• Journal of the Korean Society for Heat Treatment
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• v.12 no.1
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• pp.9-20
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• 1999

The effect of post oxidation, water-quenched after holding in air for 5~420 seconds or cooling or furnace cooling, on corrosion resistance and phase formation characteristics of the surface layer of SM20C and SM45C carbon steels after gas nirtrocarbursing in the $NH_3-5%CO_2-N_2$ gas atmosphere at $580^{\circ}C$ for 3hours is studied. The compound layers of two steels consist of ${\varepsilon}-Fe_{2-3}N$, ${\gamma}^{\prime}-Fe_4N$ and $Fe_3O_4$, phases, however, the quantity of ${\gamma}^{\prime}-Fe_4N$ phase increases for the furnace cooled specimen compared to that of air cooling specimen. With increasing $NH_3$ content in the gas mixture and also increasing the keeping time in the air after gas nitrocarburising, the ${\varepsilon}-Fe_{2-3}N$ phase of compound layer increases, while the decreased current density recognizing the improvement of corrosion resistance are shown. the passive current density of SM45C steel is lower than that of SM20C steel at the same nitrocarburising conditions.

• Journal of Korea Foundry Society
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• v.40 no.6
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• pp.135-145
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• 2020

Aluminum cast iron has excellent oxidation resistance, sulfurization resistance, and corrosion resistance. However, the ductility at room temperature is insufficient, and at temperatures above 600?, the strength drops sharply and practicality is limited. In the case of heat-resistant cast iron, high-temperature materials containing Cr and Ni account for 30 to 50% or more. However, these high-temperature materials are expensive. Aluminum heat-resistant cast iron is considered as a substitute for expensive heat-resistant materials. Oxidation due to the aging temperature and holding time conditions increases more in 0 wt.% Al-cast iron than in 2 and 4 wt.% Al-cast iron according to oxidized weight and gravimetric oxide layer thickness measurements. As a result of observing the cross-section of the oxide layer, it was found to contain 0 wt.% of Al-cast iron silicon oxide-containing SiO₂ or Fe₂SiO₄ oxide film. In cast iron containing aluminum, the thickness of the internal oxide layer due to aluminum increases as the aging temperature and retention time increase, and the amount of the iron oxide layer generated on the surface decreases.

• Journal of Korea Foundry Society
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• v.27 no.2
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• pp.72-76
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• 2007

Contact materials are widely used as electrical parts. Ag-Cd alloy has a good wear resistance and stable contact resistance. But the Cd exists as coarse oxide in alloy so it have an effect on mechanical properties badly. Moreover, the Cd is an injury material to environment. Nowadays, the use of Cd is strictly restricted. Because of these disadvantage, Ag-Sn-In alloy has been developed. In Ag-Sn-In alloy, the Sn : In ratio affects the internal oxidation properties, such as the formation of the oxide layer on the surface. In this work, we changed and optimized the Sn : In ratio variety for good internal oxidation properties. We have shown that a internal oxidation process did not fully completed when the Sn : In ratio is over 4 : 1 because of the Sn oxide layer at surface. The increase of In decelerates the formation of Sn oxide layer.

• The Korean Journal of Ceramics
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• v.5 no.1
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• pp.44-49
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• 1999

In order to improve the oxidation resistance of $Ti_3Al$, Ti-25at.%Al composites containing dispersed particles of 15wt.%SiC were prepared by a tubular mixing-spark plasma sintering method. The sintered composites had $Ti_3Al$, SiC, $Ti_5Si_3$ and TiC. The presence of $Ti_5Si_3$ and TiC indicates that some of SiC particles reacted with Ti to from more stable phases. From oxidation tests at 800, 900 and $1000^{\circ}C$ under 1 atm of pure oxygen, it was found that the oxidation rate of Ti3Al was effectively reduced by the addition of SiC. The scale was primarily composed of an outer $TiO_2$ layer having some $Al_2O_3 $islands, an intermediate relatively thick $Al_2O_3 $ layer, and an inner $TiO_2+Al_2O_3+SiO_2$ mixed layer. Beneath the scale, Kirkendall voids were seen.

• Journal of the Korean institute of surface engineering
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• v.29 no.2
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• pp.120-131
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• 1996

In order to improve the mechanical properties and the high temperature oxidation resistance, aluminizing was carried out at a temperature range between $850^{\circ}C$ and $1050^{\circ}C$. The pack cementation process was used to produce uniform layer. After each treatment, the microhardness and the characteristics of high temperature oxidation were tested to evaluate the properties of the aluminide layer. The aluminide layer consisted of FeAl above $1000^{\circ}C$, and $Fe_2Al_5$ below $900^{\circ}C$, and the mixed phase of FeAl and $Fe_2Al_5$ between 90$0^{\circ}C$ and $1000^{\circ}C$ in case of the mixture powder consisted of 5%Al+5%$NH_4Cl+90%AL_2O_3$. The microhardness of $Fe_2Al_5$ was obtained much as the twice as that of FeAl. As the aluminizing temperature and time increased, the thickness of aluminide increased. After aluminizing, the high temperature oxidation resistance was remarkably improved. The high temperature oxidation resistance of FeAl was superior to the resistance of high temperature oxidation of $Fe_2Al_5$.

• Nuclear Engineering and Technology
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• v.41 no.2
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• pp.163-170
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• 2009

In order to evaluate high-temperature oxidation behavior of the advanced alloy cladding under LOCA conditions, isothermal oxidation tests in steam were performed with cladding specimens prepared from high burnup PWR fuel rods that were irradiated up to 79 MWd/kg. Cladding materials were $M5^{(R)}$ and $ZIRLO^{TM}$, which are Nb-containing alloys. Ring-shaped specimens were isothermally oxidized in flowing steam at temperatures from 1173 to 1473 K for the duration between 120 and 4000s. Oxidation rates were evaluated from measured oxide layer thickness and weight gain. A protective effect of the preformed corrosion layer is seen for the shorter time range at the lower temperatures. The influence of pre-hydriding is not significant for the examined range. Alloy composition change generally has small influence on oxidation in the examined temperature range, though $M5^{(R)}$ shows an obviously smaller oxidation constant at 1273 K. Consequently, the oxidation rates of the high burnup $M5^{(R)}$ and $ZIRLO^{TM}$ cladding are comparable or lower than that of unirradiated Zircaloy-4 cladding.

• Korean Journal of Materials Research
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• v.17 no.3
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• pp.132-136
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• 2007

Oxidation resistance of sintered ${\beta}-FeSi_{2}$ was investigated at intermediate temperature range in air atmosphere. Fully dense and porous bodies of ${\beta}-FeSi_{2}$ samples were fabricated by using the Spark Plasma Sintering (SPS). They were annealed at $900^{\circ}C$ for 5days to obtain ${\beta}-FeSi_{2}$ phase. The bulk samples were oxidized at $800,\;900\;and\;950^{\circ}C$ in air atmosphere. The high temperature oxidation tests reveal that amorphous $SiO_{2}$ layer, similar to Si was formed and grew parabolically on ${\beta}-FeSi_{2}$. Accelerated oxidation is not observed as well as cracks and grain boundary oxidation. Granular ${\varepsilon}-FeSi$ was developed below the oxide layer as a result of oxidation of ${\beta}-FeSi_{2}$. Oxidation resistance of sintered ${\beta}-FeSi_{2}$ was excellent for high-temperature thermoelectric application.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.144-148
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• 1999

The relationship between oxidation and sliding wear behavior of Fe-28 at%. Al alloys with B2 ordered structure has been investigated. Sliding wear tests of the alloys have been carried out under various environmental conditions using a pin-on-disk wear tester. The wear rate of the ordered alloys in an oxygen atmoshpere was found to be much lower than in an oxygen atmosphere showed that Fe2O oxides formed on the wearing surface. The oxide layer prevented direct contact of the two mating materials and therefore improved wear resistance of the Fe-Al intermetallic alloy. It was found that the surface Al2O3 oxide layer which provides good oxidation resistance and improved mechanical properties broke down easily and didnot function properly as an oxidation barrier.

• Corrosion Science and Technology
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• v.7 no.4
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• pp.233-236
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• 2008

Halide-activated pack cementation was utilized to deposit B-doped silicide coating. The pack powders were consisted of $3Wt.c/oNH_4Cl$, 7Wt.c/oSi, $90Wt.c/oAl_2O_3+TiB_2$. B-doped silicide coating was consisted of two layers, an outer layer of $NbSi_2$ and an inner layer of $Nb_5Si_3$. Isothermal oxidation resistance of B-doped silicide coating was tested at $1250^{\circ}C$ in static air. B-doped silicide coating had excellent oxidation resistance, because continuous $SiO_2$ scale which serves as obstacle of oxygen diffusion was formed after oxidation.

• The Korean Journal of Ceramics
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• v.5 no.2
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• pp.115-118
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• 1999

Carbon composites with $MoSi_2$ dispersion were prepared by hot-pressing at $1700^{\circ}C$ under 30 MPa for 1 h using polysilazance as binding material. The composites consisted of C, $Mo_{4.8}Si_3C_{0.6}$ and SiC. Bulk density and porosity of the carbon composites with 10 vol% $MoSi_2$ was 1.8g.$\textrm{cm}^{-3}$ and 34%, respectively. This composite was oxidized about 0.05mm from the surface of the carbon composite after oxidation test at $1500^{\circ}C$ for 10h in air. Formation of the $SiO_2$ glass layer was observed by SEM. When this composite suffered damage in the coating layer, it had hardly farther oxidation because of its self-repairing property. The composite prepared in this study indicated good oxidation resistance.