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A chromia forming thermal barrier coating system
Author(s) -
Taylor M.P.,
Evans H.E.,
Gray S.,
Nicholls J.R.
Publication year - 2011
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.201005881
Subject(s) - chromia , thermal barrier coating , spallation , materials science , corrosion , ceramic , superalloy , coating , oxide , metallurgy , layer (electronics) , gas turbines , cracking , composite material , alloy , mechanical engineering , physics , quantum mechanics , neutron , engineering
Abstract Conventional thermal barrier coating (TBC) systems consist of an insulating ceramic topcoat, a bond coat for oxidation protection and the underlying superalloy designed to combat the oxidising conditions in aero‐ and land‐based gas turbines. Under high‐temperature oxidation, the use of an alumina forming bond coat is warranted, thus all current TBC systems are optimised for the early formation of a dense, protective thermally grown oxide (TGO) of alumina. This also offers protection against Type I hot corrosion but a chromia layer gives better protection against Type II corrosion and intermediate temperatures, the conditions found in land‐based gas turbines. In this paper the authors present the first known results for a chromia forming TBC system. Tests have been performed under oxidising conditions, up to 1000 h, at temperatures between 750 °C and 900 °C, and under Type I (900 °C) and Type II (700 °C) hot corrosion conditions up to 500 h. Under all these conditions no cracking, spallation or degradation was observed. Examination showed the formation of an adherent, dense chromia TGO at the bond coat / topcoat interface. These initial results are very encouraging and the TGO thicknesses agree well with comparable results reported in the literature.