Examination of Solid State Nitrogen Absorption for Production of Nickel Free Stainless Steel
Oğuz Gürkan Bilir İsmail GÜVENİR Ersoy Erişir
AbstractCo-Cr and 316L are the commonly used alloys in biomedical industry. However, both 316L and mostly used Co-Cr alloys as F-562, L-605 contain large portions of Ni as alloying element. Ni may cause allergic and toxic impacts on human health. In recent years, N-alloyed Ni free stainless steels seemed as good candidate for replacing Ni contained metals. However, liquid steel has a limited N solubility at atmospheric pressure. Thus, high pressured melting techniques are required. In this study, N alloying of ferritic 430 stainless steel sheet was performed in solid state. Nitrogen absorption of stainless steel was performed in a furnace filled with nitrogen gas with atmospheric pressure at 1200°C. Solid state N absorption was applied in four different time periods as 4, 8, 12, 24 hours. Microstructure after absorption process was investigated by Scanning Electron Microscope and Light Microscope. Fully austenitic structure was observed in surface of specimens. However, duplex microstructure of ferrite and austenite was seen in the center of specimen. Vickers hardness was carried out to evaluate of phases. It was concluded that optimum microstructure is achieved by 4 hours of N absorption.