Evaluation of functionally graded thermal barrier coatings fabricated by detonation gun spray technique

In a new approach, an excellent functionally graded thermal barrier coating (FGM TBC) has been fabricated by the detonation gun spray process in conjunction with a newly proposed ‘shot-control method’. FGM TBCs were sprayed in the form of multi-layered coatings with a compositional gradient along the thickness direction. The gradient ranged from 100% NiCrAlY metal on the substrate to a 100% ZrO2–8 wt.% Y2O3 ceramic for the topcoat, and consisted of a finely mixed microstructure of metals and ceramics with no obvious interfaces between the layers. In the FGM layer of the FGM TBCs, the ceramics and metals maintained their individual properties without any phase transformation during the spraying process. Thermal shock properties of FGM TBCs were also investigated and the data obtained were compared with those for traditional duplex TBCs.