• Journal of the Korean institute of surface engineering
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• v.31 no.2
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• pp.73-80
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• 1998

The aim of this study is to develop sintered stainless steels (SSS) with good mechanical strength, wear resistance, and corrosion resistance by nitrogen ion implantation on the Culated SSS surface. Stainless steel compacts containg Cu (2-10 wt%) were prepared by electroless Cu-pating method which results in the increased3 homogenization in alloying powder. Nitrogen ion implantation was carried out by using N2 gas as the ion source. Nitrogen ions were embedded by an acceleratol of 130keV with doese $3.0\times10^{17}\;ions/\textrm{cm}^2$ on the SSS at $25^{\circ}C$ in$2\times10^{-6}$ torr vacuum. The nitrogen ion implanted SSS obtained from anodic ploarization curves revealed higher corrosion potential than that of nitrogen ion unimplante one. And nitrogen ion implanted 316LSSS had good resistance to pitting corrosion due to the synergistic effect of Mo and N, and the inhibition of $NH_4\;^+$<\TEX>, against $CI^-$<\TEX>.

• Journal of the Korean Electrochemical Society
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• v.9 no.2
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• pp.70-76
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• 2006

Micro-droplet cell with free droplet as a micro-electrochemical technique has been limited to apply to electrochemical systems with high wetting properties such as an acidic solution and low grade stainless steels(Type 316L). By loading negative pressure to a droplet, control of droplet size, and use of hydrophobic gasket, the cell is modified to be allowed to use for electrochemical systems with high wetting properties. For giving the reliability of new cell, studies on local corrosion were conducted for three different systems-an acidic chloride solution and high chromium ferritic stainless steel, the other acidic chloride solution and type 316, and a neutral chloride solution and type 316. stainless steel. Firstly, the modified micro-droplet cell allows the anodic polarization curves in an acidic chloride solution to show the fact that the local corrosion of high chromium stainless steel near the $\alpha/\sigma$ interface is due to the Cr depleted zone. Secondly, the local anodic polarization test of type 316 L in the other acidic chloride solution can be successfully conducted in the cell. Furthermore, the local polarization curves help elucidating the corrosion of type 316 with $\delta-ferrite$ phase. Finally, the polarization curves of type 316 L in a neutral chloride solution indicates that the factor affecting the pitting corrosion resistance was inclusions rather than $\delta-ferrite$.

• Nuclear Engineering and Technology
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• v.48 no.6
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• pp.1376-1386
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• 2016

This study investigated the loading rate effect on the fracture resistance under cyclic loading conditions to understand clearly the fracture behavior of piping materials under seismic conditions. J-R fracture toughness tests were conducted under monotonic and cyclic loading conditions at various displacement rates at room temperature and the operating temperature of nuclear power plants (i.e., $316^{\circ}C$). SA508 Gr.1a low-alloy steel and SA312 TP316 stainless steel piping materials were used for the tests. The fracture resistance under a reversible cyclic load was considerably lower than that under monotonic load regardless of test temperature, material, and loading rate. Under both cyclic and monotonic loading conditions, the fracture behavior of SA312 TP316 stainless steel was independent of the loading rate at both room temperature and $316^{\circ}C$. For SA508 Gr.1a lowalloy steel, the loading rate effect on the fracture behavior was appreciable at $316^{\circ}C$ under cyclic and monotonic loading conditions. However, the loading rate effect diminished when the cyclic load ratio of the load (R) was -1. Thus, it was recognized that the fracture behavior of piping materials, including seismic loading characteristics, can be evaluated when tested under a cyclic load of R = -1 at a quasistatic loading rate.

• Journal of Welding and Joining
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• v.35 no.1
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• pp.79-88
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• 2017

The effect of residual metallic sodium on the solidification cracking susceptibility of type 316FR stainless steel was investigated via transverse-Varestraint tests. And a solidification brittle temperature range (BTR) of type 316FR stainless steel was 37 K. However, the BTR expanded from 37 to 67 K, as the amount of metallic sodium at the specimen surface increased from 0 to $7.99mg/cm^2$. Microstructural observation of the weld metal suggested that metallic sodium existed in the weld metal, including in the cell boundaries, during welding solidification. Thermodynamic calculations suggested that sodium expanded the temperature range of solidliquid coexistence during welding solidification of the steel weld metal. Therefore, the increased solidification cracking susceptibility (i.e., expansion of the BTR) in the residual sodium environment was attributed to enhanced segregation of sodium during the welding solidification; this segregation, in turn, resulted in an expanded temperature range of solid-liquid coexistence.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1406-1411
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• 2005

The creep rupture data for type 316LN stainless steels were collected through literature survey or experimental data produced in KAERI. Using these data, polynomial equations for predicting creep life were obtained by Larson-Miller (L-M), Orr-Sherby-Dorn (O-S-D) and Manson-Haferd (M-H) etc. time-temperature parametric (TTP) methods. Standard error of estimate (SEE) values for the each parameter was obtained with different temperatures through the statistical process of the creep data. The results of L-M, O-S-D and M-H methods showed good creep-life prediction, but M-H method showed better agreement than L-M and O-S-D methods. Especially, it was found that SEE values of M-H method at $700^{\circ}C$ were lower than that of L-M and O-S-D methods.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.6
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• pp.709-715
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• 2006

The effects of thermal cycle condition and applied stress on the intergranular corrosion in austenitic 316 type stainless steels were investigated. Specimens were solution-treated at 1100$^{\circ}C$ for one hour and then sensitized in the temperature range of $500{\sim}800^{\circ}C$ by holding $2{\sim}300s$ with a various applied stresses of $0{\sim}8kg/mm^2$. Degree of sensitization. DOS %, was measured through polarization curve by electrochemical DL-EPR test. Microstructural observations were also conducted DOS % increased with an increase of sensitization temperature and/or holding time. Increase of applied stress resulted in increase of DOS % and more corroded surface because of acceleration of intergranular corrosion and fine grain size due to the stress. Cr depleted zone near grain boundary was observed. The amount of depletion was profounded with an increase of sensitization temperature, holding time and applied stress. $M_{23}C_6$ carbides were precipitated discontinuously at grain boundary. However, its amount was relatively small in the thermal cycle condition of 800$^{\circ}C$, 300sec and 4kg/mm$^2$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.1 s.232
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• pp.74-80
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• 2005

A number of creep rupture data for type 316LN stainless steels were collected through literature survey or experimental data produced in KAERI. Using these data, polynomial equations for predicting creep life were obtained by Larson-Miller (L-M), Orr-Sherby-Dorn (O-S-D) and Manson-Haferd (M-H) parameters using time-temperature parametric (TTP) methods. Standard error of estimate (SEE) values for the each parameter was obtained with different temperatures through the statistical process of the creep data. The results of L-M, O-S-D and M-H methods showed good creep-life prediction, but M-H method showed better agreement than L-M and O-S-D methods. Especially, it was found that SEE values of M-H method at $700^{\circ}C$ were lower than that of L-M and O-S-D methods.

• Corrosion Science and Technology
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• v.3 no.5
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• pp.222-225
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• 2004

A portable RF HTS SQUID-based susceptometer was applied to the measurement of fatigue behavior for type 316L(N) stainless steel containing 0.04% to 0.15% nitrogen content. Strain-controlled low cycle fatigue (LCF) tests were conducted at RT and $600^{\circ}C$ in air an atmosphere, and the magnetic moments were measured after the fatigue test using HTS SQUID. The magnetic moment of an as-received sample is higher than that of a fatigued sample in all the temperature ranges irrespective of the nitrogen content. The fatigue life decreased with an increasing test temperature up to $500^{\circ}C$, but increased at $600^{\circ}C$. The change of the magnetic moments by LCF test is attributed to the stress induced micro defects.

• Corrosion Science and Technology
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• v.13 no.6
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• pp.224-232
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• 2014

Effect of pretreatments on the graphene coated bipolar plate of proton exchange membrane fuel cell(PEMFC) was investigated in simulated environments for PEMFC by using electrochemical measurement techniques. Interfacial contact resistance(ICR) between the graphene coated bipolar plate and the gas diffusion layer(GDL) was measured. The value of ICR decreased with an increase in compaction stress($20N/cm^2{\sim}220N/cm^2$). ICR of graphene coated bipolar plate was higher than that of bare 316L stainless steel. However, Potentiodynamic measurement results showed that the corrosion resistance of graphene coated bipolar plate was higher than that of bare 316L stainless steel. $H_2SO_4$ acid pretreatment was the most effective among various pretreatments. The lowest ICR and the corrosion current density were obtained when using $H_2SO_4$ solution pretreatment.

• Nuclear Engineering and Technology
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• v.53 no.3
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• pp.920-926
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• 2021

Capsules containing NaCl-MgCl₂ salt with 316L stainless steel or alloy N samples were irradiated in the Ohio State University Research Reactor for 21 nonconsecutive hours. A custom irradiation vessel was designed for this purpose, and details on its design and construction are given. Stainless steel samples that were irradiated during exposure had less corrosive attack than samples exposed to the same conditions without irradiation. Alloy N samples showed no significant effect of irradiation. This work shows a method for conducting in-reactor irradiation-corrosion experiments in static molten salts and presents preliminary data showing that neutron irradiation may decelerate corrosion of alloys in molten chloride salts.