Effect of Bond Coats Pretreatment on Oxidation Behavior of 7YSZ Thermal Barrier Coating Deposited by Plasma Spray-Physical Vapor Deposition

The work aims to improve resistance to high temperature oxidation of 7YSZ thermal barrier coating deposited by plasma spray-physical vapor deposition. The columnar structure 7YSZ thermal barrier coatings (TBCs) were prepared by plasma spray-physical vapor deposition (PS-PVD) on pretreated (polishing+pre-oxidation) and un-pretreated bond coat surfaces, respectively. The static resistance to high temperature oxidation of 7YSZ thermal barrier coatings was tested in atmospheric environment at 950 ℃. Interfacial morphology of the ceramic layer/bond coat as well as structure evolution of TGO layer during high-temperature oxidation process were characterized by virtue of scanning electron microscope (SEM), X-ray diffractometer and (XRD) and energy dispersive spectrometer (EDS). Polishing of bond coats could reduce parts subject to non-uniform geometric stress and inhibit the formation of micro-crack at the interface of ceramic layer/TGO/bond coats. Meanwhile, the thin and continuous TGO layer formed as a result of pre-oxidation treatment of bond coats could effectively reduce the growth rate of TGO and inhibit the element interdiffusion between ceramic layer and bond coats. The isothermal oxidation kinetic curve of columnar 7YSZ thermal barrier coatings conformed to Wagner parabolic law. The oxidation rate constant of 7YSZ coatings with bond coats pretreated and un-pretreated was 0.101×1012- cm2 /s and 0.115×1013- cm2 /s, respectively. The pretreated of bond coats can effectively improve the oxidation resistance of 7YSZ thermal barrier coating deposited by plasma spray-physical vapor deposition. © 2017, Chongqing Wujiu Periodicals Press. All rights reserved.