A Wall Protection Material for Laser Drilling of Cavity Parts and a Microstructure Regulation Method

Abstract

The present invention discloses a wall protection material for laser drilling of cavity parts and a microstructure regulation method. The protection material includes a matrix material and a reinforcing material with a mass ratio of 10:1 to 10:4. The matrix material is a two-component epoxy resin of A and B. Component A is bisphenol A epoxy resin, and component B is polyetheramine. The mass ratio of component A to component B is 1.2:1 to 1:1. The reinforcing material is a high-temperature oxide, which is a micron-sized particle mixture of 200 to 6000 mesh. The particle mixture is a mixture of Al2O3, SiO2, and TiO2 in a mass ratio of 1:1:1. The microstructure regulation method is to add hydrogel particles into the protection material, release water during the curing process of the protection material, hinder the curing of the protection material within a specific range, and form controllable microstructural channels inside the protection material. The present invention is applicable to the effective wall protection of laser processing of complex cavity parts, and has the characteristics of controllable protection strength of the filling material, easy filling and easy removal; the filling material has little influence on the laser processing process, and the slag discharge channel is easy to form.

Description

Technical Field

[0001] The present invention relates to the technical field of laser processing, and particularly relates to a wall protection material and a microstructure regulation method for laser hole drilling of cavity parts. Background Art

[0002] Continuous or long-pulse laser processing utilizes the linear absorption effect of materials on laser photons. The laser energy is absorbed by the lattice, causing its vibration to intensify, and the material is removed through processes such as heating, melting, and sublimation. This process is inevitably accompanied by thermal effects on the surrounding area of the processing region, including remelting layers, microcracks, residual stresses, etc. Different from the thermal action mechanism of traditional lasers, because the action time of ultrafast laser pulses is shorter than the "relaxation time" (about 10 -12 seconds) of the energy transfer between electrons and the lattice (atomic nucleus), the lattice temperature of the material remains at a very low level after the laser action, that is, the "cold processing" process is realized.

[0003] However, the conclusion of "cold processing" of ultrafast lasers is obtained under the constraints of single pulses and short time. The process of material removal is accompanied by an increase in lattice temperature. Due to the extremely short laser action time, this heat is rapidly dissipated on the time and space scales, which macroscopically manifests as a "cold process". However, when laser pulses act continuously on the material, especially when high-repetition-rate pulses act, the heating effects of individual pulses are superimposed, resulting in a "thermal accumulation" effect. Improper setting of processing parameters will cause the final processing effect to be similar to that of traditional lasers. In addition, in the specific application scenario of laser hole drilling, the laser pulses continuously act on the material repeatedly in a narrow space, and the removed material forms a high-temperature plasma, which continuously absorbs the laser energy. At this time, the material is strongly thermally radiated by the plasma, causing the temperature to rise. Therefore, in the application of ultrafast laser hole drilling, there are still huge challenges brought by thermal effects.

[0004] The problem of wall damage defects is a new problem arising with the design upgrade. The narrow space between the surface layer and the opposite wall of the double-wall structure makes it extremely easy for laser energy to penetrate the surface layer and cause ablation damage to the opposite wall, seriously affecting the fatigue life of the part. Especially for complex-shaped parts, the plastic plate filling protection process widely used in electric discharge hole drilling is difficult to apply. Therefore, it is urgent to develop a wall protection technology for ultrafast laser hole drilling of complex parts with narrow cavities.

[0005] The essence of the damage to the opposite wall is that during the hole-making process, the center is pierced first, and in the subsequent process, the laser passes through the center and directly acts on the opposite wall. Therefore, the strategies for protecting the opposite wall can be divided into the following two categories: Precision control strategy: Its core idea is to optimize the laser parameters so that the laser energy density acting on the opposite wall is lower than its damage threshold. First, calibrate the damage threshold of the material to be processed, and obtain the corresponding laser parameter threshold through the calculation of the cavity size and hole pose of the part to be processed; during the hole-making process, through an on-line monitoring system, monitor the moment when the through-hole is formed and feedback it to the control system of the drilling equipment to reduce the laser energy input until the drilling is completed. The bottleneck problem of this strategy is that after reducing the laser energy, it is impossible to guarantee the morphology of the lower end outlet of the hole, and at the same time, the processing efficiency is greatly reduced. For a narrow cavity with a thickness of about 1 mm, the attenuation of the laser power density along the propagation direction is limited, and it is impossible to guarantee the removal of the surface wall material and the suppression of the damage to the opposite wall at the same time.

[0006] Filling material strategy: The filling material strategy does not make any adjustments to the laser processing parameters, and the laser energy passing through the through-hole is blocked by adding a protective material in the cavity. According to the different protective materials, it is subdivided into two categories: physical barriers such as energy absorption and scattering, and reaction ablation barriers. Among them, the physical barrier method includes passing water in the cavity, and suppressing the damage to the opposite wall through the disturbance, scouring and cooling effects of water flow (US6547645) or air flow (US6303901). This method has limited interference with high-energy lasers. At the same time, the presence of water flow will cause the processing state to be disordered and affect the processing quality; CN107999957A proposes a laser protection method using a composite material composed of alumina particles and a binder. The high-melting-point oxide can fully absorb the laser energy to achieve efficient and stable laser blocking. However, this method faces problems of difficult filling and removal when applied to parts with narrow and complex cavities.

[0007] The reaction ablation barrier method mostly uses materials with low melting points and easy heat absorption. For example, paraffin is filled into the cavity (US5773790), and PTFE is also used as a filling material for laser protection (US5049722). CN104801857A uses a mixture of carbon powder and water, which has the advantages of good fluidity and suitability for complex cavities. However, such protective materials generally have common problems such as weak protection ability, poor stability, and reaction with the part material.

[0008] In summary, extensive research work has been carried out on the wall protection technology for laser drilling of cavity parts both at home and abroad, and a series of research results have been obtained. However, the current wall protection technology still faces huge challenges: 1. The protection effect of the non-filling material protection strategy is weak and the applicable scenarios are limited; 2. The stability of the filling material during the drilling process is poor; 3. It is difficult to fill and remove the narrow and complex cavity parts; 4. The ablation-type filling material is prone to chemical reactions with the part material; 5. As a process supplement, the filling material will to a certain extent hinder the formation of the slag discharge channel after filling, reducing the processing quality. Summary of the Invention

[0009] The purpose of the present invention is to propose a wall protection material and a microstructure regulation method for laser drilling of cavity parts, which can start from the laser ablation mechanism, propose a wall protection strategy of using organic polymer to fill and dissipate laser energy, and has the characteristics of complete liquid filling - reliable solid protection - non-destructive gas removal, and can achieve effective wall protection for laser processing of narrow-gap complex cavity parts.

[0010] To achieve this purpose, the present invention adopts the following technical solutions:

[0011] A wall protection material for laser drilling of cavity parts, comprising a matrix material and a reinforcing material, the mass ratio of the matrix material to the reinforcing material is 10:1 to 10:4, the matrix material is a two-component epoxy resin, the two-component epoxy resin includes components A and B, component A is bisphenol A epoxy resin, component B is polyetheramine, the mass ratio of component A to component B is 1.2:1 to 1:1, the reinforcing material is a high-temperature oxide, the high-temperature oxide is a micron-sized particle mixture of 200 to 6000 mesh, and the particle mixture is a mixture of Al2O3, SiO2, and TiO2 in a mass ratio of 1:1:1.

[0012] Further, the mass ratio of component A to component B of the two-component epoxy resin is selected as: the mass ratio of component A to component B is 1:1, the mesh number of the high-temperature oxide is selected as: for the inner cavity channel of the part not less than 0.6 mm, a 200-mesh micron-sized particle mixture is selected, for the inner cavity channel of the part less than 0.6 mm, a 6000-mesh micron-sized particle mixture is selected, and the mass ratio of the matrix material to the reinforcing material is selected as: 10:1.

[0013] A microstructure regulation method for laser drilling of cavity parts, comprising the following steps:

[0014] Step 1: Prepare hydrogel particles;

[0015] Step 2: Prepare the protection material;

[0016] Step 3: Mix the hydrogel particles with the protection material to obtain a protection material mixed solution;

[0017] Step 4: Fill the protective material mixed solution into the part to be processed;

[0018] Step 5: Air-dry the part to be processed;

[0019] Step 6: After the part processing is completed, remove the protective material inside the part.

[0020] Furthermore, the preparation method of the hydrogel particles in Step 1 is as follows: Using sodium alginate as the base material and calcium chloride as the cross-linking agent, add 1% by mass of sodium alginate powder to pure water, stir and heat at 95 °C until it is fully dissolved and transparent; Atomize the sodium alginate solution and add it to a 3% by mass calcium chloride aqueous solution to cross-link with calcium ions to form sodium alginate hydrogel microspheres, and the diameter of the sodium alginate hydrogel microspheres is less than 0.2 mm.

[0021] Furthermore, the preparation method of the protective material in Step 2 is as follows: Place each high-temperature oxide material in an oven and dry it at 100 °C for 30 minutes for standby to remove water vapor; After weighing all the raw materials of Component A of the matrix material, Component B of the matrix material, and the reinforcing material according to the mass ratio, add them to an ultrasonic oscillator and mix well. Place the mixed liquid in a vacuum degassing box and evacuate it at a vacuum degree of not less than 0.1 MPa for 5 - 10 min to remove the bubbles in the mixed liquid and avoid voids after curing.

[0022] Furthermore, the mixing method of the hydrogel particles and the protective material in Step 3 is as follows: Add hydrogel particles to the mixed liquid according to the volume ratio to obtain a protective material mixed solution. The addition ratio of the hydrogel particles is selected as follows: The volume ratio of the hydrogel particles to the protective material is 1:4, that is, reserve 1 / 4 slag discharge channel; The maximum addition ratio does not exceed 1:2 to avoid reducing the protective effect of the material. During the curing process of the protective material, water is released, which hinders the curing of the protective material and forms a controllable microstructural channel inside the protective material.

[0023] Furthermore, the method of filling the protective material mixed solution into the cavity part in Step 4 is as follows: Use a syringe to extract the protective material mixed solution and fill and inject it into the inner cavity of the part by manual extrusion or hydraulic extrusion.

[0024] Furthermore, for parts with an inner cavity diameter less than 0.6 mm, after the above filling method, the part to be processed can be placed entirely in the protective material mixed solution and evacuated in a vacuum degassing box at a vacuum degree of not less than 0.1 MPa for 5 - 10 min.

[0025] Furthermore, the air-drying method in Step 5 is as follows: After the protective material is filled, place the part to be processed at room temperature for 3 - 4 hours to completely air-dry naturally or heat it to 60 °C - 100 °C and then air-dry naturally to dry and cure the protective material.

[0026] Further, the method for removing the protective material in step 6 is as follows: after the parts are processed, the protective material can be completely removed by vacuum heating + ultrasonic cleaning. The vacuum heating temperature is 300 - 600 °C, and the ultrasonic cleaning time does not exceed 10 min.

[0027] The beneficial effects of the present invention are as follows:

[0028] First, the present invention first proposes a pair - wall protection strategy for filling organic polymers to dissipate laser energy. The two - component epoxy resin used has the advantages of good fluidity, stable physical and chemical properties after curing, large chemical inertness with metal materials, and easy removal without residue, realizing effective protection against pair - wall damage under the condition of narrow gaps of parts.

[0029] Second, by adding an appropriate proportion of reinforcing particles to the modified organic matter and utilizing its scattering effect on laser, the protection threshold of the filling material is further improved, meeting the protection requirements for pair - wall damage under the condition that the double - layer wall gap is less than 0.6 mm.

[0030] Third, with the increase of the drilling depth, too high a protection threshold may bring difficulties in slag discharge during the drilling process, reducing the quality of the exit hole shape. In addition, with the further increase of the depth - diameter ratio, the method of vaporizing to generate a slag discharge channel can no longer meet the drilling efficiency requirements. The present invention proposes a process for reserving a slag discharge channel. By adding low - density hydrogel particles to the liquid protective material, they float on the surface after filling the cavity and gradually release water during the curing process of the protective material, hindering the curing of the protective material within a certain range. Thus, a slag discharge channel with a controllable thickness is formed between the drilling wall and the protective material, ensuring the rapid discharge of the removed material during the drilling process with a large depth - diameter ratio, and then solving the problem of slag discharge during the drilling process and improving the drilling efficiency.

[0031] Fourth, it is applicable to the protection against pair - wall damage in the process of laser - processing cavity parts, with controllable protection strength of the filling material, easy filling and removal; the filling material has little influence on the laser - processing process, and the slag discharge channel is easy to form. Description of the Drawings

[0032] Figure 1 It is a schematic diagram of the addition of the protective material of the present invention;

[0033] Figure 2 It is a schematic diagram of the effect of laser drilling without microstructure regulation;

[0034] Figure 3 It is a schematic diagram of the effect after microstructure regulation of the laser drilling of the parts of the present invention;

[0035] Figure 4 It is a schematic diagram of the pair - wall protection effect of the laser drilling of the parts of the present invention. Detailed implementation manners

[0036] To make the technical problems solved by the present invention, the adopted technical solutions and the achieved technical effects clearer, the technical solutions of the embodiments of the present invention will be further described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present invention.

[0037] A wall protection material for laser drilling of cavity parts includes a matrix material and a reinforcing material. The mass ratio of the matrix material to the reinforcing material is 10:1 to 10:4. The matrix material is a two-component epoxy resin, which includes components A and B. Component A is bisphenol A epoxy resin, and component B is polyetheramine. The mass ratio of component A to component B is 1.2:1 to 1:1. The reinforcing material is a high-temperature oxide, which is a 200-6000 mesh micron-sized particle mixture, and the particle mixture is a mixture of Al2O3, SiO2, and TiO2 in a mass ratio of 1:1:1.

[0038] The principle for selecting the mass ratio of component A to component B of the two-component epoxy resin is as follows: When the mass ratio of component A to component B is selected as 1:1, the cured protection material has a higher ablation threshold; for complex cavities, a higher proportion of component A can reduce the viscosity of the protection material and is more conducive to filling. The principle for selecting the mesh number of the high-temperature oxide is as follows: For larger particles with a smaller mesh number, the anti-laser ablation time of the protection material is longer; in an extremely narrow gap, such as when the inner cavity channel of the part is less than 0.6 mm, larger particles with a smaller mesh number have large voids and poor protection effects, and particles with a larger mesh number can be selected. The principle for selecting the ratio of the matrix material to the reinforcing material is as follows: Increasing the proportion of the reinforcing material will reduce the fluidity of the protection material. Under the condition of meeting the protection performance, a lower proportion of the reinforcing material should be selected.

[0039] A microstructure regulation method for laser drilling of cavity parts is to add hydrogel particles into the protection material, release water during the curing process of the protection material, hinder the curing of the protection material within a specific range, and form controllable microstructural channels inside the protection material.

[0040] The preparation method of the hydrogel particles is as follows: Using sodium alginate as the base material and calcium chloride as the cross-linking agent, add 1% by mass of sodium alginate powder to pure water, stir and heat at 95°C until it is fully dissolved and transparent; atomize the sodium alginate solution and add it to a 3% by mass calcium chloride aqueous solution to cross-link with calcium ions to form sodium alginate hydrogel microspheres, and the diameter of the sodium alginate hydrogel microspheres is less than 0.2 mm.

[0041] The preparation method of the protective material is as follows: Place each high-temperature oxide material in an oven and dry it at 100°C for 30 minutes for later use to remove moisture; After weighing all the raw materials of component A of the matrix material, component B of the matrix material, and the reinforcing material according to the mass ratio, add them to an ultrasonic oscillator and mix well. Place the mixed liquid in a vacuum degassing box and evacuate it at a vacuum degree of not less than 0.1 MPa for 5 - 10 minutes to remove the bubbles in the mixed liquid and avoid voids after curing.

[0042] The method of mixing the hydrogel particles with the protective material is as follows: Add hydrogel particles to the mixed liquid according to the volume ratio to obtain a protective material mixed solution. The addition ratio of the hydrogel particles is selected as follows: The volume ratio of the hydrogel particles to the protective material is 1:4, that is, a 1 / 4 slag discharge channel is reserved; The maximum addition ratio does not exceed 1:2 to avoid reducing the protective effect of the material. After the low-density hydrogel particles are filled, they will float on the surface layer and gradually release water during the curing process of the protective material, hindering the curing of the protective material within a certain range. Thus, a slag discharge channel with a controllable thickness is formed between the workpiece to be processed and the protective material.

[0043] The method of filling the protective material mixed solution into the cavity part is as follows: Use a syringe to extract the protective material mixed solution and fill it into the inner cavity of the part by manual extrusion or hydraulic extrusion.

[0044] For parts with an inner cavity diameter less than 0.6 mm, after the above filling method, the workpiece to be processed can be placed entirely in the protective material mixed solution and evacuated in a vacuum degassing box at a vacuum degree of not less than 0.1 MPa for 5 - 10 minutes.

[0045] After the protective material is filled, place the workpiece to be processed at room temperature for 3 - 4 hours to dry completely naturally or heat it to 60°C - 100°C and then dry it naturally to dry and cure the protective material.

[0046] After the part is processed, the protective material can be completely removed by vacuum heating + ultrasonic cleaning. The vacuum heating temperature is 300 - 600°C, and the ultrasonic cleaning time does not exceed 10 minutes.

[0047] Test example: The following three methods are used for comparative tests on laser drilling of cavity parts, and the test results are shown in Table 1.

[0048] I. Low-energy density laser protection, epoxy resin, no reinforcing material added;

[0049] II. High-energy density laser protection, reinforcing material added, no hydrogel particles;

[0050] III. Optimization of deep hole diameter ratio slag discharge channel, hydrogel particles added.

[0051]

[0052] Table 1

[0053] The technical principle of the present invention is described above in conjunction with specific embodiments. These descriptions are only for explaining the principle of the present invention and cannot be interpreted as limiting the scope of protection of the present invention in any way. Based on the explanations herein, those skilled in the art can associate other specific implementations of the present invention without paying creative labor, and these methods will fall within the scope of protection of the present invention.

Claims

1. A method for microstructural regulation of laser drilling of cavity parts, characterized in that, Step 1: Prepare hydrogel particles; Step 2: Prepare a protective material; Step 3: Mix the hydrogel particles with the protective material to obtain a mixed solution of the protective material; Step 4: Fill the mixed solution of the protective material into the part to be processed; Step 5: Air-dry the part to be processed; Step 6: After the part processing is completed, remove the protective material inside the part; The method for preparing the hydrogel particles in Step 1 is as follows: Using sodium alginate as the base material and calcium chloride as the cross-linking agent, add 1% by mass of sodium alginate powder to pure water, stir and heat at 95 °C until it is fully dissolved and transparent; Atomize the sodium alginate solution and add it to a 3% by mass calcium chloride aqueous solution to cross-link with calcium ions to form sodium alginate hydrogel microspheres, and the diameter of the sodium alginate hydrogel microspheres is less than 0.2 mm; The method for preparing the protective material in Step 2 is as follows: Place each high-temperature oxide material in an oven and dry it at 100 °C for 30 minutes for standby to remove water vapor; Weigh all the raw materials of Component A of the matrix material, Component B of the matrix material, and the reinforcing material according to the mass ratio, add them to an ultrasonic oscillator and mix well, and place the mixed liquid in a vacuum degassing box. Under a vacuum degree of not less than 0.1 MPa, evacuate for 5 - 10 min to remove the air bubbles in the mixed liquid to avoid voids after curing; The mass ratio of the matrix material to the reinforcing material is 10:

1. The matrix material is a two-component epoxy resin. The two-component epoxy resin includes Components A and B. Component A is bisphenol A epoxy resin, and Component B is polyetheramine. The mass ratio of Component A to Component B is 1:

1. The reinforcing material is a high-temperature oxide. The high-temperature oxide is a micron-sized particle mixture of 200 - 6000 mesh. The particle mixture is a mixture of Al2O3, SiO2, and TiO2 in a mass ratio of 1:1:1; The selection of the mesh number of the high-temperature oxide is as follows: When the inner cavity channel of the part is not less than 0.6 mm, select a 200-mesh micron-sized particle mixture; when the inner cavity channel of the part is less than 0.6 mm, select a 6000-mesh micron-sized particle mixture; The method of mixing the hydrogel particles with the protective material in Step 3 is as follows: Add hydrogel particles to the mixed liquid according to the volume ratio to obtain a mixed solution of the protective material. The addition ratio of the hydrogel particles is selected as follows: The volume ratio of the hydrogel particles to the protective material is 1:4, that is, reserve 1 / 4 of the slag discharge channel; The hydrogel particles release water during the curing process of the protective material, hindering the curing of the protective material and forming a controllable microstructural channel inside the protective material.

2. The microstructure regulation method for laser hole drilling of a cavity part according to claim 1, wherein The method of filling the mixed solution of the protective material into the cavity part in Step 4 is as follows: Use a syringe to extract the mixed solution of the protective material and fill it into the inner cavity of the part by manual extrusion or hydraulic extrusion.

3. The microstructure regulation method for laser hole drilling of a cavity part according to claim 2, characterized in that, For parts with an inner cavity diameter less than 0.6 mm, after the above filling method, the part to be processed can be placed entirely in the mixed solution of the protective material and subjected to a vacuum treatment in a vacuum degassing box. Under a vacuum degree of not less than 0.1 MPa, evacuate for 5 - 10 min.

4. A microstructure regulation method for laser hole drilling of a cavity part according to claim 1, characterized in that, The drying method in Step 5 is as follows: after the filling of the protective material is completed, the part to be processed is placed at room temperature for 3 to 4 hours to be completely air-dried naturally or heated to 60°C - 100°C and then air-dried naturally, so that the protective material is dried and cured.

5. A microstructure regulation method for laser hole drilling of a cavity part according to claim 1, characterized in that, The method for removing the protective material in Step 6 is as follows: after the part is processed, the protective material can be completely removed by vacuum heating + ultrasonic cleaning. The vacuum heating temperature is 300~600°C, and the ultrasonic cleaning time does not exceed 10 minutes.

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