Effect Of TGO Evolution On Interfacial Properties And Cycle Life Of YSZ Thermal Barrier Coatings

YSZ(yttria-stabilized zirconia)thermal barrier coating is widely used in hot-end components because of its low thermal conductivity and good high-temperature stability.After a long period of service,a new thermal growth oxide(TGO)will appear between the metal bonding layer and the ceramic layer.It plays a good role in preventing oxidation reaction in the early stage of thermal barrier coating service,but later it becomes the root cause of thermal barrier coating failure.Therefore,TGO is the most critical factor affecting and controlling the service life of thermal barrier coatings.In this paper,a gas thermal shock test bed is used to simulate the real working conditions,and the effect of TGO evolution on the interface performance and cycle life of the YSZ thermal barrier coating is studied.the result shows:(1)The evolution of TGO has changed the interface performance of the YSZ thermal barrier coating system.The microhardness and fracture toughness of the ceramic layer,the bonding layer and the TGO layer showed a trend of first increasing and then decreasing,and the peak value appeared in the middle oxidation period,indicating that the large amount of spinel oxides generated in the late oxidation period is the interface of the thermal barrier coating system.Performance has a negative impact.(2)The evolution of TGO leads to the trend of the cycle life data of YSZ thermal barrier coating first increasing and then decreasing under the same cycle experimental conditions.Coating failure and shedding is a massive shedding from the edge.The occurrence area is inside the ceramic layer,and the fracture is caused by the intersection of horizontal and vertical crack propagation inside the ceramic layer.Moreover,only the thermal barrier coating after 70 h oxidation had horizontal cracks in its TGO layer.(3)The TGO evolution of the YSZ thermal barrier coating causes a competition mechanism between the ceramic layer and the TGO layer: when the composition of the TGO layer is mainly Al2O3,the fracture toughness of the TGO layer is high,and theinterface performance of the thermal barrier coating is good,ceramic The layer is more prone to stress concentration,and the fracture failure area mostly appears in the upper middle part of the TC layer;when the main component of the TGO layer begins to become spinel-like oxide,the fracture toughness of the TGO layer begins to deteriorate,and the interface performance of the thermal barrier coating begins After the descent,the stress concentration and fracture failure areas began to move down,the TGO layer began to crack under increasing interlayer shear stress,and the failure of the coating system began to appear in the interface and the TGO layer.In summary,TGO has played a vital role in the entire YSZ thermal barrier coating system.When Al2O3 dominates,TGO improves the interface performance and cycle life of the YSZ thermal barrier coating;when a large amount of spinel oxide is generated,TGO begins to reduce the interface performance and cycle life of the YSZ thermal barrier coating.