| In response to the trend of increasing operating temperature of aeroengines hot components,it has become inevitable to apply thermal barrier coatings on Ni-base alloy surface.At present,NiAl coatings are highly applied in engines,but the defect such as brittleness,makes the spallation phenomena much earlier than expectation of time.In order to further improve the anti-high temperature oxidation property of coatings and prolong its service life,Pt modified Ni-Al-Pt coating is prepared by electroplating and vacuum diffusion method.Firstly,a platinum plating with controllable thickness is prepared on NiAl bond coat by electroplating process.By adjusting the process parameters,a single platinum layer with high consistency,average particle size of 0.22?m and thickness of about 5?m is prepared.Then,vacuum diffusion method is used to prepare a uniform single-layer(Ni,Pt)Al diffusion layer.Effects of shot peening,diffusion time and temperature on the morphology and thickness of the diffusion layer are discussed.The concentration distribution curve is fitted by least-square method and the diffusion coefficients of each element is calculated.The results show that interdiffusion of Pt atoms with Ni and Al atoms occurs mainly in Ni-Al-Pt bond coat.The solid solution of Pt atoms promotes the diffusion of Al while suppressing the outward diffusion of Ni,which plays a positive role on the oxidation resistance of bond coat.Finally,the Ni-Al-Pt coating is prepared by APS,and compared with NiAl coating which prepared through the same method,from fracture toughness,phase composition,microstructure,oxidation kinetics and oxidation performance.The results indicate that Ni-Al-Pt coating has higher fracture toughness and strong brittle fracture resistance.Moreover,in the initial oxidation,Ni-Al-Pt coating can rapidly form a dense Al2O3 film,and still maintain a low oxidation rate in subsequent oxidation,therefore,it has a better anti-high temperature oxidation performance. |
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