阅读说明：本技术 一种提高热障涂层抗cmas腐蚀能力的方法 (Method for improving CMAS corrosion resistance of thermal barrier coating ) 是由 钱伟 花银群 蔡杰 戴峰泽 陈瑞芳 于 2021-08-31 设计创作，主要内容包括：本发明涉及热障涂层表面腐蚀与防护技术领域,具体为一种提高热障涂层抗CMAS腐蚀能力的方法。本发明所述的热障涂层为多层结构,其中包括粘结层、陶瓷层、激光重熔部分陶瓷层形成的重熔层以及采用高温预处理形成的预腐蚀层。利用激光重熔陶瓷层的表面裂纹,在其表面涂覆一层预先设计的混合氧化物。重熔层是利用纳秒脉冲激光对陶瓷层进行表面改性处理,可以优化陶瓷层表面组织,提高致密度,降低孔隙率,封堵CMAS的扩散通道。预腐蚀层为利用预先设计的混合氧化物与锆酸钆类陶瓷层在高温条件下先期反应,形成磷灰石相反应层,从而大幅度提高热障涂层抗CMAS腐蚀能力。(The invention relates to the technical field of surface corrosion and protection of thermal barrier coatings, in particular to a method for improving CMAS corrosion resistance of a thermal barrier coating. The thermal barrier coating has a multilayer structure and comprises a bonding layer, a ceramic layer, a remelted layer formed by remelting part of the ceramic layer by laser and a pre-etched layer formed by adopting high-temperature pretreatment. And (3) remelting surface cracks of the ceramic layer by using laser, and coating a layer of pre-designed mixed oxide on the surface of the ceramic layer. The remelted layer is formed by performing surface modification treatment on the ceramic layer by using nanosecond pulse laser, so that the surface structure of the ceramic layer can be optimized, the density is improved, the porosity is reduced, and a CMAS diffusion channel is blocked. The pre-corrosion layer is formed by the advanced reaction of a pre-designed mixed oxide and a gadolinium zirconate ceramic layer at a high temperature to form an apatite phase reaction layer, so that the CMAS corrosion resistance of the thermal barrier coating is greatly improved.)

1. A method for improving CMAS corrosion resistance of a thermal barrier coating is characterized in that the thermal barrier coating is of a multilayer structure and comprises a bonding layer, a ceramic layer, a laser remelting layer and a pre-corrosion layer, and the method is characterized in that: after the step of plasma spraying the bonding layer and the ceramic layer, modifying the surface of the prepared ceramic layer by adopting a laser remelting technology to obtain a laser remelting layer; and then uniformly coating the prefabricated oxide suspension on the surface of the laser remelting layer, and preserving heat in a high-temperature furnace to form a compact apatite phase pre-corrosion layer, thereby further improving the CMAS corrosion resistance of the thermal barrier coating.

2. The method of claim 1, wherein the steps of improving CMAS corrosion resistance of the thermal barrier coating comprise:

the method comprises the following steps: grinding, polishing and sand blasting the surface of a high-temperature alloy sample to be processed;

step two: preparing a NiCoCrAlY bonding layer on the surface of a sample by adopting a plasma spraying process;

step three: carrying out vacuum heat treatment and surface sand blasting treatment on the sample sprayed with the bonding layer;

step four: spraying a ceramic layer on the surface of the sample treated in the step three by adopting a plasma spraying process;

step five: grinding and polishing the surface of the ceramic layer prepared in the step four;

step six: performing preheating treatment on the ceramic layer processed in the fifth step;

step seven: clamping the sample subjected to the preheating treatment in the sixth step on a workbench of a laser, and performing laser remelting processing to obtain a laser remelting layer;

step eight: weighing CaO and Al₂O₃、TiO₂、La₂O₃And SiO₂Adding absolute ethyl alcohol into the mixed oxide powder, performing first ball milling in a ball mill, and drying to obtain dry powder; placing the dried powder into a high-temperature furnace for high-temperature calcination, cooling along with the furnace, then adding absolute ethyl alcohol, performing secondary ball milling in a ball mill, drying, and then grinding and sieving the obtained powder;

step nine: mixing the powder sieved in the step eight with absolute ethyl alcohol, continuously stirring until the mixture is uniform to obtain a required suspension, and coating the suspension on the surface of the laser remelting layer obtained in the step seven;

step ten: and (4) putting the sample obtained in the ninth step into a high-temperature furnace for heat preservation, cooling to room temperature, and taking out to obtain an apatite phase pre-corrosion layer and obtain the final thermal barrier coating.

3. The method for improving the CMAS corrosion resistance of a thermal barrier coating of claim 2, wherein in the second step, the NiCoCrAlY bonding layer has a thickness of 50 to 100 μm.

4. The method for improving the CMAS corrosion resistance of the thermal barrier coating as claimed in claim 2, wherein in the fourth step, the ceramic layer has a thickness of 100 to 300 μm; the ceramic layer is made of rare earth zirconate materials with a chemical formula of RE₂Zr₂O₇RE is La or Gd.

5. The method for improving the CMAS corrosion resistance of a thermal barrier coating as claimed in claim 2, wherein in step six, the preheating temperature is: preheating for 10-20 min at 200-400 ℃.

6. The method for improving the CMAS corrosion resistance of the thermal barrier coating as claimed in claim 2, wherein in the seventh step, the preset laser process parameters are 1064nm wavelength, 100ns pulse width, 100-300W laser power, 10kHz repetition frequency, 5-30 mm/s scanning speed, 300mm focal length, 30 microns of spot diameter, and 10-20 microns of laser remelted layer thickness.

7. The method of claim 2, wherein in step eight, powders of 22% CaO and 14% Al by weight are mixed₂O₃、10％TiO₂、9％La₂O₃And 45% SiO₂(ii) a The first ball milling time is 6-8 h, and the drying is performed at 120 DEG CDrying for 10 hours in the drying box; the high-temperature calcination temperature is 1300 ℃, and the calcination time is 8 h; the time of the second ball milling is 24 hours, and the sieving refers to sieving by a 200-mesh sieve.

8. The method for improving the CMAS corrosion resistance of a thermal barrier coating as claimed in claim 2, wherein in the ninth step, the mass ratio of the sieved powder to the absolute ethyl alcohol is 1:10, and the coating density is 20mg/cm²。

9. The method for improving the CMAS corrosion resistance of the thermal barrier coating as claimed in claim 2, wherein in the tenth step, the temperature is 1150-1250 ℃ and the time is 0.5 h; the thickness of the apatite phase pre-corrosion layer is 5-10 microns.

Technical Field

The invention relates to the technical field of surface corrosion and protection of thermal barrier coatings, in particular to a method for improving CMAS corrosion resistance of a thermal barrier coating.

Background

The thermal barrier coating is widely applied to high-temperature components of an aviation turbine engine, so that the efficiency and the comprehensive performance of the engine are improved. With the development requirement of high propulsion ratio and high efficiency, the ambient temperature inside the engine is already as high as 1600 ℃, and the traditional 8YSZ (8% Y) is₂O₃-Zr₂O₃) The materials have not been able to meet the use requirements. Rare earth zirconate-based materials, e.g. gadolinium zirconate (Gd)₂Zr₂O₃) And the like, the material is expected to replace 8YSZ to become a candidate material of a next-generation thermal barrier coating due to lower thermal conductivity, more excellent high-temperature phase stability, more matched expansion coefficient and better fracture toughness.

Research shows that CMAS (CaO-MgO-Al) in service environment is in service when aviation components such as airplanes are in service₂O₃-SiO₂) May be deposited on the surface of the thermal barrier coating resulting in failure of the coating. As engine temperatures increase, CMAS becomes increasingly corrosive to thermal barrier coatings. The failure mechanism of CMAS to thermal barrier coatings includes: on one hand, in a high-temperature environment, molten CMAS can be deposited on the surface of a thermal barrier coating, and can be diffused into a ceramic layer through a porous channel formed by inherent defects of plasma spraying, and in the cooling process, an unstable brittle glass phase product formed by the CMAS can seriously reduce the strain tolerance of the ceramic layer, so that the stress of the coating is increased to accelerate the peeling of the coating; on the other hand, molten CMAS accelerates sintering of the ceramic layer, increasing thermal conductivity, leading to failure of the coating.

How to form an effective barrier layer on the surface of the ceramic layer to slow down the CMAS corrosion without affecting the thermal insulation performance of the ceramic layer becomes a key direction for the research of CMAS corrosion resistance. Laser remelting is a technical means of modifying the surface of a material by using high-energy laser beams. The surface of the ceramic layer is processed by adopting a laser remelting technology, so that the surface structure can be optimized, crystal grains can be refined, the surface density can be improved, holes and large particles on the surface can be reduced, and longitudinal large cracks with inherent defects in spraying and CMAS diffusion channels in the ceramic layer can be blocked. However, after laser remelting, the surface still has some fine cracks with a net structure, and a new CMAS diffusion channel is formed. A secondary treatment with a dense blocking layer is necessary. The apatite phase generated by the reaction of the CMAS and the rare earth zirconate has compact structure, high melting point, good high-temperature phase stability, high matching degree with the ceramic layer and good interface compatibility, and becomes an ideal material of the blocking layer.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for improving the CMAS corrosion resistance of a thermal barrier coating, which adopts a multi-layer thermal barrier coating design and comprises a bonding layer, a ceramic layer, a laser remelting layer and a pre-corrosion layer to improve the surface state of the thermal barrier coating, can effectively solve the problem of CMAS corrosion of the thermal barrier coating in the service process and prolong the service life of the thermal barrier coating.

A method for improving CMAS corrosion resistance of a thermal barrier coating is characterized by comprising the following steps:

the method comprises the following steps: grinding, polishing and sand blasting the surface of a high-temperature alloy sample to be processed;

step two: preparing a NiCoCrAlY bonding layer on the surface of the sample by adopting a plasma spraying process, wherein the thickness of the NiCoCrAlY bonding layer is 50-100 mu m;

step three: carrying out vacuum heat treatment and surface sand blasting treatment on the sample sprayed with the bonding layer;

step four: spraying a ceramic layer on the surface of the sample treated in the step three by adopting a plasma spraying process, wherein the thickness of the ceramic layer is 100-300 mu m;

the ceramic layer is made of rare earth zirconate materials with a chemical formula of RE₂Zr₂O₇RE is La or Gd.

Step five: grinding and polishing the surface of the ceramic layer prepared in the step four;

step six: carrying out preheating treatment on the ceramic layer treated in the step five, wherein the temperature is as follows: keeping the temperature for 10-20 min at 200-400 ℃;

step seven: and (3) clamping the sample subjected to the preheating treatment in the sixth step on a workbench of a laser, presetting the process parameters of the laser to be 1064nm in wavelength, 100ns in pulse width, 100-300W in laser power, 10kHz in repetition frequency, 5-30 mm/s in scanning speed, 300mm in focal length and 30 mu m in spot diameter, and carrying out laser remelting processing while controlling the thickness of a laser remelting layer to be 10-20 mu m.

Step eight: weighing 22 percent of CaO and 14 percent of Al in percentage by mass₂O₃、10％TiO₂、9％La₂O₃And 45% SiO₂Adding absolute ethyl alcohol into the mixed powder, ball-milling the mixture in a ball mill for 6-8 hours, putting the ball-milled mixture in a drying oven at 120 ℃, and drying the ball-milled mixture for 10 hours to obtain dry powder;

step nine: putting the dry powder in the step eight into a high-temperature furnace at 1300 ℃ for calcining for 8h, cooling along with the furnace, adding absolute ethyl alcohol, carrying out ball milling for 24h in a ball mill, drying for 10h in a drying box at 120 ℃, grinding the obtained powder, and sieving with a 200-mesh sieve;

step ten: and mixing the powder obtained in the step nine with absolute ethyl alcohol according to the mass ratio of 1:10, and continuously stirring until the mixture is uniform to obtain the required suspension.

Step eleven: the suspension of the step ten is added at the concentration of 20mg/cm²And (4) coating the laser remelting layer obtained in the step seven on the surface of the laser remelting layer.

Step twelve: and (4) placing the sample obtained in the step eleven in a high-temperature furnace at 1150-1250 ℃, preserving heat for 0.5h, cooling to room temperature, taking out, and obtaining an apatite phase pre-corrosion layer with the thickness of 5-10 microns to obtain the final thermal barrier coating.

The invention has the advantages that:

1. the ceramic layer after plasma spraying is subjected to surface modification treatment by adopting a laser remelting technology, so that the surface structure of the ceramic layer of the thermal barrier coating is further optimized, grains are refined, the surface density is improved, holes and large particles on the surface are reduced, and longitudinal large cracks and CMAS diffusion channels in the ceramic layer, which are inherent defects of plasma spraying, are effectively blocked;

2. the apatite phase pre-corrosion layer has a compact structure, high melting point, good high-temperature phase stability, high matching degree with a ceramic layer and good interface compatibility, can effectively fill secondary micro cracks and holes generated after laser remelting, and further improves the CMAS resistance of the thermal barrier coating;

3. the thermal barrier coating provided by the invention does not damage the structure and performance of the original thermal barrier coating, and has the advantages of small weight increment, simple process, greenness, high efficiency and low pollution.

Detailed Description

Embodiments of the present invention will now be described.

Example 1

(1) The surface of a DD6 nickel-based single crystal sample is respectively ground, polished and sandblasted, and a NiCoCrAlY bonding layer is prepared by a plasma spraying method, wherein the specific process comprises the steps of spraying distance of 110mm, spraying voltage of 42V, spraying current of 710A, argon flow of 80L/min, powder feeding rate of 60g/min and thickness of 60 mu m. Then carrying out vacuum heat treatment on the prepared bonding layer, wherein the specific process is that the vacuum degree is 10^-3pa, keeping the temperature at 900 ℃ for 10h, cooling to room temperature along with the furnace, and then carrying out surface sand blasting treatment, wherein the specific process comprises the following steps: the working pressure of sand blasting is 0.2Mpa, and the diameter of medium particles is 50 μm. Gd is sprayed on the surface of the sample with the prepared bonding layer₂ Zr₂O₇The ceramic layer is prepared by the specific process that the spraying distance is 110mm, the spraying voltage is 60V, the spraying current is 850A, the argon flow is 80L/min, the powder feeding rate is 80g/min, and the thickness of the prepared ceramic layer is 160 mu m, so that the thermal barrier coating is obtained. In addition, for the sake of comparison, the thermal barrier coatings required for the implementation of the comparative examples were prepared simultaneously using the same process.

(2) And (3) preheating the sample at 200 ℃ for 20 min. Then, laser remelting treatment is carried out on the surface of the ceramic layer by using an Nd-YAG laser. The specific process parameters are as follows: the wavelength is 1064nm, the pulse width is 100ns, the laser power is 120W, the repetition frequency is 10kHz, the scanning speed is 8mm/s, the focal length is 300mm, and the diameter of a light spot is 30 μm. And carrying out laser remelting processing and controlling the thickness of the laser remelting layer to be 10 mu m.

(3) CaO and 14 with the weight proportion of 22 percent％Al₂O₃、10％TiO₂、9％La₂O₃And 45% SiO₂Adding absolute ethyl alcohol into the mixed powder, ball-milling the mixed powder in a ball mill for 6 hours, then drying the mixed powder in a drying oven at 120 ℃ for 10 hours, calcining the obtained dried powder in a high-temperature furnace at 1300 ℃ for 8 hours, cooling the calcined powder to room temperature along with the furnace, then adding absolute ethyl alcohol, ball-milling the calcined powder in the ball mill for 24 hours, taking out the calcined powder, and drying the calcined powder in the drying oven at 120 ℃ for 10 hours to obtain dried powder. The powder is subsequently milled. And sieving with 200 mesh sieve to obtain uniform and fine powder. And mixing the prepared powder with absolute ethyl alcohol according to the mass ratio of 1:10, and continuously stirring until the mixture is uniform to obtain a suspension.

(4) The suspension was brought to 20mg/cm²The coating density of (a) is applied to the surface of the ceramic layer sample after laser remelting. Then the sample is placed in a high temperature furnace at 1150 ℃ and calcined for 0.5h, and then cooled to room temperature along with the furnace to obtain a pre-etched layer of dense apatite phase with the thickness of 5 mu m

(5) The prepared thermal barrier coating and the conventional thermal barrier coating implementing the comparative example were subjected to a CMAS corrosion test. Experiments show that: after a 5 hour, 1250 ℃ CMAS corrosion test, the mean depth of diffusion of the CMAS was only 25.2 μm, while the diffusion depth of the conventional thermal barrier coating CMAS without surface treatment, which was the comparative example implemented, was 80 μm, a significant improvement.

Example 2

(1) The surface of a DD6 nickel-based single crystal sample is respectively ground, polished and sandblasted, and a NiCoCrAlY bonding layer is prepared by a plasma spraying method, wherein the specific process comprises the steps of spraying distance of 110mm, spraying voltage of 42V, spraying current of 710A, argon flow of 80L/min, powder feeding rate of 60g/min and thickness of 60 mu m. Then carrying out vacuum heat treatment on the prepared bonding layer, wherein the specific process is that the vacuum degree is 10^-3pa, keeping the temperature at 900 ℃ for 10h, cooling to room temperature along with the furnace, and then carrying out surface sand blasting treatment, wherein the specific process comprises that the sand blasting working pressure is 0.2Mpa, and the diameter of the medium particles is 50 mu m. Gd is sprayed on the surface of the sample with the prepared bonding layer₂ Zr₂O₇The ceramic layer is prepared by spraying at a distance of 110mm and a voltage of 60V at a current of 850A under argonThe air flow is 80L/min, the powder feeding rate is 80g/min, and the thickness of the prepared ceramic layer is 160 mu m, thus obtaining the thermal barrier coating. In addition, for the sake of comparison, the thermal barrier coatings required for the implementation of the comparative examples were prepared simultaneously using the same process.

(3) And (3) preheating the sample, wherein the preheating temperature is 300 ℃, and the preheating time is 15 min. And performing laser remelting treatment on the surface of the ceramic layer by using an Nd-YAG laser. The specific process parameters are as follows: the wavelength is 1064nm, the pulse width is 100ns, the laser power is 220W, the repetition frequency is 10kHz, the scanning speed is 12mm/s, the focal length is 300mm, and the spot diameter is 30 μm. And performing laser remelting processing, and controlling the thickness of the laser remelting layer to be 15 mu m.

(3) Weighing 22 percent of CaO and 14 percent of Al in percentage by mass₂O₃、10％TiO₂、9％La₂O₃And 45% SiO₂Adding absolute ethyl alcohol into the mixed powder, ball-milling the mixed powder in a ball mill for 6 hours, then drying the mixed powder in a drying box at 120 ℃ to obtain dry powder, calcining the dry powder in a high-temperature furnace at 1300 ℃ for 8 hours, cooling the calcined powder to room temperature along with the furnace, then adding the absolute ethyl alcohol, ball-milling the calcined powder in the ball mill for 24 hours, taking out the calcined powder, and drying the calcined powder in the drying box at 120 ℃ for 10 hours to obtain the dry powder. The powder is subsequently milled. And sieving with 200 mesh sieve to obtain uniform and fine powder. And mixing the prepared powder with absolute ethyl alcohol according to the mass ratio of 1:10, and continuously stirring until the mixture is uniform to obtain a suspension.

(4) The suspension was brought to 20mg/cm²The coating density of (a) was applied to the surface of the ceramic layer sample. The sample was then calcined in a high temperature furnace at 1250 ℃ for 0.5h and then cooled in the furnace to room temperature to give a dense apatite phase barrier layer of 5 μm thickness.

(5) The prepared thermal barrier coating and the conventional thermal barrier coating implementing the comparative example were subjected to a CMAS corrosion test. Experiments show that: after a 5 hour, 1250 ℃ CMAS corrosion test, the mean depth of diffusion of the CMAS was only 20.2 μm, while the diffusion depth of the conventional thermal barrier coating CMAS without surface treatment, which is the comparative example implemented, was 80 μm, a significant improvement.