New Medical High Nitrogen Nickel Austenitic Stainless Steel, Mechanical And Biocompatibility Studies

Considering the potential harmfulness of nickel ions in biomedical stainless steel, a new Fe-18Cr-15Mn-2Mo-0.62N biomedical high nitrogen nickel-free austenitic stainless steel(BHNNFASS), has been studied in this paper. The structure and mechanical properties of BHNNFASS has been researched by metallurgical structure and X-ray diffraction test,tensile test,impact test and Vickers hardness test; the biocompatibility of BHNNFASS has been estimated by hemolysis test and anticoagulant performance test (include blood platelet adhesion test, kinetic clotting test and coagulation factors test); the corrosion resistance of BHNNFASS has been estimated by electrochemical test in 0.9% NaCl solution,artificial blood plasma solution and Hank's solution at 37℃.The results show that the new biomedical high nitrogen nickel-free austenitic stainless steel possess almost single austenite structure, and compared with 316L stainless steel and Co-Cr alloy, it has a higher strength and hardness, but the plasticity and toughness can still be kept at rather high level.The hemolytic rate of BHNNFASS was less than 1%, and the result of hemolytic test of it is clearly better than that of 316L stainless steel and Co-Cr alloy. BHNNFASS has excellent adhesion resistance in blood platelet adhesion test, the number of platelet cling to BHNNFASS samples is clearly less than that to 316L and Co-Cr alloy samples after long time dip in fresh human blood plasma, and the platelet on BHNNFASS has few agglomeration and distortion, but 316L stainless steel and Co-Cr alloy have more.The kinetic clotting times and plasma recalcification times of BHNNFASS were longer, while their prothrombin times were almost equivalent, which reveals that the activation of BHNNFASS on the intrinsic coagulation factors is weaker than the 316L stainless steel and Co-Cr alloy, and the anticoagulant property of BHNNFASS is better than the 316L stainless steel and Co-Cr alloy .The corrosion resistance of BHNNFASS is best in 0.9% NaCl solution,artificial blood plasma solution and Hank's solution at 37℃, especially the pitting corrosion resistance. The pitting corrosion potential of BHNNFASS is clearly higher than that of 316L stainless steel and Co-Cr alloy, reached more than 1000mV.The new biomedical high nitrogen nickel-free austenitic stainless steel has prominent advantage as a biomaterial because of its excellent combination of strength and toughness, better corrosion resistance, favorable biocompatibility, low cost and good processability, compared with the traditional biomedical materials. With absence of noxious nickel element in BHNNFASS , it will greatly improve the security of long time service of implant in human body.