Effect of Surface Strengthening on High Temperature Oxidation and Bonding Strength of EB-PVD Thermal Barrier Coating

A two-layered thermal barrier coating (TBC) consisting of NiCoCrAlY bonding coat and YSZ (yttria stabilized zirconia) topcoat was deposited onto DZ22 alloy using electron beam-physical vapor deposition (EB-PVD). The effect of shot-peening strengthened NiCoCrAlY bonding coat on the resistance to isothermal oxidation of the thermal barrier coating was investigated. The bonding strength of the coating exposed at 1 050°C for different times was evaluated by MTS (materials tensile system), and the interface and phase constituents in the coating was also studied by SEM and XRD. It was found that, the bonding strength of the coating exposed at elevated temperature greatly decreases, and under the conditions of tensile and shear strains, failure of the thermal barrier coating may occur along thermally grown oxide (TGO) layer between the bond coat and YSZ topcoat. Shot-peening with strength of 0. 3 MPa can greatly improve bonding strength of thg TGO layer and the resistance to oxidation of the coating.