Surface modification of austenitic stainless steel with plasma nitriding for biomedical applications

In the present study, plasma nitriding of AISI type 303 austenitic stainless steel (SS) specimens was performed using a microwave system. The nitrided layers were characterized by performing scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and a Vickers microhardness test. The antibacterial activities of the nitrided layers were evaluated. XRD and TEM showed that a single γN phase was formed by plasma nitriding at the plasma power of 700 W and 450 °C. The analytical results demonstrated that the hardness of type 303 specimens could be enhanced by plasma nitriding because of the formation of the γN phase. A bacterial test also demonstrated that the nitrided layer exhibited excellent antibacterial properties.

► The phase transformation sequence on the nitrided layers of the alloys was found to be γ → (γ + γN). ► The surface hardness of AISI 303 stainless steel could be enhanced with the formation of γN phase. ► Fe+ ions releasing from the γN phase on the nitrided layers came into the bacterial suspension to kill bacteria.