Enhancement of corrosion resistance to sterilization stages of a biomedical grade AISI 316L stainless steel by means of low-temperature machining

Abstract

Austenitic stainless steels are currently used for the manufacture of reusable medical instruments, thanks to their combination of elevated strength, corrosion resistance, biocompatibility and low cost. However, during their service life, they are subjected to repeated sterilization cycles, which lead to the loosening of the surface oxide stability and, as a consequence, the decrease of their durability.In the present study, the in-service corrosion behaviour of the AISI 316L stainless steel was investigated after being machined using two low-temperature coolants, namely Liquid Nitrogen (LN2) and gaseous Nitrogen (N2) cooled by LN2 to -100°C, as well as using a conventional cutting fluid.Results showed that the AISI 316L microstructure near the machined surface was significantly affected by the machining cooling strategies with the generation of a hardened and more compressed layer when low-temperature coolants were used. Such surface integrity enhancements contributed to improve both the general and localized corrosion resistance to sterilization stages. From this basis, machining using low temperature coolants can be considered a suitable technique to manufacture medical devices of increased durability.