Wear and Electrochemical Behavior of High-Nitrogen, Nickel-Free Austenitic Stainless Steel Produced by Hot Powder Forging

The microstructure, wear-resistance, and electrochemical behavior of high-nitrogen, nickel-free, nanostructured austenitic stainless steel, containing a biocompatible additive (Mn-11.5 wt% Si), and prepared by the hot forging powder route are investigated. The results are compared with conventional 316L steel. The microstructure of the samples was investigated by x-ray diffraction (XRD), metallography, field emission scanning electron microscopy, transmission electron microscopy, and selected area diffraction (SAD). The wear properties of samples were characterized by dry sliding wear tests. Finally, the electrochemical behaviors of the samples were determined by potentiodynamic polarization measurements in a simulated body fluid. The XRD and SAD results prove that the fabricated alloys contain two phases in the structure involving austenitic nanocrystalline and amorphous phases. The sliding analysis shows that increasing additive content causes decreased weight loss in samples during the wear test. However, samples with less additive have a lower friction coefficient; however, they have weaker wear resistance. Nevertheless, all of the forged samples have significantly better wear resistance than commercial 316L. The electrochemical results show that cavities, microstructure, and nitrogen concentration affect corrosion behavior. Consequently, the sample containing 6 wt.% additive has the best corrosion resistance among 316L and other forged samples.