A. Vardelle, S. Cartel, G. Mariaux, M. Vardelle, University of Limoges, Limoges, France
The top-coat of the thermal barrier used for the protection of the hot sections components of gas turbine engines is conventionally deposited by either plasma spraying or electron beam physical vapor deposition. The latter produces coatings with a columnar microstructure and defects generally normal to the metal-ceramic interface whereas the plasma-sprayed coatings exhibit a layered and porous microstructure with defects generally parallel to the metal-ceramic interface. Because of these defects, the plasma sprayed coatings exhibit a lower thermal conductivity than the EBPVD deposits but also an inferior strain tolerance.
This study deals with a novel technique which should make it possible to carry out ceramic deposits with a fine microstructure, a low thermal conductivity and a high rate of deposition.
It uses a powder feedstock to avoid the problems involved in the handling of nanometric particles and a thermal plasma source to evaporate the material and transport it to the substrate. An emodel of the heating and evaporation of droplets is used to determine the effects of particle size and injection conditions on the evaporation rate.
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