High-temperature environment barrier coating layer structure and preparation method thereof

Abstract

The invention provides a high-temperature environment barrier coating layer structure and a preparation method thereof. The structure comprises a Gd2O3 doped Si bonding bottom layer, a Gd2SiO5 middlelayer and a Yb2SiO5 surface layer laminated on the surface of a SiC/SiC composite material basal body in sequence. An environment barrier coating layer is of a three-layer structure of vacuum plasma spraying gadolinium oxide doped Si bonding bottom layer+vacuum plasma spraying gadolinium silicate middle layer+vacuum plasma spraying ytterbium silicate surface layer. A Gd2SiO5 coating layer and a Yb2SiO5 coating layer are prepared by adopting a vacuum plasma spraying process; components of the coating layers are maintained well; the material component loss and the silicate decomposition are hardly generated; the phase composition is stable; and the thermal shock resistance of the coating layers is excellent. The physical performance matchability of all the layers is excellent to effectivelyrelieve the thermal stress of the coating layers; the working temperature can reach 1400 DEG C; and the thermal shock resistance, the thermal circulation resistance and the service life of the environment barrier coating layer are greatly improved.

Description

technical field [0001] The invention relates to the technical field of preparation of high-temperature coatings for aero-engines and ground gas turbines, in particular to a high-temperature environment barrier coating structure and a preparation method thereof. Background technique [0002] SiC fiber-reinforced SiC composites (SiC / SiC) have the advantages of light weight, high structural strength, high temperature resistance, oxidation resistance, and erosion resistance. As a high-temperature thermal structural material, it has important applications in the fields of aeroengines and ground gas turbines. However, in the gas environment of high-temperature water vapor of the engine and the temperature is higher than 1300 ° C, the SiC / SiC composite material is easily corroded by water vapor, which seriously degrades the performance of the SiC / SiC material and even fails the material. SiC / SiC composite materials for thermal protection. [0003] At present, the environmental bar...

AI Technical Summary

Problems solved by technology

This is mainly because mullite (3Al 2 o 3 2SiO2 2 ) and BSAS have serious chemical stability problems when working in an environment above 1300 °C, and BSAS will interact with SiO 2 The reaction produces a low-melting glass phase (melting point below 1300°C), which leads to premature peeling and failure of the coating when the working temperature exceeds 1300°C, which limits its use at higher temperatures

Moreover, BSAS has high chemical activity at high temperature, and can chemically react with water vapor, molten salt and other substances in the engine environment, and does not have the ability to resist CMAS corrosion

CMAS is CaO, MgO, Al 2 o 3 , SiO 2 CMAS melts at about 1250°C. It can melt the BSAS coating material, infiltrate the environmental barrier coating, and penetrate into the interior of the coating through capillary action along the pores, making the surface of the coating rough and the interior of the coating rough. become loose, and during the cooling cycle of the engine shutdown, the CMAS molten salt solidifies into a glassy substance, the modulus of the penetrating layer will increase, and the strain tolerance of the environmental barrier coating will drop sharply. During the subsequent thermal cycle, the environmental barrier coating The layer will be peeled off in a large area, which will greatly reduce the durability of the environmental barrier coating

[0004] At present, there are also Si bonding bottom layer + mullite middle layer + rare earth silicate surface layer environmental barrier coating, rare earth silicate Re 2 SiO 5 / Re 2 Si 2 o 7 (Re is Yb, Gd, Er and Dy, etc.) has good high-temperature chemical stability, and its resistance to water vapor corrosion and CMAS corrosion at 1400 ° C is better than BSAS, but the melting point of the bonding bottom Si material is only 1414 ° C. The Si bonding bottom layer softens above 1300°C, and the strength drops rapidly, resulting in the use temperature of the environmental barrier coating of this system is also below 1300°C

And at present, the mullite intermediate layer and the rare earth silicate surface layer are basically prepared by atmospheric plasma spraying method. The rare earth silicate decomposes during the atmospheric plasma spraying process, and generates rare earth oxides and silica glass phases, which will significantly affect the coating quality. The high temperature stability of the coating leads to a decrease in the thermal shock resistance of the coating and a shortened service life

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