Austenitic stainless steels generally have a favorable combination of strength and ductility as well as a sufficient resistance against corrosion. This and the reported biocompatibility lead to the use of 304- and later 316 L-type steels in medical applications. Especially in orthopedics these steels were applied as implants for e.g. fracture fixation as bone plates, intermedullary nails, and screws. But these steels contain a high amount of Ni, which was attributed to cause Ni-allergies for an growing amount of patients. Thus, alternatives were needed and — beside the already known CoCrMo-alloys — implants of Ti and its alloys emerged increasingly into the medical market. The aim of this paper is to introduce a new austenitic Ni-free CrMnMo-steel X13CrMnMoN18-14-3 (Material No.: 1.4452, brand name: P2000), which makes use of about 1 % N in order to gain a combination of high strength, high ductility, and a superior corrosion resistance.
In a first step the cyclic fatigue behavior in air and in Ringer solution in the solution annealed state is investigated. This is accompanied by electrochemical testing in Ringer solution as well as in-vitro cytotoxicity tests against MC3T3 cells in bovine serum.
The tests revealed that the solution annealed X13CrMnMoN18-14-3 at 5 Hz has an 50 % endurance limit of 346 MPa in air and of 302 MPa in Ringer solution, which is markedly higher compared to solution annealed CrNiMo-steels. In addition it was found that the CrMnMoN-steel shows no distinct susceptibility to stress-corrosion cracking in the entire region of finite life between stress amplitudes of 400 to 550 MPa. The pitting potential in Ringer solution was measured to be 1.1 V, which is in the range of common Ni-containing high-Nitrogen steels as well as of CoCr20Mo6 alloys. No reduction of MC3T3 cell adhesion could be observed.
Thus, the Ni-free CrMnMoN-steels might be a promising alternative to the CrNiMo- steels in medical applications.