In situ synthesis of alpha-alumina layer on thermal barrier coating for protection against CMAS (CaO-MgO-Al2O3-SiO2) corrosion

Author:

Zhang, Xiao-feng  Zhou, Ke-song  Xu, Wei  Chen, Bo-yu  Song, Jin-bing  Liu, Min  

Journal:

SURFACE & COATINGS TECHNOLOGY

Issue Date:

2015

Abstract(summary):

In general, it is accepted that thermal barrier coating (TBC) with good CMAS (CaO-MgO-Al2O3-SiO2) corrosion resistance has long lifetime. A columnar Al film was firstly deposited in this work at the top of 7 wt.% yttria-stabilized zirconia (7YSZ) TBC by magnetron sputtering. Then a vacuum treatment of Al-deposited TBC was carried out at 700 degrees C for 1 h and 900 degrees C for 5 h. An alpha-Al2O3 layer was in situ synthesized at the top of 7YSZ TBC through the reaction of Al and ZrO2 after vacuum heat treatment. The CMAS corrosion resistance of as-sprayed TBC and treated TBC was compared after isothermal test of 1200 degrees C for 24 h. The results indicated that the Al-deposited TBC after vacuum heat treatment has better CMAS corrosion resistance than the as-sprayed TBC. Two mechanisms are considered to contribute to the protective effect of in situ synthesized alpha-Al2O3 layer: the first is alpha-Al2O3 partially filling existed open pores and cracks in the top 7YSZ coating to hinder the penetration of molten CMAS; and the second is alpha-Al2O3 a reacted with CMAS forming CaAl2Si2O8 and MgAl2O4 that play the role in inhibiting further infiltration of CMAS. (C) 2014 Elsevier B.V. All rights reserved.

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