Study Of Surface State For Bond Coat On The Service Life Of Thermal Barrier Coating

In aero gas turbines, the sercice life of blades and vanes can substantially be increased by the use of ceramic thermal barrier coatings (TBC). In addition to providing the thermal insulation to based superalloy components, TBC also provide protection against high temperature oxidation and hot corrosion attack.The application of TBC is widely used in gas turbine engines and durability of the components.Thermal barrier coatings were deposited onto GH99 superalloy by atmospheric plasma spraying (APS). The NiCoCrAlY bond coat was treated by supersonic fine particles bombarding technology. Microstructures and oxidation behavior of TBC was analysed by transmission electron microscope (TEM), scan electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD).Basing on experimental result.The oxidation mechanism of TGO was discussed. The relationship between stress state and thermally grown oxide (TGO) was analysed. As shown in the results:In atmospheric plasma spraying TBC specimens, thermally grown oxide layers formed after 96h thermal exposure at 1050°C. TGO was consisted of a protective Al2O3 layer and a detrimental oxides layer.Voids and cracks were observed in the TGO layer.In supersonic fine particles bombarding TBC (SFPB-TBC), TGO has been in steady-state growth stage after 3h thermal exposure.e at 1050°C. Uphill diffusion of Al was observed near the surface area of bond coat. The aluminum concentration of bond coat was found to be along TGO/bond coat interface region. The enrichment of Al can extend the steady-state growth stage of TGO. After 196h thermal exposure, TGO was still in the steady-state growth stage. During thermal cycling of TBC, bond coat afford oxidation at high temperature, subsequently, lot kinds of stresses formed.in TBC. The largerset stresses occured in the TGO layer in thermal cycling. Evolution of residual stress in the TGO has been studied as a function of thermal cycling using ruby fluorescence spectroscopy (RFS). Stress concentration of TGO was observed in the area of heave and hollow, where void and scracks were extend. The failure of TBC is associated with spallation close to the TGO interfaces within either the YSZ or the bond coats. SFPB-TBC made better oxidation resistance, Also controlled the stress state of the TGO layer.The techonlogy of supersonic fine particles bombarding amend the original state of bond coat. Oxidation and thermal cycling behavior of APS-TBC improved. Supersonic fine particles bombarding on bond coat lead to better performance of APS-TBC.