High-precision nondestructive evaluation of a thermal barrier coating based on perovskite quantum dot anion exchange

Thermal barrier coatings (TBCs) in gas turbine engines are used in expressly harsh environments; thus, assessing TBC integrity status is critical for safety and reliability. However, traditional periodic maintenance involves visual inspections of the TBCs, requiring the gas turbine to be decommissioned and partially dismantled. Most importantly, tiny defects or internal damages that easily cause coating failure cannot be identified. In this work, a new nondestructive evaluation (NDE) technique of TBCs based on quantum dot (QD) anion exchange is first explored internationally. By exchanging anions between the Cl ions and the CsPbBr₃ QDs, the degrees of salt corrosion of the TBCs are evaluated. The resultant NDE technique shows that the colour of the TBCs obviously changes from green to blue, accompanied by a large blueshift (~ 100 nm) of the photoluminescence (PL) peak position. In addition, the relationship between the PL peak position and coating thermophysical properties indicates that the precision of this NDE technique may easily identify the μm-level of the thermal growth oxide (TGO) changes inside the TBCs.