阅读说明：本技术 一种等离子物理气相沉积用纳米莫来石粉体及其制备方法 (Nano mullite powder for plasma physical vapor deposition and preparation method thereof ) 是由 肖飞 王铀 闫牧夫 许壮志 王东升 于 2020-04-17 设计创作，主要内容包括：一种等离子物理气相沉积用纳米莫来石粉体及其制备方法。本发明属于航空发动机及地面燃气轮机高温涂层制备技术领域。本发明的目的在于解决现有EBC涂层用粉体材料晶粒分布不均匀,制备的涂层致密度不高、涂层易产生气孔、裂纹等缺陷而影响涂层使用寿命的技术问题。本发明采用高纯、纳米级Al<Sub>2</Sub>O<Sub>3</Sub>与SiO<Sub>2</Sub>粉体,通过湿法混合、喷雾造粒、高温烧结工艺,制备出纳米莫来石粉体。在莫来石粉体制备过程中加入有机造孔剂,通过高温烧结有机物挥发后会留下孔隙,使造粒粉体变得疏松、多孔,便于在等离子物理气相沉积过程中气化。通过浆料中含水量及造孔剂等的调整来控制喂料的孔隙率、尺寸大小等参数。制备的喂料具有良好的流动性,能满足不同涂层制备工艺的要求。(A nano mullite powder for plasma physical vapor deposition and a preparation method thereof. The invention belongs to the technical field of preparation of high-temperature coatings of aircraft engines and ground gas turbines. The invention aims to solve the technical problems that the grain distribution of the existing powder material for the EBC coating is not uniform, the density of the prepared coating is not high, and the service life of the coating is influenced by the defects of pores, cracks and the like easily generated by the coating. The invention adopts high-purity nanoscale Al 2 O 3 With SiO 2 The nano mullite powder is prepared from the powder through wet mixing, spray granulation and high-temperature sintering. Organic pore-forming agent is added in the preparation process of mullite powder, and pores are left after the organic matter is volatilized through high-temperature sintering, so that the granulated powder becomes loose and porous, and the plasma physical vapor deposition process is convenientAnd (4) gasifying. Parameters such as porosity, size and the like of the feeding are controlled by adjusting the water content in the slurry, the pore-forming agent and the like. The prepared feed has good fluidity and can meet the requirements of different coating preparation processes.)

1. A nano-mullite powder for plasma physical vapor depositionCharacterized in that the nano mullite powder is made of Al₂O₃Powder, SiO₂The material is prepared from powder, SiC powder, gum arabic, ammonium citrate, an organic pore-forming agent and deionized water; the Al is₂O₃Powder and SiO₂The mass ratio of the powder is (2-3): 1; the addition amount of the SiC powder is Al₂O₃Powder and SiO₂0-20% of the total mass of the powder; the addition amount of the Arabic gum is Al₂O₃Powder, SiO₂1% -2% of the total mass of the powder and the SiC powder; the addition amount of the ammonium citrate is Al₂O₃Powder, SiO₂1% -2% of the total mass of the powder and the SiC powder; the addition amount of the organic pore-forming agent is Al₂O₃Powder, SiO₂0 to 5 percent of the total mass of the powder and the SiC powder; the water and Al₂O₃Powder, SiO₂The total mass ratio of the powder, the SiC powder, the gum arabic, the ammonium citrate and the organic pore-forming agent is (0.8-2): 0.5.

2. the nano mullite powder for plasma physical vapor deposition according to claim 1, wherein the nano mullite powder for plasma physical vapor deposition is porous and spherical, the particle size of the powder is 1-45 μm, and the flowability is 10-25 g/min.

3. The nano mullite powder for plasma physical vapor deposition as claimed in claim 1, wherein the Al is₂O₃The purity of the powder is more than or equal to 99.9 percent, and the granularity D₅₀: 10 to 30nm, SiO₂The purity of the powder is more than or equal to 99.9 percent, and the granularity D₅₀: 10-30 nm, the purity of the SiC powder is more than or equal to 99%, and the granularity D₅₀：20～50nm。

4. The nano mullite powder for plasma physical vapor deposition as claimed in claim 1, wherein the Al is₂O₃Powder and SiO₂The mass ratio of the powder is 71.83: 28.17; the addition amount of the SiC powder isAl₂O₃Powder and SiO₂10 percent of the total mass of the powder.

5. The nano mullite powder for the plasma physical vapor deposition as claimed in claim 1, wherein the organic pore-forming agent is an organic lipid material capable of completely volatilizing at 600-1000 ℃.

6. The nano mullite powder for plasma physical vapor deposition as claimed in claim 1, wherein the organic pore-forming agent is one or a mixture of more of polystyrene, phenolic resin and polystyrene.

7. The preparation method of the nano mullite powder for the plasma physical vapor deposition as claimed in any one of claims 1 to 6, which is characterized by comprising the following steps:

firstly, ball milling, ① dissolving Arabic gum in water to obtain Arabic gum aqueous solution, ② mixing Al₂O₃Powder, SiO₂Ball-milling and mixing the powder, the SiC powder, the gum arabic aqueous solution, the ammonium citrate, the organic pore-forming agent and deionized water, and sieving the mixture after mixing to obtain slurry;

secondly, spray granulation: putting the slurry obtained in the step one into a stirring cylinder, setting the inlet and outlet temperatures of a centrifugal spray granulation tower, wherein the inlet temperature is 220-250 ℃, the outlet temperature is 90-110 ℃, the rotation speed of an atomizing disc is 33-40 Hz, the feeding speed is 4-6L/h, and drying and sieving are carried out after spray granulation to obtain powder;

thirdly, high-temperature sintering: and (2) putting the powder obtained in the step two into a mullite crucible, sintering under the protection of inert gas, heating to 450-550 ℃ at a heating rate of 4-6 ℃/min, preserving heat for 0.8-1.2 h, then continuously heating to 900-1100 ℃ at a heating rate of 5-10 ℃/min, preserving heat for 0.8-1.2 h, finally continuously heating to 1300-1500 ℃ at a heating rate of 5-10 ℃/min, and preserving heat for 2-5 h to obtain the nano mullite powder for plasma physical vapor deposition.

8. The preparation method of the nano mullite powder for the plasma physical vapor deposition according to claim 7, wherein the mass fraction of the gum arabic aqueous solution in the first step is 8-12%, the ball milling medium in the first step is alumina balls or zirconia balls, and the ball-to-material ratio is 1.5: 0.5, ball milling and mixing for 6 to 20 hours.

9. The method for preparing nano mullite powder for plasma physical vapor deposition according to claim 7, wherein the lining of the stirring cylinder in the second step is made of polyurethane, the rotating speed of the atomizing disc in the second step is 38Hz, the feeding rate is 5L/h, and the drying process in the second step is as follows: drying for 1.5-2.5 h at 90-110 ℃.

10. The method for preparing nano mullite powder for plasma physical vapor deposition according to claim 7, wherein the temperature is raised to 500 ℃ at a temperature raising rate of 5 ℃/min in the third step, the temperature is maintained for 1h, then the temperature is raised to 1000 ℃ at a temperature raising rate of 5 ℃/min, the temperature is maintained for 1h, and finally the temperature is raised to 1400 ℃ at a temperature raising rate of 5 ℃/min, and the temperature is maintained for 2 h.

Technical Field

The invention belongs to the technical field of preparation of high-temperature coatings of aero-engines and ground gas turbines, and particularly relates to nano mullite powder for plasma physical vapor deposition and a preparation method thereof.

Background

With the development of aerospace technology, turbine engines are developing in the direction of high flow ratio, high thrust-weight ratio and high inlet temperature. Among the above characteristics, a high inlet temperature is an important factor in achieving a high thrust ratio and high thermal efficiency of the engine. The traditional Ni-based high-temperature alloy is widely used as a hot end component, and the tolerable limit temperature of the traditional Ni-based high-temperature alloy is close to 1075 ℃. The thermal barrier coating can further increase the service temperature of the nickel-based superalloy material, but the service temperature of the nickel-based superalloy material under high thrust-weight ratio conditions of an engine is not reached. Therefore, the temperature performance of the nickel-based superalloy is close to the limit, and the urgent requirement of rapid development of advanced aeroengines cannot be met. Silicon-based non-oxide ceramic materials (such as SiC ceramic matrix composites) have excellent high-temperature strength and durability, and have replaced nickel-based high-temperature alloys as the first choice materials of aircraft engines. However, in a high-temperature environment of water-oxygen coupling, SiC reacts with oxygen and water, and the service performance thereof is reduced.

Environmental Barrier Coatings (EBC) are protective coatings on the surface of high temperature structural materials used in the engine environment, which generally consist of an oxide or a mixture of oxides. The high-temperature structural material can be isolated from the harsh environment in the engine, and the influence of the engine environment on the performance of the high-temperature structural material is reduced.

The so far relatively mature environmental barrier coating should be of the third generation, consisting of a bonding layer of silicon, an intermediate layer of mullite and a top layer of rare earth silicate. Mullite plays a vital role in relieving thermal mismatch and resisting oxidation in a third-generation environmental barrier coating system. The mullite powder is the key for preparing the high-performance coating, and the purity, the granularity, the surface appearance, the powder structure and the like of the powder material are important indexes for determining the powder characteristics. The common coating preparation processes mainly comprise Atmospheric Plasma Spraying (APS) and electron beam-physical vapor deposition (EB-PVD), wherein the APS technology has the advantages of simple process, high spraying efficiency and the like, the prepared coating is mainly a lamellar structure, the defects of gaps, cracks, air holes and the like are mixed in the coating, and the porosity of the coating is high and is generally more than 10%. The coating prepared by the EB-PVD technology has a unique columnar crystal structure, so that the coating has higher strain tolerance, the thermal cycle life of the coating is far longer than that of an APS coating, the surface of the coating is smooth, the density of the coating is high, and the coating prepared by the process has low efficiency and high cost. The plasma physical vapor deposition (PS-PVD) technology developed in recent years combines the advantages of the two processes, the morphology of the coating can realize a lamellar structure or a columnar crystal structure through process control, or the morphology of the coating is between the two structures, and the coating preparation efficiency is high. Compared with the traditional APS process, the Low Pressure Plasma Spraying (LPPS) process has the advantages of high vacuum degree, difficult oxidation in the feeding and deposition process, stable chemical components, good coating binding force and the like. PS-PVD and LPPS are the future development directions in the field of surface engineering, especially in the field of two machines.

At present, the mechanism for researching the EBC coating at home and abroad generally adopts micron-sized powder, and the prepared coating has low density and is easy to generate defects such as air holes, cracks and the like, thereby influencing the service life. The patent applied by Beijing Jinlunkuntan special machinery, Inc. is mainly rare earth silicate material (excluding mullite material), which is mainly prepared by blending micron-sized raw materials with different granularities, or nanometer-sized material is sintered at high temperature in advance and then mixed with original nanometer powder, the size of the nanometer material is increased after high-temperature treatment, crystal grains in the prepared feed consist of two granularities, and the uniformity of the coating structure is influenced because the size distribution of the crystal grains is not uniform.

Disclosure of Invention

The invention aims to solve the technical problems that the grain distribution of the existing powder material for the EBC coating is not uniform, the prepared coating has low density, and the service life of the coating is affected by the defects of pores, cracks and the like easily generated by the coating, and provides the nano mullite powder for plasma physical vapor deposition (PS-PVD, including LPPS) and the preparation method thereof.

The nano mullite powder for plasma physical vapor deposition consists of Al₂O₃Powder, SiO₂The material is prepared from powder, SiC powder, gum arabic, ammonium citrate, an organic pore-forming agent and deionized water; the Al is₂O₃Powder and SiO₂The mass ratio of the powder is (2-3): 1; the addition amount of the SiC powder is Al₂O₃Powder and SiO₂0-20% of the total mass of the powder; the addition amount of the Arabic gum is Al₂O₃Powder, SiO₂1% -2% of the total mass of the powder and the SiC powder; the addition amount of the ammonium citrate is Al₂O₃Powder, SiO₂1% -2% of the total mass of the powder and the SiC powder; the addition amount of the organic pore-forming agent is Al₂O₃Powder, SiO₂0 to 5 percent of the total mass of the powder and the SiC powder; the water and Al₂O₃Powder, SiO₂The total mass ratio of the powder, the SiC powder, the gum arabic, the ammonium citrate and the organic pore-forming agent is (0.8-2): 0.5.

further limited, the nano mullite powder for plasma physical vapor deposition is non-porous or porous and spherical powder, the particle size of the powder is 1-45 mu m, and the fluidity of the powder is 10-25 g/min.

In a further definition, the Al₂O₃The purity of the powder is more than or equal to 99.9 percent, and the granularity D₅₀: 10 to 30nm, SiO₂The purity of the powder is more than or equal to 99.9 percent, and the granularity D₅₀: 10-30 nm, the purity of the SiC powder is more than or equal to 99%, and the granularity D₅₀：20～50nm。

In a further definition, the Al₂O₃Powder and SiO₂The mass ratio of the powder is 71.83: 28.17; the addition amount of the SiC powder is Al₂O₃Powder and SiO₂10 percent of the total mass of the powder.

Further limiting, the organic pore-forming agent is an organic lipid material which can be completely volatilized at the temperature of 600-1000 ℃.

Further limiting, the organic pore-forming agent is one or a mixture of several of polystyrene, phenolic resin and polystyrene according to any ratio.

The preparation method of the nano mullite powder for the plasma physical vapor deposition is carried out according to the following steps:

firstly, ball milling, ① dissolving Arabic gum in water to obtain Arabic gum aqueous solution, ② mixing Al₂O₃Powder, SiO₂Ball-milling and mixing the powder, the SiC powder, the gum arabic aqueous solution, the ammonium citrate, the organic pore-forming agent and deionized water, and sieving the mixture after mixing to obtain slurry;

secondly, spray granulation: putting the slurry obtained in the step one into a stirring cylinder, setting the inlet and outlet temperatures of a centrifugal spray granulation tower, wherein the inlet temperature is 220-250 ℃, the outlet temperature is 90-110 ℃, the rotation speed of an atomizing disc is 33-40 Hz, the feeding speed is 4-6L/h, and drying and sieving are carried out after spray granulation to obtain powder;

thirdly, high-temperature sintering: and (2) putting the powder obtained in the step two into a mullite crucible, sintering under the protection of inert gas, heating to 450-550 ℃ at a heating rate of 4-6 ℃/min, preserving heat for 0.8-1.2 h, then continuously heating to 900-1100 ℃ at a heating rate of 5-10 ℃/min, preserving heat for 0.8-1.2 h, finally continuously heating to 1300-1500 ℃ at a heating rate of 5-10 ℃/min, and preserving heat for 2-5 h to obtain the nano mullite powder for plasma physical vapor deposition.

In the first step, the mass fraction of the arabic gum aqueous solution is 8-12%.

In the first step, the ball milling medium is alumina balls or zirconia balls, and the ball-to-material ratio is 3: 1.

in the first step, the mixing time of the ball mill is 6-20 h, the ball milling speed is 30-40 Hz, and the mixture is sieved by a 200-mesh sieve.

And in the second step, the lining of the stirring cylinder is made of polyurethane material.

In the second step, the rotating speed of the atomizing disc is 38Hz, and the feeding rate is 5L/h.

The drying process in the second step is as follows: drying for 1.5-2.5 h at 90-110 ℃.

And in the third step, the temperature is increased to 500 ℃ at the heating rate of 5 ℃/min, the temperature is kept for 1h, then the temperature is continuously increased to 1000 ℃ at the heating rate of 5 ℃/min, the temperature is kept for 1h, finally the temperature is continuously increased to 1400 ℃ at the heating rate of 5 ℃/min, and the temperature is kept for 2 h.

Compared with the prior art, the invention has the remarkable effects as follows:

since the mass of the nanopowder is small, it is easy to blow away and ablate in high temperature air stream, and it is not suitable for direct spraying, so the nanopowder is made into micron-sized agglomerates, which we usually refer to as spray feed. The preparation of the feed adopts high-purity nanoscale Al₂O₃、SiO₂The powder is a main material, nano SiC powder with different proportions is added to serve as a self-healing material, polyphenyl ester and the like serve as pore-forming agents, and the materials are prepared according to the set proportion through wet ball milling, spray granulation and high-temperature sintering.

The invention aims to prepare a nano ceramic powder material by adopting nano Al₂O₃、SiO₂The powder is used as a main material, and the high-purity nano mullite feed is prepared by ball milling pulping, spray granulation and high-temperature sintering processes. The nano material does not need to be processed independently, and the original nano size and state of each powder are kept. Parameters such as porosity, size and the like of the feeding material can be controlled by adjusting the water content in the slurry, the pore-forming agent and the like according to different requirements of the PS-PVD process and the LPPS process. The prepared feed has good fluidity and can meet the requirements of different coating preparation processes.

Drawings

FIG. 1 shows Al₂O₃SEM photograph of the powder;

FIG. 2 is SiO₂SEM photograph of the powder;

FIG. 3 is an SEM photograph of SiC powder;

FIG. 4 is an SEM photograph of a nano mullite powder in accordance with the first embodiment;

fig. 5 is an SEM photograph of the nano mullite powder of the second embodiment;

fig. 6 is an SEM photograph of the nano mullite powder of the third embodiment;

fig. 7 is an XRD graph of the nano mullite powder in the first embodiment.

Detailed Description