Hot corrosion of MCrAlY coatings in sulphate and SO2 environment at 900 °C: Is SO2 necessarily bad?

SURFACE & COATINGS TECHNOLOGY

卷:261

Article

Yuan, Kang¹  Peng, Ru Lin¹  Li, Xin-Hai²  Talus, Annika³  Johansson, Sten¹  Wang, Yan-Dong⁴ 

[1] Linkoping Univ, Dept Management & Engn, SE-58183 Linkoping, Sweden

[2] Siemens Ind Turbomachinery AB, SE-61283 Finspang, Sweden

[3] Swerea KIMAB, Kista 16407, Sweden

[4] Univ Sci & Technol Beijing, Beijing 100083, Peoples R China

关键词: Hot corrosion;    Basic fluxing;    MCrAlY;    SO2;    Alumina;   

DOI  :  10.1016/j.surfcoat.2014.11.065

来源: Elsevier

【 摘 要 】

MCrAlY coatings can be corroded due to the basic fluxing (type-I hot corrosion) of the supposed-to-be protective alumina scale in a molten sulphate environment. In this study, two MCrAlY coatings, coating A (10 wt.% Al, 20 wt.% Cr) and coating B (7 wt.% Al, 28 wt% Cr), were tested in 48-hour cycles at 900 degrees C in a sodium potassium sulphate environment with and without SO2 (500 ppm). The aim was to study the effect of SO2 at the typical type-I-hot-corrosion temperature-900 degrees C. The results showed that the corrosion behavior of the MCrAlY coatings depended not only on the coating composition but also on the corrosion environment. It was found that in coating A alumina scale was more resistant in the sulphate-plus-SO2 condition than that in the sulphate-only condition. Such phenomenon indicated a beneficial effect of SO2. On Coating B, however, mixed oxide layers, consisting of alumina and other oxides and sulfides, formed after a certain number of cycles in the sulphate environments with or without SO2 gas. In this coating, the addition of SO2 in the sulphate environment promoted the formation of non-dense chromia oxides which may form from oxidation of Cr-sulfides. (C) 2014 Elsevier B.V. All rights reserved.

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