Characterization of porous nickel-free austenitic stainless steel prepared by mechanical alloying

Abstract

Nickel-free austenitic powder metallurgy stainless steels were prepared and characterized. The main issue was to obtain potential biocompatible materials. Mechanical alloying in a nitrogen atmosphere was used to obtain these powders. The main factor to be controlled was the milling time. Powder metallurgy was the technique to obtain massive samples from alloyed powders. Two sintering processes were applied by controlling the sinter-cooling rate (furnace and water-cooling). The sintering atmosphere applied was nitrogen because of its gammagenic effect. Samples made of powders milled for 48 h, sintered in nitrogen and water-cooled showed a clean austenitic microstructure, which is a suitable microstructure for biological applications. A complete microstructural characterization, including optical metallography, image analysis, Scanning Electron Microscopy with X-ray microanalysis, X-Ray diffraction and Vickers hardness and microhardness, was carried out. The electrochemical behaviour in a simulated body fluid, phosphate buffered saline, was also studied. The biocorrosion behaviour was evaluated in terms of anodic polarization measurements.