Impact Toughness Properties of Nickel- and Manganese-Free High Nitrogen Austenitic Stainless Steels
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DEVELOPMENT of high nitrogen austenitic stainless steels (HNASSs) has attracted attention in order to reduce the content of expensive nickel.[1–4] This new category of austenitic stainless steels exhibits a superior property combination of high yield strength, high toughness, high corrosion resistance, and nonmagnetic and more stable austenitic structure.[1] Generator rotor retaining rings are a classical application of HNASSs.[5] Recently, HNASSs have been used in the building industry as bolts and other fixtures that are stressed in aggressive environments for long times where stress corrosion resistance is important.[6] Also, nickel ions act as an antigenic substance,[7–9] which may cause cutaneous inflammations such as swelling, reddening, eczema, and itching of the skin in locations where direct contact between skin and material happens.[7,10] Nickel-free high nitrogen austenitic stainless steels (Ni-free HNASSs) have been introduced to medical applications in recent decades all over the world ROGHAYEH MOHAMMADZADEH, Assistant Professor, is with the Department of Materials Engineering, Azarbaijan Shahid Madani University, Tabriz, Iran. Contact email: r.mohammadzadeh@ azaruniv.ac.ir ALIREZA AKBARI, Associate Professor, is with the Department of Materials Engineering, Sahand University of Technology, Tabriz, Iran. MINA MOHAMMADZADEH, Graduate Student, is with the Department of Materials Engineering, University of Tehran, Tehran, Iran. Manuscript submitted April 16, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS A
to solve the allergetic problems of nickel ions in human skin. BIOSSN4 and BIODUR 108 biomaterial stainless steels are commercial Ni-free HNASSs. Some potential applications of Ni-free HNASS are as an implantation material and in orthopedic and orthodontic devices.[11,12] Ni-free HNASSs contain a large amount of manganese (10 to 24 wt pct), which enables high nitrogen addition (0.45 to 1.10 wt pct) to stainless steel.[13] Brigham and Tozer[14] reported in 1976 that manganese improves localized corrosion resistance of austenitic stainless steels. On the other hand, Lunarska et al.[15] reported that manganese can be less detrimental if the environment is less aggressive. Also, Baba et al.[16] and Lim et al.[17] showed that manganese is detrimental to the pitting corrosion resistance of stainless steels. Baba et al. reported that high manganese containing steel (20 wt pct Mn and 0.45 wt pct N), despite having high nitrogen content, exhibited a pitting corrosion potential (Epit) lower than low manganese stainless steel (0.01 wt pct Mn and 0.45 wt pct N). This phenomenon is attributed to the presence of nonmetallic MnS inclusions in the microstructure, which lower the local corrosion resistance.[16] Also, recently, Toor[18] reported that as the manganese content of alloy increases, the number and size of inclusions increase and, conclusively, the overall corrosion rate of the 1Ni-4Mn alloy increases in chloride and acidic chloride solutions in comparison to 4Ni-1Mn alloy. Though there have been few re
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