Thermal shock resistance of Al₂O₃ and Al₂O₃-13%TiO₂ coatings deposited by supersonic atmospheric plasma spraying

The thermal shock resistance of FeAl/Al₂O₃, FeCrAl/Al₂O₃, FeAl/Al₂O₃-13%TiO₂, and FeCrAl/Al₂O₃-13%TiO₂ coatings deposited by supersonic atmospheric plasma spraying (SAPS) on the stainless steel matrix was investigated in this paper. The microstructure of the coatings was characterized by scanning electron microscope, the porosity was measured by image analysis, the mass fraction of α-Al₂O₃ was calculated by multi peak method, and the bonding strength was tested. The results show that, the mass fraction of α-Al₂O₃ in Al₂O₃ coating is 40.3%~42.5%, the porosity is 3.47%~3.52%; the mass fraction of α-Al₂O₃ in Al₂O₃-13%TiO₂ coating is about 24.0%~29.7%, the porosity is 3.12%~3.31%. The results of water-quenching tests at 800 ℃ for 30 min show that, the FeCrAl/Al₂O₃ coating presents the highest thermal shock resistance, and the FeCrAl/Al₂O₃-13%TiO₂ coating takes the second place. The FeAl/Al₂O₃ and FeAl/Al₂O₃-13%TiO₂ coatings exhibite the same thermal shock resistance, which are the worst in four kinds of coatings.