Papers by Keyword: Cyclic Oxidation

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Authors: Julien Sniezewski, Yannick Le Maoult, Philippe Lours
Abstract: Based on a coupled numerical and experimental approach, the design and implementation of an in situ thermal-gradient-controlled cyclic oxidation test, dedicated to the investigation of the TGO and TBC spallation, is presented. The influence of the specimen through thickness thermal gradient as well as the benefits of the video real-time monitoring of the cooling phase of an oxidation test is discussed in the case of the spallation of an alumina scale grown on FeCrAl alloys.
Authors: Y.P. Jacob, V.A.C. Haanappel, Eric Caudron, Henri Buscail, M.F. Stroosnijder
Authors: L. Tan, Kumar Sridharan, T.R. Allen
Abstract: Grain boundary engineering (GBE) was employed to improve the oxide exfoliation resistance and mitigate oxide growth by optimizing the grain boundary character distribution. Studies were performed on alloys of Incoloy 800H and Inconel 617. Alloys 800H and 617 were selected due to their potential applications for the Generation IV nuclear power systems. The effect of GBE on the corrosion response was evaluated using supercritical water exposure tests and cyclic oxidation tests. The microstructure of the tested samples was analyzed by means of optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, electron backscatter diffraction, and gravimetry. The effects of thermal expansion mismatch and Cr volatilization on the corrosion response are discussed.
Authors: Chang Liang Wang, Chun Gen Zhou, Sheng Kai Gong, Hui Bin Xu
Abstract: The cyclic oxidation of thermal barrier coating (TBC) specimens consisting of nickel-base superalloy, low pressure plasma sprayed Ni-24Cr-6Al-0.7Y (wt.%) bond coatings and air plasma sprayed 7.5 wt.% yttria stabilized zirconia top coatings was studied at 1050°C in air, (air + 5%H2O), O2 and (O2 + 5%H2O) respectively. The oxidation kinetics of the TBC in each test environment accords with parabolic law at the initial stage and obeys almost liner law at the final stage. The cyclic oxidation life of the TBC is 500h (1h/cyc) in O2 and (O2 + 5%H2O) and 900 h in air and (air + 5%H2O). The SEM observations indicated the oxide formed along the bond coat and top coat interface after failure at 1050°C in different environments are all consisted of Al2O3, Ni(Al,Cr)2O4, NiO and Cr2O3.
Authors: Yi Qi Wang, W.K. Joo, Chae Sil Kim, Jung I. Song
Abstract: High-temperature oxidation resistance of 7 wt.%Y2O3-ZrO2 thermal barrier coatings (TBCs) irradiated by high-intensity pulsed ion beam (HIPIB) has been investigated in a cyclic oxidation condition at 1050 °C ×1 h. The ceramic coating of a tetragonal ZrO2 phase structure was prepared on GH33 superalloy substrates with a NiCoCrAlY bond coat by using electron-beam physical-vapor deposition (EB-PVD). The ceramic coating is composed of columnar grains forming dense clusters spacing with several-μm gaps among grain clusters. The characteristics of the columnar grains disappeared after HIPIB irradiation at the ion current densities of 100-200 A/cm2, and the irradiated surface presented a smoothed, densified feature after the remelting and ablation due to the HIPIB irradiation. The thickness of the densified layer is about 1 μm. After oxidation with 15 cycles at 1050 °C ×1 h, the oxidation kinetics curves of the as-deposited and irradiated TBCs showed a parabolic shape. The weight gain of original sample is about 0.8-0.9 mg/cm2, while the values of the HIPIB-irradiated TBCs decreased to some extent. The lowest weight gain is obtained for the irradiated TBCs at 200 A/cm2 with one shot, being 0.3-0.4 mg/cm2, and those at 100 A/cm2 have a medium weight gain of 0.6-0.7 mg/cm2. The cross-sectional morphologies of HIPIB-irradiated TBCs show less oxidation of the NiCoCrAlY bonding layer, with a thinner thermally grown oxide (TGO) layer. The morphology observation is consistent with the results of cyclic oxidation test. It is found that the inward diffusion of oxygen through TBCs can be significantly impeded by the densified top layer by the HIPIB irradiation, thus limiting the oxidation of the bonding layer, improving the overall oxidation resistance of the irradiated TBCs.
Authors: Małgorzata Garbiak, Pawel Kaczmarek
Abstract: The oxidation behaviour of niobium and titanium enriched, heat resistant cast steel 30Ni-18Cr has been evaluated under cyclic conditions. Cyclic testing was carried out in the air, at temperature of 800, 900 and 1000°C. The alloys underwent oxidation in 5 cycle tests. Characterization of the corrosion products was performed using SEM and X-ray examinations. The cross section and the surface of tested alloys were examined. It has been found that the oxidation resistance of cast steel 30Ni-18Cr in thermal cycling is higher when niobium or especially titanium are added to chemical composition of the alloy. The formation of scale rich in titanium oxides TiO2 was contributed to better oxidation behaviour.
Authors: James L. Smialek
Authors: F.J. Pérez, F. Pedraza, M.P. Hierro, M.C. Carpintero, C. Gómez
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