• Korean Journal of Materials Research
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• v.26 no.7
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• pp.353-358
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• 2016

The hydrogen embrittlement of two austenitic high-manganese steels was investigated using tensile testing under high-pressure gaseous hydrogen. The test results were compared with those of different kinds of austenitic alloys containing Ni, Mn, and N in terms of stress and ductility. It was found that the ultimate tensile stress and ductility were more remarkably decreased under high-pressure gaseous hydrogen than under high-pressure gaseous argon, unlike the yield stress. In the specimens tested under high-pressure gaseous hydrogen, transgranular fractures were usually observed together with intergranular cracking near the fracture surface, whereas in those samples tested under high-pressure gaseous argon, ductile fractures mostly occurred. The austenitic high-manganese steels showed a relatively lower resistance to hydrogen embrittlement than did those with larger amounts of Ni because the formation of deformation twins or microbands in austenitic high-manganese steels probably promoted planar slip, which is associated with localized deformation due to gaseous hydrogen.

• Proceedings of the Materials Research Society of Korea Conference
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• 2002.05a
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• pp.29-29
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• 2002

• Proceedings of the Korean Nuclear Society Conference
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• 2001.05a
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• pp.374.2-374
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• 2001

• Proceedings of the Korean Nuclear Society Conference
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• 2001.10a
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• pp.277.1-277
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• 2001

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2003.11a
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• pp.373-378
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• 2003

As a part of assessment of the structural material for the molten salt handling system, corrosion behavior of austenitic alloys, Fe-base and Ni-base in the molten salt of $LiCl-Li_2O_2$ was investigated in the range of temperature; 650~$725^{\circ}C$, time; 24- 168h, $Li_2O$; 3wt%, mixed gas; Ar-10%$O_2$. In the molten salt of $LiCl-Li_2O_2$, Ni-base alloys showed higher corrosion resistance than Fe-base alloys. Fe-base alloy with low Fe and high Ni contents exhibited better corrosion resistance. The scales of $Cr_2O_3$, $FeCr_2O_4$ on Fe-base alloys were showed, and $Cr_2O_3$, $NiFe_2O_4$ on Ni-base alloys were also showed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.12
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• pp.1415-1420
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• 2014

Super-critical $CO_2$ ($S-CO_2$) Brayton cycle has been considered to replace the current steam Rankine cycle in Sodium-cooled Fast Reactor (SFR) in order to improve the inherent safety and thermal efficiency. Several austenitic alloys are considered as the structural materials for high temperature $S-CO_2$ environment.. Microstructural change after long-term exposure to high temperature $S-CO_2$ environment could affect to the mechanical properties. In this study, candidate materials (austenitic stainless steels and Alloy 800HT) were exposed to $S-CO_2$ to assess oxidation resistance and the change in tensile properties. Loss of ductility was observed for some austenitic stainless steels even after 250 h exposure. The contribution of $S-CO_2$ environment on such changes was analyzed based on the characterization of the surface oxide and carburization of the materials in which 316H and 800H showed different oxidation behaviors.

• Korean Journal of Metals and Materials
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• v.46 no.4
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• pp.209-216
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• 2008

Super austenitic stainless steels shows the high PRE (Pitting Resistance Equivalent) number and the good corrosion resistance. This work controlled the Co contents in Fe-31Cr-1.7Mo-27Ni-0.25N alloys to elucidate the effect of cobalt contents on the biocompatibility and corrosion resistance. Increasing Co contents, the hardness of the annealed alloys tends to be reduced. In aged alloys, cobalt decreased the increments of hardness by aging treatment. Cobalt decreased the critical pitting temperature (CPT) in 6% $FeCl_3$ + 1% HCl solution, but improved the anodic polarization behavior in Hanks' balanced salt solution and artificial saliva solution. Repassivation rate in artificial body solutions was improved by increasing cobalt contents, but didn't show the linear relationship to PRE number of the alloys. The experimental alloys showed the non-cytotoxicity because of its high corrosion resistance.

• Journal of the Korean Magnetics Society
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• v.3 no.4
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• pp.277-283
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• 1993

The temperature dependence of DC magnetic susceptibilities of three austenitic Fe-Cr-Ni stainless alloys were measured in the temperature range of 4.2 and 300 K. Two alloys support a general magnetic description of austen-itic stsinless steels in terms of a two-magnetic-phase (spin glass + superparamagnetic cluster) model and one alloy shows magnetic double transition phenomena. Also this study shows that incressing the Ni/Cr ratio in Fe-Cr-Ni alloys causes a increase of the DC susceptibility peak value and a decrease of the magnetic transition temperature.

• Journal of Welding and Joining
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• v.16 no.1
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• pp.114-124
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• 1998

The effect of matrix phase (austenite, pearlite, martensite) on the low stress abrasion resistance in the chromium-carbide-type high Cr white iorn hardfacing weld deposites has been investigated. In order to examine matrix phase, a series of alloys with different matrix phase by changing the ratio of Cr/C system by heat treatment were employed. The alloys were deposited twice on a mild steel plate using self-shielding flux cored arc welding process. The low stress abrasion resistance of the alloys against sands was measured by the Dry Sand/Rubber Wheel Abrasion Test(RWAT). Even though formation of pearlite phase in the matrix showed higher hardness than that of austenite, there was no observable difference in wear resistance between the pearlite and austenite phase for the same amount of chromium-carbide in the matrix. On the other hand, the formation of martensitic phase,, from heat treated austenitic alloys (high content of Cr), enhanced wear resistance due to its fine secondary precipitates.

• Journal of the Korean Society for Heat Treatment
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• v.11 no.4
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• pp.274-282
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• 1998

The effect of Al addition on the fatigue properties of austenitic Fe-25Mn-Al-0.5C steels was studied. When Al was not added to the Fe-25Mn 0.5C steel, the strain induced ${\varepsilon}$ martensites, deformation twins and slip bands were formed during fatigue deformation. When 2wt% of Al was added to the steel, the deformation twins and slip bands were formed during fatigue deformation. When 5wt% of Al was added, only slip bands were formed. In low cycle fatigue test, the alloys containing 0wt% and 2wt%Al showed the cyclic hardening due to ${\varepsilon}$ martensites and deformation twins, resulting in shorter fatigue lives than the alloy containing 5wt%Al. In fatigue crack propagation test, the alloy without Al showed the highest crack propagation rate. The fracture surface of the alloy without Al was flat, whereas that of the alloy with 2% or 5%Al was rough. The ${\Delta}K_{th}$, values of the alloys with 0%, 2% and 5%Al were 16, 17.5, and $20.5MPam^{1/2}$, respectively.