%0 Journal Article
%T Influence of Partial Replacement of Nickel by Nitrogen on Microstructure and Mechanical Properties of Austenitic Stainless Steel
%A A. Ahmed
%A S. N. Ghali
%A M. Eissa
%A S. A. El Badry
%J Journal of Metallurgy
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/639283
%X A new modified austenitic stainless steel has been developed through partial replacement of nickel by nitrogen. Nitrogen stainless steel was produced in 10£¿kg induction furnace under nitrogen pressure, while reference one, AISI 316 steel grade, was produced in open-induction furnace. Both were cast and hot forged, and the total nitrogen was determined. Furthermore, the produced forged steels were subjected to solution treatment at different temperatures. The microstructure of produced stainless steels was observed. The X-ray diffractmeter and Mossbauer effect spectroscopy were used to follow the phase change in reference and modified steels after different heat treatment temperatures. The influence of grain-size, soluble, and insoluble nitrogen on tensile strength and hardness was investigated. The major phase in the modified steel has a fcc structure similar to the reference one, but with finer grains and more expanded lattice. The yield strength and hardness of the nitrogen-modified stainless steel are higher than the reference steel. On the other hand, the increase of nitrogen content deteriorates the steel ductility. 1. Introduction Over the past few decades, there is a trend in the that world aims at the replacement of nickel by nitrogen as an austenitic stabilizer element [1¨C4], as nitrogen is considered as the strongest austenitic stabilizer element among all the austenitic stabilizers, that is, C, Mn, Ni, and Cu. The partial replacement of nickel by nitrogen increases mechanical properties, besides the improvement of corrosion resistance [5]. High-nitrogen stainless steels can be produced in the liquid state [6] by different techniques such as induction furnace, electric arc furnace, gas bubbling in liquid steels, pressure electroslag remelting (PESR), plasma arc melting, and arc-slag melting. Each melting technique has advantages and disadvantages. For example, PESR is complicated and expensive. On the other hand, nitrogen gas alloying and addition of nitrided ferroalloys under normal atmospheric conditions is a simple and feasible method, but the nitrogen content of produced steel is limited. To increase the nitrogen content, the nitrogen partial pressure must be increased. This can take place through melting in induction furnace under nitrogen pressure [6]. The main problem¡ªfaced by steel-making researchers¡ªis not only how to introduce nitrogen into molten stainless steel but also how to keep it during the solidification and heat treatment. This paper aims at developing an innovating grade of austenitic stainless steel by nickel partial
%U http://www.hindawi.com/journals/jm/2011/639283/