• Korean Journal of Metals and Materials
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• v.49 no.2
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• pp.153-160
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• 2011

The AISI 216L stainless steel with a composition of Fe-16Cr-6Ni-6Mn-1.7Mo (wt.%) was oxidized at $700{\sim}900^{\circ}C$ in air for 100 h. At $700^{\circ}C$, a thin $Mn_{1.5}Cr_{1.5}O_4$ oxide layer with a thickness of $0.4{\mu}m$ formed. At $800^{\circ}C$, an outer thin $Fe_2O_3$ oxide layer and a thick inner $FeCr_2O_4$ oxide layer with a total thickness of $30{\mu}m$ formed. The non-adherent scale formed at $800^{\circ}C$ was susceptible to cracking. At $900^{\circ}C$, an outer thin $Fe_2O_3$ oxide layer and a thick inner $Mn_{1.5}Cr_{1.5}O_4$ oxide layer formed, whose total thickness was $10{\sim}15{\mu}m$. The scales formed at $900^{\circ}C$ were non-adherent and susceptible to cracking. 216 L stainless steel oxidized faster than 316 L stainless steel, owing to the increment of the Mn content and the decrement of Ni content.

• Journal of Korea Foundry Society
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• v.5 no.4
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• pp.271-282
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• 1985

In order to investigate the mold reaction characteristics of Mn steel and Cr steel castings individually, the mold reaction products were examined by scanning electron microscopy, electron prove microanalyzer and X-ray diffractometer. From this experiment, the results were summarized as follows: 1) The mold reaction depth increased with increase of Mn content, while it decreased with increase of Cr content. 2) Mold reaction depth decreased with Mn content at $1200^{\circ}C$. 3) Mn, among the reaction products, forms a low fusion silicate, Mn $O.SiO_2$ while Cr forms a stable oxide, $CrO_3$ which hindering the reaction between FeO and $SiO_2$ thus the formation of $FeO.SiO_2$ was depressed.

• Corrosion Science and Technology
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• v.20 no.6
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• pp.373-383
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• 2021

The effect of Cr addition to high Mn steel on flow-accelerated corrosion (FAC) behavior in a neutral aqueous environment was evaluated. For comparison, two types of conventional ferritic steels (API X70 steel and 9% Ni steel) were used. A range of experiments (electrochemical polarization and impedance tests, weight loss measurement, and metallographic observation of corrosion scale) were conducted. This study showed that high Mn steel with 3% Cr exhibited the highest resistance to FAC presumably due to the formation of a bi-layer scale structure composed of an inner Cr enriched Fe oxide and an outer Mn substituted partially with Fe oxide on the surface. Although the high Mn steels had the lowest corrosion resistance at the initial corrosion stage due to rapid dissolution kinetics of Mn elements on their surface, the kinetics of inner scale (i.e. Cr enriched Fe oxide) formation on Cr-bearing high Mn steel was faster in dynamic flowing condition compared to stagnant condition. On the other hand, the corrosion scales formed on API X70 and 9% Ni steels did not provide sufficient anti-corrosion function during the prolonged exposure to dynamic flowing conditions.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.385-388
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• 2009

Dry-sliding-wear behavior of Fe-18Cr-l0Mn steel with various carbon and nitrogen contents was characterized, and the effect of carbon and nitrogen contents on the wear was investigated. Dry sliding wear tests of the steel were carried out at room temperature against an AISI 52100 bearing steel ball using a pin-on-disk wear tester. Applied wear loads were varied from 10 N to 100 N, and the sliding distance was fixed as 720 m. Worn surfaces and the wear debris of the steel were examined using an SEM to find out the wear mechanism. It was found that the Fe-18Cr-10Mn with both carbon and nitrogen exhibited superior wear resistance to the steel with only nitrogen. The wear resistance of the Fe-18Cr-10Mn-xC-yN alloy increased with the increase of the carbon content. The excellent wear resistance of the Fe-18Cr-10Mn-xC-yN alloy was explained by the increased strain-hardening capability with the interstitial atoms.

• Journal of the Korean Society for Heat Treatment
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• v.4 no.4
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• pp.44-52
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• 1991

The effect of deformation temperature and manganes contents on the tensile properties of duplex stainless steels with the structure of both ferrite and austenite were investigate. For this investigation, Fe-19% Cr-5% Ni-4~8% Mn alloys were prepared. The result obtained from this experiment are summerized as follows. With decreasing deformation temperature, tensile strengths of duplex stainless steel increased. Elongation showd to be increased and then decreased after representing the highest value at specific temperature. Tensile properties of duplex stainless steel were controlled by TRIP behavior in this experimental range of austenite contents. Tensile strengths decreased with increasing Mn contents. With increasing Mn contents, elongation decreased in the high temperature region, but increased in the low temperature region. The peak temperature representing the maximum elongation were changed to low temperature and the width of peak appeared to be broaden with increasing Mn contents.

• Journal of the Korean Ceramic Society
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• v.40 no.2
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• pp.139-145
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• 2003

We studied oxidation behaviors of anti-oxidative Y-Cr oxide coated sol on ferritic steel for application of the Fe-Cr alloys as interconnectors of planar-type Solid Oxide Fuel Cells(SOFCs). In coated$YCrO_3$on the ferritic steel, the phases of $YCrO_3$,$Cr_2O_3$and $Mn_{1.5}Cr_{1.5}O_4$on the coated surface were detected, but iron base scales were not observed after oxidation at 80$0^{\circ}C$ for 40 h. The Mn-Cr oxide scales were grown with oxidation by diffusing components in the ferritic steel from inner. The Log(ASR/T) value that expresses electrical resistance of coated$YCrO_3$on the ferritic steel was -4.57~$-4.70{omega}cm^2K^{-1}$, lower in comparison with the one of the uncoated ferritic steel,$-3.99{omega}cm^2K^{-1}$. This indicates the applicability of Fe-l6Cr alloy as interconnector materials for SOFCs.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.421-424
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• 2006

High nitrogen steels (HNS) exhibit both high strength and ductility during tensile deformation. In the present study the Fe-18Cr-14Mn-4Ni-0.9N high nitrogen steel was heat treated at $1000^{\circ}C$ and $1100^{\circ}C$ to produce $Cr_2N$ precipitates in austenite matrix and full austenite microstructures, respectively. Tensile tests of the heat treated specimens were performed at two different strain rates of 0.05/sec and 0.00005/sec. Each tensile curve of the specimens could be well characterized by the the modified Ludwik equation. Plastic deformation of the steel was adequately represented by the four parameters of the modified Ludwik equation. At 0.05/s strain rate, the specimen with the $Cr_2N$ precipitate exhibited higher strength than the full austenite specimen, while the full austenite specimen showed better mechanical properties at 0.00005/s strain rate. It was found that the $Cr_2N$ precipitates influences deformation behavior of the high nitrogen steel significantly.

• Journal of the Korean Society for Heat Treatment
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• v.27 no.3
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• pp.121-126
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• 2014

High-nitrogen Fe-18Mn-18Cr-N austenitic steels with higher yield strength have been recently developed and used for generator retaining rings because they have non-magnetic, high strength, high ductility, and good corrosion resistance. In the present study, a high-nitrogen Fe-18Mn-18Cr-0.61N austenitic steel was fabricated and then tensile and Charpy impact tests were conducted on them in order to investigate the effect of cold working on the mechanical properties. Although the yield and tensile strengths usually increased with cold working, the ductility and impact toughness significantly decreased after cold working. On the other hand, the high-nitrogen austenitic steel exhibited a ductile-brittle transition due to unusual brittle fracture at low temperatures despite having a face-centered cubic structure. The ductile-brittle transition temperature obtained from Charpy impact tests could be remarkably increased by $60^{\circ}C$ after 20% cold working because of the enhanced cleavage-like brittle fracture.

• Transactions of Materials Processing
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• v.15 no.2 s.83
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• pp.112-117
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• 2006

Sliding wear mechanism of a high nitrogen austenitic 18Cr-18Mn-2Mo-0.9N steel has been investigated. Dry sliding wear tests of the steel were carried out at various loads of IN-10N under a constant sliding speed condition of 0.15m/s against AISI 52100 bearing steel balls. Solution ($1050^{\circ}C$) and isothermal aging ($900^{\circ}C$) heat treatments were performed on the steel and the effect of the heat treatments on the wear was investigated. Wear rates of the solution-treated steel specimen remained low until 5N load, and then increased abruptly at loads above 5N. The rates of isothermally aged specimens were low and increased gradually with the applied load. Worn surfaces, their cross sections, and wear debris of the steel specimens were examined with a scanning electron microscopy. Phases of the heat-treated specimen and the wear debris were identified using XRD. The transformed phase underneath a sliding track was investigated and analyzed using a TEM. Effects of the phase transformation during the wear and $Cr_{2}N$ precipitates formed during the isothermal aging on the wear of the austenitic steel were discussed.

• Journal of the Korean Ceramic Society
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• v.33 no.12
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• pp.1421-1425
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• 1996

Sintered Si3N4 and Inconel composed of Ni(58-63%) Cr(21-25%) Al(1-17%) Mn(<1%) fe(balance) were pressurelessly joined by using Ag-Cu-Ti brazing filler metal at 950℃ and 1200℃ under N2 gas atmosphere of 1atm and their interfacial structures were investigated. In case that the reaction temperature was low as 950℃ its interfacial structure was "Inconel metal/Ti-rich phase layer/brazing filler metal layer/Si3N4 " Ti used as reactive metal existed in between inconel steel and brazing metal and moved to the interface of between brazing filler metal nd Si3N4 according as reaction temperature increased up to 1200℃. The interfacial structure of inconel steel-Si3N4 reacted at 1200℃ was ' inconel metal/Ni-rich phase layer containing of Fe. Cr and Si/Cu-rich phase layer containing of Mn and Si/Si3N4 " Cr Mn, Ni and Fe diffused to the interface of between brazing filler metal and Si3N4 and reacted with Si3N4 The most reactive components of ingredients of inconel metal were Cr and Mn. On the other hand Ti added as reactive components to Ag-Cu eutectic segregated into Ni-rich phase layer,.