A method for preparing plasma-deposited aluminum-silicon coating on aircraft engine turbine blades

Abstract

The present invention belongs to the technical field of high-temperature protective coatings, and specifically relates to a method for preparing plasma-deposited aluminum-silicon coatings for turbine blades of aircraft engines. The present invention evaporates and gasifies solid aluminum-silicon alloy targets layer by layer in a vacuum furnace by means of arc discharge to form high-density aluminum-silicon plasma, and utilizes an electric field to accelerate aluminum-silicon ions to bombard the surface of parts to generate high-density vacancies, dislocations and other lattice defects, and achieves high-quality and efficient preparation of aluminum-silicon coatings through element diffusion.

Description

Technical Field

[0001] The invention belongs to the technical field of high-temperature protective coatings, and specifically relates to a method for preparing a plasma-deposited aluminum-silicon coating for an aircraft engine turbine blade. Background Art

[0002] Aircraft engine turbine blades are subjected to the impact and erosion of high-temperature combustion gases for a long time and have a harsh service environment. Their surfaces are invariably coated with high-temperature protective coatings to meet the requirements of high reliability and long service life.

[0003] Aluminide coating is a typical high-temperature protective coating with the ability to form aluminum oxide film. It is one of the main means of high-temperature oxidation and corrosion protection for hot-end parts of aircraft engines such as turbine blades. Aluminide coating mainly relies on thermal diffusion. By reasonably controlling the supply of active aluminum source, diffusion temperature and time, a β-NiAl coating is finally obtained on the surface of nickel-based high-temperature alloy. The coating and the substrate are metallurgically bonded. The supply method of active aluminum source has an important influence on the performance of the coating and is also one of the key technologies for obtaining high-performance aluminide coating.

[0004] Aluminum silicon coating, also known as silicon-modified aluminide coating, is composed of Si-doped β-NiAl phase and has excellent high-temperature corrosion resistance. It is widely used in high-temperature protection of hot end parts such as low-pressure turbine blades and tail nozzles of aircraft engines. The existing preparation methods of aluminum silicon coating are mainly chemical and physical slurry methods. Aluminum silicon slurry is one of the key technologies for coating preparation. It is usually composed of aluminum, silicon, or aluminum silicon alloy powder plus liquid organic / inorganic salts as binders and activators. Due to the problem of element reaction, the storage period of the slurry is generally no more than 1 year, and it is often prepared and used immediately. The typical brand of foreign aluminum silicon slurry is the inorganic salt system of Sermaloy J in the United States. It has been developed and used since the 1970s and is widely used in the working blades and guide blades of multiple models of aircraft engines. Domestic aluminum silicon slurries such as WL-1 and SKAS-3 equivalent to this system have also been developed. Aluminum silicon coatings mainly include diffusion type and melting type, which mainly include the following process procedures.

[0005]

[0006] From the above, it can be seen that the production cycle of aluminum-silicon coating prepared by the slurry method is long and the production efficiency is low. The coating thickness depends entirely on manual control by workers during the coating slurry brushing process. The product quality consistency and stability are poor. It is difficult to protect parts such as tenons, which can easily cause leakage and lead to the risk of brittle fracture of the blades. Summary of the invention

[0007] In view of the long production cycle, low production efficiency, poor coating quality consistency and stability of slurry infiltrated aluminum-silicon coating, the present invention provides a method for preparing plasma-deposited aluminum-silicon coating for aircraft engine turbine blades. By means of arc discharge in a vacuum furnace, the solid aluminum-silicon alloy target material is evaporated and gasified layer by layer to form a high-density aluminum-silicon plasma, and the aluminum-silicon ions are accelerated by an electric field to bombard the surface of the parts to generate high-density vacancies, dislocations and other lattice defects, and high-quality and efficient preparation of the aluminum-silicon coating is achieved through element diffusion.

[0008] The technical solution of the present invention is:

[0009] A method for preparing a plasma-deposited aluminum-silicon coating on an aircraft engine turbine blade comprises the following steps:

[0010] Step 1, performing wet sand blasting activation pretreatment on the surface of the hot end component of the aircraft engine, the specific parameters are as follows: the sand blasting medium is white corundum, the particle size is 180-250 mesh, the content is 20w.t.%-35w.t.%, the wind pressure is 0.25MPa-0.35MPa, the water pressure is greater than 0.2MPa, and the sand blasting distance is 180mm-350mm;

[0011] Step 2, ultrasonically cleaning the hot end parts of the aircraft engine in acetone, performing surface degreasing treatment, and then drying;

[0012] Step 3: Place the hot end parts of the aircraft engine in a plasma deposition aluminum silicon coating device and evacuate the vacuum to less than 1×10 -3 Pa, adjust the arc current of the aluminum-silicon target to 150-200A, and superimpose a 250-300A pulse to ignite the arc to evaporate and gasify the solid aluminum-silicon alloy target layer by layer to form a high-density aluminum-silicon plasma;

[0013] Step 4, applying a negative bias voltage of -500 to -700 V to the hot end component of the aircraft engine, wherein the duty cycle is 40 to 80%, and superimposing a 1000 V pulse to accelerate the aluminum silicon ions under the action of the electric field, thereby generating lattice defects such as high-density vacancies and dislocations on the surface of the substrate of the hot end component of the aircraft engine;

[0014] Step 5: The hot end component substrate of the aircraft engine is irradiated and heated by aluminum silicon plasma, and the surface temperature rises to 800-1000° C. The aluminum silicon ions diffuse with the hot end component substrate of the aircraft engine to form an aluminum silicon coating.

[0015] Furthermore, in the above-mentioned method for preparing plasma-deposited aluminum-silicon coating for aircraft engine turbine blades, the aluminum-silicon target is used as an aluminum infiltration source and is block-shaped. The composition of the aluminum-silicon target can be adjusted according to the coating requirements, and the silicon content is 6w.t.% to 25w.t.%.

[0016] Furthermore, in the above-mentioned method for preparing plasma-deposited aluminum-silicon coating on aircraft engine turbine blades, the tenon and blade tip of the turbine blade are protected by a conformal high-temperature alloy fixture box to avoid over-coating in non-coated areas.

[0017] Advantages and beneficial effects of the present invention:

[0018] (1) Production efficiency increased by more than 5 times;

[0019] (2) The blade tenon can be effectively protected by using a custom tooling to avoid the problem of leakage and over-coating caused by the slurry method, which reduces the mechanical properties of the tenon;

[0020] (3) The coating preparation process is greatly simplified. The existing slurry process mainly includes slurry preparation, pretreatment, slurry spraying, low-temperature drying, aluminum silicon infiltration, high-temperature diffusion and post-treatment. The new process only requires two steps: pretreatment and short-time plasma deposition.

[0021] (4) Obtain high-purity aluminum-silicon plasma in a high vacuum environment, avoiding the problem of harmful element doping in the coating in the traditional slurry method and improving the coating performance;

[0022] (5) By utilizing the spatial dispersion distribution and diffraction characteristics of plasma, uniform preparation of aluminum-silicon coating can be achieved on the surface of multi-unit blades;

[0023] (6) Flexible automated operation, coating can be quickly prepared on one to dozens of blades, the coating preparation process is automatically controlled, and the coating quality batch stability and consistency are good;

[0024] (7) Based on physical vapor permeation source, it is suitable for porous blades and does not have the problem of easy pore blocking in the existing slurry method;

[0025] (8) Based on the physical gas phase, there is no corrosive gas in the vacuum chamber, the preparation process has no environmental pollution problem, it is green and environmentally friendly, the equipment is highly stable and easy to maintain;

[0026] (9) The raw materials have a long shelf life. As block target materials, they will not degrade after being stored for decades. However, the storage period of aluminum silicon slurry in existing processes is generally no more than 1 year. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The embodiment of the present invention is a schematic diagram of a deposition process;

[0028] Figure 2 A high-temperature alloy conformal fixture for blades;

[0029] Figure 3 The cross-sectional photo and element quantitative analysis results of the K417G alloy turbine blade surface after 15 minutes of plasma deposition of aluminum silicon coating;

[0030] Figure 4 It is a schematic diagram of the present invention. DETAILED DESCRIPTION

[0031] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples.

[0032] A method for preparing a plasma-deposited aluminum-silicon coating for an aircraft engine turbine blade is prepared by a plasma deposition process. The preparation method is as follows:

[0033] Step 1: Perform wet sand blowing activation pretreatment on the aircraft engine turbine blades. The specific process parameters are as follows: the particle size of white corundum sand is 230 mesh, the content of white corundum sand is 25%, the wind pressure is 0.30MPa, the water pressure is 0.25MPa, and the sand blowing distance is 210mm;

[0034] Step 2: Immerse the turbine blades in acetone for ultrasonic cleaning, remove oil from the surface, and then dry them;

[0035] Step 3: If Figure 2 As shown, a high temperature alloy conformal fixture is used to protect the blade tenon and blade tip;

[0036] Step 4: Figure 1 As shown, the blade is placed in a plasma deposition aluminum silicon coating device and evacuated to a vacuum of less than 1×10 -3 Pa, the arc current of the aluminum-silicon target with a silicon content of 16w.t.% is adjusted to 200A, and a 280A pulse is superimposed to ignite the arc to evaporate and gasify the solid aluminum-silicon alloy target layer by layer to form a high-density aluminum-silicon plasma.

[0037] Step 5: Apply a negative bias of -600V to the blade, with a duty cycle of 40%, and superimpose a 1000V pulse to accelerate the aluminum silicon ions under the action of the electric field, generating high-density vacancies, dislocations and other lattice defects on the surface of the blade substrate.

[0038] Step 6: The blade substrate is heated by aluminum-silicon plasma irradiation, the surface temperature rises to 900°C, and the deposition takes 30 minutes. The aluminum-silicon ions diffuse with the blade substrate to form a 35μm aluminum-silicon coating.

[0039] Step 7: Turn off the target arc current, arc power supply and bias power supply, maintain the vacuum degree of the vacuum chamber ≤5×10-3Pa, wait until the part cools down to below 50℃, open the hatch, take out the blade, and complete the coating preparation.

[0040] like Figure 3 As shown, it is a cross-sectional photograph and element quantitative analysis results of the aluminum silicon coating plasma deposited on the surface of the K417G alloy turbine blade 15 minutes later. It can be seen that the coating thickness is about 35μm and the composition meets the service environment requirements.

[0041] like Figure 4 As shown is the principle diagram of the present invention, it can be seen that in a vacuum, arc discharge is used to evaporate and gasify the solid aluminum-silicon alloy target layer by layer to form a high-density aluminum-silicon plasma, and the electric field accelerates the bombardment of the material surface to produce lattice defects such as high-density vacancies, thereby greatly enhancing the aluminum-silicon diffusion rate on the material surface and directly forming an aluminum-silicon coating to achieve high-quality and efficient preparation.

Claims

1. A method for preparing plasma-deposited aluminum-silicon coating on turbine blades of aircraft engines, characterized in that: The following steps are involved: Step 1, performing wet sand blasting activation pretreatment on the surface of the hot end component of the aircraft engine, the specific parameters are as follows: the sand blasting medium is white corundum, the particle size is 180-250 mesh, the content is 20 wt %-35 wt %, the wind pressure is 0.25MPa-0.35MPa, the water pressure is greater than 0.2MPa, and the sand blasting distance is 180mm-350mm; Step 2, ultrasonically cleaning the hot end parts of the aircraft engine in acetone, performing surface degreasing treatment, and then drying; Step 3: Place the hot end parts of the aircraft engine in a plasma deposition aluminum silicon coating device and evacuate the vacuum to less than 1×10 - 3 Pa, adjust the arc current of the aluminum-silicon target to 150-200A, and superimpose a 250-300A pulse to ignite the arc to evaporate and gasify the solid aluminum-silicon alloy target layer by layer to form a high-density aluminum-silicon plasma; Step 4, applying a negative bias voltage of -500~-700V to the hot end component of the aircraft engine, wherein the duty cycle is 40~80%, and superimposing a 1000V pulse to accelerate the aluminum silicon ions under the action of the electric field, thereby generating high-density vacancy and dislocation lattice defects on the surface of the substrate of the hot end component of the aircraft engine; Step 5: The hot end component substrate of the aircraft engine is irradiated and heated by aluminum silicon plasma, and the surface temperature rises to 800-1000° C. The aluminum silicon ions diffuse with the hot end component substrate of the aircraft engine to form an aluminum silicon coating.

2. The method for preparing plasma-deposited aluminum-silicon coating for aircraft engine turbine blades according to claim 1, characterized in that: The aluminum silicon target is used as the aluminum diffusion source, has a block shape, and the silicon content is 6 wt% ~25w.t.%.

3. The method for preparing an aero-engine turbine blade plasma-deposited aluminum-silicon coating according to claim 1, characterized in that: The tenon and blade tip of the turbine blade are protected by a conformable high-temperature alloy fixture box to avoid over-coating in the non-coating area.

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