Fabrication Processes And Properties Of 8YSZ/PtAl Thermal Barrier Coatings On DD5 Alloy Surface

As a thermal insulation and protective coating,thermal barrier coatings can help engine blades,combustor and other components to resist high temperature and corrosion environment during service,and effectively improve the service life of high temperature components of engine.According to the needs of a blade in the service,PtAl bonding layer and YSZ ceramic surface layer was prepared on DD5 single crystal alloy by the method of platinum plated aluminized and electron beam physical vapor deposition(EB-PVD).The process parameters of YSZ ceramic surface layer prepared by EB-PVD was optimized and the structure,combination strength,oxidation resistance,corrosion resistance and other properties of coating system were investigated in detail.The coating has been applied to the actual parts.A diffusion layer formed between matrix and PtAl bonding layer which prepared by plated aluminized Pt and treated with the vacuum diffusion;The wet blowing sand pretreatment can effectively remove pollutants on the surface of the PtAl bonding layer,improve the interface between the bonding layer and the ceramic layer,improve the binding force of the coating;The YSZ ceramic surface layer showed a typical columnar structure and the phase structure of tetragonal zirconia.A thin and uniform Al2O3 layer is preformed between PtAl bonding layer and YSZ ceramic surface layer.The effect on the properties of YSZ coating by EB-PVD process parameters were studied and optimized,the optimum deposition temperature of YSZ coating was 950? and the oxygen content is 200 m L/min,Good binding property with tensile strength of 69.175 MPa performed by 8YSZ/PtAl thermal barrier coatings prepared under the optimum parameters.The oxidation and corrosion resistance of the coating were analyzed.The results showed that the average oxidation weight gain rate was 0.0205g/(m2·h)and there was no obvious oxidation phenomenon on the surface of the samples oxidized 200 h at 1100 ?;the average heat corrosion weight gain rate was 0.093g/(m2·h)and no obvious corrosion phenomenon on the surface after 100 h hot corrosion test;8YSZ/PtAl coating stilled without the occurrence of failure in high temperature cyclic oxidation test by 300 h,and the tetragonal phase of ceramic coating has not changed.The mechanical properties of DD5 single crystal samples with 8YSZ/PtAl coating were tested.The results show that the transient performance at high temperature of Rm ? 975 MPa,Rp0.2 ? 940 MPa,section shrinkage rate after elongation of A?11.0%,Z?24.5%,high temperature endurance test time for a minimum of 29.7h.After coating,the high temperature endurance and high temperature transient performance of the sample have decreased,but they all exceed the requirements in the alloy manual and meet the needs of the use.According to the coating process study based on thermal barrier coating in actual parts,the thickness distribution of the coating in different position of the blade is studied and the coating was applied partly on the blade,and the heating uniformity of different parts of the blade was controlled.The thermal barrier coating prepared on the blade does not fall off after 30 times water cooled thermal shock test,which meets the engineering requirement of the blade.