Research On Properties Of Fiber Reinforcement Modified Plasma Spraying Thermal Barrier Coatings

To meet the demand of developing high flow ratio and thrust-weight ratio in aerospace field,thermal Barrier Coatings(TBC),a technology which utilize the properties of ceramic materials with high-temperature resistance and low conductivity combines the ceramic phase and metal surface,increasing the thermal insulation property of substrate.Moreover,with the increasing desire of the inlet temperature of gas turbine engine,traditional TBCs material,is also known as yttrium partially stabilized zirconia(YSZ)which potentials are already exhausted.Therefore,the improvement of properties of TBCs by structural design and materials innovation are becoming the prioritized development direction.YSZ fibers has excellent mechanical properties,although the concept of fiber-reinforced composite have been presented and applied in bulk materials a long time ago,there are few literatures avaliable in TBCs field.Functionally gradient thermal barrier coatings(FGTBC),as a novel coatings system,the structural design and failure mechanisms are not fully understood;as for new material with high-temperature insulation,such as rare-earth co-stabilized zirconia,generally shares the inferior mechanical property.This study is based on the urgent issue mentioned above and three kinds of TBCs systems have been designed and researched.The aim of this study is to make insight into the influence of structural design and fiber reinforcement on the lifetime and mechanical properties of TBCs.In supersonic plasma sprayed nickel-coated aluminum bondcoat/YSZ system,YSZ fibers with thin electroless plated nickel films are introduced into the nickel-coated aluminum bond coat.Compared the coatings without fibers,the thermal shock resistance is increased by 59.4%.The fiber bridging and fiber debonding are regarded as the main mechanisms.In the research of the design of FGTBCs and fiber reinforcement,it turns out to be that the gradient design can lead the surface residual stress to be more compressive whereas the fiber introduction makes the residual stress change into more tensile.In addition,both gradient and fiber reinforcement can improve the thermal shock resistance of coatings.Compared with the raw coatings,the thermal resisitance of modified nickel-coated aluminum bondcoat/YSZ coatings is increased for over 80%.The improvement is own to the fiber debonding,crack deflection and fiber breakage mechanisms and gradient design which decreases the cumulative rate of stress in thermal cycling process.YSZ fibers are introduced in the system with rare earth co-stabilized zirconia(CSZ)as top coat,YSZ as transitional layer and NiCoCrAlY as bond coat.Compared with the single layered CSZ and double layered CSZ/YSZ,double layered CSZ/YSZ with fibers shows the supreme erosion resistance and the thermal resistance property is increased for 128%.The erosion fracture mechanism,intergranular fracture,remains unchanged after the introduction of fibers.However,fiber addition increases the property of sticking erosion media which is beneficial to the erosion resistance of coatings.In thermal shock experiment,double-ceramic structure relieve the thermal-physical incompatibility of CSZ coating and bond coat.Fiber debonding consumes the work of fracture in thermal cycling process and improves the lifetime of coatings.