Solvents for removing high temperature coatings and their use and methods for removing high temperature coatings

Abstract

The application discloses a solvent for removing high-temperature coating and application and a method for removing high-temperature coating. The solvent comprises 30-40% of 36-38 wt.% concentration hydrochloric acid, 8-12% of 83-86 wt.% concentration phosphoric acid, 3-5% of 25-30 wt.% concentration hydrogen peroxide and 0.5-1% of corrosion inhibitor. The hydrochloric acid is the main corrosion solvent, and the phosphoric acid can enhance the corrosion ability. The Ni3Al phase of the coating is preferentially corroded through the grain boundary to form pores, so that the coating is stripped. The addition of the corrosion inhibitor avoids the corrosion of the substrate by the hydrochloric acid and the phosphoric acid, so that the dense high-temperature protective coating can be removed, and the influence of the pickling on the surface structure and morphology of the substrate can be relieved. In addition, the sand blasting treatment is conducted on the alloy after pickling, the mechanical cutting action is utilized, the corrosion pits and interdiffusion zones are removed, and the mechanical properties of the substrate are ensured not to be influenced.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology, and more specifically, to a solvent for removing high-temperature coatings, its application, and a method for removing high-temperature coatings. Background Technology

[0002] MCrAlY coatings are commonly used high-temperature alloy materials for surface protection, where M represents the matrix element, typically Ni and Co. To further improve the mechanical and oxidation resistance of the coating, other elements, represented by X, are added to the alloy coating, thus forming MCrAlYX multi-component alloy materials. MCrAlYX coatings prepared by physical vapor deposition (PVD) have excellent high-temperature oxidation resistance due to their dense structure and good adhesion to the substrate, and are widely used for the protection of high-temperature turbine components. During the preparation of high-temperature coatings, even minor metallurgical defects in the matrix alloy, excessive coating thickness, or deviations in chemical composition can lead to substandard blade coatings. Considering the processing costs of high-temperature alloy substrates, scrapping blades solely due to coating defects would result in even greater waste. Therefore, the technology for removing and recoating turbine blade protective coatings is of great significance for engine maintenance.

[0003] MCrAlYX coatings prepared by physical vapor deposition (PVD) exhibit a denser structure compared to coatings prepared by plasma spraying, especially after vacuum heat treatment, resulting in a more uniform composition and a absence of pores. Furthermore, after vacuum heat treatment or service, MCrAlYX coatings prepared by PVD can develop an interdiffusion zone at the coating-substrate interface due to elemental interdiffusion. Residual material in this zone during coating removal can affect the mechanical properties of the substrate. Therefore, completely removing the dense high-temperature coating from the surface of the high-temperature alloy substrate while eliminating the interdiffusion zone and ensuring the integrity of the alloy substrate is a pressing problem in this field.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a solvent for removing high-temperature coatings, its application, and a method for removing high-temperature coatings, so as to improve the above-mentioned technical problems.

[0006] This invention is implemented as follows:

[0007] In a first aspect, the present invention provides a solvent for removing high-temperature coatings, comprising 30%–40% hydrochloric acid by volume, 8%–12% phosphoric acid by volume, 3%–5% hydrogen peroxide by volume, and 0.5%–1% corrosion inhibitor by mass; wherein the mass percentage concentration of hydrochloric acid is 36%–38%, the mass percentage concentration of phosphoric acid is 84%–86%, and the mass percentage concentration of hydrogen peroxide is 25%–30%.

[0008] Optionally, the corrosion inhibitor is hexamethylenetetramine.

[0009] Secondly, the present invention also provides a method for removing a high-temperature coating, comprising: acid washing the high-temperature coating with the above-mentioned solvent, and then performing sandblasting treatment, wherein the high-temperature coating is an MCrAlYX coating, wherein M is at least one of Ni and Co, and X is at least one of La, Ru, Re, Y, Hf, Zr, Ce, Pt and Dy.

[0010] Thirdly, the present invention also provides the application of the solvent for removing high-temperature coatings in the removal of high-temperature coatings.

[0011] This invention offers the following advantages: Hydrochloric acid is the primary corrosive solvent for removing high-temperature coatings. The addition of phosphoric acid and hydrogen peroxide further enhances the corrosive power of hydrochloric acid. Furthermore, this solvent exhibits high coating removal efficiency at low temperatures, preventing excessive heat release during prolonged removal that could lead to a rise in solution temperature and severe corrosion of the substrate. Particularly when removing MCrAlYX coatings, the solvent utilizes phase differences and microscopic defects such as grain boundaries to preferentially corrode the Ni3Al phase within the coating, forming micropores and thus allowing the coating material to peel off. Additionally, the addition of corrosion inhibitors to the pickling solution prevents corrosion of the substrate by hydrochloric acid, phosphoric acid, and hydrogen peroxide. This allows the solvent to remove the dense high-temperature protective coating from the substrate surface while effectively mitigating the impact of pickling on the substrate's surface structure and morphology. Moreover, the method involves sandblasting the pickled sample. The mechanical cutting action of sandblasting further removes corrosion pits and the interdiffusion zone formed at the coating-substrate interface due to heat treatment, ensuring that the mechanical properties of the substrate remain unaffected. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a scanning electron microscope image of the alloy surface after pickling in Example 1 of the present invention;

[0014] Figure 2 This is a scanning electron microscope image of the alloy cross-section after pickling in Example 1 of the present invention;

[0015] Figure 3 This is a scanning electron microscope image of the alloy cross-section after sandblasting in Embodiment 1 of the present invention;

[0016] Figure 4This is a scanning electron microscope image of the alloy cross-section obtained in Example 2 of the present invention;

[0017] Figure 5 This is a scanning electron microscope image of the alloy cross-section obtained in Example 3 of the present invention;

[0018] Figure 6 This is a scanning electron microscope image of the alloy cross-section obtained in Comparative Example 1 of this invention;

[0019] Figure 7 This is a scanning electron microscope image of the alloy cross-section of Comparative Example 2 of the present invention;

[0020] Figure 8 This is a scanning electron microscope image of the alloy cross-section of Comparative Example 3 of the present invention;

[0021] Figure 9 This is a scanning electron microscope image of the alloy cross-section of Comparative Example 4 of the present invention;

[0022] Figure 10 This is a scanning electron microscope image of the alloy cross-section of Comparative Example 5 of the present invention;

[0023] Figure 11 This is a scanning electron microscope image of the alloy cross-section of Comparative Example 6 of the present invention;

[0024] Figure 12 This is a scanning electron microscope image of the alloy cross-section of Comparative Example 7 of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0026] The following is a detailed description of a solvent for removing high-temperature coatings provided by the present invention, its application, and a method for removing high-temperature coatings.

[0027] Some embodiments of the present invention provide a solvent for removing high-temperature coatings, the main components of which include hydrochloric acid, phosphoric acid, hydrogen peroxide, and a corrosion inhibitor. The volume fraction of hydrochloric acid in the solvent is 30% to 40%, for example, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, or 40%; the volume fraction of phosphoric acid in the solvent is 8% to 12%, for example, 8%, 9%, 10%, 11%, or 12%; the volume fraction of hydrogen peroxide in the solvent is 3% to 5%, for example, 3%, 3.5%, 4%, 4.5%, or 5%; and the mass fraction of the corrosion inhibitor in the solvent is 0.5% to 1%, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%. The concentration of hydrochloric acid is 36-38% by mass, the concentration of phosphoric acid is 84-86% by mass, and the concentration of hydrogen peroxide is 25-30% by mass.

[0028] Generally, existing technologies primarily remove dense coatings by increasing acidity and temperature. However, excessively strong acidity can corrode the substrate, and the exothermic reaction and increased solution temperature make it difficult to control the corrosion process, leading to substrate corrosion. Based on this, the inventors, through extensive research and practice, proposed a solvent for the above-mentioned technical solution. This solvent can remove both heat-treated physical vapor deposition (PVD) MCrAlYX coatings and PVD MCrAlYX coatings after a certain service life. In other words, this solvent can effectively remove the dense high-temperature protective coating from the sample surface to a certain extent, while also mitigating the impact of acid pickling on the substrate's surface microstructure and mechanical properties. The reason for achieving these effects may be that hydrochloric acid is used as the main corrosive solvent, while phosphoric acid and hydrogen peroxide enhance the corrosive power of hydrochloric acid. This allows the Ni3Al phase in the coating to preferentially dissolve through defects such as grain boundaries, forming micropores. Simultaneously, the corrosion inhibitor in the solvent prevents the substrate containing the high-temperature coating from being corroded by hydrochloric acid, thus achieving the goal of removing the dense high-temperature protective coating from the substrate surface while effectively mitigating the impact of acid pickling on the substrate's surface microstructure and morphology.

[0029] In some embodiments, the solvent for removing high-temperature coatings contains 30-40% hydrochloric acid (by volume), 8-12% phosphoric acid (by volume), 3-5% hydrogen peroxide (by volume), and 0.5-1% corrosion inhibitor (by mass), with the balance being water. The pickling solvent prepared by the inventors through the compounding of the above raw materials in specific proportions exhibits superior coating corrosion resistance while simultaneously preventing the solvent from affecting the surface morphology of the substrate during coating removal.

[0030] In some embodiments, the specific choice of corrosion inhibitor can also affect the corrosion effect to some extent; preferably, hexamethylenetetramine can be selected as the corrosion inhibitor. In some embodiments, the water in the solvent is deionized water.

[0031] Furthermore, the solvent for removing the high-temperature coating is prepared by mixing hydrochloric acid, phosphoric acid, hydrogen peroxide and corrosion inhibitor by magnetic stirring.

[0032] Some embodiments of the present invention also provide a method for removing a high-temperature coating, comprising: acid washing the high-temperature coating using the solvent described above for removing the high-temperature coating, and then performing sandblasting. It should be noted that the high-temperature coating is an MCrAlYX coating, wherein M is at least one of Ni and Co, and X is at least one of La, Ru, Re, Y, Hf, Zr, Ce, Pt, and Dy.

[0033] The solvents described above preferentially dissolve the Ni3Al phase in the coating through defects such as grain boundaries, forming micropores. The acid-washed sample is then sandblasted, utilizing the mechanical cutting force of the sandblasting to thoroughly remove the corroded and interdiffusion zones in the substrate, ensuring the substrate's mechanical properties. Simultaneously, the corrosion inhibitors in the solvent prevent the sample substrate from being corroded by hydrochloric acid. This method effectively removes the dense, high-temperature protective coating from the sample surface while mitigating the impact of acid washing on the substrate's surface microstructure and morphology. The process is simple and can be applied to large-scale production.

[0034] In some embodiments, pickling involves immersing the component containing the high-temperature coating in the solvent to react, thereby improving the removal effect of the coating. Of course, in other embodiments, the removal can also be achieved by continuously spraying the solvent onto the surface of the coating.

[0035] In some embodiments, the high-temperature coating is deposited using at least one of magnetron sputtering, arc ion plating, or electron beam evaporation, and the high-temperature coating has undergone vacuum treatment or service. The MCrAlYX coating obtained by the above methods has a very uniform composition, high density, and forms an interdiffusion region with the substrate. Furthermore, the solvents and methods for removing the high-temperature coating described in the above embodiments can effectively remove the coating, especially the MCrAlYX coating on the surface of nickel-based superalloys.

[0036] Furthermore, in some embodiments, during immersion removal, the pickling reaction time is 5-10 minutes, and the solvent temperature is 30°C-40°C. Preferably, the pickling reaction is ultrasonic pickling with an ultrasonic frequency of 20-50 kHz. For high-temperature coatings that have undergone vacuum heat treatment or a certain period of service, their composition is very uniform, their structure is dense, and they lack macroscopic defects such as pores and uneven composition, and they exhibit some elemental interdiffusion with the substrate. While increasing the acidity or temperature under existing pickling conditions can improve the process, this also results in a longer pickling time. Due to the intense exothermic reaction during coating removal, a prolonged pickling time can cause the solution temperature to rise, making the corrosion process difficult to control and easily leading to substrate corrosion. The inventors have improved the preparation of the pickling solution, enabling the pickling solution to dissolve and remove the coating on the sample surface at a lower temperature and faster speed, further preventing the substrate from being damaged by the pickling solution's etching. In other words, in this application, a pickling time that is too short cannot adequately remove the high-temperature coating, while a pickling time that is too long can easily corrode the substrate. Simultaneously, a high solvent temperature can also lead to poor corrosion results.

[0037] In some embodiments, the high-temperature coating is located on a nickel-based superalloy substrate. Nickel-based superalloys are better compatible with the solvent and are less susceptible to corrosion by the solvent in the short term.

[0038] Furthermore, to prevent the residual acidic solvent on the substrate surface from continuously causing corrosion, in some embodiments, the above-mentioned method for removing high-temperature coatings also includes alkaline washing after pickling. Alkaline washing can neutralize the acid and adjust the pH of the component surface.

[0039] Specifically, the alkaline washing is ultrasonic alkaline washing. In some embodiments, the ultrasonic time is 3 to 7 minutes, and the ultrasonic frequency is 30 kHz to 50 kHz. The solution used for alkaline washing can be a sodium bicarbonate solution. In some embodiments, the concentration of sodium bicarbonate in the sodium bicarbonate solution is 3 wt% to 7 wt%.

[0040] In some embodiments, the sandblasting treatment is wet sandblasting. Specifically, the sand particles used in wet sandblasting include either corundum or quartz sand; the particle size is 60-80 mesh, the sandblasting pressure is 0.3-0.5 MPa, the distance between the sample and the wet sandblasting nozzle is 10-15 cm, and the sandblasting angle is 80°-90°. The above sandblasting process parameters can effectively remove the corrosion zone and interdiffusion zone of the substrate without causing significant damage to the substrate.

[0041] In some implementations, the components may be cleaned before sandblasting.

[0042] Furthermore, in some embodiments, prior to pickling, the uncoated areas of the component containing the high-temperature coating are coated with a resin material. This protects the uncoated areas from corrosion by the pickling solution.

[0043] Specifically, in some embodiments, the resin material is acrylic epoxy resin; the coating method includes either ultraviolet curing or infrared curing. The thickness of the coated resin material is 3mm to 5mm, for example, 3mm, 4mm, or 5mm.

[0044] In some embodiments, the method for removing the high-temperature coating further includes post-treatment of the component after the sandblasting process, the post-treatment including removal of resin material, cleaning, and drying;

[0045] Specifically, removing the resin material includes immersing the component in water at 85°C to 95°C for 5 to 10 minutes; cleaning is performed with water after the resin has detached.

[0046] In some embodiments, drying includes removing moisture with compressed air followed by hot air drying; preferably, the pressure of the compressed air is 0.25 MPa to 0.3 MPa, the blowing time is 0.5 min to 2 min, the temperature of the hot air drying is 110°C to 130°C, and the drying time is 20 min to 40 min.

[0047] Furthermore, the present invention also provides the application of the solvent described above for removing high-temperature coatings in the removal of high-temperature coatings.

[0048] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0049] Example 1

[0050] This embodiment provides a method for removing a high-temperature coating, wherein the coating is a vacuum-heat-treated NiCrAlY coating deposited on the surface of a nickel-based superalloy DZ22B using an arc ion plating process. The method includes the following steps:

[0051] S01, Prepare a solvent for removing high-temperature coatings.

[0052] A solvent for removing high-temperature coatings is obtained by mixing a 30% hydrochloric acid solution (37 wt.%), a 12% phosphoric acid solution (85 wt.%), a 5% hydrogen peroxide solution (27 wt.%), and a 1 wt.% hexamethylenetetramine solution, and then magnetically stirring until homogeneous.

[0053] S02, pickling

[0054] An uncoated area of ​​the nickel-based superalloy surface was coated with acrylic epoxy resin, and then irradiated with a UV lamp for 6 minutes to allow the resin to fully cure. The thickness of the acrylic epoxy resin was 2 mm.

[0055] The alloy was placed in a solvent at 30°C to remove the high-temperature coating and subjected to an ultrasonic reaction, ensuring the coating was completely submerged in the solvent. The temperature was kept constant, the reaction time was 15 minutes, and the ultrasonic frequency was 35 kHz. After the reaction, the mixture was rinsed with clean running water for 1 minute.

[0056] S03, alkaline washing

[0057] Prepare a 3% (w / w) Na₂HCO₃ solution and stir it on a magnetic stirrer until the Na₂HCO₃ is completely dissolved. Place the alloy obtained in step SO₂ into a 3 wt.% Na₂HCO₃ solution for ultrasonic cleaning for 5 minutes at a frequency of 35 kHz.

[0058] S04, Sandblasting

[0059] The cleaned alloy was removed and wet-blasted with 60-mesh corundum to remove residual coating. The wet-blasting pressure was 0.3 MPa, the distance between the coating and the blasting nozzle was 10 cm, the wet-blasting angle was 90°, and the wet-blasting time was 4 minutes. After wet-blasting, the surface was rinsed with clean water to remove any adhering sand particles.

[0060] S05, Post-processing

[0061] The alloy obtained in step S04 was washed in clean running water, then immersed in deionized water at 90°C for 5 minutes. As the resin surface gradually expanded and separated from the alloy substrate in the protected area, the resin was directly peeled off, and the alloy was removed. Most of the moisture on the alloy surface was removed using compressed air, and then it was dried in a hot air drying oven.

[0062] like Figure 1 As shown, in this embodiment, after pickling the alloy coated with NiCrAlY and vacuum heat-treated with a solvent for removing high-temperature coatings, a large number of micropores are generated in the coating on the alloy surface, and macroscopic pores are formed after the micropores connect. Figure 2 As shown, due to the high density of the coating, the corrosive liquid did not penetrate into the coating to cause it to pulverize. The coating material dissolved and detached from the alloy matrix from the surface, resulting in corrosion zones in the interdiffusion region of the matrix. Figure 3 As shown in the figure, the coating after pickling was subjected to wet sandblasting treatment. The resulting alloy surface and cross section had no residual coating, and there was no corrosion of the alloy substrate. The interdiffusion zone was removed, and no recrystallization occurred on the substrate surface.

[0063] Testing revealed that after removing the NiCrAlY coating from the vacuum heat-treated surface of the DZ22B nickel-based alloy in this embodiment, the tensile strength of the substrate was 1099 MPa and the elongation after fracture was 8.8%, indicating that coating removal did not reduce its room temperature tensile properties.

[0064] Example 2

[0065] This embodiment provides a method for removing a high-temperature coating, wherein the coating is a NiCoCrAlYTa coating deposited on the surface of a nickel-based superalloy DD3 using a magnetron sputtering process and then subjected to vacuum heat treatment. The method includes the following steps:

[0066] S01, Prepare a solvent for removing high-temperature coatings.

[0067] A solvent for removing high-temperature coatings is obtained by mixing a 40% hydrochloric acid solution (37 wt.%), an 8% phosphoric acid solution (85 wt.%), a 3% hydrogen peroxide solution (30 wt.%), and a 0.5 wt.% hexamethylenetetramine solution by volume and stirring magnetically until homogeneous.

[0068] S02, pickling

[0069] An uncoated area of ​​a nickel-based superalloy surface is coated with acrylic epoxy resin, and then irradiated with a UV lamp for 5 minutes to allow the resin to fully cure.

[0070] The alloy was placed in a solvent at 40°C to remove the high-temperature coating and subjected to ultrasonic reaction at a frequency of 50 kHz, ensuring the coating was completely submerged in the solvent. The temperature was kept constant, and the reaction time was 10 minutes. After the reaction, the mixture was rinsed with clean running water for 1 minute.

[0071] S03, alkaline washing

[0072] Prepare a 7 wt.% Na2HCO3 solution, and place the alloy obtained in step S04 into the 7 wt.% Na2HCO3 solution for ultrasonic cleaning at an ultrasonic frequency of 50 kHz for 7 min.

[0073] S04, Sandblasting

[0074] The cleaned alloy was removed and wet-blasted with 80-mesh corundum to remove residual coating. The wet blasting pressure was 0.5 MPa, the distance between the coating and the blasting nozzle was 15 cm, the wet blasting angle was 80°, and the wet blasting time was 2 minutes. After wet blasting, the surface was rinsed with clean water to remove any adhering sand particles.

[0075] S05, Post-processing

[0076] The alloy obtained in step S04 was washed in clean running water, and then immersed in deionized water at 85°C for 5 minutes. As the resin surface gradually expanded and separated from the alloy substrate in the protected area, the resin was directly peeled off, and the alloy was removed. Most of the moisture on the alloy surface was removed using compressed air, and then it was placed in a hot air drying oven at a pressure of 0.3 MPa and a drying temperature of 120°C.

[0077] Testing revealed that, in this embodiment, after removing the dense NiCoCrAlYTa coating from the surface of the DD3 nickel-based alloy and using wet sandblasting to remove the remaining coating, there was no residual coating on the alloy surface or cross-section. Furthermore, there was no corrosion or recrystallization of the alloy substrate. Figure 4 As shown, the tensile strength of the substrate is 1035 MPa and the elongation after fracture is 27%, indicating that removing the coating does not reduce its room temperature tensile properties.

[0078] Example 3

[0079] This embodiment provides a method for removing a high-temperature coating, wherein the coating is a heat-treated NiCrAlYSiHf coating deposited on the surface of a nickel-based superalloy K423 using an arc ion plating process and then serviced for 100 hours. The method includes the following steps:

[0080] S01, Prepare a solvent for removing high-temperature coatings.

[0081] A solvent for removing high-temperature coatings is obtained by mixing a 35% hydrochloric acid solution (37 wt.%), a 10% phosphoric acid solution (85 wt.%), a 4% hydrogen peroxide solution (25 wt.%), and a 0.8 wt.% hexamethylenetetramine solution, and then magnetically stirring until homogeneous.

[0082] S02, pickling

[0083] An uncoated area of ​​a nickel-based superalloy surface is coated with acrylic epoxy resin, and then irradiated with a UV lamp for 5 minutes to allow the resin to fully cure.

[0084] The alloy was placed in a solvent for removing the coating at 35°C, ensuring the coating was completely submerged. The temperature was kept constant, and the reaction time was 8 minutes. After the reaction, the mixture was rinsed with clean running water for 2 minutes.

[0085] S03, alkaline washing

[0086] Prepare a 6 wt.% Na2HCO3 solution, and place the alloy obtained in the SO2 step into the 6 wt.% Na2HCO3 solution for ultrasonic cleaning for 7 min.

[0087] S04, Sandblasting

[0088] The cleaned alloy was removed and wet-blasted with 80-mesh corundum to remove residual coating. The wet-blasting pressure was 0.45 MPa, the distance between the coating and the blasting nozzle was 13 cm, the wet-blasting angle was 80°, and the wet-blasting time was 3 minutes. After wet-blasting, the surface was rinsed with clean water to remove any adhering sand particles.

[0089] S05, Post-processing

[0090] The alloy obtained in step S04 was washed in clean running water, and then immersed in deionized water at 95°C for 5 minutes. After the resin surface gradually expanded and separated from the alloy substrate in the protected area, the resin was directly peeled off, and the alloy was removed. Most of the moisture on the alloy surface was removed using compressed air, and then it was placed in a hot air drying oven at a pressure of 0.3 MPa and a drying temperature of 110°C.

[0091] Observation revealed that the solvent and method for removing high-temperature coatings provided in this embodiment can also remove the dense NiCrAlYSiHf coating on the surface of K423 nickel-based alloy. The cross-sectional morphology of the substrate after removal is as follows: Figure 5 As shown, the tensile strength of the substrate is 1050 MPa and the elongation after fracture is 13%, indicating that removing the coating does not reduce its room temperature tensile properties.

[0092] Comparative Example 1

[0093] This comparative example provides a method for removing high-temperature coatings, wherein the coating and alloy sample are the same as in Example 1, and the removal methods are similar, except that there is no SO3 in the coating removal process and no alkaline washing step.

[0094] like Figure 6 As shown, the sample surface has many micropores after pickling. Lacking the neutralizing effect of the alkali washing step, the minimal amount of acid that seeps in still corrodes the matrix, forming a thin layer of corrosion products that adversely affects the matrix's mechanical properties. The matrix tensile strength is 937 MPa, and the elongation after fracture is 5%, significantly reducing the sample's room temperature tensile properties.

[0095] Comparative Example 2

[0096] This comparative example provides a method for removing high-temperature coatings, wherein the coating and alloy sample are the same as in Example 1, and the removal method is similar, except that: no hexamethylenetetramine corrosion inhibitor is added to the solvent used to remove the coating.

[0097] like Figure 7 As shown, the solvent used alone to remove the high-temperature coating can completely remove the surface coating. However, observation of the cross-section of the alloy substrate reveals that the solvent used to remove the coating causes localized pitting corrosion on the substrate. Even after wet sandblasting, the base still has deep corrosion pits.

[0098] Comparative Example 3

[0099] This comparative example provides a method for removing high-temperature coatings, wherein the coating and alloy sample are the same as in Example 1, and the removal method is similar, except that the volume fraction of hydrochloric acid added to the solvent for removing the coating is 20%, and the volume fraction of phosphoric acid is 15%.

[0100] Because the hydrochloric acid content in the solvent used to remove high-temperature coatings is reduced, even with the addition of more phosphoric acid, the chemical etching ability of the solvent decreases during the pickling process, and the rate at which the solvent corrodes the coating decreases. Figure 8 As shown, even after wet sandblasting, some coating remains on the alloy surface.

[0101] Comparative Example 4

[0102] This comparative example provides a method for removing a high-temperature coating, wherein the coating and alloy sample are the same as in Example 1, except that the volume percentage of hydrogen peroxide in the solvent for removing the high-temperature coating is 2 wt.%.

[0103] Observation revealed that the solvent and method for removing coatings provided in this comparative example cannot completely remove the coating from the alloy surface, and the corrosion process is slow. Figure 9 As shown.

[0104] Comparative Example 5

[0105] This comparative example provides a method for removing high-temperature coatings, wherein the coating and alloy sample are the same as in Example 1, except that the temperature of the solvent during pickling is 60°C when removing the high-temperature coating.

[0106] Observation revealed that the solvent and method for removing high-temperature coatings provided in this comparative example cannot completely remove the coating from the alloy surface, such as... Figure 10 As shown. Although the corrosion temperature is high, the corrosion process is slow because the added hydrogen peroxide decomposes, reducing the oxidizing power of the solution.

[0107] Comparative Example 6

[0108] This comparative example provides a method for removing a high-temperature coating, wherein the coating and alloy sample are the same as in Example 1, except that the solvent for removing the high-temperature coating is 50% hydrochloric acid by volume and 2 wt.% hexamethylenetetramine by mass.

[0109] like Figure 11 As shown, the solvent and method for removing the coating provided in this comparative example completely remove the coating and cause severe corrosion to the alloy substrate.

[0110] Comparative Example 7

[0111] This comparative example provides a method for removing a high-temperature coating, wherein the coating and alloy sample are the same as in Example 1, except that the solvent for removing the high-temperature coating is 6% phosphoric acid by volume, 2 wt.% hydrogen peroxide by volume, and 0.3 wt.% butylene.

[0112] like Figure 12 As shown, the solvent and method for removing coatings provided in this comparative example cannot completely remove the coatings from the alloy surface, and the corrosion process is slow.

[0113] Comparative Example 8

[0114] This comparative example provides a method for removing high-temperature coatings, wherein the coating and alloy sample are the same as in Example 1, the only difference being that the pickling time is 20 min.

[0115] The solvent and method for removing high-temperature coatings provided in this comparative example cause severe corrosion of the alloy substrate due to excessively long corrosion time.

[0116] Comparative Example 9

[0117] This comparative example provides a method for removing high-temperature coatings, wherein the coating and alloy sample are the same as in Example 1, the only difference being: the sandblasting angle is 70°.

[0118] Observation shows that the method for removing high-temperature coatings provided in this comparative example cannot completely remove the coating on the alloy surface. Due to the small sandblasting angle and insufficient shear force, the interdiffusion zone cannot be completely removed.

[0119] In summary, the solvent for removing high-temperature coatings and the method for removing high-temperature coatings provided by the embodiments of the present invention have at least the following advantages:

[0120] In the solvent for removing high-temperature coatings provided in this invention embodiment, hydrochloric acid is the main corrosive solvent. The addition of phosphoric acid solution helps to enhance the corrosive power of hydrochloric acid, thereby etching the coating into a loose structure by addressing defects on the coating surface, such as uneven thickness or pits. Simultaneously, a corrosion inhibitor is added to the pickling solution to prevent the sample substrate from being corroded by hydrochloric acid. This solvent can remove the dense high-temperature protective coating from the sample surface while effectively mitigating the impact of pickling on the surface structure and morphology of the substrate. The pickled sample is then subjected to sandblasting, utilizing the mechanical cutting action of sandblasting to completely remove the residual coating. The entire removal process is simple and can be applied to large-scale production.

[0121] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A solvent for removing high-temperature coatings, characterized in that, It comprises 30%–40% hydrochloric acid (by volume), 8%–12% phosphoric acid (by volume), 3%–5% hydrogen peroxide (by volume), and 0.5%–1% corrosion inhibitor (by mass), with the balance being water; wherein the mass percentage concentration of hydrochloric acid is 36%–38%, the mass percentage concentration of phosphoric acid is 83%–86%, and the mass percentage concentration of hydrogen peroxide is 25%–30%; the corrosion inhibitor is hexamethylenetetramine. The temperature during acid washing with the solvent is 30℃~40℃, and the acid washing reaction time is 5~10min; The high-temperature coating has undergone vacuum treatment or service, and has a dense structure that allows for elemental interdiffusion with the substrate. The high-temperature coating is an MCrAlYX coating, wherein M is at least one of Ni and Co, and X is at least one of La, Ru, Re, Y, Hf, Zr, Ce, Pt, and Dy.

2. A method for removing high-temperature coatings, characterized in that, It includes: The high-temperature coating is pickled using the solvent described in claim 1, and then sandblasted.

3. The method according to claim 2, characterized in that, The pickling process involves immersing the component containing the high-temperature coating in the solvent for reaction. And / or, the pickling reaction is ultrasonic pickling.

4. The method according to claim 2, characterized in that, The high-temperature coating is located on a nickel-based high-temperature alloy substrate; And / or, the high-temperature coating is deposited using at least one of magnetron sputtering, arc ion plating, or electron beam evaporation.

5. The method according to claim 2, characterized in that, This also includes alkaline washing after pickling; The alkaline washing is ultrasonic alkaline washing, with an ultrasonic time of 3-7 minutes and an ultrasonic frequency of 30KHz-50KHz. The alkaline washing solution is a sodium bicarbonate solution, and the concentration of sodium bicarbonate in the sodium bicarbonate solution is 3wt%~7wt%.

6. The method according to any one of claims 2 to 5, characterized in that, The sandblasting process is a wet sandblasting process; The sand particles used in the wet sandblasting process include either corundum or quartz sand. The particle size of the sand is 60~80 mesh, the sandblasting pressure is 0.3~0.5MPa, the distance between the sample and the wet sandblasting nozzle is 10cm~15cm, and the sandblasting angle is 80°~90°. The process of sandblasting also includes cleaning the components.

7. The method according to any one of claims 2 to 5, characterized in that, Before pickling, the process also includes coating the uncoated areas of the component containing the high-temperature coating with a resin material; The resin material is acrylic epoxy resin; The coating method includes either UV curing or infrared curing; The thickness of the resin material coating is 3mm to 5mm.

8. The method according to claim 7, characterized in that, It also includes post-treatment of the component after the sandblasting process, the post-treatment including removal of the resin material, cleaning and drying; Removing the resin material includes immersing the component in water at 85°C to 95°C for 5 to 10 minutes; The cleaning includes rinsing with water; The drying process includes dehydration with compressed air followed by hot air drying; the pressure of the compressed air is 0.25MPa~0.3MPa, the blowing time is 0.5min~2min, the temperature of the hot air drying is 110℃~130℃, and the drying time is 20min~40min.

9. The application of the solvent for removing high-temperature coatings as described in claim 1 in the removal of high-temperature coatings.

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