The document discusses characterization of nickel-free austenitic stainless steels. It describes how nitrogen can be used to replace nickel in stainless steel alloys. Nitrogen increases the strength of the steel through solid solution strengthening and stabilizes the austenite phase. The introduction of nitrogen leads to higher yield strength, tensile strength, and hardness. Cold working the steel further increases its strength but decreases ductility. Heat treatment is needed to restore ductility. High-nitrogen stainless steels exhibit high strength, corrosion resistance and are suitable for applications like medical implants due to their biological compatibility.