• Title/Summary/Keyword: oxidation behavior

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Fracture Behavior of Graphite Material at Elevated Temperatures Considering Oxidation Condition (산화환경을 고려한 흑연 내열재의 고온파단특성)

  • Choi, Hoon Seok;Kim, Jae Hoon;Oh, Kawng Keun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.11
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    • pp.1091-1097
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    • 2015

  • Graphite material has been widely used for making the rocket nozzle throat because of its excellent thermal properties. However, when compared with typical structural materials, graphite is relatively weak with respect to both strength and toughness, owing to its quasi-brittle behavior, and gets oxidized at $450^{\circ}C$. Therefore, it is important to evaluate the thermal and mechanical properties of this material for using it in structural applications. This study presents an experimental method to investigate the fracture behavior of ATJ graphite at elevated temperatures. In particular, the effects of major parameters such as temperature, loading, and oxidation conditions on strength and fracture characteristics were investigated. Uniaxial compression and tension tests were conducted in accordance with the ASTM standard at room temperature, $500^{\circ}C$, and $1,000^{\circ}C$. Fractography analysis of the fractured specimens was carried out using an SEM.

  • https://doi.org/10.3795/KSME-A.2015.39.11.1091 인용 PDF KSCI

Effect of Fe on the High Temperature Oxidation of Ti-Al-Fe Alloys (Ti-Al-Fe계 합금의 고온산화거동에 미치는 Fe의 영향)

  • Yoon, Jang-Won;Hyun, Yong-Taek;Kim, Jeoung-Han;Yeom, Jong-Taek;Yoon, Seog-Young
    • Korean Journal of Materials Research
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    • v.21 no.7
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    • pp.357-363
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    • 2011

  • In this paper, high temperature oxidation behavior of newly developed alloys, Ti-6Al-4Fe and Ti-6Al-1Fe, is examined. To understand the effect of Fe on the air oxidation behavior of the Ti-Al-Fe alloy system, thermal oxidation tests are carried out at $700^{\circ}C$ and $800^{\circ}C$ for 96 hours. Ti-6Al-4V alloy is also prepared and tested under the same conditions for comparison with the developed alloys. The oxidation resistance of the Ti-Al-Fe alloy system is superior to that of Ti-6Al-4V alloy. Ti-6Al-4V shows the worst oxidation resistance for all test conditions. This is not a result of the addition of Fe, but rather it is due to the elimination of V, which has deleterious effects on high temperature oxidation. The oxidation of the Ti-Al-Fe alloy system follows the parabolic rate law. At $700^{\circ}C$, Fe addition does not have a noticeable influence on the amount of weight gain of all specimens. However, at $800^{\circ}C$, Ti-6Al-4Fe alloy shows remarkable degradation compared to Ti-6Al-1Fe and Ti-6Al. It is discovered that the formation of $Al_2O_3$, a diffusion resistance layer, is remarkably hindered by a relative decrease of the ${\alpha}$ volume fraction. This is because Fe addition increases the volume fraction of ${\beta}$ phase within the Ti-6Al-xFe alloy system. Activities of Al, Ti, and Fe with respect to the formation of oxide layers are calculated and analyzed to explore the oxidation mechanism.

  • https://doi.org/10.3740/MRSK.2011.21.7.357 인용 PDF KSCI

Effect of KCl(s) and K2SO4(s) on Oxidation Characteristics of the 2.25Cr-1Mo Steel in 10%O2+10%CO2 Gas Environment at 650 ℃ (650 ℃의 10%O2+10%CO2 가스 환경에서 2.25Cr-1Mo강의 산화특성에 미치는 KCl(s)과 K2SO4(s)의 영향)

  • Jung, Kwang-Hu;Kim, Seong-Jong
    • Corrosion Science and Technology
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    • v.19 no.1
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    • pp.43-50
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    • 2020

  • In this study, the effects of KCl(s) and K2SO4(s) on the oxidation characteristics of 2.25Cr-1Mo steel were investigated for 500 h in 10O2 + 10CO2 (vol%) gas environmen at 650 ℃. Oxidation kinetics were characterized by weight gain, oxide layer thickness, and fitted models for the experiment data were proposed. The fitted models presented considerable agreement with the experimental data. The oxide layer was analyzed using the scanning electron microscope, optical microscope, and energy dispersive X-ray spectroscopy. The oxidation kinetics of 2.25Cr-1Mo steel with KCl and K2SO4 coatings showed significantly different oxidation kinetics. KCl accelerated the oxidation rate very much and had linear oxidation behavior. In contrast, K2SO4 had no significant effect, which had parabolic kinetics. The oxide layer was commonly composed of Fe2O3, Fe3O4, and FeCr2O4 spinel. KCl strongly accelerated the oxidation rates of 2.25Cr-1Mo steel in the high-temperature oxidation environment. Conversely, K2SO4 had little effect on the oxidation rates.

  • https://doi.org/10.14773/cst.2020.19.1.43 인용 PDF KSCI