Slurry aluminide coatings were elaborated on IN-800HT and pure Ni. After spray of the slurry, the annealing treatment was performed in Ar(g) at 400 8C for 3 h, then by 650 8C for up to 5 h. This brought about major Al diffusion into the substrate following parabolic kinetics. After 5 h at 650 8C, stabilization of the B2-(Fe,Ni)Al and b-NiAl coatings in, respectively, the IN-800HT and pure Ni substrates was achieved at 1100 8C for 1 h. The coatings were then exposed to air, argon and steam for 2000 h at 650 8C.The Al diffusion profiles were acquired by EDS analyses and were equivalent in Ar(g) and steam whereas significant consumption of Al occurred in the external coatings exposed to air. Five hundred hours annealing steps were thus carried out in Ar(g) to gather the Al composition profiles with exposure time till 2000 h to model diffusion and to estimate lifetime. These were performed using a numerical model and the so-called inverse problem solution, which appeared to be unsuccessful due to the insufficient quality of experimental data expressed through a quantitative criterion ("informativity"). Some recommendations are proposed to increase the accuracy of the assessment of the model parameters.
The results of analysis and forecasting of the radioactive aerosols (RA) spread in the New Safe Confinement (NSC) under various conditions are presented. The conditions for the commissioning NSC, operation, dismantling of the OS (early dismantling) and removal of radioactive waste from the central hall of the OS are considered. Such analysis and forecasting was performed using computer CFD (computational fluid dynamics) model of the OS and NSC. The model takes into account sedimentation, accumulation and secondary dust emissions on the surfaces under the NSC, which allows obtaining distributions of surface contamination and determine the places of the highest contamination. References 5, tables 1, figures 5.
The present work is devoted to the estimation of the coating lifetime by modeling aluminum diffusion in a slurry‐applied coating on P92 at 650 °C employing the computational and experimental approach. This coating protects ferritic steels from both steam and fireside corrosion on new coal‐fired power plants operating under super‐supercritical steam parameters. The computer model of the diffusion and oxidation based on a numerical solving of the differential equations of diffusion was developed, and its unknown parameters, namely the concentration‐dependent aluminum diffusion coefficient, were identified from relatively short‐term experimental tests up to 8000 h using the inverse problem solution approach. The model was then used for coating lifetime estimation and furthermore for obtaining the dependency of the lifetime on the initial coating thickness and on the critical beneath‐surface aluminum content defined for the estimation. The resulting simulated concentration profiles were compared with experimental data yielding an adequate fit.
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