Investigating the effects of aging time on corrosion resistance and antibacterial property of newly designed medium-entropy super austenitic stainless steels

In this study, a newly developed medium-entropy austenitic stainless steel (MEASS) was subjected to a heat treatment to examine the effects of different aging times on its strength, corrosion resistance, and antibacterial performance. The properties of the MEASS were compared with those of a commercial stainless steel (UNS S31254). All of the aged MEASS specimens exhibited higher hardness than the solution-treated S31254 and MEASS owing to the precipitation of the Cu-rich phase, as characterized by a transmission electron microscope (TEM) and scanning TEM (STEM). However, as aged at a temperature of 700 °C for longer than 4 h, the aged MEASS specimens were prone to intergranular corrosion. This was owing to the lower integrity of the passive film as a result of the precipitation of the M23C6 carbides and σ phases at the grain boundaries. Although the antibacterial rate increased from 83.9% to 98.1% as the aging time was prolonged from 4 h to 48 h, the preliminary results suggested that the MEASS specimen subjected to the aging treatment for 4 h exhibited an optimal combination of strength, corrosion resistance, and antibacterial performance.