Thermal Cycling Behavior of HVOF-NiCrAlY + APS-YSZ Thermal Barrier Coatings

The oxidation and crack propagation behavior of HVOF-NiCrAlY + APS-YSZ thermal barrier coatings in a furnace cycling environment were investigated. It was found that TGO growth yields a power-law relationship, δTGO−δ0=kTGOtnTGO, with nTGO < 0.5. Crack propagation exhibits a steady-state propagation stage followed by an accelerating propagation stage, and the crack length likely has a power-law relationship with TGO thickness, amax−a0=kcrackδTGOncrack, with ncrack > 3. Although lower Cr and Y contents favor the formation and continuous growth of near-Al2O3-TGO, this might compromise the FCT life of the TBC.