Nickel-free austenitic stainless steels for medical applications

Abstract

The adverse effects of nickel ions being released into the human body have prompted the development of high-nitrogen nickel-free austenitic stainless steels for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also much improves steel properties. Here we review the harmful effects associated with nickel in medical stainless steels, the advantages of nitrogen in stainless steels, and emphatically, the development of high-nitrogen nickel-free stainless steels for medical applications. By combining the benefits of stable austenitic structure, high strength and good plasticity, better corrosion and wear resistances, and superior biocompatibility compared to the currently used 316L stainless steel, the newly developed high-nitrogen nickel-free stainless steel is a reliable substitute for the conventional medical stainless steels.

Keywords: austenitic stainless steel; biocompatibility; high-nitrogen steel; medical stainless steel; nickel-free.

Figure 1

Percentage of young people sensitized to nickel allergy has risen dramatically over the years (reproduced with permission from [28] ©1998 vdf Hochschulverlag AG an der ETH Zürich).

Figure 2

Development of biocompatible nitrogen-containing austenitic stainless steels (reproduced with permission from [21] © 1996 The Iron and Steel Institute of Japan).

Figure 3

Comparison of yield strengths of medical alloys after cold working [72].

Figure 4

Histological sections of Ni-free P558 (left), ISO 5832-9 SSt (middle) and Ti6Al4 V (right), 26 weeks after surgical implantation into sheep tibial diaphysis. The higher magnification clearly reveals direct bone apposition to the material surface. The bone tissue near the implant surface is of high quality, and resembles the compact bone (basic fuchsine and light green ×4) (reproduced with permission from [86] © 2003 Elsevier Ltd).

Figure 5

Microscopic images of the cells cultured on the disks of 316L, Fe–Cr–Mo and Fe–Cr–Mo–N stainless steels sterilized by UV-irradiation (reproduced with permission from ref. [94] © 2004 Elsevier Ltd).

Figure 6

S–N curves from axial tensile/tensile fatigues of BIOSSN4 and 316L steels at ambient conditions and in 0.9% NaCl solution at 37 °C (reproduced with permission from [110] © 2006 Metallurgical Industry Press).

Figure 7

Blood platelets on BIOSSN4 and 316L steels dipped in fresh human blood plasma for 25 minutes, (a) BIOSSN4, (b) 316L and (c) size distribution of blood platelets (reproduced with permission from [109] © 2005 Elsevier Ltd).

Figure 8

Blood platelets on BIOSSN4 and 316L steels dipped in fresh human blood plasma for 3 hours, (a) BIOSSN4, (b) 316L and (c) size distribution of blood platelets (reproduced with permission from [109] © 2005 Elsevier Ltd).

Figure 9

Kinetics of blood clotting on nickel-free stainless steel and 316L stainless steel (reproduced with permission from [111] © 2007 Scientific.net).