Mechanical and Corrosion Properties of Forged Hip Stems made of High-NitrogenStainless Steel
SourceThe purpose of the study was to determine the mechanical and corrosion roperties of forged, commercially available, femoral hip stems. Two different stem designs were selected (the MS-30, sizes 6 and 16, and the MUELLER straight stem, sizes 7.5 and 15.0). They were made of high-nitrogen stainless steel according to ISO 5832-9 and ASTM F1586. The samples for determining the mechanical properties were taken from the proximal part of the prostheses. The metallurgical and the potentio-dynamic corrosion behaviours were investigated in three different transverse cross-sectional planes. The mechanical properties in the forged condition were as follows: Yield strength 1051 – 1172 MPa, tensile strength 1138 – 1238 MPa and elongation 15 – 19%. Vickers hardness values of between 354 and 393 HV were measured. The breakdown potential fell from +1000 mV(SCE) (wrought bar) to +600 to +950 mV(SCE) (forged hip stems) for pH 4 and 37°C. The rotational bending fatigue value for 10 million cycles was 587 MPa.