Enhanced tribological performance of a gradient nanostructured interstitial-free steel

A gradient nanostructured (GNS) surface layer was fabricated on a commercial interstitial-free (IF) steel by means of surface mechanical grinding treatment (SMGT). Reciprocating dry sliding tests of the GNS IF steel in air at room temperature were carried out in comparison with the coarse-grained (CG) sample. Worn surface morphologies, chemical compositions and worn subsurface microstructures were investigated for both IF steel samples. IF steel with a GNS surface layer exhibits lowered coefficients of friction (COFs) and significantly enhanced wear resistance under high testing loads. The superior tribological performance of the GNS IF steel sample is attributed to the finer dynamic recrystallized grains, and the grain coarsening layer that can accommodate large plastic strain and suppress the formation of cracking vortical structure.