• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.373-378
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• 2000

The heat resistant material, in service, may experience static loading, cyclic loading, or a combination of two. An experimental study of crack growth behavior of STS 316L austenitic stainless steel under fatigue, and creep-fatigue loading conditions were carried out on compact tension specimens at various tensile hold times. In the crack growth experiments under hold times. In the crack growth experiments under hold time loading conditions, tensile hold times were ranged from 5 seconds to 100 seconds and its behavior was characterized using the $\Delta$K parameter. The crack growth rates generally increase with increasing hold times. However in this material, the trend of crack growth rates decreases with increasing hold times for short hold time range relatively. It is attributed to a decline in the cyclic crack growth rate as a result of blunting at the crack tip by creep deformation. The effect of grain size on the creep behavior of STS 316L was investigated. Specimens with grain size of 30, 65 and 125${\mu}{\textrm}{m}$ were prepared through various heat treatments and they were tested under various test conditions. The fracture mode of 316L changed from transgranular to intergranular with increasing grain size.

• Korean Journal of Materials Research
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• v.27 no.10
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• pp.552-556
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• 2017

Evaluation of the durability and stability of materials used in power plants is of great importance because parts or components for turbines, heat exchangers and compressors are often exposed to extreme environments such as high temperature and pressure. In this work, high-temperature corrosion behavior of 316 L stainless steel in a carbon dioxide environment was studied to examine the applicability of a material for a supercritical carbon dioxide Brayton cycle as the next generation power plant system. The specimens were exposed in a high-purity carbon dioxide environment at temperatures ranging from 500 to $800^{\circ}C$ during 1000 hours. The features of the corroded products were examined by optical microscope and scanning electron microscope, and the chemical compound was determined by x-ray photoelectron spectroscopy. The results show that while the 316 L stainless steel had good corrosion resistance in the range of $500-700^{\circ}C$ in the carbon dioxide environment, the corrosion resistance at $800^{\circ}C$ was very poor due to chipping the corroded products off, which resulted in a considerable loss in weight.

• Korean Journal of Materials Research
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• v.25 no.6
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• pp.293-299
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• 2015

In this study, nitrogen ions were implanted into STS 316L austenitic stainless steel by plasma immersion ion implantation (PIII) to improve the corrosion resistance. The implantation of nitrogen ions was performed with bias voltages of -5, -10, -15, and -20 kV. The implantation time was 240 min and the implantation temperature was kept at room temperature. With nitrogen implantation, the corrosion resistance of 316 L improved in comparison with that of the bare steel. The effects of nitrogen ion implantation on the electrochemical corrosion behavior of the specimen were investigated by the potentiodynamic polarization test, which was conducted in a 0.5 M $H_2SO_4$ solution at $70^{\circ}C$. The phase evolution and texture caused by the nitrogen ion implantation were analyzed by an X-ray diffractometer. It was demonstrated that the samples implanted at lower bias voltages, i.e., 5 kV and 10 kV, showed an expanded austenite phase, ${\gamma}_N$, and strong (111) texture morphology. Those samples exhibited a better corrosion resistance.

• Journal of the Korean institute of surface engineering
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• v.41 no.1
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• pp.38-42
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• 2008

316L stainless steel welding tube was electrolytically polished and the inner surface characteristics of the tube were tested. Electro-polishing variables such as current, voltage, concentration of electrolyte and electropolishing time were changed to seek for optimum condition. These makes a optimum conditions for the electro-polishing as 4000 A, 9 V, 1.7 specific gravity of electrolyte, and 30 minute of electro-polishing time. It makes the surface roughness as Ra < $0.25{\mu}m$. XPS test resulted as the ratio of CrO/FeO equals or more to 3/1. AES test resulted as the thickness of CrO film of $38{\AA}$. DTA test resulted as the tube did not react with $N_2,\;H_2\;and\;O_2$ gas below 1073K. As summarize above results, the electro- polished 316L stainless steel welding tube satisfied the conditions to apply as a pipeline for semi- conductor production facility and clean room.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.4
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• pp.333-342
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• 2004

Tensile and low cycle fatigue (LCF) tests on prior cold worked 316L stainless steel were carried out at various temperatures from room temperature to 650$^{\circ}C$. At all test temperatures, cold worked material showed the tendency of higher strength and lower ductility compared with those of solution treated material. The embrittlement of material occurred in the temperature region from 300$^{\circ}C$ to 600$^{\circ}C$ due to dynamic strain aging. Following initial cyclic hardening for a few cycles, cycling softening was observed to dominate until failure occurred during LCF deformation, and the cyclic softening behavior strongly depended on temperature and strain amplitude. Non-Masing behavior was observed at all test temperatures and hysteresis energy curve method was employed to describe the stress-strain hysteresis loops at half$.$life. The prediction shows a good agreement with the experimental results.

• Korean Journal of Metals and Materials
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• v.46 no.12
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• pp.817-822
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• 2008

Metal matrix composite (MMC) materials having low electrical contact resistance based on 316L stainless steel (STS) matrix alloy with $ZrB_2$ particles were fabricated for PEMFC (Polymer Electrolyte Membrane Fuel Cell) separator by powder metallurgy (PM). The effects of the boride particle addition into the matrix alloy on microstructure, surface morphology, and interfacial contact resistance (ICR) between the samples and gas diffusion layer (GDL) were investigated. Both conventional and PM 316L STS samples showed high ICR due to the existence of non-conductive passive film on the alloy surface. The addition of the boride particles, however, remarkably reduced ICR of the samples. SEM observation revealed that the boride particles were protruded out of the matrix surface and particle density existing on the surface increased with increasing the boride content, causing increase of the total contact area between the conductive particles and GDL. ICR of the samples also decreased with increasing the boride content resulted from the increased contact area.

• Korean Journal of Metals and Materials
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• v.49 no.7
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• pp.515-521
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• 2011

Small punch creep testing has received attention due to the convenience of using smaller specimens than those of conventional uniaxial creep tests, which enables creep testing on developing or currently operational components. However, precedent studies have shown that it is necessary to consider friction between the punch and specimen when computing uniaxial equivalent stress from a finite element model. In this study, small punch creep behaviors of AISI 316L stainless steel, which is widely used in high temperature-high pressure machineries, have been compared for the two different ceramic balls such as $Si_3N_4$ and $Al_2O_3$. The optimal range of the friction coefficient is 0.4~0.5 at $650^{\circ}C$ for the best fit between experimental and simulation data of AISI 316 L stainless steel. The higher the friction coefficient, the longer the creep rupture time is. Therefore, the type of ceramic ball used must be specified for standardization of small punch creep testing.

• Corrosion Science and Technology
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• v.21 no.4
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• pp.300-313
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• 2022

Interest in polymer electrolyte fuel cell is growing to replace fossil fuels. In particular, in order to reduce the cost and volume of the fuel cell, research on a metallic bipolar plate is being actively conducted. In this research, investigated the effects of temperature and chloride concentration on the electrochemical characteristics and damage behavior of 316L stainless steel in an accelerated solution simulating the cathodic operating condition of PEMFC(Polymer electrolyte membrane fuel cell). As a result of the experiments, the corrosion current density, damage size, and surface roughness increased as the temperature and chloride concentration increased. In particular, the temperature had a significant effect on the stability of the oxide film of 316L stainless steel. In addition, it was described that the growth of the pit was affected by the chloride concentration rather than the temperature. As a result of calculating the corrosion tendency to compare the pitting corrosion rate and the uniform corrosion rate, the uniform corrosion tendency became larger as the temperature increased. And the effects of chloride concentration on corrosion tendency was different according to temperature.

• Corrosion Science and Technology
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• v.22 no.1
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• pp.55-63
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• 2023

The aim of this study was to propose a multiple linear regression (MLR) equation to predict ultimate tensile strength (UTS) of 316L stainless steel with unspecified pit corrosion. Tensile specimens with pit corrosion were prepared using a potentiostatic acceleration test method. Pit corrosion was characterized by measuring ten factors using a confocal laser microscope. Data were collected from 22 tensile tests. At 85% confidence level, total pit volume, maximum pit depth, mean ratio of surface area, and mean area were significant factors showing linear relationships with UTS. The MLR equation using these three significant factors at a 85% confidence level showed considerable prediction performance for UTS. Determination coefficient (R²) was 0.903 with training and test data sets. The yield strength ratio of 316L stainless steel was found to be around 0.85. All specimens with a pit corrosion presented a yield ratio of approximately 0.85 with R² of 0.998. Therefore, pit corrosion did not affect the yield ratio.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.19 no.1
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• pp.11-19
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• 2023

Additive manufacturing technology, called as 3D printing, is one of fourth industrial revolution technologies that can drive innovation in the manufacturing process, and thus should be applied to nuclear industry for various purposes according to the manufacturing trend change in the future. In this paper, we performed tensile tests of 3D printed stainless steel 316L as-built specimens manufactured by two types of technology; DED (Directed Energy Deposition) and PBF (Powder Bed Fusion). Their mechanical properties (tensile strength, yield strength, elongation and reduction of area) were compared. As a result of comparison, the mechanical properties of the PBF specimens were slightly better than those of DED specimens. In the same additive type of specimens, the tensile and yield strength of specimens in the X and Y direction were higher than those in the Z direction, but the elongation and ROA were lower.