The effects of spray parameters on the microstructure and thermal stability of thermal barrier coatings formed by solution precursor flame spray (spfs)

Solution precursor spraying is a new method of applying thermal barrier coatings (TBCs) on metallic substrates. In this work, the injection of a solution precursor has been made axially into an oxy-acetylene flame to deposit 7wt.% yttria stabilized zirconia (7wt.% YSZ) coatings. For this purpose a h...

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Bibliographic Details
Published in:Surface & coatings technology 2013-04, Vol.220, p.44-51
Main Authors: Saremi, M., Valefi, Z.
Format: Article
Language:English
Subjects:
Alloy plating
Alloy steels
Applied sciences
Coatings
Cross-disciplinary physics: materials science
rheology
Exact sciences and technology
Materials science
Metals. Metallurgy
Nonmetallic coatings
Physics
Precursors
Production techniques
Solution precursor flame spray
Solution precursor plasma spray
Sprayers
Sprays
Surface treatment
Surface treatments
Thermal barrier coatings
Yttria stabilized zirconia
Zirconium dioxide
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Summary:Solution precursor spraying is a new method of applying thermal barrier coatings (TBCs) on metallic substrates. In this work, the injection of a solution precursor has been made axially into an oxy-acetylene flame to deposit 7wt.% yttria stabilized zirconia (7wt.% YSZ) coatings. For this purpose a home-made atomizer has been inserted into the nozzle of a flame spray torch. The precursor used was an aqueous solution containing zirconium and yttrium salts to make a solid solution of 93wt.% ZrO2 and 7wt.% Y2O3 (7YSZ) in the coating. A martensitic stainless steel plate has been used as substrate on which a bond coat of NiCrAlY alloy was applied by atmospheric plasma spray process. The effects of spray distance and atomizing gas (oxygen and hydrogen) on the microstructure, phase composition, thermal shock and thermal exposure resistance of the coatings have been examined. The results show that the use of H2 as the precursor atomizing gas instead of oxygen increases the enthalpy of the flame the result of which is coatings with the least non decomposed precursor and highest crystalline YSZ. This effect causes the severe cracking at thermal shock and thermal exposure tests in coatings made by oxygen atomizing due to higher amount of non-decomposed precursor. By contrast, coatings made by hydrogen atomizing showed very little cracking because of increased enthalpy of the flame and a small quantity of non-decomposed precursor.
ISSN:0257-8972
1879-3347
DOI:10.1016/j.surfcoat.2012.08.019