Research On Microstructure And Properties Of Modified Composite Thermal Barrier Coatings

Thermal barrier coatings?TBCs?is a kind of thermal protection technology that ceramic materials are coated on the surface of superalloy substrate to reduce the surface temperature,and improve high temperature oxidation resistance and corrosion resistance.As one of core technologies,TBCs plays a significant role in advanced gas turbine.In view of poor toughness and short thermal cycling lifetime of existing TBCs,three kinds of TBCs modified by different toughening materials were prepared by atmospheric plasma spraying,so as to improve comprehensive performance.In this paper,the effect of toughening materials on fracture toughness,thermal shock resistance and erosion resistance of coatings were systematically studied.In coatings of Al₂O₃/YSZ?yttria stabilized zirconia?system,the fracture toughness of coatings doped with 8wt.%YSZ fibers is increased by 27.5%compared to that of undoped coatings.Meanwhile,the coatings exhibits the best thermal shock resistance and erosion resistance,which thermal shock resistance is increased by 58.8%,and erosion rate is decreased by 61.0%.In coatings of YSZ system,the fracture toughness of coatings doped with 8wt.%SiC whiskers is increased by 35.14%.Meanwhile,the coatings exhibits the best thermal shock resistance and erosion resistance.Moreover,the improvement mainly attributes to the fiber debonding,fiber pull-out and crack deflection mechanisms which can hinder the initiation and propagation of cracks,consume fracture energyand improve the toughness of coatings.In double layered ceramic coatings of La₂Zr₂O₇-YSZ system,the design of the double layered TBCs can avoid the thermal physical mismatch between the La₂Zr₂O₇and bond layer.Carbon nanotubes?CNTs?were uniformly mixed into the ceramic powders,and the composite powders were prepared by spray granulation.The toughness of the coatings doped with 1wt.%CNTs is increased by 28.7%compared to that of undoped coatings.Meanwhile,the coatings exhibits the best thermal shock resistance and erosion resistance,which thermal shock resistance is increased by 73.0%,and erosion rate is decreased by 27.5%.Moreover,the improvement mainly attributes to CNTs uniform distribution,CNTs debonding,CNTs pull-out mechanisms which can hinder the initiation and propagation of cracks,resulting in enhancing the service performance of TBCs.