Study Of Microstructure And Properties Of YSZ Thermal Barrier Coatings Before And After Laser Glazing

It is gradually difficult for conventional thermal barrier coatings?TBCs?to satisfy the more demanding work environment with the development of modern aeronautic and space industry.How to improve the thermal barrier properties of the coating so that it can work better,become a hot research.In recent years,researchers have laser glazing surface treatment technology applied to the thermal barrier coatings in order to prepare TBCs with batter performance.In this thesis,the two-layer structure thermal barrier coatings were manufactured by electron beam physical vapor deposition technology on the Ni alloy substrate,which the adhesive layer is NiCrAlY and the ceramic layer is YSZ.And the Nd:YAG laser beam was applied to the laser glazing of TBCs in order to obtain organizational structure different from the conventional ceramic layer.On this basis,this paper systematically studied the process parameters influence on microstructure and composition of laser glazing ceramic layer,combined with X-ray diffraction analysis?XRD?,scanning electron microscopy?SEM?and so on.And the microstructures,phase composition and properties analysis?high temperature stability and corrosion resistance?of laser glazing TBCs were systematically investigated compared to conventional TBCS.The experimental results show that the EB-PVD coating prepared primarily c-ZrO₂ and t-ZrO₂,the coatings composed of columnar crystals.So it has some diffusion paths,The TGO which between the ceramic layer and adhesive layer grow faster.And after laser glazing,the coatings become dense,reducing the oxygen diffusion path,whose TGO grow slower and the main phase is t'-ZrO₂ which have lower thermal conductivity,this phase is good to improve the coating oxidation resistance.High temperature oxidation results show that:in the constant temperature oxidation process,YSZ coatings weight gain rate is 0.0215,while the laser glazing coatings is less than YSZ coatings,it is 0.0169.After 90h the curve of YSZ become flattens,which show that coatings is saturation,while the curve of laser glazing coatings become flattens after 11Oh.The time prolonged by 22%.The total weight of YSZ specimen and laser glazing sample is 4.65mg/cm²and 5.42 mg/cm² respectively.Laser glazing coatings is less 16%than YSZ coatings.After all,the laser glazing coatings showed better high temperature oxidation resistance.In electrochemical corrosion experiments,laser glazing coatings corrosion potential shifted positively,and the corrosion current decrease,they all indicated that the laser glazing coatings have high resistance to corrosion.