Effect of intersplat interface bonding on the microstructure of plasma-sprayed Al2O3 coating

The interface bonding between lamellae dominates the properties and performance of plasma-sprayed ceramic coatings. In this study, the interlamellar interface bonding and its effect on the splat microstructure were examined using TEM analysis of the microstructure of a plasma-sprayed Al2O3 coating. The obtained results revealed that the intersplat interface microstructure depends significantly on the intersplat bonding. An amorphous phase was observed in the interface region in which the bonding was formed, while the gamma-Al2O3 phase was observed at the interface where no bonding was formed. In addition, it was found that the interface bonding significantly influenced the interface microstructure of the coating. After heat treatment, the phase of the bonding between adjacent splats was transformed from amorphous to gamma-Al2O3. In the interface region in which the amorphous phase recrystallization occurred, nanosized pores evolved owing to the volume shrinkage accompanying the transformation of alumina from the amorphous to the gamma-Al2O3 phase.