Hot section components of gas turbines are exposed to a high operating temperature environment. To protect these components, thermal barrier coatings (TBC) are applied to their surfaces. Yttria-stabilized zirconia (YSZ), which is widely used as a TBC material, faces limitations at temperatures above 1200 °C. To mitigate these issues, research has focused on adding lanthanide rare earth oxides and tetravalent oxides to prevent the phase-transformation of the monoclinic phase in zirconia. This study investigated the effects of varying TiO2 content in Nd2O3 and Yb2O3 co-doped YSZ composites. Increasing TiO2 content effectively suppressed formation of the monoclinic phase and increased the thermal degradation resistance compared to YSZ in environments over 1200 °C. These findings will aid in developing more thermally stable and efficient TBC materials for application in high-temperature environments.

Stainless steel, a type of steel used for high-temperature parts, may cause damage when exposed to high temperatures, requiring additional coatings. In particular, the Cr2O3 product layer is unstable at 1000oC and higher temperatures; therefore, it is necessary to improve the oxidation resistance. In this study, an aluminide (Fe2Al5 and FeAl3) coating layer was formed on the surface of STS 630 specimens through Al diffusion coatings from 500oC to 700oC for up to 25 h. Because the coating layers of Fe2Al5 and FeAl3 could not withstand temperatures above 1200oC, an Al2O3 coating layer is deposited on the surface through static oxidation treatment at 500oC for 10 h. To confirm the ablation resistance of the resulting coating layer, dynamic flame exposure tests were conducted at 1350oC for 5–15 min. Excellent oxidation resistance is observed in the coated base material beneath the aluminide layer. The conditions of the flame tests and coating are discussed in terms of microstructural variations.

A literature review on the effects of high temperature and radiation on radiation shielding concrete in Spent Fuel Dry Storage is presented in this study with a focus on concrete degradation. The general threshold is 95℃ for preventing long-term degradation from high temperature, and it is suggested that the temperature gradient should be less than 60℃ to avoid crack generation in concrete structures. The amount of damage depends on the characteristics of the concrete mixture, and increases with the temperature and exposure time. The tensile strength of concrete is more susceptible than the compressive strength to degradation due to high temperature. Nuclear heating from radiation can be neglected under an incident energy flux density of 1010 MeV·cm-2·s-1. Neutron radiation of >1019 n·cm-2 or an integrated dose of gamma radiation exceeding 1010 rads can cause a reduction in the compressive and tensile strengths and the elastic moduli. When concrete is highly irradiated, changes in the mechanical properties are primarily caused by variation in water content resulting from high temperature, volume expansion, and crack generation. It is necessary to fully utilize previous research for effective technology development and licensing of a Korean dry storage system. This study can serve as important baseline data for developing domestic technology with regard to concrete casks of an SF (Spent Fuel) dry storage system.

노후화된 고온설비의 안정성 및 효율적인 운전조건을 확보하고, 고온부재의 취성파괴 방지를 위해서는 재질열화의 정량적 평가는 매우 중요하다. 그러나 현장실기에서 기계적 성질의 평가를 위한 대량의 시험편 채취는 거의 불가능하다. 따라서, 실기부재의 강도에 영향을 미치지 않는 범위에서 플랜트 구조물의 재질열화 평가를 비파괴적으로 검출 평가할 수 있는 새로운 시험방법들의 개발이 요구된다. 본 연구에서는 화력설비 부재의 다양한 탄소강을 대상으로 재질열화도 평가를 위한 전기화학적 양극분극시험법의 적용 가능성을 조사하였다. 또한 양극분극시험에 의한 재질열화평가 유효성을 조사하기 위해 전기화학적 시험결과를 입계부식시험결과와 비교.검토해 보았다.

고온.고압하에서 장시간 사용되는 고온부재용 구조물은 경년열화현상을 나타낸다 그러므로 구조물의 안정성 측면에서 재질열화의 정도를 정량적으로 평가하는 것이 중요하다. 그러나 실기 구조물에서 채취할 시험편의 크기와 수는 제한이 되기 때문에 새로운 비파괴적인 평가법이 요구되고 있다. 따라서 본 연구에서는 화력발전설비에 이용되는 탄소강과 페라이트강에 대한 열화도의 평가를 위해 입계부식법의 적용 가능성을 조사한다. 시험결과, 재질열화의 정도는 사용시간보다 사용온도에 더 큰 영향을 받았으며, Larson-Miller인자와 열화도([δDBTT]SP)사이의 관계는 선형적이었으나, 강종에 따라 다른 기울기를 보였다. 반면, 연성-취성천이온도 ([δDBTT]SP)와 격자절단비(Ni/No)와 관계는 강종에 무관하게 선형적인 비례관계를 나타내었다. 또한, [δDBTT]SP와 Ni/No 의 관계로부터 입계부식법은 페라이트계 강뿐만아니라 탄소강에 대해서도 유용한 재질열화 평가 방법임을 알 수 있었다.

Concrete has been recognized as a material which is resistant to the high temperature, but chemicophysical property of concrete is changed by the high temperature. So, mechanical properties of concrete may be reduced. Therefore, concrete is evaluated mechanical properties for safety inspection. However, research of ultrasonic pulse method is not much. Therefore, the purpose of this study is to Non-Destructive Test of 30, 70, 110MPa concrete exposed high temperature using ultrasonic pulse velocity.

Concrete has been recognized as a material which is resistant to the high temperature, but chemicophysical property of concrete is changed by the high temperature. So, mechanical properties of concrete may be reduced. Therefore, concrete is evaluated mechanical properties for safety inspection. However, research of ultrasonic pulse method is not much. Therefore, the purpose of this study is to Non-Destructive Test of 30, 70, 110MPa concrete exposed high temperature using ultrasonic pulse velocity.