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Factors affecting the microstructural stability and durability of thermal barrier coatings fabricated by air plasma spraying
Author(s) -
Helminiak M. A.,
Yanar N. M.,
Pettit F. S.,
Taylor T. A.,
Meier G. H.
Publication year - 2012
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.201206646
Subject(s) - materials science , thermal barrier coating , temperature cycling , microstructure , composite material , yttria stabilized zirconia , spallation , durability , thermal conductivity , electron beam physical vapor deposition , cubic zirconia , chemical vapor deposition , thermal , ceramic , nanotechnology , physics , quantum mechanics , meteorology , neutron
The high‐temperature behavior of high‐purity, low‐density (HP‐LD) air plasma sprayed (APS) thermal barrier coatings (TBCs) with NiCoCrAlY bond coats deposited by argon‐shrouded plasma spraying is described. The high purity yttria‐stabilized zirconia resulted in top coats which are highly resistant to sintering and transformation from the metastable tetragonal phase to the equilibrium mixture of monoclinic and cubic phases. The thermal conductivity of the as‐processed TBC is low but increases during high temperature exposure even before densification occurs. The porous topcoat microstructure also resulted in good spallation resistance during thermal cycling. The actual failure mechanisms of the APS coatings were found to depend on topcoat thickness, topcoat density, and the thermal cycle frequency. The failure mechanisms are described and the durability of the HP‐LD coatings is compared with that of state‐of‐the‐art electron beam physical vapor deposition TBCs.