Assessment of thermal treatments on commercial steel probes of AISI 304l and AISI 316l for bone implants

Abstract

This work presents the results of studying austenitic stainless steel to determine the feasibility of applying them in bone prostheses and orthotics for low cost veterinary applications. AISI 316L and AISI 304L steel samples were modified by thermal treatments. Three alternative thermal treatments were applied: (A) solubilization; (B) solubilization plus stress relief; and (C) solubilization plus stress relief, followed by a second solubilization step. After every treatment, microstructural analysis was performed, susceptibility to intergranular attack was evaluated, and hardness, tensile and bend testing were probed. The microstructural analysis showed that both austenitic stainless steels have experienced grain size increase. The final grain size achieved was similar in both sorts of steel samples after any of the three thermal treatments. In the case of AISI 316L, the tensile strength decreased by 10% after treatment A. This decline was lower after treatment B or C. In contrast, tensile strength was less influenced in AISI 304L, with changes lower than 5%. All thermal treatments diminished the hardness of both steels by approximately 15%. Probes subjected to bend testing showed no defects or discontinuities. Evaluation of susceptibility to corrosion, performed according to ASTM standard practice A262, showed that both AISI 304L and AISI 316L can be accepted as free of intergranular attack in all cases. However, evidence of long term corrosion was observed