SWR was computed by weighing the specimens. To identify the wear mechanism, the worn surfaces and cross-sections were analyzed using XRD, FESEM, and EDS. The results showed that the retained austenite volume fraction and carbon content of austenite (the stabilizer of the retained austenite) of high-strength nanostructured bainitic steels are not the only determinants of wear behavior. Indeed, the thickness of bainitic ferrite plates (strength source) is the major parameter affecting wear resistance. An increase in the Vαb/tαb ratio due to a decreased austempering temperature reduced the SWR and enhanced wear resistance. Moreover, the change from a normal load of 50 N to a load of 150 N changed the dominant wear mechanism from oxidative to adhesive. Also, increasing the isothermal transformation temperature and applied load by increasing the thickness of the tribological-transition-zone (TTZ) causes a decrease in sliding wear resistance. In summary, the formation of a thin TTZ due to the increase in the Vαb/tαb ratio is the main reason for the improvement of the wear resistance of the austempered sample at the lowest temperature (250 °C).

Keywords

• Nanostructured bainitic steel
• The carbon content of retained austenite
• The thickness of bainitic ferrite plates
• Oxidative
• Adhesive