Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7709675 | International Journal of Hydrogen Energy | 2017 | 13 Pages |
Abstract
Atmospheric plasma spray is employed to deposit Mn1.5Co1.5O4 (MCO) coatings onto T441 and porous 430L substrates respectively at room temperature and 400 °C. The coatings are then subjected to redox treatments to achieve a desirable gas tightness. The gas permeability, area specific resistance (ASR) and microstructure homogenization of MCO coatings are evaluated in different stages. The gas permeability of MCO coating deposited at 400 °C and exposed to redox treatments can be as low as â¼8.2 Ã 10â8 cm4 sâ1 gfâ1, which is essential for sufficient protection of metallic substrate against oxidation. The MCO-coated T441 without pre-reduction presents a nonuniform microstructure characterized by isolated precipitates rich in Co and dark matrix rich in Mn. In comparison, the MCO coating with 5 h pre-reduction presents a uniform and dense spinel structure. The ASR tests indicates that a homogeneous structure has contributed to an increase in the overall conductivity. While bare T441 shows a substantial increase in interfacial ASR during the 200 h test, MCO-coated T441 exhibites a high stability and a much lower ASR value of 13 mΩ cm2. Besides, the dense MCO coatings effectively inhibit the oxide scale growth and block outward diffusion of Cr during the oxidation tests. Cr-rich oxide scale formed at the MCO/T441 interface is less than 1.2 μm and no further migration of Cr was detected.
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Authors
Ying-Zhen Hu, Shu-Wei Yao, Cheng-Xin Li, Chang-Jiu Li, Shan-Lin Zhang,