The effect of plasma nitriding temperature on the electrochemical and semiconducting properties of thin passive films formed on 316 L stainless steel implant material in SBF solution

• 316 L stainless steel samples were nitrided at different process temperatures to obtain s-phase.
• Structural, corrosion and semiconductor properties of passive film were investigated.
• It was observed that nitriding at low temperatures was necessary to form s-phase in the modified layer.

In this study, 316 L stainless steel samples were nitrided plasma at temperatures of 350, 400 and 450 °C for 2 h under a gas mixture of 50% N2–50% H2. The effect of plasma nitriding temperature on the corrosion performance and semiconductor properties of the passive film on the 316 L stainless steel was evaluated in simulated body fluid (SBF) using electrochemical test and Mott–Schottky analysis. In literature study, the effect of plasma nitriding temperature on corrosion behavior of 316 L stainless steel was evaluated in solutions of NaCl, H2SO4 and acidic for biomedical applications. However, corrosion studies are more suitable to test in simulated body solution. Also, there are no enough studies on the effects of plasma nitriding temperature on semiconductor properties of the passive film obtained on film 316 L stainless steels in SBF solution. So, in this study the effects of plasma nitriding temperature on the electrochemical and semiconducting properties of thin passive films formed on 316 L stainless steel implant material in SBF solution at 37 °C were investigated. The effects of microstructure and phase structure on corrosion properties of samples were determined. The results showed that the phase composition and microstructure of the treated samples were affected from the nitriding temperatures. It was obtained that s-phase formed at the lower temperature than 400 °C. According to electrochemical test results, the plasma nitriding process at 350 °C was the most suitable process condition for improving the corrosion resistance in SBF. All oxide films showed p-type (acceptor) semiconductor behavior at low potentials and n-type (donor) behavior at high potentials.