A spraying process for preparing a stable, non-fissile, thickness-controllable aluminum-silicon diffusion coating

Abstract

The application discloses a spraying process for preparing an aluminum-silicon diffusion coating with stable thickness and controllable thickness, which comprises the following steps: firstly, preparing a slurry; then, sequentially performing a series of preliminary preparations, such as sieving, hot degreasing, sanding and cleaning, and shielding before spraying; then, selecting appropriate spraying equipment and spraying environment; before spraying, using a spray gun to perform test spraying on an air outlet; after the spraying state is stable, sequentially performing gun spraying; after spraying, performing coating solidification treatment on the workpiece; then, performing vacuum diffusion heat treatment; and finally, sanding and cleaning. The process adopts AI-Si and AI-Cr multi-element diffusion technology. The aluminum-silicon slurry is coated on a nickel-based component, and after diffusion heat treatment, an aluminum-silicon compound coating is formed, so that the nickel-based component has the properties of high-temperature oxidation resistance, sulfidation resistance or erosion resistance and heat shock resistance. The process can be applied to part blades of a gas turbine and an aero-engine.

Description

TECHNICAL FIELD

[0001] The present application relates to a spraying process for preparing an aluminum-silicon diffusion coating with stable thickness and controllable cracking, and belongs to the technical field of coating preparation. BACKGROUND

[0002] Heavy-duty gas turbines (heavy-duty gas turbines) are large-scale strategic high-end technical equipment for national defense security, energy security and industrial competitiveness, and are widely used in power generation, ship power and other fields. High-temperature turbine blades are even more served in high-temperature, high-load, high-corrosion and other harsh working conditions, far exceeding the current use limit of high-temperature alloy substrates, and a functional coating with uniform thickness and organization must be prepared on the surface of the substrate.

[0003] In order to improve the efficiency and power of heavy-duty gas turbines, turbine blades are usually designed into complex structures such as bending, twisting, super-long and super-wide. There are many key problems in uniform spraying of coatings on large-scale blades with complex shapes. First, the current coating spraying method is mainly manual spraying, and the technical level and working state of the operator will seriously affect the stability of the thermal barrier coating spraying, resulting in a large percentage of defective products and low efficiency. Secondly, the complex high-temperature alloy blade has high technical requirements for spraying. The existing spraying process leads to uneven coating thickness, which seriously affects the quality of spraying and ultimately affects the service life of high-temperature blades and the life cycle of heavy-duty gas turbines. Therefore, a process method is needed to reduce cracking, cracking after diffusion heat treatment, and thickness control problems. SUMMARY

[0004] In view of the problems existing in the prior art, the present application provides a spraying process for preparing an aluminum-silicon diffusion coating with stable thickness and controllable cracking, thereby providing a coating with high-temperature oxidation, sulfuration or erosion resistance and heat shock resistance.

[0005] To achieve the above purpose, the technical scheme adopted by the present application is: a spraying process for preparing an aluminum-silicon diffusion coating with stable thickness and controllable cracking, comprising the following steps:

[0006] Step S1: slurry preparation, preparing the slurry components 5μm Al powder 40%-60%, 5μm silicon powder 5%-10%, glycerol 3%-8%, phosphoric acid 3%-8%, water 20%-28%, chromium sesquioxide 3%-8%, chromium hydroxide 0.5%-1.5%, and placing the above components in a container for regular stirring;

[0007] Step S2: preparation before operation, the spray gun needs to be cleaned with alcohol to ensure cleanliness and no foreign matter, the slurry is placed in a stirring box and stirred for at least 24 hours, and the slurry is sieved through 50, 100 and 150 mesh screens to remove all clumped materials;

[0008] Step S3: Heat degreasing to remove surface oil, using air circulation drying furnace, processing time is 0.8-1.2 hours, control processing temperature at 330 ± 5°C;

[0009] Step S4: Sanding cleaning, sanding cleaning before spraying;

[0010] Step S5: Visual inspection, check if the spraying area is abnormal, if there is still a lot of oil or foreign matter, a lot of sand particles remain, then repeat steps S2-S4;

[0011] Step S6: Masking before spraying, using paper protective film and masking tape to mask the non-spraying area before painting, check if the protective film remains intact, if it is broken, it needs to be masked again, pay attention not to touch the spraying area during masking, which may cause quality problems in subsequent spraying, and dry after masking to remove moisture;

[0012] Step S7: Select appropriate spraying equipment and spraying environment;

[0013] Step S8: Load aluminum paint, add slurry to the spray gun tank, the spray gun tank must be cleaned before loading paint to prevent other impurities from mixing in, and immediately cover the aluminum slurry sealing tank after loading is completed and place it on the stirrer again;

[0014] Step S9: Test spray using a spray gun against the air outlet before painting, wait until the paint spraying state is stable and the atomization degree is appropriate, then turn off the spray gun; the distance between the spray gun nozzle and the workpiece surface is 80-120 mm, and the gun is walked in order, spraying 2-3 layers each time; if the part has a circular arc or bridging area, only one layer of spraying is needed; use a brush dipped in paint to evenly brush the paint on the position that cannot be sprayed; after spraying is completed, remove the masking; after spraying, the workpiece needs to be treated for coating solidification;

[0015] S10: Visual treatment of the part coating, if abnormal conditions are found, carry out post-processing;

[0016] S11: Measure the paint thickness

[0017] Use German Fischer high-precision coating thickness gauge to measure the paint thickness;

[0018] S12: After the abnormal state treatment is completed, repeat steps S3-S7, according to the desired thickness of the diffusion coating, determine the number of cycles, the thickness of each layer of paint cannot exceed 30 μm;

[0019] S13: After the cycle is completed, the part is treated by vacuum diffusion heat treatment;

[0020] S14: Sand blasting cleaning, after diffusion heat treatment, the parts need to be sprayed with glass sand to remove surface powder dross.

[0021] Further, the slurry prepared in step S1 is stored at a temperature of 5-10℃, and is regularly stirred for 24 hours once a month. The slurry is stored in a closed container, and has a use period of 3-6 months.

[0022] Further, the sand blasting cleaning conditions in step S4 are as follows: medium: #220 alumina; pressure: 1-3 bar; angle: 60°-90°; distance from workpiece: 10-20 cm.

[0023] Further, in step S6, after shielding, the workpiece is placed under a short-wave infrared paint baking lamp for drying for 5-10 minutes to remove surface moisture of the workpiece, and the surface temperature of the part before painting is kept below 35℃.

[0024] Further, in step S7, painting is performed using a SATA Jet 1000 or ANEST IWATA 77-21G gravity type manual spray gun, and the painting pressure is 35 psi. Parts that cannot be painted using a spray gun can be locally brushed using a camel hair or squirrel hair brush. The painting room is a dry back type or a wet back type painting room. It is ensured that the aluminum paint has been stirred for more than 24 hours and is always stirred on the stirrer after being taken to the painting room.

[0025] Further, in step S8, no impurities such as water and dust should touch the workpiece during the spraying process. The appropriate air pressure, oil amount, and atomization size are adjusted. The distance between the spray gun and the workpiece is always controlled to be about 10 cm. Non-woven fabric or pure cotton gloves can be used to wipe the bridging position. The angle between the spray gun and the workpiece during painting is between 60° and 90°. After painting, the unused paint in the spray gun should be immediately put into the original packaging can. The brush and the spray gun should be immediately cleaned after painting. The ventilation system should be ensured to work normally during the painting process.

[0026] Further, in step S9, after painting, the workpiece needs to be subjected to coating curing treatment, specifically, the painted vane is subjected to surface drying treatment, and is baked at 80℃ for 15 minutes using an infrared paint baking lamp. Then, the workpiece is heat treated at 330℃ for 1 hour using an air circulation furnace.

[0027] Further, in step S10, the post-processing step is specifically as follows: if there is rough and uneven paint surface, obviously uneven painted surface, and protruding particles on the paint surface, sandpaper can be used to polish and repair the abnormal area. If there is a crack in the coating, the state of the workpiece is evaluated according to the size and depth of the crack. If the crack is not penetrating, the workpiece can be re-sprayed after being polished and removed using a sand belt machine. If the crack penetrates the body, the workpiece needs to be reworked.

[0028] Further, in the step S13, after being heated to 870 degrees Celsius, it is kept for two hours, and then cooled to 200 degrees Celsius under the argon environment, and then it can be taken out from the furnace and cooled to room temperature. The diffusion furnace is a controlled atmosphere furnace, and pure argon gas with a dew point of not higher than-40 degrees Celsius is used. The temperature of the furnace should be able to be as high as 1065±15 degrees Celsius, and the standard argon gas inert gas partial pressure is 0.05 TORR (6.6661 Pa).

[0029] Further, in the step S13, sanding is performed using 180# glass sand; pressure: 1-2 bar (low pressure); angle: 60-90 degrees; distance: 10-20 cm.

[0030] The beneficial effects of the present application are: the present process adopts AI-Si, AI-Cr multi-element diffusion technology. The aluminum silicon slurry is coated on the nickel-based parts, and after diffusion heat treatment, an aluminum silicon compound coating is formed, thereby having the properties of high temperature oxidation, sulfidation or erosion resistance, and heat shock resistance. This process can be applied to the partial blades of gas turbines and aircraft engines. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 It is a schematic diagram of four abnormal states in the embodiment of the present application;

[0032] Figure 2 It is a schematic diagram of sanding the abnormal area using sandpaper in the embodiment of the present application;

[0033] Figure 3 It is a schematic diagram of surface changes in the spraying process in the embodiment of the present application;

[0034] Figure 4 It is a microstructure test piece diagram of the aluminum silicon diffusion coating prepared in the embodiment of the present application. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present application more clear and obvious, the following will further describe the present application through the drawings and examples. However, it should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the scope of the present application.

[0036] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs, and the terms used herein in the specification are only for the purpose of describing the specific embodiments and are not intended to limit the present application.

[0037] The present application mainly improves the spraying of the modified aluminum diffusion coating (chromium aluminum silicon coating) on the parts by using the slurry method. The present process adopts AI-Si, AI-Cr multi-element diffusion technology. The aluminum silicon slurry is coated on the nickel-based parts, and after diffusion heat treatment, an aluminum silicon compound coating is formed, thereby having the properties of high temperature oxidation resistance, sulfuration resistance or corrosion resistance, and heat shock resistance. The present process can be applied to the part blades of gas turbines and aero-engine.

[0038] The preparation of the aluminum silicon compound coating is prone to cracking during the preparation process, cracking after the diffusion heat treatment, and thickness control problems. The present process introduces how to stably prepare the thickened aluminum silicon diffusion coating which is not easy to crack and has controllable thickness.

[0039] The slurry method is to mix the metal powder to be penetrated with a certain proportion of binder and activator into a suspension, also called "slurry", which is brushed on the surface of the workpiece, dried, and then subjected to high temperature diffusion treatment in vacuum or argon protection. The proportioned slurry is a kind of heavy pigment material, and the layering speed is fast, and the pigment is easy to block, so it needs to be stirred regularly during storage; it needs to be stirred all the time during use.

[0040] Step S1: composition and analysis of slurry

[0041] 1. Composition: 5 μm Al powder 50%, 5 μm silicon powder 10%, glycerol 5%, phosphoric acid 5%, water 24%, chromium sesquioxide 5%, and chromium hydroxide 1%

[0042] 2. Component analysis

[0043] The aluminide coating has good high temperature oxidation resistance, but the NiAl phase rich in nickel is prone to martensitic transformation and is not resistant to sulfuration and hot corrosion.

[0044] Cr is an excellent high-temperature hot corrosion element, so introducing chromium elements into pure aluminizing coating can improve the element interdiffusion between the coating and the substrate, prolong the service life. The preparation of aluminum-chromium co-permeation on the surface of nickel-based alloy can also prevent the martensitic transformation of the β-NiAl phase rich in nickel during high temperature oxidation. The presence of chromium can promote the selective oxidation of aluminum on the surface of the coating and reduce the critical aluminum content required to form a protective aluminum oxide film.

[0045] Al-Si co-permeation has good high temperature oxidation resistance, and can improve its hot corrosion resistance after co-permeation. The co-permeation coating has small brittleness and is not easy to crack and fall off. The coating structure is mainly β-NiAl phase, and the silicon element is distributed in the coating as a second phase of silicon-rich particles. However, the silicon content in the coating should not be too high, otherwise the silicon and nickel in the substrate will form a harmful low-melting-point phase at high temperature, and the coating will become brittle and easily fall off during oxidation. Therefore, the content of silicon in the slurry should not be higher than 10%.

[0046] Step S2: Preparation before work, the spray gun needs to be cleaned with alcohol to ensure cleanliness and no foreign matter, the slurry is put into the stirring box for at least 24 hours of stirring, and the slurry is screened through 50, 100 and 150 mesh screens in sequence to remove all caked materials;

[0047] Step S3: Hot degreasing of the required spraying part to remove surface oil stains, air circulation type drying furnace is adopted for treatment, the treatment time is 0.8-1.2 hours, and the treatment temperature is controlled at 330 ± 5°C;

[0048] Step S4: Sanding cleaning, sanding cleaning is performed on the part before spraying;

[0049] Step S5: Visual inspection, whether the spraying area is abnormal is checked, if there is still a large amount of oil stains or foreign matter, and a large amount of sand particles are left, steps S2-S4 are repeated;

[0050] Step S6: Masking before spraying, paper protection film and masking tape are used to mask the non-spraying area before spraying, whether the protection film is left intact is checked, if it is broken, it needs to be masked again, attention should be paid to not touch the to-be-sprayed area during the masking process, so as to cause quality problems in subsequent spraying, and the masking is dried to remove water after the masking;

[0051] Step S7: Selection of appropriate spraying equipment and spraying environment;

[0052] Step S8: Loading of aluminum paint, slurry is added into the spray gun tank, the spray gun tank must be cleaned before loading of the paint, so as to prevent other impurities from being mixed therein, and the aluminum slurry sealing tank is immediately covered after the loading is completed, and is placed on the stirrer again;

[0053] Step S9: Test spraying is performed on the air outlet place by using the spray gun before spraying, the spray gun is closed after the paint spraying state is stable and the atomization degree is appropriate; the distance between the spray gun nozzle and the surface of the workpiece is 80-120 mm, the spray gun is sequentially walked, 2-3 layers of paint are sprayed each time; if the part has a circular arc or a bridging area, only one layer of paint needs to be sprayed; the positions that cannot be sprayed are uniformly brushed with paint by using a brush; after the spraying is completed, the masking is removed; the workpiece needs to be subjected to coating curing treatment after the spraying;

[0054] S10: Visual treatment is performed on the coating of the part, and post-treatment is performed if abnormal state is found;

[0055] S11: Measurement of paint spraying thickness

[0056] A German Fischer high-precision coating layer thickness gauge is used to measure the paint spraying thickness;

[0057] S12: After the abnormal state is handled, the steps S3-S7 are repeated, and the number of cycles is determined according to the thickness of the diffusion coating to be prepared. The thickness of each layer of paint cannot exceed 30 μm;

[0058] S13: After the cycles are completed, the part is subjected to vacuum diffusion heat treatment;

[0059] S14: Sand blasting cleaning. After the diffusion heat treatment, the part needs to be sprayed with glass sand to remove the surface powder dregs.

[0060] In the preferred embodiment of the present example, the slurry prepared in step S1 is stored at a temperature of 5-10°C, and is regularly stirred for 24 hours, once a month. The slurry is stored in a closed container, and has a service life of 3-6 months.

[0061] In the preferred embodiment of the present example, the sand blasting cleaning conditions in step S4 are as follows: medium: #220 aluminum oxide; pressure: 1-3 bar; angle: 60°-90°; distance from the workpiece: 10-20 cm.

[0062] In the preferred embodiment of the present example, after shielding in step S6, the workpiece is placed under a short-wave infrared paint baking lamp for 5-10 minutes to remove the surface moisture of the workpiece. The surface temperature of the part before painting is kept below 35°C.

[0063] In the preferred embodiment of the present example, in step S7, a gravity type manual spray gun is used for painting, the painting pressure is 35 psi, and parts that cannot be painted using a spray gun can be locally brushed using a camel hair or squirrel hair brush. Painting room: dry back or wet back painting room; check whether the aluminum paint has been stirred for more than 24 hours, and ensure that it is always stirred on the stirrer after being taken to the painting room.

[0064] In the preferred embodiment of the present example, in step S8, no impurities such as water and dust can touch the workpiece during the spraying process; adjust the appropriate air pressure, oil quantity, and atomization size; always control the distance between the spray gun and the workpiece to be about 10 cm; when spraying to the bridging position, non-woven fabric or pure cotton gloves can be used for wiping; the spray gun should have an included angle of 60°-90° with the workpiece during painting; after the spraying is completed, the unused paint in the spray gun should be immediately packed into the original packaging can; the brush and spray gun should be immediately cleaned after the spraying is completed; and the ventilation system should be ensured to work normally during the spraying process.

[0065] In the preferred embodiment of the present example, in step S9, after painting, the workpiece needs to be subjected to coating curing treatment, specifically, the painted vane is subjected to surface drying treatment, and is baked at 80°C for 15 minutes using an infrared paint baking lamp; then, the air circulation furnace is used for heat treatment at 330°C for 1 h.

[0066] The preferred embodiment of the present application, step S10, the post-processing step is specifically: if there is a rough, uneven paint surface; painting surface is obviously uneven; paint has protruding particles, then the sandpaper can be used to polish repair the abnormal area; if the coating has cracks, the workpiece state needs to be evaluated according to the size and depth of the crack, if the crack is not penetrating, the sand belt machine can be used to polish and remove for re-spraying. If the crack penetrates to the body, rework is required.

[0067] The preferred embodiment of the present application, step S13, after heating to 870 degrees Celsius for two hours, and then cooled to 200 DEG C or less in an argon environment, and then can be removed from the furnace and cooled to room temperature. Diffusion furnace is a controlled atmosphere furnace, using the dew point is not higher than-40 DEG C of pure argon. The furnace temperature should be able to reach 1065±15 DEG C, argon inert gas partial pressure standard is 0.05 TORR (6.6661 Pa).

[0068] The preferred embodiment of the present application, step S13, sanding using 180# glass sand; pressure: 1-2 bar (low pressure); angle: 60 DEG-90 DEG distance: 10-20 cm.

[0069] The present process uses AI-Si, AI-Cr multi-element diffusion technology. The aluminum silicon slurry is coated on the nickel-based parts, and after diffusion heat treatment, an aluminum silicon compound coating is formed, thereby having high temperature oxidation, sulfidation or erosion resistance, and heat shock resistance. This process can be applied to the part blades of gas turbines and aircraft engines.

[0070] The above only for the preferred embodiment of the present application, and not to limit the present application, any modification, equivalent replacement or improvement within the spirit and principles of the present application, should be included in the protection scope of the present application.

Claims

1. A process for the production of a stable, non-crazing, thickness controllable, aluminum-silicon diffusion coating by spraying, characterized in that Comprising the following steps: Step S1: slurry preparation, preparing slurry components 5 μm Al powder 40%-60%, 5 μm silicon powder 5%-10%, glycerol 3%-8%, phosphoric acid 3%-8%, water 20%-28%, chromium trioxide 3%-8%, chromium hydroxide 0.5%-1.5%, placing the above components in a container and stirring regularly; Step S2: pre-job preparation, the spray gun needs to be cleaned with alcohol to ensure cleanliness and no foreign matter, the slurry is placed in a stirring box and stirred for at least 24 hours, and the slurry is sieved through 50, 100 and 150 mesh screens in turn to remove all clumped materials; Step S3: heat degreasing to remove surface oil stains on the required sprayed parts, air circulation type drying oven is used for treatment, the treatment time is 0.8-1.2 hours, and the treatment temperature is controlled at 330 ± 5°C; Step S4: sand blasting cleaning, sand blasting cleaning is performed on the parts before spraying; Step S5: visual inspection, checking whether the sprayed area is abnormal, if there are still a large amount of oil stains or foreign matter, and a large amount of sand particles are left, steps S2-S4 are repeated; Step S6: masking before spraying, paper protection film and masking tape are used to mask the non-sprayed areas before spraying, it is checked whether the protection film is left intact, if it is broken, it needs to be masked again, attention should be paid not to touch the to-be-sprayed area during masking to cause quality problems in subsequent spraying, and the protection film is dried after masking to remove water; Step S7: selecting appropriate spraying equipment and spraying environment; Step S8: aluminum paint loading, slurry is added to the spray gun tank, the spray gun tank must be cleaned before loading the paint to prevent other impurities from being mixed in, and the aluminum slurry sealing tank is immediately covered after loading is completed and is placed on the stirrer again; Step S9: test spraying is performed on the air outlet using the spray gun before spraying, the spray gun is closed after the paint spraying state is stable and the atomization degree is appropriate, the distance between the spray gun nozzle and the surface of the workpiece is 80-120 mm, the spray gun is sequentially walked, 2-3 layers of paint are sprayed each time, only one layer of paint is sprayed if the part has a circular arc or a bridging area, a brush is used to evenly brush the paint on the position that cannot be sprayed, the masking is removed after spraying, and the workpiece needs to be subjected to coating curing treatment after spraying; S10: visual treatment is performed on the coating of the part, and post-treatment is performed if abnormal conditions are found; S11: measuring the sprayed thickness A German Fischer high-precision coating thickness gauge is used to measure the sprayed thickness; S12: after the abnormal condition treatment is completed, steps S3-S7 are circularly performed, the thickness of each layer of sprayed paint cannot exceed 30 μm according to the thickness of the diffusion coating to be prepared, and the number of cycles is determined; S13: vacuum diffusion heat treatment is performed on the part after the circular execution is completed; S14: sand blasting cleaning, glass sand is used to remove the surface powder dregs of the part after the diffusion heat treatment.

2. A process for the production of a stable, non-porous, crack-free, thickness controllable aluminium-silicon diffusion coating by thermal spraying, according to claim 1, characterized in that The storage temperature of the slurry prepared in step S1 is 5-10°C, the slurry is continuously stirred for 24 hours or more regularly, once a month, the slurry is stored in a closed container, and the use period is 3-6 months.

3. A process for the production of a stable, non-cleft, thickness controllable aluminosilicate diffusion coating by spraying, according to claim 1, characterized in that, The sand blasting cleaning condition in step S4 is that the medium is #220 aluminum oxide; Pressure: 1-3 bar; Angle: 60°-90°; Distance from workpiece: 10-20 cm.

4. A process for producing a stable, non-crazing, thickness controllable aluminosilicate diffusion coating according to claim 1, characterized in that In step S6, after masking, the workpiece is placed in a short-wave infrared baking paint lamp or an air circulation oven for drying for 5-10 minutes to remove the surface moisture of the workpiece, and the surface temperature of the part before painting is kept below 35℃.

5. A process for producing a stable, non-cleft, thickness controllable aluminosilicate diffusion coating according to claim 1, characterized in that In step S7, the painting uses a gravity type manual spray gun, the painting pressure is 35 psi, and the parts that cannot be painted using a spray gun can be locally painted using a camel hair or squirrel hair brush; the painting room: dry back or wet back painting room; check whether the aluminum paint has been stirred for more than 24 hours, and ensure that it is always stirred on the stirrer after being taken to the painting room.

6. A process for producing a stable, non-cleft, thickness controllable aluminosilicate diffusion coating according to claim 1, characterized in that, In step S8, no impurities such as water and dust should touch the workpiece during spraying; adjust the appropriate air pressure, oil quantity, and atomization size; always control the distance between the spray gun and the workpiece to be about 10 cm; non-woven fabric or pure cotton gloves can be used to wipe the bridging position; the spray gun should be at an angle of 60°~90° with the workpiece during spraying; the unused paint in the spray gun should be immediately packed into the original packaging can after spraying; the brush and spray gun should be immediately cleaned after spraying; The ventilation system should work normally during spraying.

7. A process for producing a stable, non-cleft, thickness controllable aluminosilicate diffusion coating according to claim 1, characterized in that In step S9, after spraying, the workpiece needs to be cured, specifically, the painted surface of the vane is dried at 80℃ for 15 minutes using an infrared baking paint lamp or an air circulation oven; then the workpiece is heat treated at 330℃ for 1h using an air circulation oven.

8. A process for producing a stable, non-cleft, thickness controllable aluminosilicate diffusion coating according to claim 1, characterized in that In step S10, the post-processing step is specifically: if there is rough and uneven paint surface, obviously uneven paint surface after brushing, and protruding particles on the paint surface, sandpaper can be used to polish and repair the abnormal area; if the coating has cracks, the state of the workpiece needs to be evaluated according to the size and depth of the cracks; if it is not a penetrating crack, the workpiece can be re-sprayed after polishing and removing using a sanding machine; if the crack is penetrating, rework is needed.

9. A process for producing a stable, non-cleft, thickness controllable aluminosilicate diffusion coating according to claim 1, characterized in that, In step S13, the temperature is raised to 870℃ and held for two hours, then cooled to below 200℃ in an argon environment, and then taken out of the furnace and cooled to room temperature; the diffusion furnace is a controlled atmosphere furnace, and pure argon gas with a dew point not higher than -40℃ is used. The furnace temperature should be able to reach 1065±15℃, and the argon gas partial pressure standard is 0.05 TORR (6.6661Pa).

10. A process for producing a stable, non-cleft, thickness controllable aluminosilicate diffusion coating according to claim 1, characterized in that, In step S13, sanding uses 180# glass sand; Pressure: 1-2 bar (low pressure); Angle: 60°-90° Distance: 10-20 cm.

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