Micromechanical Characteristics of the Surface Layer of Metastable Austenitic Steel after Frictional Treatment

The effect of the frictional treatment with a sliding indenter on the micromechanical properties of the austenitic corrosion-resistant chromium–nickel AISI 321 steel (16.80 wt % Cr, 8.44 wt % Ni) has been investigated. The instrumented microindentation results, which was performed on the surface of the steel and at different depths from the surface, has shown the exponential distribution of maximum h_max and permanent h_p indentation depths, Martens hardness HM, indentation hardness at the maximum load H_IT, elastic reverse deformation work of indentation W_e, total mechanical work of indentation W_t, elastic recovery R_е, ratio of indentation hardness to contact elastic modulus Н_IT/Е*, power ratio \({{H_{{{\text{IT}}}}^{3}} \mathord{\left/ {\vphantom {{H_{{{\text{IT}}}}^{3}} {{{E}^{{*2}}}}}} \right. \kern-0em} {{{E}^{{*2}}}}}\), and plasticity index δ_A over the depth of the hardened gradient layer. In this case, the HM, H_IT, W_e, R_е, Н_IT/Е*, and \({{H_{{{\text{IT}}}}^{3}} \mathord{\left/ {\vphantom {{H_{{{\text{IT}}}}^{3}} {{{E}^{{*2}}}}}} \right. \kern-0em} {{{E}^{{*2}}}}}\) values are the highest, whereas the h_max, h_p, W_t, and δ_A values are the lowest for the steel surface. The E* contact elastic modulus of AISI 321 steel also increases after the frictional treatment. It is distributed nonmonotonously over the depth of the hardened layer. This can be explained by the formation of different dislocation structures on the steel surface and in the underlying layers. The indentation results have shown that the frictional treatment increases the resistance to mechanical action of both the steel surface and the hardened layer with a depth of to 500 µm.