In this study, equal-channel angular pressing (ECAP) of austenitic 316L and Cr-Ni-Ti stainless steels was carried out. Effect of ECAP at 400°C on the evolution of the microstructure, mechanical properties, and biocompatibility of these steels was investigated. The biocompatibility of samples with the ultrafine grain structure obtained in the ECAP process did not deteriorate in comparison with an austenitic 316L stainless steel in coarse-grained state. However, this treatment enhances the multipotent mesenchymal stromal/stem cell proliferation by 26% for 316L steel and by 17% for Cr-Ni-Ti stainless steel in comparison with coarse-grained counterparts. At the same time, ECAP contributes to a significant improvement in performance and weight reduction of medical devices, which is especially important for the creation of implanted prostheses for replacement of skeletal defects, due to significant increase in specific strength of steels. The strength properties of austenitic stainless steels were remarkably improved due to the grain refinement and deformation twinning resulted from ECAP at 400°C. After ECAP, the yield strength of 316L and Cr-Ni-Ti stainless steels increased by 4.2 and 2.9 times up to 950 and 900 MPa, and the fatigue limit by 2 and 1.7 times up to 500 and 475 MPa, respectively, comparing to coarse-grained counterparts.
Keywords: austenitic stainless steels; biocompatibility in vitro; equal-channel angular pressing; strength and fatigue properties; ultrafine grained structures.
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