Élaboration et caractérisation de barrières thermiques à base de zircone obtenues par dépôt chimique en phase vapeur assisté par un plasma micro-ondes : mise au point du procédé, propriétés physiques et stabilité des revêtements vis-à-vis du vieillissement thermique

Abstract : A reactor for manufacturing zirconia-based thermal barrier coatings by microwave plasma enhanced chemical vapour deposition has been optimised. Deposition rates higher than 250 [micro]m/h have been achieved (on 20 mm diameter plane substrates). A new evaporation and gas injection deviee has been designed to obtain coatings exhibiting uniform thickness and yttria content. Plasma activity has been homogenised. A new sample-holder has been designed to investigate coating morphologies at deposition temperature between 500°C and 900°C. Once optimum deposition parameters were defined, three morphologies of yttria partially stabilised zirconia coatings were studied by scanning electron microscopy and X-ray diffraction. A dendritic growth of columns of the tetragonal nontransformable t' phase along the [100] direction at high deposition temperature was observed. The coatings deposited at 700°C and 900°C exhibited satisfactory stability towards isothermal heat treatments at 1100°c to 1400°C. Using X-ray diffraction analysis, a destabilisation scheme of the metastable " t' " phase has been proposed. Investigations of the coating porosity, roughness, thermal conductivity and resistance towards thermal cycling supplemented this microstructural and crystallographic study. These properties would allow the use of these yttria-zirconia coatings in typical thermal barrier applications.
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Boris Préauchat. Élaboration et caractérisation de barrières thermiques à base de zircone obtenues par dépôt chimique en phase vapeur assisté par un plasma micro-ondes : mise au point du procédé, propriétés physiques et stabilité des revêtements vis-à-vis du vieillissement thermique. Autre [cond-mat.other]. Institut National Polytechnique de Lorraine, 2001. Français. ⟨NNT : 2001INPL043N⟩. ⟨tel-01749880⟩

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