A method of preforming and applying longitudinal cracks in an environmental barrier coating

Abstract

The present application belongs to the technical field of coating, and particularly relates to a method for pre-preparing longitudinal cracks of environmental barrier coating and application. The method for pre-preparing longitudinal cracks of environmental barrier coating comprises the following steps: processing microstructure on the surface of a substrate, and then depositing a coating to form longitudinal cracks in the coating; the microstructure comprises a plurality of U-shaped straight grooves, a plurality of V-shaped straight grooves or a plurality of U-shaped blind holes; the method for depositing the coating comprises any one of plasma spraying-physical vapor deposition and low-pressure plasma spraying. By processing microstructure of a specific shape on the surface of a substrate and combining with a specific coating deposition method, the present application can improve the bonding strength of the coating and the substrate, and prevent the coating from falling off during preparation. In addition, by performing high-temperature annealing treatment on the sample containing longitudinal cracks, the healing of the longitudinal cracks can be promoted, the penetration of corrosive substances into the coating during service can be prevented, and the coating can be prevented from failing prematurely, so that the service requirement in the later period can be well met.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and specifically relates to a method for prefabricating longitudinal cracks in environmental barrier coatings and its application. Background Technology

[0002] Environmental barrier coatings are a type of high-temperature protective coating for hot-end components of aero engines. They are applied to the surface of ceramic matrix composite structural components of aero engines and function to create a barrier between the ceramic matrix composite structural components and the harsh working environment, preventing or reducing the negative impact of high-temperature environments on component performance.

[0003] The turbine inlet temperature of aero-engines is high, which correspondingly requires its hot-end components to have superior high-temperature stability and thermal shock resistance. Ceramic matrix materials, due to their advantages such as high temperature resistance, low density, and high strength, have become the preferred material for aero-engine hot-end components. However, because ceramic matrix materials are extremely susceptible to corrosion in high-temperature water and oxygen environments (up to 1350℃), it is necessary to coat their surface with a rare-earth silicate coating to protect them from corrosion by high-temperature water and oxygen and external deposits, and to effectively block the penetration of high-temperature water and oxygen and external corrosive substances, thus achieving a protective effect on the ceramic matrix material. However, during the spraying and preparation process of rare-earth silicate coatings, the stress within the coating leads to low bonding strength between the coating and the ceramic matrix material, and the coating is even prone to peeling off during the spraying and preparation process, failing to meet subsequent service requirements.

[0004] Therefore, it is of great significance to provide a method that can effectively release the stress generated during the coating deposition process, reduce the internal stress of the coating, thereby improving the bonding strength between the coating and the substrate and preventing the coating from falling off during the preparation process. Summary of the Invention

[0005] The present invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial option or create conditions. Specifically, the present invention provides a method for pre-forming longitudinal cracks in environmental barrier coatings, which can effectively release the stress generated during coating deposition, reduce the internal stress of the coating, thereby improving the bonding strength between the coating and the substrate and preventing the coating from falling off during the preparation process.

[0006] The inventive concept of this invention: The method for pre-fabricating longitudinal cracks in environmental barrier coatings includes the following steps: processing microstructures on a substrate surface, then depositing a coating to form longitudinal cracks within the coating; the microstructures include multiple U-shaped straight grooves, multiple V-shaped straight grooves, or multiple U-shaped blind holes; the coating deposition method includes any one of plasma spraying-physical vapor deposition and low-pressure plasma spraying. This invention improves the bonding strength between the coating and the substrate by processing microstructures of specific shapes on the substrate surface and combining them with a specific coating deposition method. The microstructures can adjust the internal stress of the coating, especially for high-density environmental barrier coatings. The coating deposited at the groove locations of the microstructures generates in-plane compressive stress, while the protruding locations of the microstructures generate in-plane tensile stress. The tensile and compressive stresses interact, forming pre-fabricated microcracks at or near the protruding locations of the microstructures. This effectively releases the stress generated during coating deposition, reduces the internal stress of the coating, increases the coating strain tolerance, and, combined with a specific coating deposition method, improves the success rate of coating deposition, enhances the bonding strength between the coating and the substrate, and prevents the coating from detaching during the preparation process. The bonding strength between the coating with longitudinal cracks and the substrate of this invention is significantly higher than that between the coating and the substrate prepared by traditional sandblasting roughening technology, and is 2.1-3.6 times that of traditional sandblasting roughening technology.

[0007] Therefore, a first aspect of the present invention provides a method for pre-forming longitudinal cracks in an environmental barrier coating.

[0008] Specifically, the method for pre-fabricating longitudinal cracks in the environmental barrier coating includes the following steps:

[0009] Microstructures are fabricated on the substrate surface, and then a coating is deposited, forming longitudinal cracks within the coating.

[0010] The microstructure includes multiple U-shaped straight grooves, multiple V-shaped straight grooves, or multiple U-shaped blind holes;

[0011] The method for depositing the coating includes any one of plasma spraying-physical vapor deposition and low-pressure plasma spraying.

[0012] Specifically, "multiple" in the multiple U-shaped straight grooves, multiple V-shaped straight grooves, or multiple U-shaped blind holes refers to two or more.

[0013] Preferably, the matrix comprises silicon carbide ceramic, silicon carbide fiber-reinforced silicon carbide (SiC) f / SiC) ceramic matrix composites, carbon fiber reinforced silicon carbide (C f Any one of the following: (SiC) ceramic matrix composites.

[0014] Preferably, a laser is used to process the substrate surface to form a microstructure.

[0015] Preferably, the laser includes any one of a millisecond laser, a nanosecond laser, a picosecond laser, and a femtosecond laser; more preferably, the laser includes a femtosecond laser.

[0016] Preferably, the process parameters for processing microstructures with the femtosecond laser are as follows: laser power of 4.4-22W, repetition frequency of 9-110KHz, scanning speed of 0.45-22mm / s, number of scans of 1-22, scanning interval of 0.1-1.1mm, and defocusing amount of greater than or equal to -2.2mm and less than or equal to 2.2mm.

[0017] More preferably, the process parameters for processing microstructures with the femtosecond laser are as follows: laser power of 5-20W, repetition frequency of 10-100KHz, scanning speed of 0.5-20mm / s, number of scans of 1-20, scanning interval of 0.1-1mm, and defocusing amount of greater than or equal to -2mm and less than or equal to 2mm.

[0018] Preferably, the substrate needs to be ultrasonically cleaned before and after processing the microstructure.

[0019] Preferably, the detergent used for ultrasonic cleaning includes at least one of anhydrous ethanol and acetone.

[0020] Preferably, the ultrasonic cleaning time is 25-35 minutes; more preferably, the ultrasonic cleaning time is 27-33 minutes; and even more preferably, the ultrasonic cleaning time is 30 minutes.

[0021] Preferably, the environment in which the laser is used to process the microstructure on the substrate surface includes any one of a solution environment, an inert gas environment, and an atmospheric environment.

[0022] Preferably, the width of the U-shaped straight groove is 55μm-330μm, the depth of the U-shaped straight groove is 18μm-220μm, and the distance between two adjacent U-shaped straight grooves is 0μm-550μm; more preferably, the width of the U-shaped straight groove is 60μm-300μm, the depth of the U-shaped straight groove is 20μm-200μm, and the distance between two adjacent U-shaped straight grooves is 50μm-300μm.

[0023] Preferably, the width of the V-shaped straight groove is 45μm-550μm, the depth of the V-shaped straight groove is 27μm-330μm, and the distance between two adjacent V-shaped straight grooves is 0μm-550μm; more preferably, the width of the V-shaped straight groove is 50μm-500μm, the depth of the V-shaped straight groove is 30μm-300μm, and the distance between the V-shaped straight grooves is 50μm-300μm.

[0024] Preferably, the diameter of the U-shaped blind hole is 65μm-880μm, the depth of the U-shaped blind hole is 18μm-330μm, and the spacing between two adjacent U-shaped blind holes in the X direction is 9μm-550μm; the spacing between two adjacent U-shaped blind holes in the Y direction is 9μm-550μm. More preferably, the diameter of the U-shaped blind hole is 70μm-800μm, the depth of the U-shaped blind hole is 20μm-300μm, the spacing between two adjacent U-shaped blind holes in the X direction is 10μm-500μm; the spacing between two adjacent U-shaped blind holes in the Y direction is 10μm-500μm.

[0025] Preferably, the microstructure includes multiple U-shaped blind holes.

[0026] Preferably, the method for depositing the coating includes plasma spraying-physical vapor deposition.

[0027] Preferably, the process conditions for plasma spraying-physical vapor deposition are as follows: spraying distance of 750-1300mm, current of 2200-3000A, argon flow rate of 80-120L / min, and substrate preheating temperature of 750-1100℃.

[0028] More preferably, the process conditions for plasma spraying-physical vapor deposition are as follows: spraying distance of 800-1200mm, current of 2500-2700A, argon flow rate of 90-110L / min, and substrate preheating temperature of 800-1000℃.

[0029] Preferably, the coating composition includes any one of Re2Si2O7 and Re2SiO5; the Re includes any one of Yb, Y, Sc, Lu and Er.

[0030] Preferably, the coating comprises Yb2Si2O7.

[0031] Specifically, the coating is a rare earth silicate coating.

[0032] Preferably, the particle size of rare earth silicates is 13-80 μm when depositing the coating; more preferably, the particle size of rare earth silicates is 15-75 μm when depositing the coating.

[0033] Preferably, the thickness of the coating is 45-220 μm; more preferably, the thickness of the coating is 50-200 μm.

[0034] Preferably, the width of the longitudinal crack is 200 nm to 3.3 μm; more preferably, the width of the longitudinal crack is 300 nm to 3 μm.

[0035] A second aspect of the present invention provides an engine.

[0036] Specifically, the engine includes a coating prepared using the pre-fabrication method for longitudinal cracks in the environmental barrier coating as described in the first aspect of the present invention.

[0037] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows:

[0038] (1) This invention improves the bonding strength between the coating and the substrate by processing microstructures of specific shapes on the substrate surface and combining them with a specific coating deposition method. The microstructures can adjust the internal stress of the coating, especially for high-density environmental barrier coatings. The coating deposited at the groove positions of the microstructure generates in-plane compressive stress, while the protrusion positions of the microstructure generate in-plane tensile stress. The tensile and compressive stresses interact with each other, forming pre-made microcracks at or near the protrusion positions of the microstructures. This effectively releases the stress generated during the coating deposition process, reduces the internal stress of the coating, increases the coating strain tolerance, and improves the coating deposition success rate by combining it with a specific coating deposition method. This, in turn, improves the bonding strength between the coating and the substrate and prevents the coating from falling off during the preparation process. The bonding strength between the coating with longitudinal cracks and the substrate of this invention is significantly higher than that between the coating and the substrate prepared by traditional sandblasting roughening technology, and is 2.1-3.6 times that of traditional sandblasting roughening technology.

[0039] (2) The present invention uses a laser to process low-damage microstructures on the substrate surface. The microstructures are evenly distributed and can replace the traditional sandblasting roughening method to improve the bonding strength between the coating and the substrate. Because ceramic materials have high hardness, it is not easy to obtain a rough surface by using the traditional sandblasting roughening method, and excessive sandblasting pressure will damage the ceramic substrate.

[0040] (3) After obtaining longitudinal cracks, the present invention can promote the healing of longitudinal cracks by performing high-temperature annealing on the sample containing longitudinal cracks, preventing corrosive substances from penetrating into the coating during service and causing premature failure of the coating. After the longitudinal cracks are healed, the coating still has good thermal shock resistance and can well meet the service requirements in the later stage. Attached Figure Description

[0041] Figure 1 This is a scanning electron microscope image of the surface morphology of the microstructure on the silicon carbide ceramic substrate in Embodiment 1 of the present invention;

[0042] Figure 2 This is a scanning electron microscope image of the cross-section of the environmental barrier coating prepared in Example 1 of the present invention;

[0043] Figure 3 This is a scanning electron microscope image of the cross-section of the environmental barrier coating prepared in Comparative Example 1 of the present invention;

[0044] Figure 4This is a scanning electron microscope image of the cross-section of the environmental barrier coating after the longitudinal crack in Embodiment 1 of the present invention has healed. Detailed Implementation

[0045] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0046] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0047] Example 1

[0048] A method for pre-forming longitudinal cracks in an environmental barrier coating includes the following steps:

[0049] (1) Place the silicon carbide ceramic sample in a beaker containing anhydrous ethanol and ultrasonically clean it for 30 min. Then place it in a fixture containing deionized water, adjust the position of the silicon carbide ceramic substrate, and maintain the water film thickness at 0.5 mm. Use a femtosecond laser to process the surface of the silicon carbide ceramic substrate with a U-shaped straight groove structure. The process parameters are: laser power of 10 W, repetition frequency of 50 kHz, scanning speed of 1 mm / s, number of scans of 5, scanning interval of 0.2 mm, defocusing amount of -1 mm, processing environment of deionized water, the width of the processed U-shaped straight groove is 150 μm, the depth of the U-shaped straight groove is 80 μm, and the distance between two adjacent U-shaped straight grooves is 160 μm. Place the processed silicon carbide ceramic substrate in a beaker containing anhydrous ethanol and ultrasonically clean it for 30 min to obtain a silicon carbide ceramic substrate with a microstructure.

[0050] (2) A Yb2Si2O7 coating was prepared on the silicon carbide ceramic substrate with microstructure obtained in step (1) by plasma spraying-physical vapor deposition. The plasma spraying-physical vapor deposition process parameters were: spraying distance of 1000 mm, current of 2600 A, argon flow rate of 110 L / min, and substrate preheating temperature of 800 °C. The particle size range of the raw material (Yb2Si2O7) was 15-45 μm. The sample after spraying was air-cooled in the plasma spraying-physical vapor deposition equipment to obtain the silicon carbide ceramic with the deposited coating.

[0051] Example 1: Scanning electron microscope image of the surface morphology of the silicon carbide ceramic substrate microstructure. Figure 1 As shown.

[0052] The cross-section of the environmental barrier coating prepared in Example 1 was observed by scanning electron microscopy, and the results are as follows: Figure 2 As shown. By Figure 2It can be seen that longitudinal microcracks were successfully pre-formed at the protrusions between microstructures within the Yb2Si2O7 coating due to internal stress, with crack widths ranging from 700 nm to 2 μm. This is because the coating deposited at the groove locations of the microstructures generates in-plane compressive stress, while the protrusion locations of the microstructures generate in-plane tensile stress. The tensile and compressive stresses interact with each other, forming microcracks at or near the protrusion locations of the microstructures.

[0053] Example 2

[0054] A method for pre-forming longitudinal cracks in an environmental barrier coating includes the following steps:

[0055] (1) SiC f The SiC ceramic matrix composite sample was placed in a beaker containing anhydrous ethanol and ultrasonically cleaned for 30 minutes. Then, it was placed in a fixture and the SiC was adjusted. f / The location of the SiC ceramic matrix composite sample was determined using a femtosecond laser. f A V-shaped groove structure was fabricated on the surface of SiC ceramic matrix composite material. The process parameters were: laser power of 10W, repetition frequency of 50KHz, scanning speed of 5mm / s, number of scans of 5, scanning interval of 0.2mm, defocusing amount of -1mm, and processing environment of atmospheric environment. The resulting V-shaped grooves had a width of 90μm, a depth of 170μm, and a spacing of 200μm between adjacent V-shaped grooves. The processed SiC... f The SiC ceramic matrix was placed in a beaker containing anhydrous ethanol and ultrasonically cleaned for 30 minutes to obtain SiC with microstructures. f / SiC ceramic matrix composite material;

[0056] (2) The SiC with microstructure obtained in step (1) was processed using the plasma spraying-physical vapor deposition method. f Yb₂Si₂O₇ coatings were prepared on SiC ceramic matrix composite substrates using plasma spraying-physical vapor deposition (PPVD) with the following parameters: spraying distance 1000 mm, current 2600 A, argon flow rate 110 L / min, and substrate preheating temperature 800 °C. The particle size range of the raw material (Yb₂Si₂O₇) was 15-45 μm. The coated samples were then air-cooled in the PPVD equipment to obtain the deposited SiC coating. f / SiC ceramic matrix composites.

[0057] Longitudinal microcracks were successfully pre-formed at the protrusions between the microstructures inside the Yb2Si2O7 coating due to internal stress, with crack widths ranging from 700 nm to 1.5 μm.

[0058] Example 3

[0059] A method for pre-forming longitudinal cracks in an environmental barrier coating includes the following steps:

[0060] (1) C f The SiC ceramic matrix composite material was placed in a beaker containing anhydrous ethanol and ultrasonically cleaned for 30 minutes. Then, it was placed in a fixture filled with inert gas, and the C2O2 content was adjusted. f The position of the SiC ceramic matrix composite material was determined to maintain the airtightness of the device, and a femtosecond laser was used to target the SiC matrix. f A V-shaped groove structure was machined on the surface of a SiC ceramic matrix composite material. The process parameters were: laser power of 10W, repetition frequency of 50KHz, scanning speed of 5mm / s, number of scans of 5, scanning interval of 0.2mm, defocusing amount of -1mm, and processing environment of N2. The width of the machined V-shaped groove was 80μm, the depth of the V-shaped groove was 150μm, and the spacing between two adjacent V-shaped grooves was 220μm. The machined SiC ceramic matrix composite material was then processed. f The SiC ceramic matrix composite sample was placed in a beaker containing anhydrous ethanol and ultrasonically cleaned for 30 minutes to obtain C with microstructures. f / SiC ceramic matrix composite material;

[0061] (2) The microstructured C obtained in step (1) was processed using the plasma spraying-physical vapor deposition method. f Yb₂Si₂O₇ coatings were prepared on SiC ceramic matrix composite substrates using plasma spraying-physical vapor deposition (PPVD) with the following process parameters: spraying distance 1000 mm, current 2600 A, argon flow rate 110 L / min, and substrate preheating temperature 800 °C. The particle size range of the raw material (Yb₂Si₂O₇) was 15-45 μm. The sprayed samples were air-cooled in the PPVD equipment to obtain the C₂Si₂O₇ coating. f / SiC ceramic matrix composites.

[0062] Longitudinal microcracks were successfully pre-formed at the protrusions between the microstructures inside the Yb2Si2O7 coating due to internal stress, with crack widths ranging from 800 nm to 1.5 μm.

[0063] Example 4

[0064] A method for pre-forming longitudinal cracks in an environmental barrier coating includes the following steps:

[0065] (1) SiC f The SiC ceramic matrix sample was placed in a beaker containing anhydrous ethanol and ultrasonically cleaned for 30 minutes. Then, it was placed in a fixture containing deionized water, and the SiC matrix was adjusted. fThe position of the SiC ceramic matrix composite material was maintained, with a water film thickness of 0.5 mm. A femtosecond laser was used to precipitate the SiC matrix. f U-shaped blind hole microstructures were fabricated on the surface of SiC ceramic matrix composite material. The process parameters were: laser power of 10W, repetition frequency of 50KHz, scanning speed of 1mm / s, number of scans of 5, scanning interval of 0.2mm, defocusing amount of -1mm, and processing environment of deionized water. The diameter of the fabricated U-shaped blind holes was 150μm, the depth of the U-shaped blind holes was 90μm, and the spacing between two adjacent U-shaped blind holes in the X and Y directions was 60μm. The fabricated SiC... f The SiC ceramic matrix composite sample was placed in a beaker containing anhydrous ethanol and ultrasonically cleaned for 30 minutes to obtain SiC with microstructures. f / SiC ceramic matrix composite material;

[0066] (2) The SiC with microstructure obtained in step (1) was processed using the plasma spraying-physical vapor deposition method. f Yb₂Si₂O₇ coatings were prepared on SiC ceramic matrix composite substrates using plasma spraying-physical vapor deposition (PPVD) with the following parameters: spraying distance 1000 mm, current 2600 A, argon flow rate 110 L / min, and substrate preheating temperature 800 °C. The particle size range of the raw material (Yb₂Si₂O₇) was 15-45 μm. The coated samples were then air-cooled in the PPVD equipment to obtain the deposited SiC coating. f / SiC ceramic matrix composites.

[0067] Longitudinal microcracks were successfully pre-formed at the protrusions between the microstructures inside the Yb2Si2O7 coating due to internal stress, with crack widths ranging from 800 nm to 1.5 μm.

[0068] Example 5

[0069] A method for pre-forming longitudinal cracks in an environmental barrier coating includes the following steps:

[0070] (1) C f The SiC ceramic matrix composite material was placed in a beaker containing anhydrous ethanol and ultrasonically cleaned for 30 minutes. Then, it was placed on a tooling fixture, and the C2 ratio was adjusted. f The location of the SiC ceramic matrix was determined using a femtosecond laser. fA V-shaped groove microstructure was fabricated on the surface of a SiC ceramic matrix composite material. The process parameters were: laser power of 10W, repetition frequency of 50KHz, scanning speed of 1mm / s, number of scans of 5, scanning interval of 0.2mm, defocusing amount of -1mm, and processing environment of atmospheric environment. The width of the fabricated V-shaped groove was 75μm, the depth of the V-shaped groove was 130μm, and the spacing between two adjacent V-shaped grooves was 210μm. The fabricated SiC ceramic matrix composite material was then processed. f The SiC ceramic matrix composite sample was placed in a beaker containing anhydrous ethanol and ultrasonically cleaned for 30 minutes to obtain C with microstructures. f / SiC ceramic matrix composite material;

[0071] (2) The microstructured C obtained in step (1) was processed using the plasma spraying-physical vapor deposition method. f Yb₂Si₂O₇ coatings were prepared on SiC ceramic matrix composite substrates using plasma spraying-physical vapor deposition (PPVD) with the following parameters: spraying distance 1000 mm, current 2600 A, argon flow rate 110 L / min, and substrate preheating temperature 800 °C. The particle size range of the raw material (Yb₂Si₂O₇) was 15-45 μm. The coated samples were air-cooled in the PPVD equipment to obtain the C₂Si₂O₇ coating. f / SiC ceramic matrix composites.

[0072] Longitudinal microcracks were successfully pre-formed at the protrusions between the microstructures inside the Yb2Si2O7 coating due to internal stress, with crack widths ranging from 700 nm to 1.5 μm.

[0073] Example 6

[0074] A method for pre-forming longitudinal cracks in an environmental barrier coating includes the following steps:

[0075] (1) Place the silicon carbide ceramic sample in a beaker containing anhydrous ethanol and ultrasonically clean it for 30 min. Then place it in a fixture containing deionized water, adjust the position of the silicon carbide sample, and maintain the water film thickness at 0.5 mm. Use a femtosecond laser to process the U-shaped straight groove structure on the surface of the silicon carbide ceramic. The process parameters are: laser power of 10 W, repetition frequency of 50 kHz, scanning speed of 1 mm / s, number of scans of 5, scanning interval of 0.2 mm, defocusing amount of -1 mm, processing environment of deionized water, the width of the processed U-shaped straight groove is 150 μm, the depth of the U-shaped straight groove is 80 μm, and the distance between two adjacent U-shaped straight grooves is 160 μm. Place the processed silicon carbide ceramic sample in a beaker containing anhydrous ethanol and ultrasonically clean it for 30 min to obtain a silicon carbide ceramic substrate with a microstructure.

[0076] (2) A Yb2Si2O7 coating was prepared on the silicon carbide ceramic substrate with microstructure obtained in step (1) by low-pressure plasma spraying. The process parameters of low-pressure plasma spraying were: spraying distance of 350 mm, current of 650 A, hydrogen flow rate of 12 L / min, substrate preheating temperature of 600 °C; the particle size range of the raw material (Yb2Si2O7) was 15-45 μm. After spraying, the sample was air-cooled in the low-pressure plasma spraying equipment to obtain silicon carbide ceramic with deposited coating.

[0077] Longitudinal microcracks with a width of 900 nm to 2 μm were successfully pre-formed at the protrusions between the microstructures inside the Yb2Si2O7 coating due to internal stress.

[0078] Comparative Example 1

[0079] Comparative Example 1 uses a traditional sandblasting method to pre-create longitudinal cracks. The specific method is as follows:

[0080] The silicon carbide ceramic sample was placed in a beaker containing anhydrous ethanol and ultrasonically cleaned for 30 min. The sample surface was then sandblasted with corundum gravel at a pressure of 0.4 MPa. A Yb2Si2O7 coating was then prepared using a plasma spraying-physical vapor deposition method: the spraying distance was 1000 mm, the current was 2600 A, the argon flow rate was 110 L / min, and the substrate preheating temperature was 800 °C. The particle size range of the raw materials was 15-45 μm, resulting in a silicon carbide ceramic with a deposited coating.

[0081] Scanning electron microscopy was used to observe the cross-section of the environmental barrier coating in Comparative Example 1. The results are as follows: Figure 3 As shown. By Figure 3 It can be seen that longitudinal cracks are obtained in the coating, with a crack width of 800nm-3μm.

[0082] Comparative Example 2

[0083] The only difference between Comparative Example 2 and Example 1 is that Comparative Example 2 uses an atmospheric plasma spraying method to deposit a coating on the substrate surface, while the rest is the same as Example 1.

[0084] A method for pre-forming longitudinal cracks in an environmental barrier coating includes the following steps:

[0085] (1) Place the silicon carbide ceramic sample in a beaker containing anhydrous ethanol and ultrasonically clean it for 30 min. Then place it in a special fixture containing deionized water, adjust the position of the silicon carbide sample, and maintain the water film thickness at 0.5 mm. Use a femtosecond laser to process the U-shaped straight groove structure on the surface of the silicon carbide ceramic. The process parameters are: laser power of 10 W, repetition frequency of 50 kHz, scanning speed of 1 mm / s, number of scans of 5, scanning interval of 0.2 mm, defocusing amount of -1 mm, processing environment of deionized water, the width of the processed U-shaped straight groove is 150 μm, the depth of the U-shaped straight groove is 80 μm, and the distance between two adjacent U-shaped straight grooves is 160 μm. Place the processed silicon carbide ceramic sample in a beaker containing anhydrous ethanol and ultrasonically clean it for 30 min to obtain a silicon carbide ceramic substrate with a microstructure.

[0086] (2) A Yb2Si2O7 coating was prepared on the silicon carbide ceramic substrate with microstructure obtained in step (1) by atmospheric plasma spraying. The process parameters of plasma spraying-physical vapor deposition were: spraying distance of 130 mm, current of 600 A, hydrogen flow rate of 8 L / min, and substrate preheating temperature of 150 °C. The particle size range of the raw material (Yb2Si2O7) was 15-45 μm. After spraying, the sample was air-cooled in an atmospheric environment to obtain silicon carbide ceramic with deposited coating.

[0087] Due to the large number of pores inside the atmospheric plasma sprayed Yb2Si2O7 coating and insufficient coating density, regular longitudinal microcracks could not be successfully pre-fabricated at the microstructure protrusions.

[0088] Performance testing

[0089] 1. Combined strength test

[0090] The bonding strength between the coating and the substrate in Examples 1-6 and Comparative Examples 1-2 was tested. The specific test method for bonding strength was in accordance with GB / T8642–2002.

[0091] Table 1 shows the bonding strength results between the coating and the substrate in Examples 1-6 and Comparative Examples 1-2.

[0092] Table 1: Bond strength between coating and substrate in Examples 1-6 and Comparative Examples 1-2

[0093]

[0094] As can be seen from Table 1, the coating and the substrate of the present invention have good bonding strength, indicating that by processing microstructures on the surface of the ceramic substrate and then obtaining longitudinal cracks in the coating, the stress generated during the coating deposition process can be released, the bonding strength between the coating and the ceramic substrate can be improved, and the coating can be prevented from peeling off during the spraying deposition process.

[0095] Although longitudinal cracks were obtained in the coating by the traditional sandblasting method in Comparative Example 1, the bonding force between the coating and the ceramic substrate was small, which was significantly worse than the bonding strength between the coating and the ceramic substrate prepared in this invention. The bonding strength between the coating and the ceramic substrate prepared in Example 4 of this invention is 3.6 times that of Comparative Example 1.

[0096] Comparative Example 2 used atmospheric plasma spraying to deposit a coating. Due to the difference in deposition methods, longitudinal cracks were not pre-induced in the coating of Comparative Example 2, and the adhesion between the coating and the ceramic substrate was weak, significantly worse than the adhesion strength between the coating and the ceramic substrate prepared in Example 1 of this invention. This demonstrates that the specific coating deposition method has a significant impact on the adhesion strength between the coating and the ceramic substrate.

[0097] 2. High-temperature oxidation resistance

[0098] The coatings of Examples 1-6 and Comparative Examples 1-2 were subjected to high-temperature oxidation resistance tests. The specific test method was as follows: the ceramic samples of the deposited coatings prepared in Examples 1-6 and Comparative Examples 1-2 were placed in a constant temperature environment of 1400℃ and kept there for a certain period of time. The coating was observed to see if it peeled off. The high-temperature oxidation resistance of the coating was measured by whether the coating peeled off from the substrate after being kept in a constant temperature environment of 1400℃ for a certain period of time. If the coating peeled off from the ceramic substrate in a short time, it indicated that the coating had poor high-temperature oxidation resistance. The longer the coating and the ceramic substrate maintained a good bonding state, the better the high-temperature oxidation resistance of the coating.

[0099] The results of the high-temperature oxidation resistance of the coatings of Examples 1-6 and Comparative Examples 1-2 are shown in Table 2.

[0100] Table 2: High-temperature oxidation resistance of coatings in Examples 1-6 and Comparative Examples 1-2

[0101]

[0102] As can be seen from Table 2, the coatings with longitudinal cracks obtained in Examples 1-6 of the present invention did not peel off from the ceramic substrate after being kept in a constant temperature environment of 1400℃ for at least 150 hours, indicating that the coatings have good adhesion to the substrate, and further indicating that the coatings with longitudinal cracks prepared by the present invention have good high-temperature oxidation resistance.

[0103] The coating obtained by conventional sandblasting in Comparative Example 1 detached after 50 hours, indicating that its high-temperature oxidation resistance was significantly worse than that of the coating prepared in this invention. This demonstrates that the present invention, by processing microstructures on the ceramic substrate surface to create longitudinal cracks in the coating, not only improves the bonding strength between the coating and the ceramic substrate, preventing peeling during the spraying deposition process, but also enhances the coating's high-temperature oxidation resistance. Even in high-temperature environments, the coating and ceramic substrate maintain good adhesion, and the coating is less prone to peeling off. Comparative Example 2 used atmospheric plasma spraying to deposit the coating. Due to the difference in deposition methods, Comparative Example 2 did not pre-create longitudinal cracks in the coating, resulting in weaker bonding between the coating and the ceramic substrate. Consequently, the coating detached from the substrate after 100 hours. The high-temperature oxidation resistance of the coating in Comparative Example 2 was lower than that in Example 1.

[0104] 3. Thermal shock resistance

[0105] The purpose of this invention in creating longitudinal cracks in the coating by processing microstructures on the surface of the ceramic substrate is to release the stress generated during the coating deposition process, improve the bonding strength between the coating and the ceramic substrate, and prevent the coating from peeling off during the spraying deposition process. However, even with a coating that is not easily peeled off, corrosive substances may penetrate into the coating through the longitudinal cracks during service, leading to premature coating failure. Therefore, this invention employs high-temperature annealing to promote the healing of longitudinal cracks. The specific process is as follows: the ceramic samples prepared in Examples 1-6 and Comparative Examples 1-2 are placed in a muffle furnace, and the temperature is raised from room temperature to 1300℃ at a heating rate of 5℃ / min, and held for 10 hours.

[0106] After the ceramic sample prepared in Example 1 underwent the above treatment, the cross-section of the environmental barrier coating was observed by scanning electron microscopy. The results are as follows: Figure 4 As shown, by Figure 4 It can be seen that the pre-formed longitudinal cracks in the coating have healed.

[0107] After treatment, the longitudinal cracks in the coatings of Examples 1-6 and Comparative Example 1 were all healed. Then, the thermal shock resistance performance of the samples prepared in Examples 1-6 and Comparative Examples 1-2 was tested. The specific test methods are as follows:

[0108] The samples from Examples 1-6 and Comparative Examples 1-2 were placed in a furnace at 1300℃ and held for 5±1 min, then removed and air-cooled for 5 min, constituting one cycle. Before the next thermal shock test, moisture on the coating surface should be blown away. After the thermal shock test, the coating surface should be observed to show no peeling or flaking. Peeling along the perimeter of the sample and within 3 mm of the edge of the process holes is disregarded. Test results show that after 500, 520, 510, 550, 505, and 500 cycles respectively, the coating peeling area in Examples 1-6 reached the failure standard (a peeling area greater than 20% is considered failure); after 300 and 450 cycles respectively, the peeling area in Comparative Examples 1-2 reached the failure standard (a peeling area greater than 20% is considered failure). This indicates that the pre-formed longitudinal crack-healed coating of this invention still possesses good thermal shock resistance and can well meet the requirements of later service.

[0109] In summary, this invention improves the bonding strength between the coating and the substrate by processing microstructures of specific shapes on the substrate surface and combining them with a specific coating deposition method. The microstructures can adjust the internal stress of the coating, particularly for high-density environmental barrier coatings. The coating deposited at the groove locations generates in-plane compressive stress, while the raised locations generate in-plane tensile stress. These compressive and tensile stresses interact, forming pre-fabricated microcracks at or near the raised locations of the microstructures. This effectively releases the stress generated during coating deposition, reduces internal stress in the coating, increases the coating's strain tolerance, and improves the coating deposition success rate by combining it with a specific coating deposition method. This, in turn, enhances the bonding strength between the coating and the substrate, preventing coating detachment during preparation. The bonding strength between the coating with longitudinal cracks and the substrate in this invention is significantly higher than that of coatings prepared by traditional sandblasting roughening technology, being 2.1-3.6 times higher. Furthermore, high-temperature annealing after obtaining the longitudinal cracks allows them to heal, and the healed coating still exhibits good thermal shock resistance, well meeting the requirements for later service.

[0110] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for pre-fabricating longitudinal cracks in an environmental barrier coating, characterized in that, Includes the following steps: Microstructures are fabricated on the substrate surface, and then a coating is deposited, forming longitudinal cracks within the coating. The microstructure consists of multiple U-shaped blind holes; The method for depositing the coating includes any one of plasma spraying-physical vapor deposition and low-pressure plasma spraying. The diameter of the U-shaped blind hole is 65μm-880μm, the depth of the U-shaped blind hole is 18μm-330μm, the distance between two adjacent U-shaped blind holes in the X direction is 9μm-550μm, and the distance between two adjacent U-shaped blind holes in the Y direction is 9μm-550μm. The coating is composed of RE2Si2O7, wherein RE is selected from any one of Yb, Y, Sc, Lu, and Er; The width of the longitudinal crack is 200 nm to 3.3 μm.

2. The prefabrication method according to claim 1, characterized in that, The matrix includes any one of silicon carbide ceramics, silicon carbide fiber-reinforced silicon carbide ceramic matrix composites, and carbon fiber-reinforced silicon carbide ceramic matrix composites.

3. The prefabrication method according to claim 1, characterized in that, A laser is used to process the surface of the substrate to form a microstructure.

4. The prefabrication method according to claim 1, characterized in that, The coating thickness is 45-220 μm.

5. An engine, characterized in that, This includes coatings prepared using the pre-fabrication method for longitudinal cracks in environmental barrier coatings as described in any one of claims 1-4.

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