Fabrication and Evaluation of Plasma-Sprayed Nanostructured and Conventional YSZ Thermal Barrier Coatings
Reza Shoja Razavi,
Mohammad Reza Loghman-Estarki.
Yttria stabilized zirconia (YSZ) nanostructured and conventional coatings have been prepared by atmospheric plasma spraying
(APS) on NiCoCrAlY-coated superalloy substrates. Bonding strength test was carried out based on the ASTM-C-633-01. To evaluate
thermal insulation value of coatings, the thermal insulation capability test was designed and administered. Field emission scanning electron
microscope (FESEM) and X-ray diffractometry (XRD) were employed to characterize the microstructures and the phase compositions
of the powders and coatings. Nanostructured YSZ coating exhibited a bimodal microstructure consisting of nanosized particles retained
from the powder and microcolumnar grains formed through the resolidification of the molten part of powder, whereas the microstructure
of conventional YSZ coating consisted of columnar-grain splats. Both nanostructured and conventional YSZ coatings consisted
of the non-transformable tetragonal phase. The results revealed that nanostructured coating, due to unique microstructure container of
nanozones, presented improved bonding strength and thermal insulation capability as compared to the conventional coating.
Keywords: Thermal barrier coating, nanostructure, microstructure, YSZ, plasma spraying, bonding strength, thermal insulation capability
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