An aero-engine blade tenon pure aluminum protective coating and a preparation method thereof

Abstract

The present application belongs to the technical field of aero-engine blade protection, and particularly relates to an aero-engine blade tenon pure aluminum protective coating and a preparation method thereof. The aero-engine blade tenon is taken as a substrate, the areas which do not need to be sprayed are protected, the areas which need to be sprayed are sandblasted, then the plasma spraying process is adopted, the Ni-Al bottom layer is sprayed first, and then the pure Al surface layer is sprayed, so that the pure aluminum protective coating is formed on the surface of the blade tenon. The protective coating forms continuous protection for the substrate in the sacrificial anode mode, and when the engine is working, a uniform transfer lubricating film is formed between the tenon and the gear engagement of the wheel disc in the process of micro-sliding of the tenon, so that the fretting wear and micro-cracks are inhibited.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aero-engine blade protection, and particularly relates to a pure aluminum protective coating for a tenon of an aero-engine blade and a preparation method thereof. BACKGROUND

[0002] The aero-engine blade is assembled with a wheel disc by means of a tree-shaped tenon. During the operation of the equipment, the tenon fitting surface bears a cyclic centrifugal load, which causes a slight reciprocating slip and initiates fretting wear and fretting fatigue damage. After the external salt mist and water vapor penetrate into the assembly gap, galvanic corrosion is formed between the blade base body and the wheel disc, which aggravates the wear of the tenon. The microcracks generated by the damage are easy to expand in the high stress area of the tenon. Lightly, it causes size out-of-tolerance and shortens the maintenance cycle. Severely, it can cause the blade to break, which threatens flight safety. With the continuous improvement of the engine thrust-to-weight ratio, the protection requirement of the tenon is becoming more and more stringent. SUMMARY

[0003] The purpose of the application is to solve the problem that the existing blade tenon protective coating cannot consider corrosion protection and anti-fretting wear at the same time. The pure aluminum coating blocks the galvanic corrosion caused by salt mist and water vapor by means of the sacrificial anode effect, and at the same time, relies on the excellent plasticity of pure aluminum to form a lubricating transfer film at the tenon slip interface, which can relieve the fretting wear under alternating load and avoid the generation of fatigue microcracks in the tenon.

[0004] To achieve the above-mentioned purpose, the application adopts the following technical solutions: The pure aluminum protective coating for the tenon of the aero-engine blade of the application has a pure aluminum protective coating formed by a Ni-Al bottom layer and a pure Al surface layer on the surface of the tenon base body. The base body is continuously protected in the form of a sacrificial anode, and during the operation of the engine, a uniform transfer lubricating film is formed between the tenon and the wheel disc teeth during the micro-slip process of the tenon, which can inhibit the generation of fretting wear and microcracks.

[0005] The base body is preferably one of a titanium alloy base body and a nickel-based alloy base body; and the tenon is preferably a tree-shaped special-shaped structure tenon.

[0006] The thickness of the Ni-Al bottom layer is 0.05mm-0.10mm, and the total thickness of the pure aluminum protective coating is 0.20mm-0.55mm.

[0007] The preparation method of the pure aluminum protective coating for the tenon of the aero-engine blade of the application includes the following contents: taking the tenon of the aero-engine blade as the base body, protecting the areas that do not need to be sprayed, and then sandblasting the areas that need to be sprayed, and then using the plasma spraying process to first spray the Ni-Al bottom layer and then spray the pure Al surface layer, so as to form a pure aluminum protective coating on the surface of the blade tenon.

[0008] The specific process for spraying Ni-Al underlayer includes: powder incident angle 90°, powder feeding rate 50±5g / min, main spraying gas is argon with a flow rate of 70±5 NLPM, secondary spraying gas is hydrogen with a flow rate of 15±2 NLPM, current 600±30A, voltage ≥65V, and spraying distance 150±10mm.

[0009] The specific process for spraying a pure Al surface layer includes: powder incident angle of 105°, powder feeding rate of 50±5g / min, argon as the main spraying gas with a flow rate of 60±5NLPM, hydrogen as the secondary spraying gas with a flow rate of 8±1NLPM, current of 500±20A, voltage of ≥55V, and spraying distance of 150±10mm.

[0010] This invention provides a high-purity aluminum dense protective coating on the surface of the aero-engine blade tenon substrate. The coating material has a purity of ≥99.9%, eliminates alloy element doping, ensures stable electrode potential, and provides continuous protection to the titanium alloy and nickel-based alloy substrates through a sacrificial anode approach. The coating exhibits excellent plasticity, forming a uniform transfer lubricating film during the micro-sliding process of the tenon, effectively inhibiting fretting wear and micro-crack initiation. A plasma spraying process is employed, matched to the tree-shaped irregular structure of the tenon, with zoned control of spraying distance, powder feed rate, and scanning speed, resulting in a uniform and controllable coating thickness and improved overall density.

[0011] This solution requires no high-temperature heat treatment, does not alter the matrix structure or fatigue properties, and features a uniform coating thickness and high bonding strength. It not only meets the precision assembly dimensional requirements of the tenon but also provides comprehensive protection against long-term corrosion, fretting wear, and cracking and detachment, making it suitable for the long-term alternating load service conditions of aero-engine blade tenons.

[0012] Compared with the prior art, the present invention has the following beneficial effects: (1) Wear-resistant and long service life: The pure aluminum coating has good plasticity and ductility. During the micro-reciprocating sliding process of the tenon, a uniform lubrication transfer film can be formed, which effectively reduces the friction coefficient, buffers the alternating impact load, and significantly inhibits fretting wear and the initiation of fretting fatigue marks. At the same time, the entire process is carried out at low temperature, which does not change the matrix structure, does not produce brittle phases, and completely preserves the original fatigue performance of the blade tenon.

[0013] (2) Wide adaptability: The process temperature of this invention is low and the process is simple. It does not damage the substrate or scratch the mating wheel tenon groove. It has low cost and is more operable, making it suitable for the mass stable production of aviation blade tenons. Attached Figure Description

[0014] Figure 1 A schematic diagram of the overall structure of an aero-engine blade with tenons; Figure 2 A partial schematic diagram of the painted and unpainted areas of a part; Figure 3 Enlarged view of the painted and unpainted areas of the part; Figure 4 This is a magnified view of the painted and unpainted areas of the part. Detailed Implementation

[0015] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. It should be noted that the embodiments described in this invention are only for further explanation and illustration, and not for limiting their application scope. Based on this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of this invention.

[0016] The integral structure of the blade with tenons in an aero engine is as follows: Figure 1 As shown, the painted area and the non-painted area are as follows: Figure 2 , Figure 3 and Figure 4 As shown. Figure 4 In the diagram, PTD represents the nickel-aluminum underlayer, and PTM represents the pure aluminum toplayer. The dimensions in the diagram are for reference only and do not affect the implementation of the present invention. The unit of measurement is mm, and the specific dimensions can be adjusted according to process requirements.

[0017] Example 1 A pure aluminum protective coating was prepared on the surface of the tenon of an aero-engine blade. The tenon teeth were then plasma-sprayed with a Ni-Al underlayer (0.05-0.10 mm thick) and a pure Al powder toplayer (0.20-0.25 mm total thickness in area A and 0.45-0.55 mm total thickness in area B). The specific process is as follows: areas not requiring coating were protected; areas requiring coating were sandblasted and cleaned before plasma spraying. The Ni-Al underlayer was sprayed first, followed by the pure Al toplayer. The spraying process is shown in Tables 1 and 2. After spraying, the tenon thickness was measured using a dial indicator. If the coating thickness exceeded the upper limit, 1200# sandpaper was used to sand the coating to ensure the required thickness.

[0018] Table 1. Process parameters for plasma spraying Ni-Al underlayer

[0019] Table 2. Process parameters for plasma spraying of pure Al surface layer

[0020] The following equipment can also be used for plasma spraying of nickel-aluminum undercoat: equipment model Multicoat, spray gun F4MB90-XL, powder feeder model Twin-120-A-HT, and other process parameters are the same as in Table 1.

Claims

1. A pure aluminum protective coating for the tenon of an aero-engine blade, characterized in that, The tenon base surface has a pure aluminum protective coating formed by a Ni-Al underlayer and a pure Al surface layer.

2. The pure aluminum protective coating for the tenon of an aero-engine blade according to claim 1, characterized in that, The pure aluminum protective coating provides continuous protection to the substrate in a sacrificial anode manner. Furthermore, during engine operation, a uniform transfer lubricating film is formed between the tenon and the wheel disc during the micro-sliding process of the tenon, inhibiting fretting wear and the generation of micro-cracks.

3. The pure aluminum protective coating for the tenon of an aero-engine blade according to claim 1, characterized in that, The matrix includes either a titanium alloy matrix or a nickel-based alloy matrix.

4. The pure aluminum protective coating for the tenon of an aero-engine blade according to claim 1, characterized in that, Tenons include tree-shaped tenons.

5. The pure aluminum protective coating for the tenon of an aero-engine blade according to claim 1, characterized in that, The Ni-Al base layer thickness is 0.05mm-0.10mm, and the total thickness of the pure aluminum protective coating is 0.20mm-0.55mm.

6. The method for preparing a pure aluminum protective coating for aero-engine blade tenons according to claim 1, characterized in that, The process includes the following: using the tenon of an aero-engine blade as the base, the areas that do not need to be coated are protected, and the areas that need to be coated are sandblasted and then plasma sprayed. First, a Ni-Al base layer is sprayed, and then a pure Al top layer is sprayed, thereby forming a pure aluminum protective coating on the surface of the blade tenon.

7. The method for preparing a pure aluminum protective coating for aero-engine blade tenons according to claim 6, characterized in that, The process of spraying Ni-Al underlayer includes: powder incident angle 90°, powder feeding rate 50±5g / min, main spraying gas is argon with a flow rate of 70±5 NLPM, secondary spraying gas is hydrogen with a flow rate of 15±2 NLPM, current 600±30A, voltage ≥65V, and spraying distance 150±10mm.

8. The method for preparing a pure aluminum protective coating for aero-engine blade tenons according to claim 6, characterized in that, The process of spraying a pure Al surface layer includes: powder incident angle of 105°, powder feeding rate of 50±5g / min, argon as the main spraying gas with a flow rate of 60±5NLPM, hydrogen as the secondary spraying gas with a flow rate of 8±1NLPM, current of 500±20A, voltage of ≥55V, and spraying distance of 150±10mm.

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