Method of de-coring ceramic cores in hollow turbine blades of aircraft engines

Abstract

This invention provides a method for removing ceramic cores from hollow turbine blades of aero-engines, comprising: repeating low-concentration core removal twice, repeating high-concentration core removal twice, neutralization, boiling in water, and drying. The concentration of the potassium hydroxide core removal solution used in the high-concentration core removal is higher than that used in the low-concentration core removal. This invention removes ceramic cores of different compositions by using potassium hydroxide core removal solutions of different concentrations; it simplifies the process steps for removing ceramic cores, significantly shortens the production cycle, reduces production costs, and meets the requirement for complete removal of ceramic cores from complex hollow turbine blades.

Description

Technical Field

[0001] This invention belongs to the field of ceramic core removal technology for high-temperature alloy hollow blades, and relates to a method for removing the core from hollow turbine blades of aero-engines. Background Technology

[0002] Turbine blades are core hot-end components of aero-engines and gas turbines. In recent years, with the increasing maturity of industries such as aviation, shipbuilding, and power generation, the requirements for the thermal efficiency and service life of turbine engines have further increased. This inevitably requires a continuous rise in turbine inlet temperature, placing increasingly stringent demands on the temperature resistance of turbine blades. Through continuous development, the industry currently improves blade cooling conditions and thus enhances their temperature resistance by pre-installing ceramic cores to form complex air-cooling channels within the blades. The cooling structure of aero-engine turbine blades has evolved from traditional methods to efficient radiative cooling and layered cooling. The cooling channels are becoming increasingly convoluted, and the internal structures are becoming more diverse. Correspondingly, the ceramic cores are also developing towards more complex shapes and smaller sizes. The complexity and diversity of ceramic cores also pose a significant challenge to their complete removal, resulting in an increasing number of residual cores remaining at the corners of the cavities.

[0003] Currently, most domestic and international methods employ traditional chemical etching, which uses a strong alkaline solution as the core-removing medium. The silicon-based ceramic core reacts chemically with the KOH solution under specific conditions, causing the ceramic core to depolymerize, dissolve, or break down, thus removing it. This method can only completely remove ceramic cores with straight cavities, but for ceramic cores with complex cavities, the residue rate can be as high as 85%. The aforementioned single chemical etching core-removal method can no longer meet production requirements. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention employs a physical-chemical corrosion core removal method. By applying a certain physical action to the core removal liquid, the alkaline solution is driven to move back and forth. Utilizing the reaction rates of ceramic cores with different compositions and alkaline solutions of varying concentrations, residual cores within the blade cavity can be removed while simultaneously improving core removal efficiency. Specifically:

[0005] Methods for removing ceramic cores from hollow turbine blades of aero-engines include:

[0006] Step 1: Repeat the low-concentration core removal operation twice. Each low-concentration core removal operation includes: placing the hollow turbine blade containing the ceramic core of the aero-engine into the tooling and then into the core removal vessel; injecting potassium hydroxide core removal solution into the core removal vessel; setting the temperature to 170-200℃, the core removal pressure to 0.6-1.0MPa, and the reaction time to 16h; after the reaction time is completed, draining the liquid from the core removal vessel; then injecting cooling water into the core removal vessel to cool the hollow turbine blade of the aero-engine; after cooling, removing and rinsing the hollow turbine blade of the aero-engine.

[0007] Furthermore, in each low-concentration decoupling process in step 1, the rinsing time after cooling the hollow turbine blades of the aero-engine is no less than 2 minutes.

[0008] Furthermore, the potassium hydroxide concentration in the potassium hydroxide stripping solution in step 1 is 30wt%-40wt%.

[0009] Step 2: Repeat the high-concentration core removal operation twice. Each high-concentration core removal includes: putting the hollow turbine blade of the aero-engine that has undergone Step 1 and is loaded into the tooling again into the core removal vessel, injecting a potassium hydroxide core removal solution with a higher concentration than that used in Step 1 into the core removal vessel, setting the temperature to 230-250℃, the pressure to natural atmospheric pressure, and the reaction time to 10 hours. After the reaction time is over, drain the liquid from the core removal vessel, then inject cooling water into the core removal vessel to cool the hollow turbine blade of the aero-engine. After cooling, remove the hollow turbine blade of the aero-engine and rinse it.

[0010] Furthermore, in each of the high-concentration de-core removal processes in step 2, the rinsing time after cooling the hollow turbine blades of the aero-engine is no less than 2 minutes.

[0011] Furthermore, the potassium hydroxide concentration in the potassium hydroxide stripping solution in step 2 is 60wt%-70wt%.

[0012] Step 3: Place the hollow turbine blades of the aircraft engine that have undergone Step 2 into the neutralization tank for neutralization;

[0013] Furthermore, during the neutralization process in step 3, the level of the neutralizing liquid is ensured to be at least 5 cm above the hollow turbine blades of the aero-engine, and the neutralization time is no less than 30 minutes.

[0014] Furthermore, the neutralizing solution used in step 3 is dilute hydrochloric acid or dilute citric acid, with a concentration of 3%-10%.

[0015] Step 4: After neutralization, the hollow turbine blades of the aircraft engine are placed in a water boiling tank to remove the acid and alkali on the surface of the blades.

[0016] Furthermore, in step 4, the boiling temperature is set to 80°C and the boiling time is no less than 30 minutes.

[0017] Furthermore, in step 4, pneumatic stirring needs to be turned on during the boiling process.

[0018] Step 5: After boiling, place the hollow turbine blades of the aircraft engine into the drying tank for drying.

[0019] Furthermore, in step 5, the drying temperature is set to 120℃ and the drying time is no less than 30 minutes.

[0020] This invention removes ceramic cores of different compositions using potassium hydroxide stripping solutions of varying concentrations. It simplifies the process steps for removing ceramic cores, significantly shortens the production cycle, reduces production costs, and meets the need for complete removal of ceramic cores from complex hollow turbine blades. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0025] For ease of description, the hollow turbine blade of an aero-engine containing a ceramic core will be referred to as a hollow blade in the embodiments.

[0026] Place the hollow blades into the tooling frame, and then place the tooling frame into the core-removing reactor. Pour the prepared 35% potassium hydroxide core-removing solution into the core-removing reactor and close the reactor.

[0027] The heating temperature of the core removal vessel was set to 180℃, the pressure to 8 bar (0.8 MPa), and the core removal time to 16 hours.

[0028] After the core removal time is over, drain the alkaline solution from the reactor and inject cooling water into the reactor to cool down the hollow blades. When the temperature inside the reactor is below 60°C, open the reactor lid, take out the hollow blade parts, and rinse each hollow blade part for at least 10 seconds.

[0029] After rinsing, the hollow blade parts are put back into the core removal kettle, and the prepared potassium hydroxide core removal solution with a concentration of 35% is injected into the core removal kettle. Then the core removal kettle is closed.

[0030] The heating temperature of the core removal vessel was set to 180℃, the pressure to 8 bar (0.8 MPa), and the core removal time to 16 hours.

[0031] After the core removal time is over, drain the alkaline solution from the reactor and inject cooling water into the reactor to cool down the hollow blades. When the temperature inside the reactor is below 60°C, open the reactor lid, take out the hollow blade parts, and rinse each hollow blade part for at least 10 seconds.

[0032] After rinsing, the hollow blade parts are put back into the core removal kettle, and the prepared potassium hydroxide core removal solution with a concentration of 65% is injected into the core removal kettle. Then the core removal kettle is closed.

[0033] Set the heating temperature of the core removal vessel to 240℃, the pressure to natural pressure, and the core removal time to 10 hours.

[0034] After the core removal time is over, drain the alkaline solution from the reactor and inject cooling water into the reactor to cool down the hollow blades. When the temperature inside the reactor is below 60°C, open the reactor lid, take out the hollow blade parts, and rinse each hollow blade part for at least 10 seconds.

[0035] After rinsing, the hollow blade parts are put back into the core removal kettle, and the prepared potassium hydroxide core removal solution with a concentration of 65% is injected into the core removal kettle. Then the core removal kettle is closed.

[0036] Set the heating temperature of the core removal vessel to 240℃, the pressure to natural pressure, and the core removal time to 10 hours.

[0037] After the core removal time is over, drain the alkaline solution from the reactor and inject cooling water into the reactor to cool down the hollow blades. When the temperature inside the reactor is below 60°C, open the reactor lid, take out the hollow blade parts, and rinse each hollow blade part for at least 10 seconds.

[0038] Place the rinsed hollow blade parts into a neutralization tank containing 5% dilute hydrochloric acid, ensuring that the liquid level in the neutralization tank is more than 5cm above the parts, and set the neutralization time to 30min.

[0039] After neutralization, transfer the blade parts to the boiling tank, set the boiling temperature to 80℃, set the boiling time to 30 minutes, start the boiling program and turn on the pneumatic stirring function.

[0040] After boiling, transfer the blade parts to the drying tank, set the drying temperature to 120℃ and the drying time to 30 minutes;

[0041] After drying, the blade parts were removed and the internal cavities of the blades were inspected using a cold light source and an endoscope. It was found that there were no residual cores inside each cavity.

[0042] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for removing the ceramic core from a hollow turbine blade of an aero-engine, characterized in that, include: Step 1: Repeat the low-concentration core removal operation twice. Each low-concentration core removal operation includes: placing the hollow turbine blade containing the ceramic core of the aero-engine into the tooling and then into the core removal vessel; injecting potassium hydroxide core removal solution into the core removal vessel; setting the temperature to 170-200℃, the core removal pressure to 0.6-1.0MPa, and the reaction time to 16h; after the reaction time is completed, draining the liquid from the core removal vessel; then injecting cooling water into the core removal vessel to cool the hollow turbine blade of the aero-engine; after cooling, removing and rinsing the hollow turbine blade of the aero-engine. Step 2: Repeat the high-concentration core removal operation twice. Each high-concentration core removal operation includes: placing the hollow turbine blade of the aero-engine that has undergone Step 1 and is loaded into the tooling into the core removal vessel, injecting a potassium hydroxide core removal solution with a higher concentration than that used in Step 1 into the core removal vessel, setting the temperature to 230-250℃, the pressure to natural atmospheric pressure, and the reaction time to 10 hours. After the reaction time is completed, drain the liquid from the core removal vessel, then inject cooling water into the core removal vessel to cool the hollow turbine blade of the aero-engine. After cooling, remove the hollow turbine blade of the aero-engine and rinse it. Step 3: Place the hollow turbine blades of the aircraft engine that have undergone Step 2 into the neutralization tank for neutralization; Step 4: After neutralization, the hollow turbine blades of the aircraft engine are placed in a water boiling tank to remove the acid and alkali on the surface of the blades. Step 5: After boiling, place the hollow turbine blades of the aircraft engine into the drying tank for drying. The concentration of the potassium hydroxide stripping solution used in step 1 is 30wt%-40wt%; The concentration of potassium hydroxide stripping solution in step 2 is 60wt%-70wt%.

2. The method for removing the ceramic core from a hollow turbine blade of an aero-engine according to claim 1, characterized in that, In each low-concentration decore removal process in step 1, the rinsing time after cooling the hollow turbine blades of the aero-engine is no less than 2 minutes.

3. The method for removing the ceramic core from a hollow turbine blade of an aero-engine according to claim 1, characterized in that, In step 2, during each high-concentration de-core removal process, the rinsing time after cooling the hollow turbine blades of the aero-engine is no less than 2 minutes.

4. The method for removing the ceramic core from a hollow turbine blade of an aero-engine according to claim 1, characterized in that, During the neutralization process in step 3, ensure that the level of the neutralizing liquid is at least 5 cm above the hollow turbine blades of the aero-engine, and that the neutralization time is no less than 30 minutes.

5. The method for removing the ceramic core from a hollow turbine blade of an aero-engine according to claim 1, characterized in that, The neutralizing solution used in step 3 is dilute hydrochloric acid or dilute citric acid, with a concentration of 3%-10%.

6. The method for removing the ceramic core from a hollow turbine blade of an aero-engine according to claim 1, characterized in that, In step 4, the boiling temperature is set to 80°C and the boiling time is no less than 30 minutes.

7. The method for removing the ceramic core from a hollow turbine blade of an aero-engine according to claim 1, characterized in that, In step 4, the pneumatic agitator needs to be turned on during the boiling process.

8. The method for removing the ceramic core from a hollow turbine blade of an aero-engine according to claim 1, characterized in that, In step 5, set the drying temperature to 120℃ and the drying time to be no less than 30 minutes.

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