Abstract No.:
5303

 Scheduled at:
Thursday, June 08, 2017, Hall 12 1:40 PM
Aviation & Power Generation Industry III


 Title:
An assessment of thermal spray technologies for deposition of environmental barrier coatings (EBC)

 Authors:
Emine Bakan* / Forschungszentrum Jülich GmbH, Germany
Georg Mauer / Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, Materials Synthesis and Processing (IEK-1), Germany
Robert Vaßen/ Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, Materials Synthesis and Processing (IEK-1), Germany

 Abstract:
Environmental barrier coatings (EBC) are currently being investigated to protect ceramic matrix composite (CMC) turbine engine components in water-vapor rich combustion environments. Dense, crack-free, uniform and well-adhered coatings are demanded for this purpose. This paper represents an assessment of different thermal spray techniques for deposition of Yb2Si2O7 and silicon (Si) EBC layers. Plasma spraying of refractory silicates is known to be complicated by undesired glass transition due to rapid solidification as well as evaporation of Si-bearing species during spraying resulting in secondary phases. Plasma spraying of low-density Si also requires careful optimizations as it tends to oxidize during spraying particularly at atmospheric conditions.
Bearing these problems in mind, the Yb2Si2O7 coatings were deposited by atmospheric plasma spraying (APS), high-velocity oxygen-fuel spraying (HVOF), suspension plasma spraying (SPS) and plasma-spray physical vapor deposition (PS-PVD) techniques. As-sprayed microstructure, amorphous content and phase composition of the coatings were analyzed. The Si coatings were sprayed by the APS utilizing TriplexProTM spray torch with 9 and 6.5 mm nozzles as well as vacuum plasma spraying (VPS). As-sprayed oxide content and porosity of these coatings were comparatively evaluated. With the selected spraying parameters Si/Yb2Si2O7 EBC systems were deposited on SiC/SiC CMC substrates and post heat treatments were performed. Based on the findings, the advantages and disadvantages of each method over other techniques are discussed with respect to process parameters and material properties.


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