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The Study Of Performance Of Thermal Barrier Coatings Prepared On The Surface Of GH586 By Plasma Spraying And Laser Remelting

Posted on:2017-04-02Degree:MasterType:Thesis
Country:ChinaCandidate:W LiuFull Text:PDF
GTID:2271330503963968Subject:Mechanical engineering
Abstract/Summary:PDF Full Text Request
Thermal barrier coatings are now widely used for turbine rotor blades, with the current aero-engine propulsion increasing ratio, the engine inlet temperature will be further enhanced, GH586 is one kind of materials for manufacturing turbine engine, but its highest using temperature is 800℃, more than the temperature, the oxidation of the material will increased and leading to destruction of its original mechanical properties.The inlet temperature of the engine is usually above 1000 ℃, and its inlet temperature will be higher in the future. Thermal barrier coatings due to good high temperature insulation performance and high temperature stability, which is widely used aviation and other high temperature areas.The thermal barrier coating system have been prepared has a double layer composed of a bond coat and a ceramic coat. Since the ceramic coat has excellent insulation properties that can reduce the actual temperature of the superalloy substrate.While bond coat assume a role antioxidant and reducing the oxidation of the substrate in one aspect, it is also beneficial to reduce the gap of thermal expansion coefficient between the ceramic coat,proventing the coating fall off by thermal stress is too large,serving as the role of transition in another aspect.In this paper, GH586 nickel-based superalloy was used for substrate material, the ceramic coat material was 8% Y2O3 stabilized ZrO2(YSZ), the bond coat material was Co CrAlYTaSi. Plasma spraying and laser remelting technology was used for prepared thermal barrier coatings on the GH586. High temperature oxidation resistance and thermal shock resistance of the coating before and after laser remelting was studied,and the individual bond coat was also studied. The main results are as follows:(1) The parameters of prepared bond coat using plasma spraying was optimized:the power is 30 kw, the distance is 100 mm,the main gas flow is 60L/min,the auxiliary gas flow is 45L/min,the feeding rate is 2r/min,the spraying movment speed is200mm/min. The thickness of bond coat is about 100μm, and the bind status is good.The antioxidant levels achieved complete oxidation at 1100 ℃, its oxidation constant is 2.62892. And finally generates a dense oxide film on the surface of the coating. The thermal shock times at 1100 ℃ is 115 times, while a TGO layer generated between the substrate and the bond coat during thermal shock and oxidation processing, the TGO layer thickness increasesd and ultimately causing coating failure.(2) The parameters of laser remeltd preparing Co Cr AlYTaSi/YSZ were optimized:the power is 400 w,the scanning speed is 700mm/min,the overlapping is1 mm,the spot size is 5×5mm,the defocusing distance is 285 mm.The thickness of bond coat was about 100μm, the thickness of ceramic coat was about 200μm. After remelted the coating structure is more compact, the surface is more smooth, generating multilateral cellular crystal on surface. During spraying the Zr O2 did not occur phase transformation, The coating adhesion strength improved 31.43% after laser remeled.(3) Plasma sprayed coatings and laser remelted coatings did not occur phase transition during thermal shock in 1000 ℃. The number of thermal shock of sprayed coating is 71 times, after laser remelting reached 123 times, The reasons for thermal coating thermal shock failure are the coefficients of thermal expansion mismatch between the ceramic coat and the metal bond coat and the growh of TGO layer.(4)The sprayed coating has good resistance to oxidation at 1000 ℃, in the oxidation process has no phase changed. While the remelted coating, the t′â†'m phase transition happened in the oxidation process, but the amount is very small. After laser remelted the high temperature oxidation resistance of the coating system did not change significantly.
Keywords/Search Tags:Thermal barrier coating, plasma spraying, laser remelting, thermal shock resistance, high temperature oxidation resistance
PDF Full Text Request
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