Leandro Beaulardi

Slurry Coating of Environmental Barrier Coating (EBC) on Silicon Carbide Based Material

In order to increase the component lifetime of SiC based materials in combustion environments, environmental barrier coatings (EBCs) based on ceramic oxides are used to improve corrosion resistance of SiC, due to their high chemical stability. In this work, mullite and barium-strontium-aluminosilicate (BSAS) coatings were deposited by slurry dip coating on SiC substrates. Slurries were prepared by suspending commercial powders in water or ethanol, using appropriate dispersants. Substrates were dipped into the slurry and subsequently dried and heat treated at high temperature to promote densification. SEM observations were carried out to investigate the microstructure of the obtained coatings and to evaluate crack formation, porosity and adhesion.

Microstructural and Thermo-Mechanical Characterization of Yttria Ceramic Cores for Investment Casting, with and without Particulate Reinforcement

Yttria is an interesting material for the production of high performance ceramic cores for Directionally Solidified investment casting. DS casting of superalloys of the last generation challenge conventional silica ceramic cores, because of the high temperatures and the long times involved. Compared to silica, yttria is characterized by improved mechanical properties and higher chemical resistance at high temperatures. Submicronic and nanometric SiC reinforcements were tested in order to increase compression creep resistance of yttria. Oxidation resistance of both reinforcements was tested in conditions simulating the industrial process. The experimental results demonstrated the increase of compression creep resistance and showed that the industrial application of yttria ceramic cores reinforced with submicronic SiC is possible with minimal changes to current practices, thanks to a high enough oxidation resistance.