A preparation method for a porous gradient protective material for laser drilling of blades

Abstract

The present invention relates to the technical field of turbine blades, and particularly relates to a preparation method for a porous gradient protective material for laser drilling of blades, comprising the steps of: mixing plastic particles with a protective material to form a first mixed filler; filling the first mixed filler into the inner cavity of the turbine blade; applying an external force to adjust the component distribution in the mixed filler to form a second mixed filler with a gradient structure; curing and molding the second mixed filler; and removing the plastic particles in the second mixed filler after curing and molding to form a porous gradient protective material. The purpose of the preparation method for the porous gradient protective material for laser drilling of blades is to solve the problems of the preparation method for the porous gradient protective material for laser drilling of blades.

Description

Technical Field

[0001] The present invention relates to the technical field of turbine blades, and particularly relates to a preparation method for a porous gradient protective material for laser drilling of blades. Background Art

[0002] Turbine blades are core components of aeroengines, and the film cooling holes distributed thereon are key structures for improving the high-temperature resistance of the blades. Ultrafast laser drilling can achieve no recast layer, thermal-induced defects such as microcracks, and can process the thermal barrier coating on the blade surface, becoming one of the preferred methods for preparing film holes in turbine blades. However, when the laser passes through the front wall of the blade and continues to propagate to the opposite wall of the inner cavity, it is easy to form irreversible damages such as micropits or microcracks on the opposite wall, reducing the reliability of the turbine blade and seriously affecting the service performance of the turbine blade.

[0003] In order to solve the problem of damage to the opposite wall of the inner cavity of the blade, there are two technical routes in the industry: using a protective material to fill the cavity and combining a professional detection system to assist in adjusting the process parameters of the drilling process.

[0004] The protective material for inner cavity filling should have the characteristics of scattering, reflecting or absorbing the laser of the corresponding wavelength. However, after being formed by using the usual protective materials and forming methods, most of them are homogeneous structures, and no obvious gradient effect is generated when the laser acts on the protective material. Using a homogeneous protective structure to block the laser to avoid damage to the opposite wall, when the laser ablation resistance of the protective material is strong, it is difficult to form a slag discharge channel in the inner cavity of the blade, and the drilling residues are easy to re-block the hole orifice when discharged from the small hole inlet, not only resulting in low drilling efficiency, but also affecting the hole shape and quality. When the laser ablation resistance of the protective material is weak, the protective material is consumed in a short time and cannot play a long-term effective role in protecting the opposite wall of the inner cavity. Due to the absence of a gradient effect in the homogeneous structure, it is difficult to ensure both the drilling efficiency and the hole shape quality at the same time, and it strictly limits the selection of process windows such as laser parameters, drilling paths and drilling times. A large number of process tests need to be carried out before drilling to confirm the protective effect on the opposite wall.

[0005] Due to certain deficiencies in the use of homogeneous protective materials, the industry has also carried out research on process control of configuring a professional detection system to detect and assist in adjusting the process parameters of the drilling process. By introducing a real-time monitoring, analysis and feedback control system, although the problem of damage to the opposite wall can be solved, the system is complex and the cost is high. In addition, after entering the stage of modifying the irradiated protective material, the processing efficiency usually drops significantly, and the overall drilling efficiency is reduced, and the cost performance is very low.

[0006] In summary, neither the homogeneous protective structure nor the introduction of an auxiliary detection feedback adjustment system can simultaneously meet the requirements of high cost performance, high efficiency and high quality for protecting the opposite wall during drilling.

[0007] Therefore, the inventor provides a preparation method for a porous gradient protective material for laser drilling of blades. Summary of the Invention

[0008] (1) Technical problem to be solved

[0009] An embodiment of the present invention provides a preparation method for a porous gradient protective material for laser drilling of blades, which solves the technical problem that the existing hole-making methods for turbine blades cannot simultaneously meet the requirements of high cost performance, high efficiency and high-quality hole-making for wall protection.

[0010] (2) Technical solution

[0011] The present invention provides a preparation method for a porous gradient protective material for laser drilling of blades, comprising the following steps:

[0012] Mix plastic particles with a protective material to form a first mixed filler;

[0013] Fill the first mixed filler into the inner cavity of the turbine blade;

[0014] Apply an external force to adjust the component distribution in the mixed filler to form a second mixed filler with a gradient structure;

[0015] Solidify and mold the second mixed filler;

[0016] Remove the plastic particles in the second mixed filler after solidification and molding to form a porous gradient protective material.

[0017] Further, the plastic particles are foam plastic particles with a density less than 0.1 g / cm 3 or foam plastic particles with a ferromagnetic substance wrapped in the center.

[0018] Further, the ferromagnetic substance is at least one of iron, cobalt nickel and its alloys, and ferrites.

[0019] Further, the plastic particles are spherical particles or irregularly shaped particles with a size in the range of 0.2 mm to 1 mm.

[0020] Further, the volume ratio of the plastic particles to the protective material is 1 / 5 to 1 / 2.

[0021] Further, the protective material is a curable composition in a liquid form having the function of scattering, reflecting or absorbing laser.

[0022] Further, the first mixed filler is a material with uniform internal component distribution formed by mixing the plastic particles into the protective material.

[0023] Further, the step of filling the first mixed filler into the inner cavity of the turbine blade specifically is:

[0024] The mixed filler is filled and compacted into the entire chamber where the hole to be machined is located along the inner cavity flow channel of the turbine blade through pressurization, pre-vacuum and ultrasonic vibration.

[0025] Furthermore, an external force is applied to adjust the component distribution in the mixed filler to form a second mixed filler with a gradient structure. Specifically:

[0026] Through the non-contact force acting on the mixed filler in the inner cavity across the blade, the plastic particles are caused to move directionally to form a gradient structure.

[0027] Furthermore, the plastic particles in the second mixed filler after curing and forming are removed to form a porous gradient protective material. Specifically:

[0028] The environmental temperature where the blade is located is heated to above the melting point of the plastic particles, which is 240 °C, and kept warm for 30 min to melt and remove them.

[0029] Furthermore, the second mixed filler formed after curing is a non-loose and non-powdery solid structure.

[0030] (3) Beneficial effects

[0031] In summary, the present invention forms a porous gradient protective material by regulating the structure of the protective material in the inner cavity of the blade, which facilitates rapid slag discharge to form a hole-making channel. When repairing the hole, the dense protective material in the lower layer can effectively block the laser, so as to achieve high-quality and high-efficiency hole-making. This method is simple to operate, does not introduce complex large-scale equipment, and has a low cost. Description of the drawings

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly introduced below. Obviously, the following described drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0033] Figure 1 is a schematic flow chart of a method for preparing a porous gradient protective material for laser hole-making of blades provided by an embodiment of the present invention;

[0034] Figure 2 is a schematic structural diagram of a porous gradient protective material provided by an embodiment of the present invention;

[0035] Figure 3 is a schematic structural diagram of laser hole-making of a turbine blade provided by an embodiment of the present invention.

[0036] In the figure:

[0037] 1 - Front wall; 2 - Opposite wall; 3 - Porous structure; 4 - Protective material; 5 - Laser; 6 - Gas film hole; 7 - Front wall of blade; 8 - Opposite wall of blade. Detailed implementation mode

[0038] The following further describes in detail the implementation mode of the present invention in conjunction with the accompanying drawings and embodiments. The detailed description and drawings of the following embodiments are used to exemplarily illustrate the principle of the present invention, but cannot be used to limit the scope of the present invention, that is, the present invention is not limited to the described embodiments, and covers any modifications, replacements, and improvements of parts, components, and connection methods without departing from the spirit of the present invention.

[0039] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The following will detail the present application with reference to the accompanying drawings and embodiments.

[0040] Figure 1 It is a schematic flow chart of a preparation method of a porous gradient protective material for laser drilling of blades provided by an embodiment of the present invention. As Figure 1 shown, the method includes the following steps:

[0041] S100. Mix plastic particles with a protective material to form a first mixed filler;

[0042] S200. Fill the first mixed filler into the inner cavity of the turbine blade;

[0043] S300. Apply an external force to adjust the component distribution in the mixed filler to form a second mixed filler with a gradient structure;

[0044] S400. Cure and mold the second mixed filler;

[0045] S500. Remove the plastic particles in the second mixed filler after curing and molding to form a porous gradient protective material.

[0046] In the above implementation mode, by regulating the structure of the protective material in the inner cavity of the blade, a porous gradient protective material is formed, which is convenient for quickly discharging slag to form a drilling channel. When repairing the hole, the dense protective material in the lower layer can effectively block the laser to achieve high-quality and high-efficiency drilling. This method is simple to operate, does not introduce complex large equipment, and has a low cost.

[0047] The gradient structure refers to a non-homogeneous or non-uniform distribution structure in which certain components, especially plastic particles, in the liquid filler in the inner cavity of the turbine blade move directionally under the action of a non-contact external force and form a dense and sparse distribution in a fixed direction in the inner cavity.

[0048] Curing refers to the process in which physical and chemical changes occur inside the filling material under certain conditions and it changes from a liquid state to a solid state.

[0049] Among them, the protective material is a curable composition in a liquid form having the function of scattering, reflecting or absorbing laser. The first mixed filler is a material with a uniform internal component distribution formed by mixing plastic particles into the protective material.

[0050] As an alternative embodiment, the plastic particles are foam plastic particles with a density less than 0.1 g / cm 3 or foam plastic particles with a ferromagnetic substance wrapped in the center. Among them, the density is selected according to actual needs.

[0051] As an alternative embodiment, the ferromagnetic substance is at least one of iron, cobalt, nickel and their alloys, and ferrites. The specific materials of the ferromagnetic substance are given above, but are not limited thereto, as long as the materials can have ferromagnetism.

[0052] As an alternative embodiment, the plastic particles are spherical particles or irregularly shaped particles with a size in the range of 0.2 mm to 1 mm. Among them, the size and shape are selected according to actual needs.

[0053] As an alternative embodiment, the volume ratio of the plastic particles to the protective material is 1 / 5 to 1 / 2. Among them, the volume ratio is selected according to actual needs.

[0054] As an alternative embodiment, the first mixed filler is filled into the inner cavity of the turbine blade. Specifically: through pressurization, pre-vacuum and ultrasonic vibration, the mixed filler is filled along the inner cavity flow path of the turbine blade and fills the entire chamber where the hole to be processed is located.

[0055] The above gives the specific method of filling the first mixed filler into the turbine blade to form a gradient structure hole.

[0056] As an alternative embodiment, an external force is applied to adjust the component distribution in the mixed filler to form a second mixed filler with a gradient structure. Specifically: through a non-contact force acting on the mixed filler in the inner cavity across the blade, the plastic particles are caused to move directionally to form a gradient structure.

[0057] Specifically, the non-contact force includes gravity, centrifugal force, magnetic force, etc. The method of applying gravity is: placing the blade ultrasonically in the drilling posture for a period of time to make the low-density plastic particles move upward to form a gradient structure. The method of applying centrifugal force is: installing the blade on a centrifuge and rotating it at high speed to make the low-density plastic particles move towards the center of rotation to form a gradient structure. The method of applying magnetic force is: using an external magnetic field such as a magnet to make the plastic particles containing ferromagnetic substances move along the magnetic field direction to form a gradient structure.

[0058] As an alternative embodiment, plastic particles in the second mixed filler after curing and forming are removed to form a porous gradient protective material. Specifically, the temperature of the environment where the blade is located is heated to above the melting point of the plastic particles, which is 240 °C, and kept warm for 30 min to melt and remove them. Among them, the temperature condition for removing the plastic particles should not affect the physical and chemical properties of the components other than the plastic particles in the protective filler and its entirety.

[0059] As an alternative embodiment, the second mixed filler formed after curing is a non-loose and non-powdery solid structure. Among them, this solid structure has a certain strength and hardness.

[0060] Example 1

[0061] A curable composition in liquid form formed by mixing a silicone oligomer with vinyl end groups and a silicone oligomer with Si-H groups is selected as the laser absorber, and the mass ratio of the two components is 1:1. Low-density foam plastic particles with a particle size of 0.3 - 0.6 mm are admixed into the liquid laser absorber according to a volume ratio of 1:3; the above-mentioned mixed filler is filled into the inner cavity structure simulation test piece of the blade, and the entire inner cavity is filled and compacted; the simulation test piece is placed horizontally and ultrasonically vibrated for 10 min to make the low-density plastic particles move upward to form a gradient structure; it is kept warm at 50 °C for 2 h to fully cure and form the mixed filler; it is kept warm at 300 °C for 1 h to fully remove the plastic particles to form a porous gradient structure. In order to facilitate observing the internal structure, the front wall and the opposite wall of the simulation specimen are disassembled, and it can be seen that the area near the front wall is a porous structure, and the area near the opposite wall is a dense protective material.

[0062] The structure of the prepared porous gradient protective material is as Figure 2 shown, including a front wall 1, an opposite wall 2, a porous structure 3 and a protective material 4. The protective material 4 is wrapped by the front wall 1 and the opposite wall 2, and the porous structure 3 is distributed inside the protective material 4.

[0063] A hole-making opposite wall protection test is carried out using a picosecond laser, and the hole diameter to be made is 0.3 mm. The pulse width of the picosecond laser is 2.5 ps, the wavelength is 1030 nm, the power is 20 W, the coaxial auxiliary blowing pressure is 0.4 MPa nitrogen, the laser scanning speed is 25.6 m / min, and the hole-making time is 40 s.

[0064] The hole-making results show that: when using the protective material with a porous gradient structure, the hole shape after 40 s of picosecond laser hole-making is fully developed, and there is no damage to the opposite wall.

[0065] Comparative Example 1

[0066] A curable composition in liquid form formed by mixing a silicone prepolymer with vinyl end groups and a silicone prepolymer with Si-H groups is used as a laser absorber, and the mass ratio of the two components is 1:1. The above protective material is directly filled into the inner cavity structure simulation test piece of the blade and the entire inner cavity is filled; it is kept warm at 50 °C for 2 h to fully cure and form the mixed filler.

[0067] The hole-making and wall protection test is carried out using a picosecond laser, and the hole diameter to be made is 0.3 mm. The picosecond laser pulse width is 2.5 ps, the wavelength is 1030 nm, the power is 20 W, the coaxial auxiliary blowing pressure is 0.4 MPa nitrogen, the laser scanning speed is 25.6 m / min, and the hole-making time is 40 s.

[0068] The hole-making results show that: when using a protective material without a porous gradient structure, the hole shape after 40 s of picosecond laser hole-making is not fully developed.

[0069] Example 2

[0070] A curable composition in liquid form formed by mixing a silicone prepolymer with vinyl end groups and a silicone prepolymer with Si-H groups is used as a laser absorber, and the mass ratio of the two components is 1:1. Low-density foam plastic particles with a particle size of 0.3 - 0.6 mm are admixed into the liquid laser absorber according to a volume ratio of 1:3; the above mixed filler is filled into and fills the inner cavity of the blade where the hole to be processed is located; the blade is placed in the punching posture and ultrasonically vibrated for 10 min to make the low-density plastic particles move upward to form a gradient structure; it is kept warm at 50 °C for 2 h to fully cure and form the mixed filler; it is kept warm at 300 °C for 1 h to fully remove the plastic particles to form a porous gradient structure. Then the hole-making and wall protection test is carried out using a picosecond laser, and the hole diameter to be made is 0.3 mm. The picosecond laser pulse width is 2.5 ps, the wavelength is 1030 nm, the power is 20 W, the coaxial auxiliary blowing pressure is 0.4 MPa nitrogen, the laser scanning speed is 25.6 m / min, and the hole-making time is 32 s.

[0071] The hole-making process is as Figure 3 shown, and the protective material 4 wrapped between the front wall 7 of the blade and the opposite wall 8 of the blade is directly irradiated by the laser 5 passing through the air-permeable film hole 6 to form a hole.

[0072] The blade hole-making results show that: when using a protective material with a porous gradient structure, the hole shape after 32 s of picosecond laser hole-making is fully developed and there is no damage to the opposite wall.

[0073] It should be clear that the various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, reference can be made to each other, and the key point of each embodiment is to illustrate the differences from other embodiments. The present invention is not limited to the specific steps and structures described above and shown in the figures. Also, for the sake of brevity, the detailed description of known methods and techniques is omitted here.

[0074] The above are only the embodiments of the present application and do not limit the present application. For those skilled in the art, various changes and modifications can be made to the present application without departing from the scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A preparation method of a porous gradient protective material for laser drilling of blades, characterized in that, the method comprises the following steps: Mix plastic particles with a protective material to form a first mixed filler; Fill the first mixed filler into the inner cavity of a turbine blade; Apply an external force to adjust the component distribution in the mixed filler to form a second mixed filler with a gradient structure; Solidify and mold the second mixed filler; Remove the plastic particles in the second mixed filler after solidification and molding to form a porous gradient protective material; The plastic particles are foam plastic particles with a density less than 0.1 g / cm 3 , or the plastic particles are foam plastic particles with ferromagnetic substances wrapped in the center; the protective material is a curable composition in a liquid form having the function of scattering, reflecting or absorbing laser light.

2. The preparation method of the porous gradient protective material for laser drilling of blades according to claim 1, characterized in that, the ferromagnetic substance is at least one of iron, cobalt, nickel and their alloys, and ferrites.

3. The preparation method of the porous gradient protective material for laser drilling of blades according to claim 1, characterized in that, the plastic particles are spherical particles or irregularly shaped particles with a size of 0.2 mm to 1 mm.

4. The preparation method of the porous gradient protective material for laser drilling of blades according to claim 1, characterized in that, the volume ratio of the plastic particles to the protective material is 1 / 5 to 1 / 2.

5. The preparation method of the porous gradient protective material for laser drilling of blades according to claim 1, characterized in that, the first mixed filler is a material with a uniform internal component distribution formed by mixing the plastic particles into the protective material.

6. The preparation method of the porous gradient protective material for laser drilling of blades according to claim 1, characterized in that, the filling of the first mixed filler into the inner cavity of the turbine blade is specifically: Fill and compact the entire chamber where the hole to be processed is located along the inner cavity flow path of the turbine blade by applying pressure, pre-vacuum and ultrasonic vibration.

7. The preparation method of the porous gradient protective material for laser drilling of blades according to claim 1, characterized in that, the applying of an external force to adjust the component distribution in the mixed filler to form a second mixed filler with a gradient structure is specifically: By a non-contact force acting on the mixed filler in the inner cavity across the blade, the plastic particles are caused to move directionally to form a gradient structure.

8. The preparation method of the porous gradient protective material for laser drilling of blades according to claim 1, characterized in that, the removing of the plastic particles in the second mixed filler after solidification and molding to form a porous gradient protective material is specifically: Heat the environmental temperature of the blade to above the melting point of the plastic particles, which is 240 °C, and keep it warm for 30 min to melt and remove them.

9. The preparation method of the porous gradient protective material for laser drilling of blades according to claim 1, characterized in that, the second mixed filler formed after solidification is a non-loose and non-powdery solid structure.

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