A blade reinforcement webbing process

Abstract

The present application relates to the technical field of blade processing, and provides a blade reinforced slurry hanging process, which comprises the following steps: S1, preparing modified slurry, adding ion responsive polymer material into silica sol slurry to obtain modified slurry; S2, dipping the blade wax mold into the modified slurry and performing slurry draining treatment; S3, sprinkling refractory sand on the surface of the modified slurry; S4, sending the blade with completed sand sprinkling into an air mist instantaneous setting channel, so that cross-linking ions in the air mist and the ion responsive polymer material are cross-linked to form a gel sand locking layer on the surface of the modified slurry to fix the refractory sand; S5, performing drying treatment on the blade; S6, repeating steps S2 to S5 to form a multilayer shell; S7, performing dewaxing and baking on the shell, so that organic components in the gel sand locking layer are pyrolyzed and lost and a microporous structure is formed on the surface of the shell; and S8, using the baked shell to perform metal casting.

Description

Technical Field

[0001] This invention relates to the field of blade processing technology, and specifically to a blade reinforcement coating process. Background Technology

[0002] Investment casting is a crucial manufacturing process for aero-engine blades, gas turbine blades, and other complex thin-walled components. During the shell preparation process, silica sol is typically used as a binder, and a ceramic shell with a certain strength and thickness is formed through impregnation with slurry, application of refractory sand, and layer-by-layer drying.

[0003] For blades with large chord lengths, large torsion angles, and complex curved surfaces, the blade surface has a large inclined surface and a region of curvature variation. After slurry application and sand spreading, the slurry and refractory sand tend to flow and accumulate in lower areas under gravity, leading to localized sand slippage, accumulation, and uneven shell thickness. These problems not only affect the surface quality of the shell but also easily lead to insufficient local strength during subsequent firing, affecting the dimensional accuracy and surface quality of the casting.

[0004] To address the issue of refractory sand slippage, existing technologies typically employ methods such as increasing slurry viscosity, reducing slurry flowability, or using wire or mesh support structures for auxiliary fixation. However, simply increasing slurry viscosity can negatively impact its wettability and leveling properties, leading to uneven coverage in complex areas of the blade. While auxiliary fixation structures like wire can suppress sand particle slippage to some extent, the difference in thermal expansion between the wire and the ceramic mold during high-temperature firing can cause localized stress concentration, potentially leading to mold cracking. Furthermore, oxidation of the wire can introduce impurities and defects, affecting mold quality. Therefore, we propose a blade-strengthening slurry application process. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention provides a blade-enhanced slurry coating process, which overcomes the shortcomings of the prior art, has a reasonable design and compact structure, and solves the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A blade reinforcement coating process includes the following steps:

[0008] S1. Preparation of modified slurry: Ion-responsive polymer material is added to silica sol slurry to obtain modified slurry;

[0009] S2. Dip the blade wax model into the modified slurry and then perform a slurry-draining treatment;

[0010] S3. Spread refractory sand on the surface of the modified slurry;

[0011] S4. The blades that have been sanded are sent into the aerosol condensation channel, so that the cross-linking ions in the aerosol react with the ion-responsive polymer material to form a gel sand-locking layer on the surface of the modified slurry to fix the refractory sand.

[0012] S5. Dry the leaves;

[0013] S6. Repeat steps S2 to S5 to form a multi-layered shell;

[0014] S7. Dewaxing and calcining the shell to thermally decompose and burn off the organic components in the gel sand-locking layer and form a microporous structure on the surface of the shell.

[0015] S8. Use the baked shell for metal casting.

[0016] Preferably, the ion-responsive polymer material is one or more of alginate, carboxymethyl cellulose salt, and chitosan derivative.

[0017] Preferably, the ion-responsive polymer material is sodium alginate.

[0018] Preferably, the ion-responsive polymer material is sodium carboxymethyl cellulose.

[0019] Preferably, the content of the ion-responsive polymer material in the modified slurry is 0.5 wt% to 1.0 wt%.

[0020] Preferably, the silica sol slurry is an alkaline silica sol slurry with a pH value of 9.5 to 10.5.

[0021] Preferably, the crosslinking ion is calcium ion, and a calcium chloride atomizing device is provided in the aerosol condensation channel to form an aerosol environment containing calcium ions, with the calcium chloride solution concentration being 1wt% to 3wt%.

[0022] Preferably, carbon dioxide gas is introduced into the aerosol condensation channel to create a weakly acidic environment on the surface of the slurry and promote the cross-linking reaction.

[0023] Preferably, the thickness of the gel-locking sand layer is 50μm to 300μm.

[0024] Preferably, during the calcination process, the organic components in the gel-locking sand layer undergo thermal decomposition and burn-off within a temperature range of 300℃ to 500℃, thereby forming a connected microporous structure on the surface of the shell.

[0025] This invention provides a blade reinforcement coating process. It has the following beneficial effects:

[0026] 1. This invention introduces ion-responsive polymer materials into silica sol slurry and then uses a calcium ion-containing aerosol environment to instantly crosslink the slurry surface after sand application, forming a flexible gel network structure on the slurry surface. This gel network can quickly form a coating effect after the refractory sand is applied, stably fixing the refractory sand to the blade surface, thereby effectively reducing the slippage and accumulation of refractory sand caused by gravity, and improving the uniformity of sand application and the consistency of shell thickness.

[0027] 2. The gel network formed by this invention is a three-dimensional network structure with open pores, which can maintain normal moisture diffusion during the subsequent drying process and will not significantly hinder the drying of the shell. At the same time, the gel network formed by this invention has an open, porous, and semi-permeable structure, allowing nanoscale inorganic colloidal particles and fluids in the new slurry formed by subsequent dip coating to penetrate the gel network and fuse in situ with the previous silica sol skeleton, thereby forming a continuous inorganic ceramic skeleton structure, improving the bonding strength between multilayer shells and reducing the risk of interlayer delamination.

[0028] 3. The gel network formed by this invention can undergo pyrolysis and complete burn-off during the calcination and heating process, leaving uniformly distributed micron-sized interconnected channels on the surface of the shell. The microporous structure can provide a channel for residual gas to escape during the subsequent casting process, and at the same time, it is beneficial to release local thermal stress, thereby reducing the risk of surface cracking and expansion cracking of large-area blade shells. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the process flow of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, what is described is only a part of this invention, not all of it. All other works obtained by those skilled in the art based on this invention without inventive effort are within the scope of protection of this invention.

[0031] Example 1

[0032] This embodiment provides a blade strengthening slurry coating process, applicable to the shell preparation process of precision cast blades such as aero-engine blades, gas turbine blades, and other blades with complex curved surfaces and large chord lengths. Alkaline silica sol is selected as the base slurry, with a silica content of 28-32% and a pH value controlled between 9.5 and 10.2. First, sodium alginate powder is weighed and added to deionized water at a mass ratio of 1:50 to prepare a 2% sodium alginate pre-solution.

[0033] Stir the pre-solution thoroughly for 30-60 minutes until it is completely dissolved and there are no obvious lumps.

[0034] The sodium alginate pre-solution was then slowly added to the silica sol slurry, and stirred for 20-30 minutes to achieve a final sodium alginate content of 0.8 wt%. After mixing, the slurry shear viscosity was checked and found to be between 50 and 150 mPa·s, ensuring good slurry flowability and smooth coverage of the blade surface without air bubbles or initial sagging. Refractory fillers, such as zircon powder or mullite powder, can be added to the slurry to enhance the shell's refractory properties.

[0035] Immerse the blade wax model in the modified slurry for 20-60 seconds, ensuring the slurry evenly covers the suction surface, pressure surface, and tip area of ​​the blade. After lifting the blade, drain the slurry for 30-120 seconds, allowing excess slurry to flow back into the slurry tank naturally. While the slurry surface is still wet, use a fluidized bed sander to evenly spread zircon sand with a particle size of 80-150 μm onto the surface, ensuring uniform sand coverage without any sand leakage or accumulation.

[0036] The blades, after being coated with sand, immediately enter a 1.5-meter-long aerosol condensation channel. An ultrasonic atomizer inside the channel atomizes a 2% (w / w) calcium chloride solution into droplets with a diameter of 3-10 μm, which are then introduced into the channel using industrial-grade CO2 gas as the carrier gas, maintaining a slightly positive pressure and weakly acidic environment. The blades remain in the channel for 2-5 seconds. Upon contact with the slurry surface, Ca²⁺ ions rapidly cross-link with the sodium alginate molecular chains. The weakly acidic environment created by CO2 dissolved in water further promotes gelation, forming a flexible mesh structure approximately 50-300 μm thick on the outermost layer of the slurry, firmly fixing the sand particles to the slurry surface.

[0037] After the blades undergo rapid coagulation treatment, they enter the air-drying station, where the temperature is controlled at 40~60°C and the relative humidity is controlled at 30~60%. The gel mesh has a semi-permeable structure, allowing moisture inside the slurry to evaporate freely. Therefore, the drying time is increased by no more than 10% compared to traditional processes.

[0038] After drying, the dip-coating-sand-aerosol-instantaneous coagulation steps are repeated according to the shell thickness requirements to form a multi-layer shell. Because the gel mesh has an open, porous, and semi-permeable structure, its micropores are much larger than those of silica sol particles. The nano-sized silica sol particles in the subsequent slurry can easily penetrate the pores of the previous gel layer and achieve in-situ fusion by capillary suction, forming a continuous inorganic framework structure and avoiding interlayer delamination.

[0039] After shell preparation, steam dewaxing (160-180°C) and calcination are performed. When the temperature rises to 300-500°C, the calcium alginate gel network completely pyrolyzes, carbonizes, and burns away, forming micron-sized interconnected pores. Subsequently, the temperature is further raised to 900-1150°C for ceramic sintering and shaping. When pouring molten metal, the surface microporous network can effectively expel residual gas, alleviate thermal stress, and reduce the risk of shell cracking and expansion.

[0040] Example 2

[0041] This embodiment is similar to Embodiment 1, but only a 2% CaCl2 solution is sprayed into the aerosol condensation channel, and compressed air is used as the carrier gas; CO2 is not used. The blades remain in the channel for 3-5 seconds. Ca²⁺ ions rapidly form a gel network with the sodium alginate surface, approximately 50-250 μm thick, fixing the sand particles. The drying and multi-layer coating treatment methods are the same as in Embodiment 1. The microporous structure formed after calcination provides a channel for gas exhaust, significantly improving the uniformity of sand coating and reducing localized dripping; however, the surface gel formation rate is slightly lower than that synergistically achieved with CO2.

[0042] Example 3

[0043] In this embodiment, sodium carboxymethyl cellulose (CMC-Na) is used as an ion-responsive polymer material. CMC-Na is pre-dissolved in deionized water to prepare a 1.5% pre-solution, which is then slowly added to an alkaline silica sol slurry, resulting in a final CMC-Na content of 0.6–0.8 wt%. The slurry viscosity is maintained at 50–150 mPa·s. The blade coating, slurry application, and sand application methods are the same as in Example 1, using calcium chloride droplets + CO2 gas phase for rapid coagulation treatment, achieving a gel thickness of 50–250 μm to fix the sand particles. The drying, shell re-coating, and calcination processes are the same as in Example 1, resulting in a uniform microporous structure and good sand-locking ability.

[0044] Example 4

[0045] In this embodiment, sodium alginate and CMC-Na are compounded at a mass ratio of 3:1, with a total content of 1.0 wt%. After pre-dissolving, the mixture is slowly added to the alkaline silica sol slurry and mixed evenly. The blade dipping, slurry application, and sanding processes are the same as in Example 1. The aerosol condensation channel uses 2% CaCl2 droplets and CO2 gas, with the blade remaining in the aerosol for 2-3 seconds. Sodium alginate provides rapid curing capability, while CMC-Na improves gel toughness, forming a composite gel mesh that combines rapid cross-linking and flexible deformation capabilities. After drying and re-shelling, calcination results in a more uniform micropore distribution, making it suitable for long blades with large chord lengths and complex twists, achieving optimal sand coating uniformity and micropore permeability.

[0046] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes the element.

[0047] The above description is only used to illustrate the technical solutions of the present invention, and is not intended to limit them. Although the present invention has been described in detail with reference to the foregoing, those skilled in the art should understand that modifications can still be made to the foregoing technical solutions, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A blade reinforcement coating process, characterized in that, Includes the following steps: S1. Preparation of modified slurry: Ion-responsive polymer material is added to silica sol slurry to obtain modified slurry; S2. Dip the blade wax model into the modified slurry and then perform a slurry-draining treatment; S3. Spread refractory sand on the surface of the modified slurry; S4. The blades that have been sanded are sent into the aerosol condensation channel, so that the cross-linking ions in the aerosol react with the ion-responsive polymer material to form a gel sand-locking layer on the surface of the modified slurry to fix the refractory sand. S5. Dry the leaves; S6. Repeat steps S2 to S5 to form a multi-layered shell; S7. Dewaxing and calcining the shell to thermally decompose and burn off the organic components in the gel sand-locking layer and form a microporous structure on the surface of the shell. S8. Use the baked shell for metal casting.

2. The blade reinforcement coating process according to claim 1, characterized in that: Ion-responsive polymers are one or more of alginate, carboxymethyl cellulose salt, and chitosan derivatives.

3. The blade reinforcement coating process according to claim 2, characterized in that: The ion-responsive polymer material is sodium alginate.

4. The blade reinforcement coating process according to claim 2, characterized in that: The ion-responsive polymer material is sodium carboxymethyl cellulose.

5. The blade reinforcement coating process according to claim 1, characterized in that: The content of ion-responsive polymer materials in the modified slurry is 0.5wt% to 1.0wt%.

6. The blade reinforcement coating process according to claim 1, characterized in that: The silica sol slurry is an alkaline silica sol slurry with a pH value of 9.5 to 10.

5.

7. The blade reinforcement coating process according to claim 1, characterized in that: The cross-linking ion is calcium ion. A calcium chloride atomizing device is installed in the aerosol condensation channel to form an aerosol environment containing calcium ions. The concentration of calcium chloride solution is 1wt% to 3wt%.

8. The blade reinforcement coating process according to claim 1, characterized in that: Carbon dioxide gas is introduced into the aerosol condensation channel to create a weakly acidic environment on the surface of the slurry and promote the cross-linking reaction.

9. The blade reinforcement coating process according to claim 1, characterized in that: The thickness of the gel-locking sand layer is 50μm to 300μm.

10. The blade reinforcement coating process according to claim 1, characterized in that: During the calcination process, the organic components in the gel-locking sand layer undergo thermal decomposition and burn-off within a temperature range of 300℃ to 500℃, thereby forming a connected microporous structure on the surface of the shell.

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