An effective low-temperature strategy for sealing plasma sprayed Al2O3-based coatings

Pores and cracks are usually inevitable in the coatings fabricated by plasma spraying. Herein, thermal chemical reaction technique was developed as an effective low-temperature strategy for addressing this issue. Dense alpha-Al2O3/AlPO4 coating was synthesized on the surface of the plasma sprayed Al2O3-based coating by thermal chemical reaction at 500 degrees C. The alpha-Al2O3/AlPO4 composites permeated into the coating and effectively filled up the pores and cracks inside. The sealed coating showed a uniform and dense morphology. The hydrogen permeation rate of the sealed coating sharply decreased by a factor of 15, which further confirmed its significantly improved compactness. In addition, the coating exhibited good thermal shock resistance and bond strength after sealing. Considering its low-temperature heat treatment, facile fabrication process and wide applicability, thermal chemical reaction method can be potentially used as a cost-saving strategy for sealing plasma sprayed ceramic coatings.