Method for removing aluminized coating of hollow turbine guide blade

Abstract

The invention provides a method for removing an aluminized coating of a hollow turbine guide blade. Comprising the following process steps: 1, blowing sand to remove carbon, black spots and the like on the surface of the blade; 2, cleaning with a degreaser and pickling to remove oil stains, oxides and the like on the surface; 3, painting to protect non-aluminized parts; 4, preparing an acidic removal solution, and removing most of the aluminized layer by ultrasonic water bath; 5, removing the protective paint layer; and 6, carrying out sand blasting to remove the residual part of the infiltrated layer. According to the method for removing the aluminized coating of the hollow turbine guide blade, the coating can be rapidly and efficiently removed on the premise that a base body is not damaged, secondary recycling of the guide blade is achieved, and great practical significance and economic value are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of repairing turbine blades of aircraft engines, and in particular relates to a method for removing an aluminized coating of a hollow turbine guide blade. Background Art

[0002] The blade coating works in harsh environments for a long time, and will be affected by the combined effects of centrifugal force caused by high-speed rotation, impact and vibration caused by high-speed airflow, and high-temperature corrosion caused by high-temperature service environment. It is easy to cause problems such as coating oxidation, corrosion, and peeling. The coating can no longer meet the standard requirements to a large extent, which in turn affects the protective performance of the guide blades. At the same time, the high-temperature alloy materials used in hollow turbine guide blades are expensive and the manufacturing process is complicated. Therefore, if the coating that no longer meets the use requirements can be repaired or removed on the basis of ensuring the original performance of the substrate, and then a new coating can be applied to achieve the secondary reuse of the turbine blades and reduce the scrap rate, it has great practical significance and research value.

[0003] The currently commonly used physical method for removing coatings is laborious and time-consuming, the removal accuracy is difficult to control, it is easy to generate stress, and some special equipment is expensive, inefficient and cannot be mass-produced. As for the chemical method, due to its strong pertinence, the corrosion solution selected for different coatings varies greatly, the solution system is complex, and it is easy to corrode the substrate and destroy the substrate structure. Summary of the invention

[0004] The invention provides a method for removing an aluminized coating of a hollow turbine guide blade, which adopts a method combining physical and chemical methods to effectively remove the aluminized layer without damaging a substrate.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for removing the aluminized coating of a hollow turbine guide blade:

[0006] The following steps are involved:

[0007] Step 1: Use sandblasting to remove carbon accumulation, black spots, etc. on the blade surface;

[0008] Step 2: Use degreasing agent to clean and pickle to remove surface oil, oxides, etc.;

[0009] Step 3: Paint the un-aluminized parts such as the hollow turbine guide blade rafters to prevent the removal solution from corroding the substrate;

[0010] Step 4: Prepare an acidic removal solution and use ultrasonic water bath heating to remove most of the aluminized layer;

[0011] Step 5: Remove the protective paint layer applied in step 2;

[0012] Step 6: Sand blasting to remove some of the residual infiltration layer in preparation for secondary aluminum infiltration.

[0013] Preferably, in the first step, dry sandblasting is adopted.

[0014] Preferably, in the first step, the sandblasting medium is corundum sand.

[0015] Preferably, in the first step, the sandblasting mesh number is 200 mesh to 240 mesh, the nozzle distance is 150 mm to 200 mm, the spraying angle is 45° ± 20°, and the spraying pressure is 0.1 to 0.2 MPa.

[0016] Preferably, in the second step, the degreasing agent is a mixed solution of sodium phosphate, sodium silicate, sodium carbonate and sodium hydroxide, the pickling is hydrochloric acid (ρ = 1.19) 100% (volume ratio), and after pickling, it is cleaned with pure water.

[0017] Preferably, in the third step, the protective paint uses DT-500 electroplating protective strippable material, which is brushed on the unaluminized parts such as the leading edge plate of the guide vane with a soft brush. After the paint is cured, it is brushed for the second time, and the brushing is repeated three times to avoid damage to the matrix by the corrosion solution during the subsequent removal process.

[0018] Preferably, in the fourth step, the acidic removal solution includes nitric acid, with a concentration of 3% to 50% (volume fraction), the content of sulfamic acid is 3 g / L to 10 g / L, the ultrasonic vibration frequency is 10 to 40 KHZ, the water bath temperature range is 20 to 80 °C, and the removal time is 5 min to 5 h.

[0019] Preferably, in the fifth step, the protective paint on the surface of the leading edge plate is removed mechanically.

[0020] Preferably, in the fifth step, it is immersed in the diluent of DT-500 to remove the protective paint on the surface of the leading edge plate.

[0021] Preferably, in the sixth step, the sandblasting medium is corundum sand.

[0022] Preferably, in the sixth step, the sandblasting mesh number is 200 mesh to 240 mesh, the nozzle distance is 150 mm to 200 mm, the spraying angle is 45° ± 20°, and the spraying pressure is 0.3 to 0.4 MPa.

[0023] Preferably, after sandblasting in the sixth step, the blade is put into alcohol and cleaned for 15 to 30 min.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. Adopting a removal method combining physics and chemistry can effectively remove the coating without damaging the matrix. At the same time, by adjusting the sandblasting pressure, stress generation can be avoided while achieving efficient removal;

[0026] 2. Protect the unaluminized parts such as the blade plates with protective paint, which can meet the requirements of high-temperature water bath, and the protective paint is easy to remove;

[0027] 3. Use ultrasonic assistance for removal, which improves the removal rate of the aluminized layer;

[0028] 4. The chemical solution system is simple, which simplifies the process operation flow. Description of the Drawings

[0029] Figure 1 SEM image one of the cobalt-based blade before removing the aluminized layer in the embodiment of the present invention;

[0030] Figure 2 SEM image two of the cobalt-based blade after removing the aluminized layer in the embodiment of the present invention;

[0031] Figure 3 SEM image one of the nickel-based blade before removing the aluminized layer in the embodiment of the present invention;

[0032] Figure 4 SEM image two of the nickel-based blade after removing the aluminized layer in the embodiment of the present invention. Detailed Embodiments

[0033] The technical solution of the present invention is further described below, but the scope of protection is not limited thereto.

[0034] Embodiment 1:

[0035] The method for removing the aluminized coating of a certain type of cobalt-based hollow turbine guide vane includes the following steps:

[0036] 1. Dry sandblasting is used to remove the carbon deposit and black spots on the blade surface. The sandblasting medium is corundum sand, the sandblasting mesh number is 200 mesh, the nozzle distance is 150 mm, the spraying angle is 45°, and the spraying pressure is 0.2 MPa;

[0037] 2. Use a degreasing agent for cleaning and pickling to remove the surface oil stain and oxide. The degreasing agent is a mixed solution of sodium phosphate, sodium silicate, sodium carbonate and sodium hydroxide, and the pickling is 100% (volume ratio) hydrochloric acid (ρ = 1.19). After pickling, it is cleaned with pure water;

[0038] 3. Use a soft brush to apply DT-500 electroplating paint on the unaluminized parts such as the blade plates of the hollow turbine guide vane for protection. After the paint is cured, apply it for the second time, and repeat it three times to avoid the corrosion of the substrate by the removal solution;

[0039] 4. Put the blade into an acidic removal solution, and use ultrasonic water bath to remove the aluminized layer. The acidic removal solution includes 10% (volume fraction) nitric acid, the concentration of sulfamic acid is 5 g / L, the ultrasonic vibration frequency is 40 KHz, the water bath temperature is 50 °C, and the removal time is 30 min;

[0040] 5. Manually strip the protective paint on the surface of the blade. If it cannot be stripped manually, immerse it in the diluent of DT-500 to remove it.

[0041] 6. Remove part of the residual infiltration layer by sandblasting. The sandblasting medium is corundum sand, the sandblasting mesh number is 200 mesh, the nozzle distance is 150 mm, the spraying angle is 45°, the spraying pressure is 0.3 MPa. After sandblasting, put the blade into alcohol and clean it for 15 min to prepare for secondary aluminizing.

[0042] Figure 1 The figure shows the scanning electron microscope image of a cobalt-based turbine blade before the removal of the aluminized layer. The thickness of the aluminized layer is about 10 μm. Figure 2 The figure shows the scanning electron microscope image of a cobalt-based turbine blade after the removal of the aluminized layer. It can be observed that the aluminized layer is completely removed and no damage is found on the substrate.

[0043] Example 2:

[0044] Step 4 of the method for removing the aluminized coating of a certain type of nickel-based hollow turbine guide vane. Put the blade into an acidic removal solution and remove the aluminized layer by ultrasonic water bath. The solution includes 15% (volume fraction) nitric acid, the content of sulfamic acid is 5 g / L, the ultrasonic vibration frequency is 40 KHz, the water bath temperature is 50 °C, and the removal time is 2 h.

[0045] The remaining steps are the same as those in Example 1.

[0046] Figure 3 The figure is the scanning electron microscope picture of a certain type of nickel-based blade before the removal of the aluminized layer. The thickness of the aluminized layer is about 55 μm. Figure 4 This is the scanning electron microscope picture of the nickel-based blade after the removal of the aluminized layer in the embodiment of the present invention. It is observed that the aluminized layer is removed cleanly.

[0047] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for removing aluminized coating of hollow turbine guide blades, characterized in that: The following steps are involved: Step 1: Use sandblasting to remove carbon accumulation, black spots, etc. on the blade surface; Step 2: Use degreasing agent to clean and pickle to remove surface oil, oxides, etc.; Step 3: Paint the un-aluminized parts such as the hollow turbine guide blade rafters to prevent the removal solution from corroding the substrate; Step 4: Prepare an acidic removal solution and use ultrasonic water bath heating to remove most of the aluminized layer; Step 5: Remove the protective paint layer applied in step 2; Step 6: Sand blasting to remove some of the residual infiltration layer in preparation for secondary aluminum infiltration.

2. The method for removing the aluminized coating of a hollow turbine guide blade according to claim 1, characterized in that: In the step 1, dry sand blowing is adopted, and the sand blowing medium is corundum sand.

3. The method for removing the aluminized coating of a hollow turbine guide blade according to claim 1, characterized in that: The sand blowing mesh number is 200-240 mesh, the nozzle distance is 150mm-200mm, the spray angle is 45°±20°, and the spray pressure is 0.1-0.2MPa.

4. The method for removing the aluminized coating of a hollow turbine guide blade according to claim 1, characterized in that: In the step 2, the degreasing agent is a mixed solution of sodium phosphate, sodium silicate, sodium carbonate and sodium hydroxide, the pickling agent is 100% (volume ratio) of hydrochloric acid (ρ=1.19), and the pickling is followed by pure water washing.

5. The method for removing the aluminized coating of a hollow turbine guide blade according to claim 1, characterized in that: In the step three, the protective paint adopts DT-500 electroplating protection strippable material, and is applied to the non-aluminized parts such as the guide blade rafters with a soft brush; after the paint is cured, it is applied a second time, and the brushing is repeated three times to avoid damage to the substrate by the corrosive solution during the subsequent removal process.

6. The method for removing the aluminized coating of a hollow turbine guide blade according to claim 1, characterized in that: In step 4, the acidic removal solution includes nitric acid with a concentration of 3% to 50% (volume fraction), the concentration of the additive aminosulfonic acid is 3g / L to 10g / L, the ultrasonic vibration frequency is 10 to 40KHz, the water bath temperature range is 20 to 80°C, and the removal time is 5min to 5h.

7. The method for removing the aluminized coating of a hollow turbine guide blade according to claim 1, characterized in that: In the step 5, the protective paint on the surface of the citron plate is mechanically removed.

8. The method for removing the aluminized coating of a hollow turbine guide blade according to claim 1, characterized in that: In the step 5, the protective paint on the surface of the citron board is removed by immersing the citron board in a diluent of DT-500.

9. The method for removing the aluminized coating of a hollow turbine guide blade according to claim 1, characterized in that: In the step six, the sand blasting medium is corundum sand, the sand blasting mesh number is 200-240 mesh, the nozzle distance is 150 mm-200 mm, the injection angle is 45°±20°, and the injection pressure is 0.3-0.4 MPa.

10. The method for removing the aluminized coating of a hollow turbine guide blade according to claim 1, characterized in that: In the step six, after sand blowing, the blades are placed in alcohol for cleaning for 15 to 30 minutes.

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