MICROSTRUCTURES, MICROHARDNESS, AND CRYSTALLIZATION BEHAVIORS OF AMORPHOUS Al₂O₃-YSZ COATINGS PREPARED BY AIR PLASMA SPRAYING

Abstract

Three types of amorphous Al 2 O 3 -yttria-stabilized zirconia (YSZ) coatings were prepared using air plasma spraying (APS). The e®ects of the APS parameters on the microstructure, porosity, amorphous-phase content, and microhardness of the coatings were investigated using scanning electron microscopy (SEM), di®erential scanning calorimetry (DSC), and transmission electron microscopy (TEM). The results indicated that the microstructure of the coatings was dependent on the APS parameters used. The porosity of the coatings and the number of unmelted particles deposited increased with the°ow rate of the primary plasma gas increasing. The amorphous-phase contents and microhardness values of the coatings exhibited a trend opposite to that of their porosity and the number of unmelted particles present in them. The crystallization behaviors and microhardness values of Al 2 O 3 -YSZ coatings annealed at di®erent temperatures were also investigated. The results indicated that the coatings with higher amorphous-phase contents possessed homogeneous nanocrystalline structure and exhibited higher microhardness values after the heat treatments.

Research on Thermal Stability and Properties of Ca3ZrSi2O9 as Potential T/EBC Materials

“…This phenomenon was due to rapid cooling after the deposition process, and the atoms hardly diffuse to form an amorphous structure. Song et al [25] also obtained the Al 2 O 3 -40 vol.% 8YSZ as-sprayed coatings with different contents of the amorphous structure by changing the primary plasma gas during the APS process. It can be found that the coating was mostly built up by well-flattened splats, and there were also some regions with partly melted splats and splash debris.…”

Formation mechanism of Al2O3‐YAG amorphous ceramic coating deposited via atmospheric plasma spraying

“…Therefore, it is not enough to fabricate the amorphous ceramic coating only with high enthalpy and ultra‐fast cooling rate under the current technology. According to the results of reported studies, it was found that the ceramic coatings contained amorphous phase successfully prepared were belong to the multicomponent system like Al 2 O 3 ‐ZrO 2 , Al 2 O 3 ‐YSZ, and Al 2 O 3 ‐ZrO 2 ‐SiO 2 21–23,29,30 . Significantly, the ratio of multicomponent in sprayable powders was at the low eutectic point, the amorphous ceramic coatings were successfully prepared.…”

“…Therefore, the stability of these amorphous alloys was poor under harsh service conditions, which changed the microstructure of the coating and further affected the performance of the coating.Recently, some manufactured amorphous ceramic coatings have been deposited. Noticeably, these amorphous ceramic coatings have high crystallization temperature [21][22][23][24], which make them have excellent microstructure stability in a wide temperature range for the application under harsh services conditions. In our previous work, the Al 2 O 3 -YAG amorphous ceramic coating was deposited via…”

Formation Mechanism of Al2O3-YAG Amorphous Ceramic Coating Deposited via Atmospheric Plasma Spraying

“…Recently, some manufactured amorphous ceramic coatings have been deposited. Noticeably, these amorphous ceramic coatings have high crystallization temperature [21][22][23][24], which make them have excellent microstructure stability in a wide temperature range for the application under harsh services conditions. In our previous work, the Al 2 O 3 -YAG amorphous ceramic coating was deposited via atmospheric plasma spraying (APS) used the Al 2 O 3 /YAG powders.…”

“…Therefore, it is not enough to form the amorphous ceramic coating only with high enthalpy and ultra-fast cooling rate under the current technology. According to the results of reported studies, it is concluded that the ceramic coatings containing the amorphous phase successfully prepared were belong to the multicomponent [22][23][24][30][31][32]. Especially, the ratio of multi-component in sprayable powders was at low eutectic point, then the amorphous ceramic coating can be successfully prepared.…”