Search

This paper aims at investigating the microstructure and phases evolution of single crystal superalloy/high temperature protective coating during high temperature static oxidation, and exploring the influence of element interdiffusion behaviour on microstructure and phase evolution of the single crystal superalloy substrate. A NiCoCrAlY high-temperature protective coating was deposited on the Ni-based single-crystal superalloy by low-pressure plasma spraying technology. The coated samples were subjected to static oxidation for 200 h at a constant temperature of 1100 &deg, C. Scanning electron microscope, energy dispersive spectrometer and X-ray diffraction were used to characterise the microstructure and phase after interdiffusion between the coating and the substrate at high temperature. The results showed that a dense thermally grown oxide layer was formed on the surface of the NiCoCrAlY coating after oxidation for over 100 h. The only interdiffusion zone was formed after oxidation for 50 h, while both interdiffusion zone and secondary reaction zone could be observed after oxidation for over 100 h. The thickness of interdiffusion zone and secondary reaction zone is increased with the extension of oxidation time, and the grain growth of topological close-packed phase in the secondary reaction zone is found. Al, Cr and Co in the coating diffuse from the coating to the substrate, while Ni and refractory materials like Ta, Mo, Re and W diffuse from the coating to the substrate. The interdiffusion of coating and substrate leads to the instability of &gamma, /&gamma, &prime, phase in the substrate, which finally results in the formation of W, Re and Cr-rich needle-like topological close-packed phase in the substrate.

Given the current situation that there is no parallel experiment of multiple stacks in China, this paper uses a fuel cell test platform independently designed and produced by a company to study the performance of three fuel cells. This article describes the construction of the experimental test platform and the multi-stack load-up experiment. The experimental results show that the power generation of the three fuel cells is almost the same, which are 9475W, 9385W, and 9512W. When carrying out multi-stack load-up experiments, it was found that as the number of stacks increased, the voltage efficiency continued to decrease. The Analysis revealed that the parallel gas supply method caused uneven gas distribution, which caused some fuel cells to be in a state of hydrogen deficiency. This article proposes amendments to this problem.