Study On The Properties Of HfH₂ Modified Thermal Barrier Coatings Prepared By Plasma Spraying And Laser Cladding

The thermal barrier coating is a multi-layer system applied to the turbine blade parts of aero-engine,which aims to improve the high temperature performance and service time of turbine blades.The traditional thermal barrier coating is usually a composite coating composed of 8wt%Y₂O₃ stable ZrO₂ ceramic layer and MCrAlY bond layer.The ceramic layer plays an insulating role,and the bonding layer is used to reduce the thermal expansion mismatch between the ceramic layer and the substrate.However,with the development of aircraft engine,turbine inlet temperature rise further,traditional thermal barrier coating can not meet the requirements of aircraft engine at present stage,thus developing a new generation of thermal barrier coating system is imminent.In this paper,thermal shock property of thermal barrier coatings and high temperature oxidation resistance of bond coatings are studied.First,the application of laser deposition method in GH586 substrate four HfH₂-CoCrAlYSi coating was prepared,and the application of scanning electron microscope?SEM?,metallographic microscope,X-ray diffraction analysis?XRD?and EDS analysis of four kinds of coating under 1100?high temperature oxidation;Secondly,applying the composite method of laser cladding and plasma spraying on GH586 substrate were prepared respectively four HfH₂-CoCrAlYSi/8YSZ thermal barrier coating,by four kinds of coating were studied and analyzed at the same time the high temperature thermal shock condition of 1100?.The main research results are as follows:?1?In this paper,laser cladding was applied to prepare four kinds of HfH₂-CoCrAlYSi coatings on GH586 nickel base superalloy,the surface morphology is mesh structure.The section of coating is divided into three layers,the surface are aircraft grains,the transition layer are columnar grains and equiaxial structure grains formed between coating and substrate;?2?The addition of HfH₂ in CoCrAlYSi coating can effectively improve the densification of 1100?high temperature oxidation products and repress the generation of spinel oxides such as CoCr₂O₄.However,the content of HfH2 in coating cannot exceed 3xwt%,otherwise the density of these high temperature oxidation products will deteriorate.?3?The addition of HfH₂ has a significant impact on the high temperature oxidation resistance of CoCrAlYSi coatings.First it suppress the rapid growth of surface oxidation film,avoid too thickness of oxide film,at the same time,it increases the adhesion between oxide film and coating.However,the content of HfH₂ in the coating cannot be too high,otherwise the high temperature oxidation resistance of coatings would be reduced,such as 3xwt%HfH₂-CoCrAlYSi coating.?4?The addition of HfH₂ can effectively improve the 1100?high temperature thermal shock of CoCrAlYSi/8YSZ thermal barrier coatings.Compared with the single CoCrAlYSi/8YSZ thermal barrier coating,2xwt%HfH₂-CoCrAlYSi thermal barrier coating has a high temperature thermal shock number of 79 times.However,when the content of HfH₂ reached 3xwt%,its thermal shock performance decreased.?5?After 1100?high temperature thermal shock failure,the coating spalling of four kinds HfH₂-CoCrAlYSi/8YSZ thermal barrier coating is obvious different.There was obvious cracking between TC/TGO and TGO/BC after the thermal shock failure of CoCrAlYSi/8YSZ coating.Only obvious craking occurred between TC and TGO layer in xwt%HfH₂-CoCrAlYSi/8YSZ after thermal shock failure.For2xwt%HfH₂-CoCrAlYSi/8YSZ thermal barrier coating,the cracking area occurred inside the ceramic layer after thermal shock failure.After the failure of high temperature thermal shock of 3xwt%HfH₂-CoCrAlYSi/8YSZ thermal barrier coating,obvious cracking occurred in TC/TGO and TGO layer.