PLASMA NITRIDED AUSTENITIC STAINLESS STEEL FOR BIOMEDICAL APPLICATIONS

摘要

Austenitic stainless steels are widely used as a non-implantable medical device because of good corrosion resistance and moderate strength. However, they have low surface hardness and wear resistance properties. In order to improve mechanical, chemical and biological properties, surface modifications have been applied to these biomaterials. In this study, AISI 316 austenitic stainless steels were plasma nitrided under different process parameters including temperature (450, 500, 550 ℃) and time (2,4 and 9 hr) at a gas mixture of 25%N_2-75% H_2. The nitrided surfaces were characterized by X-ray diffraction (XRD). MicroVickers hardness tests were done on the cross sections and the surface of the nitrided specimens to investigate the hardness profile. The important effects of nitriding temperature and time on the microstructure and hardness value of nitrided surface layers were introduced.