A method for plugging a process hole of an aero-engine high-pressure turbine blade

Abstract

The application discloses a kind of process hole brazing plugging methods of aero-engine high-pressure turbine blade, belong to the field of aeronautical equipment parts manufacturing.The method aims to solve the problems of traditional paste brazing filler metal plugging process, such as high labor intensity, poor weight control accuracy, brazing filler metal easy to contaminate non-welding area, weld easy to sag and low process consistency. Through the discharge plasma sintering process, the Co-based filler metal blank body with uniform composition and organization is prepared, and is precisely machined into a preformed brazing filler metal block that matches the process hole, achieving accurate control of size and weight. The assembly is placed in a vacuum brazing furnace and brazed according to a specific process, causing the brazing filler metal to melt and fill the holes, completing the plugging. The application replaces the manual application of paste brazing filler metal with solid preformed brazing filler metal blocks, ensuring the accuracy and consistency of the amount of brazing filler metal added, avoiding brazing filler metal contamination, and significantly improving the controllability, reliability and production efficiency of the plugging quality, providing an effective means for high-quality manufacturing of aero-engine blades.

Description

Technical Field

[0001] This invention relates to the field of brazing technology, and in particular to a brazing method for sealing process holes in high-pressure turbine blades of aero-engines. Background Technology

[0002] As a core hot-end component of an aero-engine, high-pressure turbine blades operate under extreme conditions of high temperature, high pressure, and high-speed rotation for extended periods. Their manufacturing precision and reliability directly determine the overall performance and service life of the engine. These blades are generally manufactured using investment casting precision manufacturing processes, with the internal cavity precisely controlled by a ceramic core to control the dimensions of complex cooling channel profiles. To ensure the ceramic core does not break during casting, 3-4 support points are typically left at the blade tip, ultimately forming 3-4 casting process holes at the blade tip of the casting. After the ceramic core needs to be removed by high-pressure alkaline chemical etching, it must be sealed to restore the blade's structural integrity and film cooling function.

[0003] Sealing process holes is a critical step in the manufacturing of high-pressure turbine blades. If the process holes are not sealed completely, cooling gas will leak from the blade, affecting the cooling effect of the film cooling holes and causing high-temperature ablation of the blade. If the process hole sealing is unreliable, the sealing material may fall off under high temperature and centrifugal load, damaging engine components and causing high-risk accidents such as engine failure.

[0004] Currently, vacuum brazing is the most common method used in the industry to seal process holes. Traditional hole-sealing methods involve manually mixing a solder paste, weighing it using a precision balance to accurately control the amount of paste added to each hole, and then applying it to the sealing location. However, this method has the following drawbacks: (1) High labor intensity and high skill requirements: The paste-like brazing filler metal needs to be added manually, which is difficult to operate and requires extremely high weight control accuracy (error not exceeding 0.03 grams). It is highly dependent on the skill level and sense of responsibility of the operators.

[0005] (2) Poor weight control accuracy: The fluidity and thixotropy of the paste solder make it difficult to control the weight accurately during the addition process, which can easily lead to differences between batches and individuals.

[0006] (3) Difficulty in ensuring process consistency: Manual operation is significantly affected by subjective factors, making it difficult to ensure the consistency of sealing quality for each batch of products.

[0007] (4) High quality risk: The paste-like brazing filler metal is easy to spread to non-brazing positions or flow into the inner cavity, contaminating the cooling channel and affecting the sealing effect.

[0008] (5) Poor brazing quality: After welding, the front and back of the weld are prone to depressions, and the thinnest part is only 1 / 2 of the thickness of the base material, which seriously weakens the mechanical properties and sealing reliability of the joint. Summary of the Invention

[0009] The purpose of this invention is to provide a method for brazing and sealing process holes in high-pressure turbine blades of aero-engines. This invention aims to solve the following core technical problems: (1) Eliminate the weight control error caused by manually adding paste brazing filler metal, and achieve precise and stable control of the amount of brazing filler metal added.

[0010] (2) Reduce the intensity of manual labor and skill dependence, and improve the level of process standardization.

[0011] (3) Avoid the spread and loss of brazing filler metal in non-brazing locations to eliminate the quality risks caused by it.

[0012] (4) Solve the problem of depression on the front and back of the weld after brazing, and ensure the uniformity of the sealing thickness and the integrity of the structure.

[0013] (5) Improve process consistency and batch stability to ensure the reliability of the blade sealing quality of each engine.

[0014] This invention is achieved using the following technical solution: a method for brazing and sealing process holes in high-pressure turbine blades of aero-engines, characterized by the following steps: a pre-sintering step of powdered brazing filler metal: placing brazing filler metal powder into a mold and preparing a brazing filler metal block blank through a spark plasma sintering process; a pre-forming step of pre-forming brazing filler metal: machining the brazing filler metal block blank to form a pre-forming brazing filler metal block that matches the shape of the process hole on the blade; a pre-welding cleaning step: cleaning the surface of the area to be welded on the blade where the process hole is located; a fixing step of the pre-forming brazing filler metal block: placing the pre-forming brazing filler metal block at the cleaned process hole position and fixing it by spot welding using an energy storage spot welding machine; a vacuum brazing step: placing the blade with the pre-forming brazing filler metal block fixed thereon into a vacuum brazing furnace for brazing, so that the pre-forming brazing filler metal block melts and fills the process hole.

[0015] Furthermore, the pre-sintering step of the powdered brazing filler metal is specifically as follows: the brazing filler metal powder is placed in a graphite mold and held at a temperature of 950~1050℃ and a pressure of 45~55MPa for 5~15 minutes under vacuum to perform spark plasma sintering.

[0016] Furthermore, in the step of fixing the prefabricated brazing filler block, the parameters of the energy storage spot welding machine are set as follows: energy storage voltage 200~400V, discharge time 2~6ms, and electrode pressure 10~30N.

[0017] Furthermore, the vacuum brazing step specifically involves: maintaining a vacuum level of not less than 4 × 10⁻⁶.-2 Under the Pa environment, first heat up to 600~800℃ at a rate of 5~15℃ / min and hold for 10~30 minutes, then continue to heat up to 1170~1240℃ and hold for 2.5~3.0 hours.

[0018] Furthermore, the solder powder is a Co-based solder powder, or a mixture of Co-based solder powder and alloy powder.

[0019] Furthermore, after the vacuum brazing step, a quality inspection step is also included: visual and cross-sectional metallographic inspections are performed on the process holes after brazing and sealing. The cross-sectional metallographic inspection requires that the effective thickness of the weld bead reaches 100% of the thickness of the blade base material, and that the brazing filler metal does not flow into the blade cavity.

[0020] Furthermore, the preformed brazing filler block is cylindrical or irregularly shaped to match the process hole, with a dimensional tolerance of ±0.02mm and a weight error of ±0.01g.

[0021] The brazing and plugging method for process holes in high-pressure turbine blades of aero-engines described in this invention has the following advantages: By pre-preparing solid brazing filler metal blocks through spark plasma sintering (SPS) and precision machining, the dimensional tolerance can be controlled within ±0.02mm and the weight error within ±0.01g. This ensures absolute consistency in the volume of brazing filler metal used for each process hole from the source, laying a material foundation for high-quality sealing.

[0022] Using prefabricated standardized brazing filler metal blocks, positioning and pre-fixing can be completed quickly and accurately by picking them up with tweezers and performing energy storage spot welding, completely replacing the tedious process of manually weighing and applying brazing filler metal paste. This method increases the material filling efficiency to more than four times that of the original method, significantly reduces labor intensity, reduces reliance on highly skilled personnel, and achieves process standardization and repeatability.

[0023] Because the volume of the prefabricated brazing filler blocks is precisely calculated and matched, the molten brazing filler metal during the brazing process can precisely fill the gaps in the process holes, thus completely solving the problem of concavity on the front and back sides of the weld. Sectional inspection shows that the effective weld thickness can reach 100% of the base metal thickness, with a uniform and dense metallographic structure, fundamentally improving the mechanical properties, high-temperature strength, and sealing reliability of the joint.

[0024] Solid pre-made brazing filler blocks have no fluidity during placement and spot welding, completely avoiding the risks of spreading, splashing, or flowing into the cooling channels inside the blade cavity that may occur with paste brazing filler during operation. This ensures the cleanliness of the blade cavity, improves product yield, and enhances the production environment.

[0025] The core idea of ​​this method is highly versatile and can be adapted to various structural components with similar sealing requirements. It can be quickly applied simply by adjusting the sintering parameters and machining dimensions of the prefabricated brazing block according to different base materials, brazing filler metal compositions, and hole types, providing an innovative solution for the standardization and efficiency of high-precision brazing processes. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the prefabricated brazing filler block of the present invention; Figure 2 This is a schematic diagram before the process hole is plugged. Figure 3 This is a schematic diagram after the process hole has been plugged. Figure 4 Metallographic photograph of the prefabricated brazing filler metal block; Figure 5 SEM images of prefabricated brazing filler blocks; Figure 6 Metallographic images of welds using solder paste; Figure 7 Metallographic images of welds using prefabricated brazing filler metal blocks; Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0030] Example 1: like Figure 1-7As shown in the figure, this embodiment provides a brazing sealing method for process holes in high-pressure turbine blades of aero-engines. This method mainly involves the coordinated operation of a high-pressure turbine working blade (as the workpiece to be sealed), a prefabricated brazing filler metal block, an energy storage spot welding machine, and a vacuum brazing furnace. The high-pressure turbine working blade has 3-4 process holes at its tip, formed due to the casting process, which require highly reliable sealing. The prefabricated brazing filler metal block is pre-prepared using a specific process; its shape matches the process holes, and its dimensions are precisely calculated to ensure the final sealing quality.

[0031] The specific connection relationships and implementation steps of the method are detailed below: Step 1: Pre-sintering of powder brazing filler metal First, the raw materials for preparing the pre-formed solder block are prepared. The required weight of the mixture of Co-based solder powder and alloy powder is weighed; in this embodiment, approximately 50g of Co-based solder powder of grade BCo45NiCrWB is used, and this mixture is placed into a dedicated graphite mold cavity. Subsequently, the graphite mold containing the solder powder is sent to a spark plasma sintering (SPS) apparatus for pre-sintering. The core of this process lies in applying high temperature and pressure to the powder in a vacuum environment using an SPS apparatus, causing it to initially densify and form a solder block preform with certain strength and shape retention. Specific process parameters are set as follows: sintering temperature controlled at (950~1050)℃, sintering pressure at (45~55) MPa, sintering holding time at (5~15) min, and sintering atmosphere at vacuum. The purpose of this step is to obtain a pre-formed material with highly uniform composition and microstructure, maximizing the preservation of the original alloy characteristics of the solder, and ensuring that its temperature stability is not affected during subsequent remelting.

[0032] Step 2: Machining and shaping the pre-made brazing filler metal The pre-sintered brazing filler block blank obtained in step one is removed from the mold and precision machined to form a pre-fabricated brazing filler block that precisely matches the process holes to be sealed on the blade. First, the blank can be machined into a regular shape suitable for subsequent processing, such as a cylindrical strip with a cross-section of 2mm x 2mm, using methods like wire cutting. Then, based on the specific geometry of the target process hole to be sealed, typically a cylinder or a matching irregular shape, the cylindrical material is precision-machined on a lathe. The key connection is that the final three-dimensional dimensions of the pre-fabricated brazing filler block are calculated backwards from the precise weight and volume of brazing filler required for sealing a single process hole. Its design goal is to completely fill the gaps in the process holes after brazing without any excess brazing filler loss. Through this process, the dimensional tolerance of the brazing filler block can be controlled within ±0.02mm, and the weight error does not exceed ±0.01g, ensuring the consistency of material used for each sealing point from the source.

[0033] Step 3: Pre-welding cleaning Before assembling the pre-fabricated brazing filler metal blocks onto the blades, a rigorous surface pretreatment of the areas to be brazed on the high-pressure turbine blades (i.e., around the process holes) is essential to ensure brazing quality. This step establishes the foundation for the connection between the workpiece surface and subsequent processes. First, the metal surface around the process holes is mechanically ground using a carbide grinding head to thoroughly remove the oxide layer until a uniform metallic luster is achieved. Then, the entire blade, after grinding, is placed in an ultrasonic cleaning device to remove adhering particles. Finally, the blade is immersed in an acetone solution for at least 4 hours and wiped clean to ensure the surface is completely free of oil, dirt, and other impurities, forming a clean and activated brazing surface.

[0034] Step 4: Spot welding and fixing of prefabricated brazing filler blocks This step is crucial for connecting the pre-fabricated brazing filler block to the blade workpiece and for precise positioning before subsequent vacuum brazing. The operator uses tweezers to precisely place the pre-fabricated brazing filler block, prepared in step two, onto the cleaned process hole on the blade. Subsequently, a storage spot welder is used to spot weld and fix the brazing filler block. The parameters are set as follows: storage voltage (200~400) V, discharge time (2~6) ms, and electrode pressure (10~30) N.

[0035] Step 5: Vacuum Brazing This step is the core process for completing the metallurgical bonding and achieving final sealing. The blade workpiece, with the prefabricated brazing filler block fixed in step four, is then placed into the vacuum brazing furnace. The thermal-environment connection is as follows: the entire workpiece must be kept in a highly pure vacuum environment with a vacuum level controlled at 4 × 10⁻⁶. -2 Pa undergoes programmed temperature control heating. First, the furnace temperature is raised to the preheating range of (600~800)℃ at a heating rate of 5~15℃ / min and held for (10~30)min. Then, the temperature is raised to (1170~1240)℃ and held at this temperature for (2.5~3.0)h.

[0036] After brazing, the sealing quality needs to be inspected from multiple dimensions to confirm the reliability of the connection. Inspectors first conduct a visual quality check on the weld at the process hole. A qualified seal should be full and smooth, without any visible depressions or brazing filler metal overflow. The sealed area is then dissected and examined using equipment such as a metallographic microscope. The core connectivity evaluation criteria include: the effective thickness of the weld must reach 100% of the blade base material wall thickness, i.e., there should be no thinning; the metallographic structure should be uniform and dense, without obvious component segregation or other defects; and it must be confirmed that the molten brazing filler metal has not improperly spread or flowed into the cooling channels inside the blade cavity to completely eliminate the risk of contamination to non-brazed areas.

[0037] The working principle of the method described in this embodiment is to replace the traditional manual coating of solder paste with an integrated process chain of "pre-formed solder block + energy storage spot welding pre-fixation + vacuum brazing".

[0038] Solid brazing filler metal blocks with uniform size and weight are pre-prepared through SPS sintering and precision machining, fundamentally eliminating the errors and uncertainties of manually weighing paste-like brazing filler metal. Subsequently, rapid and robust pre-fixation is achieved through energy storage spot welding, ensuring that the brazing filler metal remains in the precisely designed position before entering the brazing furnace, avoiding positional displacement or internal contamination caused by filler metal flow.

[0039] In the vacuum brazing process, the pre-fixed solid brazing filler metal block has a precisely known and fixed molten volume when heated. This allows the molten filler metal to precisely fill the gaps in the process holes under capillary action, without overflowing due to excess or causing depressions due to insufficient filling. Precisely controlled heating profiles and holding times ensure that the filler metal fully wets the base material, expels gases, and forms an excellent metallurgical bond.

[0040] This method solves several problems associated with traditional processes. First, it ensures precise addition of brazing filler metal, achieving batch consistency. Second, mechanized filling and fixing significantly reduces labor intensity and reliance on skilled personnel. Third, solid block brazing filler metal avoids the spreading and flowing of paste-like filler metal during coating and heating, eliminating the risk of contamination. Fourth, precise control of filler metal volume ensures full welds on both the front and back sides after brazing, with an effective thickness reaching 100% of the base material, no depressions, and significantly improved joint mechanical strength and sealing reliability. Fifth, the entire process is parameterized and standardized, greatly improving production efficiency and batch-level quality stability.

[0041] By eliminating the splashing and uncontrollable flow of solder paste, the production environment is cleaner, while reducing material waste and the need for secondary cleaning of parts.

[0042] The above embodiments describe the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Modifications and variations made by those skilled in the art without departing from the spirit and scope of the invention should be within the protection scope of the appended claims.

Claims

1. A method for brazing and sealing process holes in high-pressure turbine blades of an aero-engine, characterized in that, Includes the following steps: Pre-sintering steps of powdered brazing filler metal: Placing brazing filler metal powder into a mold and preparing a brazing filler metal block blank through spark plasma sintering process; Pre-forming steps of pre-made brazing filler metal: Machining the brazing filler metal block blank to form a pre-made brazing filler metal block (3) that matches the shape of the process hole (2) on the blade (1). The volume of the pre-made brazing filler metal block (3) matches the volume of brazing filler metal required to seal the process hole (2), so that the molten brazing filler metal fills the gap of the process hole (2) during brazing without excess brazing filler metal loss. ; Pre-welding cleaning step: Clean the surface of the area to be welded on the blade (1) where the process hole (2) is located; Fixing step of pre-made brazing block: Place the pre-made brazing block (3) in the cleaned process hole (2) and fix it by spot welding using an energy storage spot welding machine (4); Vacuum brazing step: Place the blade (1) with the pre-made brazing block (3) fixed in it into a vacuum brazing furnace (5) for brazing, so that the pre-made brazing block (3) melts and fills the process hole (2). The volume of the pre-made brazing block (3) matches the volume of brazing filler required to seal the process hole (2), so that the molten brazing filler filler gaps in the process hole (2) during brazing and no excess brazing filler is lost.

2. The method for brazing and sealing process holes in a high-pressure turbine blade of an aero-engine according to claim 1, characterized in that, The pre-sintering step of the powdered brazing filler metal is as follows: the brazing filler metal powder is placed in a graphite mold and held at a temperature of 950~1050℃ and a pressure of 45~55MPa for 5~15 minutes under vacuum to perform spark plasma sintering.

3. The method for brazing and sealing process holes in a high-pressure turbine blade of an aero-engine according to claim 1, characterized in that, In the step of fixing the pre-made brazing filler block, the parameters of the energy storage spot welding machine (4) are set as follows: energy storage voltage 200~400V, discharge time 2~6ms, and electrode pressure 10~30N.

4. The method for brazing and sealing process holes in a high-pressure turbine blade of an aero-engine according to claim 1, characterized in that, The vacuum brazing step specifically involves: maintaining a vacuum level of not less than 4 × 10⁻⁶. -2 Under the Pa environment, first heat up to 600~800℃ at a rate of 5~15℃ / min and hold for 10~30 minutes, then continue to heat up to 1170~1240℃ and hold for 2.5~3.0 hours.

5. The method for brazing and sealing process holes in a high-pressure turbine blade of an aero-engine according to claim 2, characterized in that, The solder powder is a Co-based solder powder, or a mixture of Co-based solder powder and alloy powder.

6. The method for brazing and sealing process holes in a high-pressure turbine blade of an aero-engine according to claim 1, characterized in that, After the vacuum brazing step, a quality inspection step is also included: the process hole (2) after brazing and sealing is subjected to appearance and cross-sectional metallographic inspection. The cross-sectional metallographic inspection requires that the effective thickness of the weld bead reaches 100% of the thickness of the base material of the blade (1) and that the brazing filler metal does not flow into the inner cavity of the blade (1).

7. The method for brazing and sealing process holes in a high-pressure turbine blade of an aero-engine according to claim 1, characterized in that, The preformed brazing filler block (3) is cylindrical or irregularly shaped to match the process hole (2), with a dimensional tolerance of ±0.02mm and a weight error of ±0.01g.

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