Abstract
YAG (Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>)-Al<sub>2</sub>O<sub>3</sub>-Pt composite TBCs have been prepared on Ni-based superalloy (0.1% C, 12% Co, 6.5% Cr, 6.2% Al, 5% W, 1% Mo, 1.5% Hf, 6.5% Ta, 0.01% B, balance Ni, wt.%) by cathode plasma electrolytic deposition (CPED). As polyethylene glycol (PEG) is added in solution, the spark ignition current density is reduced significantly, and CPED would be a promising technique to deposit the uniform coatings on large-sized cathode. The cyclic oxidation tests at 1100°C reveal that the high temperature oxidation resistance of such TBCs are significantly improved by dispersing Pt particles. These excellent performances can be attributed to the effects: the low porosity of coating can inhibit further oxidation of alloy substrate, the toughening role of Pt particles and the stress relaxation caused by the deformation in the porous structure can improve the mechanical properties remarkably. The spallation resistance of YAG-Al<sub>2</sub>O<sub>3</sub>-Pt composite coating can be significant improved by using the following two method: one is adding PEG 20000 to the solution during the CPED process; the other is using Pt particle to toughness the coating. In addition, such YAG-Al<sub>2</sub>O<sub>3</sub>-Pt composite coatings possess quite well thermal insulation owing to the thermal insulation capability of YAG and the structure of vertical block micropores.
Highlights
Thermal barrier coatings (TBCs) have been widely used in the gas turbine engines to protect the metal components performing in high temperature, oxidative, and hot corrosive environment [1, 2]
The thermal stress caused by the mismatch of thermal expansion between top coat and bond coat can lead to the cracking and spallation at the thermal grown oxide (TGO) layer, which is the key factor in the failure of TBCs [7]
YAG-Al2O3 composite coating dispersed with Pt particle were prepared by cathodic plasma electrolytic deposition
Summary
Thermal barrier coatings (TBCs) have been widely used in the gas turbine engines to protect the metal components performing in high temperature, oxidative, and hot corrosive environment [1, 2]. During service at high temperature, the interdiffusion between the metallic bond coat and superalloy substrate cannot be avoided, it would reduce the mechanical properties of turbine blade. In order to solve above problems, different materials with higher operating temperature have studied recently, such as YAG, La2Zr2O7 and LaTi2Al9O19. YAG is composed of Al2O3 and Y2O3, which possesses good oxidation resistance, and low thermal conductivity. Z. et al [17] has prepared a thick 8YSZ coating on FeCrAl alloy by cathodic micro-arc electrodeposition Later this technique was improved and termed as CPED. After researchers [18, 19] have prepared Al2O3 TBC by CPED, and the coating is continuous and combines with the substrate well. Porous YAG-Al2O3 composite TBCs dispersed with Pt particles were prepared on superalloy by CPED. The phase structures were detected by X-ray diffraction analysis (XRD, PW 3710, Philips) at room temperature using nickel filtered Cu Kα radiation in the 2θ range of 10-90° with a step size of 0.02°
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