Effect of Grain Sizes on the Friction and Wear Behavior of Dual-Phase Microstructures with Similar Macrohardness and Composition

The tribological behavior of dual-phase steels have been studied at the macroscopic scale taking the macrohardness as the main material property to control friction and wear. However, the contribution to the macroscopic behavior of the varying properties of the phase at the microscopic scale are yet to be fully understood. In this study, dual-phase microstructures with various grain sizes and martensite volume fraction are generated. Microhardness of ferrite and martensite are measured by nanoindentation tests while their friction and wear behavior are studied by conducting scratch tests with various conical tips. Results show that for martensite, friction coefficient and wear resistance are proportional to its carbon content, whatever the martensite grain size. Whereas changing the ferrite grain size has two effects on the tribological behavior of the microstructure. First, the friction and wear resistance of ferrite are related to its grain size through a Hall–Petch relationship. Second, at a given martensite volume fraction, the mean wear resistance changes from the Equal Wear mode to the Equal Pressure mode as the ratio of the contact size to the ferrite grain size increases, while the mean friction coefficient always correlates to the Equal Pressure mode.