Currently, medical austenitic stainless steel represented by 316L or 317L is widely used to make high-end medical device products such as various artificial joints, fracture internal fixation devices, and cardiovascular stents. However, after medical stainless steel is implanted into the human body, due to inevitable trace corrosion or wear, the metal ions contained in it will inevitably dissolve, which may cause adverse histological reactions such as edema, allergies, infection, and tissue necrosis. Among them, 316L stainless steel contains more than 10% nickel. Clinical studies have proven that the dissolution of nickel ions in medical metal materials, in addition to causing sensitization and inflammatory reactions, may also induce the formation of tumors or thrombosis. Therefore, the development of new medical nickel-free stainless steel has become the main development trend of medical stainless steel. Among them, the most promising is the new medical stainless steel that uses nitrogen instead of nickel, which not only avoids the potential hazards of nickel, but also has excellent mechanical properties and biocompatibility.
In 1999, the American company CARPENTER researched and developed a new type of medical high-nitrogen nickel-free austenitic stainless steel (Fe-21Cr-22Mn-1Mo-1N). This medical stainless steel has excellent biocompatibility, low inflammatory reaction, and The mechanical properties are significantly better than traditional 316L stainless steel. Through in vitro cell culture and biocompatibility tests after implantation into sheep tibia, it was proved that high-nitrogen nickel-free stainless steel has similar bone tissue compatibility with titanium alloys, and is expected to replace traditional medical 316L stainless steel and medical Ti6Al4V titanium alloy. The test also proved that high-nitrogen nickel-free stainless steel has no genotoxicity and teratogenicity. In 2004, Japan used high-temperature nitriding treatment to prepare stainless steel material Fe24Cr2Mo(0.62~0.92)N with high nitrogen content, which does not contain nickel or manganese. Its cytotoxicity evaluation results are better than medical 316L stainless steel. In 2009, Japan implanted porous high-nitrogen nickel-free stainless steel into rats. The results showed that the porous high-nitrogen nickel-free stainless steel allowed bone cells and other tissues to grow into the holes, showing excellent biocompatibility and mechanical stability. In recent years, the newly developed medical high-nitrogen nickel-free austenite not only has high strength and high hardness (close to medical cobalt-based alloys), but also has better resistance to body fluid corrosion and corrosion resistance than traditional chromium-nickel medical stainless steel and cobalt-based alloys. Biocompatibility, so it is very promising to become a new generation of low-cost medical implant stainless steel, gradually replacing medical chromium-nickel stainless steel and medical cobalt-based alloys.
At present, cardiovascular stents are tending to develop fine mesh stents. The excellent mechanical properties and blood compatibility of new medical nickel-free stainless steel show its application prospects as an ideal stent material. German research shows that cardiovascular stents made of high-nitrogen nickel-free austenitic stainless steel have better support and are suitable for the development of finer stent grids. The United States has developed a high-nitrogen nickel-free stainless steel coronary stent with a minimum mesh of 45 microns and a blood vessel surface coverage rate as low as 8% to 9%. In China, the new anticoagulant high-nitrogen nickel-free stainless steel coronary stent jointly developed by the Institute of Metal Research of the Chinese Academy of Sciences and Zhongke Yian Technology Company has an average mesh diameter of 70 microns.
Due to its good mechanical and processing properties, new high-nitrogen nickel-free stainless steel can be used as surgical implants and plays an important role in orthopedic repair treatment. Currently, new surgical implants produced in the United States using high-nitrogen and nickel-free stainless steel have been put on the market. The total amount of medical stainless steel used in surgical implant products in my country reaches more than 400 tons every year. With the deepening of the reform of my country's national medical insurance system, high-quality and low-cost medical stainless steel implant devices will be more widely used. The research and development of new high-nitrogen nickel-free stainless steel not only has huge social needs, but also has great strategic significance.
