The Study Of SiC Fiber Reinforced YSZ Based Composite Thick Coatings Thermal Protective Performance Produced By APS

Thermal barrier coating(TBC)is one of the most common high temperature protective coating and being wildly used on the surface of high-speed aircraft and some other high-speed mobile platforms.Conventional TBC systems consist of a duplex structure with a metallic bond coat and a ceramic heat-isolative topcoat.At present,most of common TBCs are made of Yttria Partially Stabilized Zirconia(YSZ)because of its relatively high expansion coefficient and fracture toughness.With the technological advances in aircraft,the surface of flight vehicle need a higher insulation performance TBC,the typical YSZ TBC can't meet the requirements of application.Research and development the high performance TBC system become a kind of inevitable trend.A study by Michael showed that increase of the TBCs thickness and decrease of thermal conductivity can effectively improve the insulation performance of the TBC,pointing out the direction of studying for high performance TBC.In this paper,the new TBC is discussed from the structure traditional TBC.The agglomerated powder had been prepared by spray granulation.Then the composite thick Si C fiber/YSZ(SFY)TBC with the ‘reinforced concrete structure' is obtained on the Ni super alloy via air plasma.The thickness of more than 4mm in the SFY composite coating system.On the basis,study the high temperature performance and failure mechanism of the SFY TBC reference to the typical YSZ TBC,and the residual stress state in coating.The nanostructure YSZ and P7216 powders were synthesized by the spray granulation technology,the micromorphology of powders were observed by SEM,and the liquidity and apparent density were test.Test results show that Reunion powder atomization process is reasonable,the best particle size range of YSZ and P7216 powders for APS were 45~ 75?m and 45 ~ 63?m.The micromorphology of composite coating were observed by the scanning electron microscope(SEM).And the porosity,thermal conductivity,heat insulation,high temperature oxidation resistance and fracture toughness were test with 1.5mm YSZ and 4mm SFY respectively.Research shows that the thicker SFY TBC have higher porosity,lower thermal conductivity,better thermal insulation performance,and higher fracture toughness,the thermal conductivity is 0.632 W/m K,the fracture toughness is 1.67 Mpa·m1/2.It's performance doubled and redoubled compared with the YSZ TBC.But the higher porosity and microcrack density of the SFY coating lead to the poor high temperature oxidation resistance.This text emphasizes on discussing the thermal shock resistance of the coating.Based the thermal cycle test standard Q/AVIC06016.1-2013 of The China Aviation Industrial,the thermal shock resistance of different thickness coating at 1000? were studied.Results indicate that the thermal cycle life is negative relation with the thickness of coating.when the topcoat ceramic layer's thickness is 1.5mm,the thermal cycle life of YSZ TBC is 24,the thermal cycle life of SFY TBC was 3.2 times higher than the YSZ coating,its value is 76.In addition,when the topcoat ceramic layer's thickness increased to 4mm,the thermal cycle life is 53.3,its still higher than 1.5mm YSZ coating.The thickness-cycle life IF(Impact Factor)? can be calculated by testing the thermal cycle life of different thickness TBC,the thickness-cycle life IF of YSZ is 129.6,the thickness-cycle life IF of SFY is 0.95,the thermal shock performance of YSZ coating is rely heavily the thickness of topcoat ceramic layer.By the microstructure,the failure coating elements distribution of coating and phase structure,the high temperature oxidation and the failure mechanism of YSZ and SFY TBC.The analysis indicates,the failure positions,failure mode and mechanism are different.The YSZ TBC failure occurs mainly in the joint part bond coating and topcoat,the failure caused by the promote each other thermally grown oxidation(TGO)and crack continuously eroded bond coating.The SFY TBC failure occurs mainly in the interface of fiber layer and YSZ layer,its failure modes is asymptomatic sudden failure,the failure is mainly due to internal crack grew up that the ‘reinforced concrete structure' was broken by the fiber oxidation,the growth of TGO can't cause the failure of SFY coating.The TGO layer was composed of Al and O elements by Energy Dispersive Spectrometer(EDS).Investigates the influence perlite on phase stability and microstructure of coating at high temperature by innovative independent topcoat system,its give the rationality of the composition ratio of the P7216 composite powders.Because the complexity source of residual stress,residual stress is hard to quantitative analysis.In the parper,we assumed that the TBC is idealized elastomer,then the stress strain model of coating was established,Combined with the XRD diffraction analysis and Raman spectroscopy to study the residual stress of the coating,its provides the theoretical basis for structure optimization of coating.