Determination method of flame-retardant and abrasion-resistant composite coating and flame-retardant and abrasion-resistant composite coating

Abstract

This application provides a method for determining a flame-retardant and wear-resistant composite coating, and the flame-retardant and wear-resistant composite coating itself. The flame-retardant and wear-resistant composite coating comprises a flame-retardant layer and a wear-resistant layer sequentially disposed on the surface of a titanium alloy substrate. The method of this application achieves high bonding between the flame-retardant layer and the wear-resistant layer, resulting in a flame-retardant and wear-resistant composite coating with a high combustion threshold. The flame-retardant and wear-resistant composite coating provided by this application can improve the combustion threshold at the interface between the titanium alloy substrate and the coating, while simultaneously improving the wear-resistant properties of the coating. Metal components using the flame-retardant and wear-resistant composite coating of this application exhibit high combustion performance, good bonding performance, surface hardness, thermal shock resistance, and bending resistance, thereby improving their service safety and service life.

Description

Technical Field

[0001] This application relates to the field of metal combustion technology, and in particular to a method for determining a flame-resistant and wear-resistant composite coating and the flame-resistant and wear-resistant composite coating itself. Background Technology

[0002] With the increasing demands for thrust-to-weight ratio in advanced aero-engines, titanium alloys are being used more and more extensively as lightweight, high-strength structural components due to their advantages such as low density, high melting point, high specific strength, good heat resistance, and corrosion resistance. However, titanium alloys are highly flammable and prone to "titanium fire" accidents under extreme thermal coupling effects such as high-speed impacts. Once a fire occurs, it can destroy the engine in a very short time. Therefore, fire-resistant design of titanium alloys has become one of the important factors restricting the development of advanced engines in my country and urgently needs to be addressed.

[0003] To address the titanium fire problem, the main proposed measures include improving structural components, using flame-retardant titanium alloys, and designing coatings. Protective coatings are currently a commonly used method, with a typical application being the wear-resistant sealing coating for the stator components of the engine casing. Its main function is to facilitate active wear between the coating and rotor components and prevent wear on the rotor components, minimizing the gap between the stator and rotor components, improving the sealing performance and power pressure difference of the air passage, and improving the overall engine efficiency. The wear-resistant sealing coating typically consists of two parts: an adhesive layer and a surface wear-resistant sealing layer. The adhesive layer includes metal systems such as NiCrAl and NiAl, while the surface sealing layer consists of a framework metal system that provides bonding and hardness, low shear strength phases such as graphite (G), bentonite, aluminum silicon (AlSi), and boron nitride (cBN) that provide wear resistance, and pores.

[0004] However, in recent years, titanium fires have still occurred during the friction process between aero-engine rotors and stators, indicating that the existing wearable coating system has limited protective effect. The fundamental reason is that during high-pressure compressor operation, when the rotor blades slightly rub against the wearable coating of the casing, the resulting abrasion can disperse heat and provide insulation, preventing heat accumulation at the high-speed friction points and reducing the temperature rise at the coating-substrate interface. Existing wearable coating systems can achieve effective fire protection. However, if severe friction occurs between the blades and the casing wearable coating, the insulation effect is limited, and the instantaneous heat accumulation at the high-speed friction points causes the energy at the substrate-coating interface to exceed the combustion threshold, leading to substrate combustion. In this case, existing wearable coating systems cannot meet the requirements of advanced engines. Therefore, providing a design concept for a flame-retardant wearable composite coating to improve the flame-retardant performance of wearable sealing coatings has become an urgent problem to be solved. Summary of the Invention

[0005] The purpose of this application is to provide a method for determining a flame-retardant abrasive composite coating and a flame-retardant abrasive composite coating itself, so as to improve the flame-retardant performance of abrasive sealing coatings. The specific technical solution is as follows:

[0006] The first aspect of this application provides a method for determining a flame-retardant and wear-resistant composite coating, which includes the following steps:

[0007] The flame-retardant and wear-resistant composite coating consists of a flame-retardant layer and a wear-resistant layer sequentially disposed on the surface of a titanium alloy substrate. Based on the combustion threshold factor, characteristic parameters affecting the combustion of the coating material are determined, and the expression for the combustion threshold factor is as follows:

[0008]

[0009] Where f represents the combustion threshold factor, h represents the coating thickness, D represents the oxygen diffusion resistance coefficient, K represents the oxygen adsorption rate on the coating surface, and Kc represents the coating reaction coefficient.

[0010] The characteristic parameters include at least one of the following: coating thickness h, oxygen diffusion resistance coefficient D, oxygen adsorption rate K on the coating surface, and coating reaction coefficient Kc.

[0011] The measured values ​​of characteristic parameters of multiple candidate coating materials are obtained and substituted into the expression of the combustion threshold factor to obtain f. The candidate coating materials with f ranging from 1.25 to 2.28 are determined as the flame-retardant layer materials.

[0012] In some embodiments of this application, the material of the flame-retardant layer is selected from Cr. m Ni n Alloy, 0≤n≤100, m=100-n.

[0013] In some embodiments of this application, the material of the wearable layer is selected from metal-based bentonite composite powder, metal-based graphite alloy powder, or aluminum-silicon powder.

[0014] In some embodiments of this application, the titanium alloy matrix includes TC11, TC4, TC17, Ti40, Ti14, TC25G, or Ti2AlNb.

[0015] In some embodiments of this application, the thickness of the flame-retardant layer is 70 μm to 130 μm, and the thickness of the wear-resistant layer is not less than 600 μm.

[0016] In some embodiments of this application, the flame-retardant and wear-resistant composite coating further includes at least one of an adhesive layer or a heat insulation layer; the material of the adhesive layer is selected from NiCrAl, NiCrAlY, NiAl or TiCrAl; the material of the heat insulation layer is selected from ZrO2-xY2O3 (6≤x≤8), Al2O3, cBN or SiC.

[0017] In some embodiments of this application, the thickness of the adhesive layer is 70 μm to 130 μm; and the thickness of the thermal insulation layer is 150 μm to 250 μm.

[0018] In some embodiments of this application, the flame-retardant and wear-resistant composite coating is composed of the adhesive layer, the flame-retardant layer, the heat-insulating layer, and the wear-resistant layer sequentially disposed on the surface of the titanium alloy substrate; or, the flame-retardant and wear-resistant composite coating is composed of the adhesive layer, the flame-retardant layer, and the wear-resistant layer sequentially disposed on the surface of the titanium alloy substrate; or, the flame-retardant and wear-resistant composite coating is composed of the flame-retardant layer, the heat-insulating layer, and the wear-resistant layer sequentially disposed on the surface of the titanium alloy substrate.

[0019] The second aspect of this application provides a flame-retardant abrasive composite coating, which is determined by the method for determining a flame-retardant abrasive composite coating provided in the first aspect of this application.

[0020] In some embodiments of this application, the flame-retardant layer is prepared by plasma spraying technology, and the wear-resistant layer is prepared by flame spraying technology.

[0021] The beneficial effects of this application are:

[0022] This application provides a method for determining a flame-retardant and wear-resistant composite coating, as well as the flame-retardant and wear-resistant composite coating itself. The flame-retardant and wear-resistant composite coating comprises a flame-retardant layer and a wear-resistant layer sequentially disposed on the surface of a titanium alloy substrate. Based on a combustion threshold factor f, characteristic parameters affecting the combustion of the coating material are determined. The measured values ​​of the characteristic parameters of multiple candidate coating materials are obtained and substituted into the expression for the combustion threshold factor to obtain f. Candidate coating materials with f ranging from 1.25 to 2.28 are determined as flame-retardant layer materials. A higher value of f indicates a higher combustion threshold value (critical pressure, ignition temperature, etc.) for the coating material. The determination method of this application achieves high bonding between the flame-retardant layer and the wear-resistant layer with a high combustion threshold value, resulting in a flame-retardant and wear-resistant composite coating with a high combustion threshold value. The flame-retardant and wear-resistant composite coating provided by this application can improve the combustion threshold value (critical pressure, ignition temperature, etc.) at the interface between the titanium alloy substrate and the coating, while simultaneously improving the wear-resistant properties of the coating. Metal components using the flame-retardant and wear-resistant composite coating of this application have high combustion performance, as well as good bonding performance, surface hardness, thermal shock resistance, and bending resistance, thereby improving their service safety and service life.

[0023] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0025] Figure 1 This is a schematic diagram of the structure of a flame-retardant and wear-resistant composite coating according to one embodiment of this application;

[0026] Figure 2 This is a schematic diagram of the structure of a flame-retardant and wear-resistant composite coating according to another embodiment of this application;

[0027] Figure 3 A schematic diagram of the structure of a flame-retardant and wear-resistant composite coating according to another embodiment of this application;

[0028] Figure 4 This is a schematic diagram of the structure of a flame-retardant and wear-resistant composite coating according to another embodiment of this application;

[0029] Figure 5 Comparison of critical pressures for flame-retardant and wear-resistant composite coatings with different structures in Examples 1 to 4, Comparative Example 1, and Comparative Example 2;

[0030] Figure 6 This is a scanning electron microscope image of the flame-retardant and wear-resistant composite coating of Example 1;

[0031] Figure 7 The image shows the ignition temperature curve of the flame-retardant and wear-resistant composite coating in Example 1.

[0032] Reference numerals: Titanium alloy substrate 10, flame-retardant and wear-resistant composite coating 20, flame-retardant layer 21, wear-resistant layer 22, adhesive layer 23, heat insulation layer 24. Detailed Implementation

[0033] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0034] The first aspect of this application provides a method for determining a flame-retardant and wear-resistant composite coating, which includes the following steps:

[0035] The flame-retardant and wear-resistant composite coating consists of a flame-retardant layer and a wear-resistant layer sequentially disposed on the surface of a titanium alloy substrate. Based on the combustion threshold factor, the characteristic parameters affecting the combustion of the coating material are determined, and the expression for the combustion threshold factor is as follows:

[0036]

[0037] Where f represents the combustion threshold factor, h represents the coating thickness, D represents the oxygen diffusion resistance coefficient, K represents the oxygen adsorption rate on the coating surface, and Kc represents the coating reaction coefficient.

[0038] The characteristic parameters include at least one of the following: coating thickness h, oxygen diffusion resistance coefficient D, oxygen adsorption rate K on the coating surface, or coating reaction coefficient Kc.

[0039] The measured values ​​of characteristic parameters of multiple candidate coating materials are obtained and substituted into the expression for the combustion threshold factor to obtain f. Candidate coating materials with f ranging from 1.25 to 2.28 are identified as fire-resistant layer materials. For example, f can be 1.25, 1.29, 1.31, 1.35, 1.55, 1.73, 1.9, 2.0, 2.05, 2.1, 2.17, 2.2, 2.28, or any range of two values ​​therein.

[0040] A higher value of f indicates a higher combustion threshold (critical pressure, ignition temperature, etc.) for the coating material. The mathematical relationship between the combustion threshold and f can be found in the coating characteristic parameter factor in Chinese Patent CN117269410A. In this application, based on a method for increasing the combustion threshold, a flame-resistant layer with a combustion threshold-increasing factor within the scope of this application is added to the existing wearable layer. Using the determination method of this application, a high bonding between the flame-resistant layer with a high combustion threshold and the wearable layer can be achieved, resulting in a flame-resistant and wearable composite coating with a high combustion threshold. The flame-resistant and wearable composite coating provided in this application can increase the combustion threshold (critical pressure, ignition temperature, etc.) at the interface between the titanium alloy substrate and the coating. Metal components using the flame-resistant and wearable composite coating of this application exhibit high combustion performance and good mechanical properties, such as bonding performance, surface hardness, thermal shock resistance, and bending resistance, thereby improving their service safety and service life.

[0041] The flame-retardant abrasive composite coating obtained by the determination method provided in this application can increase the critical combustion pressure of the substrate by more than 1 time, preferably by 2 times, and increase the ignition temperature by not less than 150°C, preferably not less than 200°C. Simultaneously, other properties of the flame-retardant abrasive composite coating can meet the requirements for aero-engine service, specifically including: the bonding force between each layer of the flame-retardant abrasive composite coating is not less than 10 MPa; the hardness of the abrasive layer is HR15Y of 40 to 60; the overall bending resistance of the flame-retardant abrasive composite coating can achieve a 90° bend without warping or peeling, and cracking is permissible; the overall thermal shock resistance of the flame-retardant abrasive composite coating meets the requirements of 10 cycles at 600°C without any spalling with a maximum distance of 2 mm.

[0042] Based on the combustion threshold factor f of the flame-retardant layer material, the material of the flame-retardant layer can be selected from Cr or its alloys, Ni or its alloys, preferably Cr or its alloys. In some embodiments of this application, the material of the flame-retardant layer is selected from Cr. m Ni n For the alloy, 0 ≤ n ≤ 100, m = 100 - n. For example, n can be 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or any two of these values, and m can be 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, or any two of these values. Selecting a flame-retardant layer material within the above range can reduce the heat flux density and heat generation rate at the interface between the titanium alloy substrate and the coating, thereby increasing the combustion threshold value at the titanium alloy substrate and coating interface.

[0043] For example, the material of the flame-retardant layer in this application can be Ni, Ni 80 Cr 20 Ni60 Cr 40 Cr 60 Ni 40 Cr 80 Ni 20 Or Cr. Table 1 shows the characteristic parameters and combustion threshold enhancement factors of the above materials when used as coating materials for the flame-retardant layer. It is assumed that when no flame-retardant coating is applied to the surface of the titanium alloy substrate, the combustion threshold enhancement factor f = 1.

[0044] Table 1

[0045]

[0046] Note: In Table 1, " / " indicates that the material or parameter does not exist.

[0047] In this application, obtaining the measured values ​​of characteristic parameters for multiple candidate coating materials includes: obtaining the measured values ​​of characteristic parameters for each candidate coating material based on published literature. Characteristic parameters obtainable from published literature include the oxygen diffusion resistance coefficient D, the oxygen adsorption rate K on the coating surface, and the coating reaction coefficient Kc.

[0048] In this application, the flame-retardant layer material can be prepared by methods including but not limited to vacuum melting, compounding, atomization, and granulation according to the alloy composition ratio. By controlling the sphericity, particle size, and internal density of the powder particles, the powder flowability is such that the flow time of a 50g standard sample is no more than 20s. This application does not have any particular restrictions on the powder particle size and purity of the flame-retardant layer material, as long as the purpose of this application can be achieved. For example, the powder particle size of the flame-retardant layer material is 10μm to 45μm, and the purity of the flame-retardant layer material is not less than 99.99%.

[0049] In some embodiments of this application, the material of the wearable layer is selected from metal-based bentonite composite powder (NiCrAl.Be), metal-based graphite alloy powder (e.g., nickel-graphite), or aluminum-silicon powder (Al-12Si), with metal-based bentonite composite powder (NiCrAl.Be) being preferred. Using materials within the above range for the wearable layer helps to fully utilize the excellent self-lubricating and wear-resistant properties of the flame-retardant wear-resistant composite coating in this application, enabling active wear-resistance, protecting the rotor and stator substrates in the compressor, and reducing the risk of "titanium fire" problems.

[0050] In some embodiments of this application, the titanium alloy matrix includes TC11, TC4, TC17, Ti40, Ti14, TC25G, or Ti2AlNb.

[0051] In some embodiments of this application, the thickness of the flame-retardant layer is 70 μm to 130 μm, and the thickness of the wear-resistant layer is not less than 600 μm, preferably 600 μm to 1100 μm. For example, the thickness of the flame-retardant layer can be 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, or any two of these values, and the thickness of the wear-resistant layer can be 600 μm, 700 μm, 800 μm, 900 μm, 1000 μm, 1100 μm, 1200 μm, 1500 μm, or any two of these values. Adjusting the thickness of the flame-retardant layer and the wear-resistant layer within the above ranges helps to highlight the flame-retardant performance while giving full play to the air passage sealing effect of the long-lasting wear-resistant layer, which helps to maintain the ideal minimum clearance between the rotor and stator components in the engine, thereby improving the high operating efficiency of the engine.

[0052] In some embodiments of this application, the flame-retardant and wear-resistant composite coating further includes at least one of a bonding layer or a heat-insulating layer; the bonding layer is made of nickel-based alloy powder, selected from NiCrAl, NiCrAlY, NiAl, or TiCrAl, preferably NiCrAl. The heat-insulating layer is made from ZrO2-xY2O3 (6≤x≤8, yttrium-stabilized zirconium oxide powder), Al2O3, cBN, or SiC, preferably ZrO2-xY2O3, such as ZrO2-8Y2O3. The inclusion of a bonding layer or a heat-insulating layer in the flame-retardant and wear-resistant composite coating is beneficial for improving the interfacial thermal matching of the coating. In addition to enhancing the flame-retardant properties of the titanium alloy substrate, it can further improve the mechanical properties of the coating, such as bonding performance, thermal shock resistance, and bending resistance.

[0053] In some embodiments of this application, the thickness of the adhesive layer is 70 μm to 130 μm; the thickness of the thermal insulation layer is 150 μm to 250 μm. For example, the thickness of the adhesive layer can be 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, or any combination of two such values; the thickness of the thermal insulation layer can be 150 μm, 170 μm, 180 μm, 200 μm, 210 μm, 230 μm, 250 μm, or any combination of two such values. Adjusting the thickness of the adhesive layer and the thermal insulation layer within the above ranges is beneficial for better utilizing the functions of the adhesive layer and the thermal insulation layer, and can further improve the bonding performance, thermal shock resistance, and bending resistance of the flame-retardant and wear-resistant composite coating.

[0054] The second aspect of this application provides a flame-retardant abrasive composite coating, which is determined by the method for determining flame-retardant abrasive composite coatings provided in the first aspect of this application. Thus, the flame-retardant abrasive composite coating provided in the second aspect of this application has good flame-retardant properties and mechanical properties.

[0055] In some embodiments of this application, the flame-retardant layer is prepared by plasma spraying, and the abrasive layer is prepared by flame spraying. Plasma spraying allows for a relatively low particle impact rate (compared to supersonic plasma spraying) while maintaining high density, reducing coating hardness and increasing coating toughness. This facilitates high bonding between different layers. Furthermore, this process effectively protects the flame-retardant material from elemental oxidation during spraying, improving coating quality (low oxidation pollution). Flame spraying, with its low particle impact rate and relatively high flame temperature, allows for the preparation of a thicker abrasive layer, ensuring abrasiveness and improving issues such as low surface hardness and porosity.

[0056] This application does not impose any particular restrictions on the equipment used for the aforementioned plasma spraying and flame spraying technologies, as long as the purpose of this application can be achieved. For example, an LBP100 plasma spraying equipment can be used for plasma spraying, and a QSH-4 oxyacetylene spray gun can be used to prepare the flame-sprayed coating.

[0057] In this application, the operating parameters of the aforementioned plasma spraying technology can be: argon flow rate of 45 L / min to 80 L / min, hydrogen flow rate of 2 L / min to 3 L / min, operating current of 400 A to 500 A, operating voltage of 50 V to 70 V, powder feed rate of 40 g / min to 50 g / min, spray gun speed of 400 mm / s to 500 mm / s, and spraying distance of 80 mm to 100 mm. For example, the operating parameters of the plasma spraying technology are: argon flow rate of 50 L / min, hydrogen flow rate of 2 L / min, operating current of 450 A, operating voltage of 60 V, powder feed rate of 40 g / min, spray gun speed of 460 mm / s, and spraying distance of 90 mm.

[0058] In this application, the operating parameters of the aforementioned flame spraying technology can be: an oxygen-fuel ratio of 4:1 to 2:1, a spray gun speed of 700 mm / s to 900 mm / s, a spraying distance of 200 mm to 400 mm, and a powder feed rate of 30 g / min to 40 g / min. For example, the operating parameters of the flame spraying technology are: an oxygen-fuel ratio of 3:1, a spray gun speed of 750 mm / s, a spraying distance of 300 mm, and a powder feed rate of 36 g / min.

[0059] This application does not impose any particular restrictions on the preparation process of the adhesive layer and the thermal insulation layer, as long as the purpose of this application can be achieved. For example, they can be prepared using a plasma spraying process, the equipment and operating parameters of which are described above.

[0060] In some embodiments of this application, such as Figure 1As shown, the flame-retardant and wear-resistant composite coating 20 is composed of a flame-retardant layer 21 and a wear-resistant layer 22 sequentially disposed on the surface of the titanium alloy substrate 10. The flame-retardant and wear-resistant composite coating can be obtained through the following steps: S1: using plasma spraying technology to spray the material powder of the flame-retardant layer onto the surface of the titanium alloy substrate to form a flame-retardant layer; S2: using flame spraying technology to spray the material powder of the wear-resistant layer onto the surface of the flame-retardant layer to form a wear-resistant coating, thereby obtaining a flame-retardant and wear-resistant composite coating on the surface of the titanium alloy substrate.

[0061] In other implementation schemes, such as Figure 2 As shown, the flame-retardant and wear-resistant composite coating 20 is composed of an adhesive layer 23, a flame-retardant layer 21, a heat-insulating layer 24, and a wear-resistant layer 22 sequentially disposed on the surface of the titanium alloy substrate 10. The flame-retardant and wear-resistant composite coating can be obtained through the following steps: S1: Plasma spraying technology is used to spray the material powder of the adhesive layer onto the surface of the titanium alloy substrate to form an adhesive layer; S2: Plasma thermal coating technology is used to spray the material powder of the flame-retardant layer onto the surface of the adhesive layer to form a flame-retardant layer; S3: Plasma spraying technology is used to spray the material powder of the heat-insulating layer onto the surface of the flame-retardant layer to form a heat-insulating layer; S4: Flame spraying technology is used to spray the material powder of the wear-resistant layer onto the surface of the heat-insulating layer to form a wear-resistant coating, thereby obtaining a flame-retardant and wear-resistant composite coating on the surface of the titanium alloy substrate.

[0062] In some other implementation schemes, such as Figure 3 As shown, the flame-retardant and wear-resistant composite coating 20 is composed of an adhesive layer 23, a flame-retardant layer 21, and a wear-resistant layer 22 sequentially disposed on the surface of the titanium alloy substrate 10. The flame-retardant and wear-resistant composite coating can be prepared by the following steps: S1: using plasma spraying technology to spray the material powder of the adhesive layer onto the surface of the titanium alloy substrate to form the adhesive layer; S2: using plasma spraying technology to spray the material powder of the flame-retardant layer onto the surface of the adhesive layer to form the flame-retardant layer; S3: using flame spraying technology to spray the material powder of the wear-resistant layer onto the surface of the flame-retardant layer to form the wear-resistant coating, thereby forming a flame-retardant and wear-resistant composite coating on the surface of the titanium alloy substrate.

[0063] In some other implementation schemes, such as Figure 4 As shown, the flame-retardant and wear-resistant composite coating 20 is composed of a flame-retardant layer 21, a heat-insulating layer 24, and a wear-resistant layer 22 sequentially disposed on the surface of the titanium alloy substrate 10. The flame-retardant and wear-resistant composite coating can be obtained through the following steps: S1: Using plasma spraying technology, the material powder of the flame-retardant layer is sprayed onto the surface of the titanium alloy substrate to form a flame-retardant layer; S2: Using plasma spraying technology, the material powder of the heat-insulating layer is sprayed onto the surface of the flame-retardant layer to form a heat-insulating layer; S3: Using flame spraying technology, the material powder of the wear-resistant layer is sprayed onto the surface of the heat-insulating layer to form a wear-resistant coating, thereby obtaining a flame-retardant and wear-resistant composite coating on the surface of the titanium alloy substrate.

[0064] In this application, the titanium alloy substrate may also undergo pretreatment, including roughening, degreasing, pickling, and sandblasting. This application does not impose any particular limitations on this, as long as the objective of this application is achieved.

[0065] In this application, during the combustion test of a titanium-fire-resistant, flame-retardant, and wear-resistant composite coating sample, the sample is fixed on a combustion device, the combustion atmosphere is adjusted, and heat is input to the sample until combustion is initiated. This application does not impose any particular limitation on the method of heat input to the sample, as long as it achieves the purpose of this application. For example, the heating method can be resistance wire heating, flame heating, high-temperature plasma spray gun, or friction heating. This application also does not impose any particular limitation on the heating rate of the sample, as long as it achieves the purpose of this application. For example, the heating rate can be from 200℃ / min to 600℃ / min.

[0066] In this application, the inventors, focusing on the flame-retardant protection requirements of titanium alloys, introduce a high-flame-threshold metal-based flame-retardant coating to improve the flame-threshold value of the titanium alloy substrate, based on the perspective of increasing the flame-threshold factor. Furthermore, based on existing flame-retardant coatings, a flame-retardant layer is introduced, improving the coating's heat insulation and wear resistance properties while simultaneously increasing its flame-threshold value. This yields a method for determining a titanium-fire-resistant, flame-retardant, and wear-resistant composite coating, achieving a significant increase in the flame-threshold value (critical pressure, ignition temperature, etc.) of the titanium alloy flame-retardant and wear-resistant coating for aero-engines compared to the metal substrate. Further in-depth research and optimization of this technical solution will bring about a leapfrog development in the flame-retardant performance of titanium alloy blades and casings for aero-engines, significantly improving the service stability and safety of aero-engines. This application not only provides new ideas and approaches for solving the "titanium fire" problem in aero-engines but also provides theoretical basis and technical support for the selection of coating materials for existing and under-development high thrust-to-weight ratio aero-engines, playing a crucial role in improving the thrust and lifespan of aero-engines.

[0067] Example

[0068] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0069] Test methods and equipment:

[0070] Coating thickness test:

[0071] A field emission scanning electron microscope (SEM) was used to photograph the cross section of a sample with a flame-resistant and wear-resistant composite coating. The SEM images of the sample were obtained, and the coating thickness at three different locations in the SEM images was measured. The average value of the three measurements was taken as the coating thickness.

[0072] Combustion performance test:

[0073] According to ASTM G124, "Standard Test Method for Determination of Combustion Characteristics of Metallic Materials in Oxygen-Enriched Environments," the specimens prepared in various embodiments or comparative examples were ignited using a vibration loading method with a load of 100N to 200N, a rotation speed of 1000 r / min, and a contact heat input method of 3s. The critical pressure P and ignition temperature T of the above specimens were tested. i .

[0074] Bonding strength test:

[0075] The adhesion of the flame-retardant and abrasion-resistant composite coating was tested according to the aviation industry standard HB 5476-1991, "Test Method for Bond Strength of Thermally Sprayed Coatings". According to this standard, the adhesion strength should not be less than 10 MPa. Five parallel samples were tested for each embodiment or comparative example, and the adhesion strength is expressed as the average value ± tolerance.

[0076] Surface hardness test:

[0077] The hardness of the wearable layer (top layer) of the flame-retardant wearable composite coating was tested according to the aviation industry standard HB 5486-1991 "Test Method for Hardness of Thermally Sprayed Coatings". According to this standard, the Rockwell hardness should be between 40 and 60 HR15Y. Three parallel samples were tested for each embodiment or comparative example, and the surface layer hardness is expressed as the average value ± tolerance.

[0078] Thermal shock performance test:

[0079] The thermal shock performance of the flame-retardant and abrasion-resistant composite coating was tested according to the AVIC standard Q / AVIC 06016.1-2013 "Coating Thermal Shock Test Method". A thermal shock testing machine with automatic sample loading and unloading function was selected. The sample specifications were: a circular disc with a diameter of 30 mm and a thickness of 5 mm. The samples prepared in each embodiment or comparative example were placed in the thermal shock testing machine and held at a set temperature of 600℃ for no less than 4 minutes (e.g., 5 minutes). Then, the samples were quickly immersed in water at a temperature not exceeding 30℃ (e.g., 25℃) for no less than 5 seconds. This cycle was required to be repeated at least 10 times, without any spalling with a maximum width of 2 mm. If no spalling with a maximum width of 2 mm occurred, the coating was considered intact. Ten parallel samples from each embodiment or comparative example were tested, and all ten parallel samples met the requirements.

[0080] Bending resistance test:

[0081] The bending resistance of the specimens was tested according to the AVIC standard Q / AVIC 06015.1-2013 "Method for Room Temperature Bending Test of Coatings". The specimens, with dimensions of 100mm × 10mm × 2mm, were prepared according to the preparation processes of the various embodiments or comparative examples below. Using a support shaft with a diameter of 12.5mm, the coated specimen was bent to 90°. The coating should not exhibit any lifting or peeling, but cracks are permissible; defects within a 2mm area at the edge of the specimen are disregarded. Five parallel specimens were tested for each embodiment or comparative example, and all five parallel specimens met the requirements.

[0082] Example 1

[0083] Pretreatment: The titanium alloy substrate TC11 was cut into block samples of 6mm×8mm×30mm. The sprayed surface of the sample was 6mm×8mm. Then, the sprayed surface was polished with 240-grit, 600-grit and 1000-grit sandpaper in sequence. Then, it was cleaned (degreasing, oil removal and pickling) and sandblasted to obtain a sample with a sprayed surface roughness of 6.3μm for later use.

[0084] S1: An adhesive layer was prepared on the sample spraying surface using plasma spraying technology. The adhesive layer used NiCrAl alloy powder.

[0085] S2: A flame-retardant layer is prepared on the surface of the adhesive layer using plasma spraying technology. The flame-retardant layer uses Cr powder.

[0086] S3: A heat insulation layer is prepared on the surface of the flame-retardant layer using plasma spraying technology. The heat insulation layer uses yttrium-stabilized zirconium oxide (ZrO2-8Y2O3, 8YSZ) powder.

[0087] S4: A wearable layer is prepared on the surface of the insulation layer using flame spraying technology. The wearable layer is made of nickel-chromium-aluminum-bentonite (NiCrAl.Be) powder.

[0088] The plasma spraying was performed using a plasma spraying equipment (LBP100). The operating parameters for the plasma spraying technology were: argon flow rate of 50 L / min, hydrogen flow rate of 2 L / min, operating current of 450 A, operating voltage of 60 V, powder feed rate of 40 g / min, spray gun speed of 460 mm / s, and spraying distance of 90 mm. The flame spraying was performed using a QSH-4 oxyacetylene spray gun. The operating parameters for the flame spraying technology were: oxygen-fuel ratio of 3:1, spray gun speed of 750 mm / s, spraying distance of 300 mm, and powder feed rate of 36 g / min. The thicknesses of the adhesive layer, flame-retardant layer, heat insulation layer, and wear-resistant layer are shown in Table 2.

[0089] Example 2

[0090] Except for the preparation of a flame-resistant and wear-resistant composite coating on the sample spraying surface of the titanium alloy substrate according to the following steps, the rest is the same as in Example 1.

[0091] S1: An adhesive layer was prepared on the sample spraying surface using plasma spraying technology. The adhesive layer used NiCrAl alloy powder.

[0092] S2: A flame-retardant layer is prepared on the surface of the adhesive layer using plasma spraying technology. The flame-retardant layer uses Cr powder.

[0093] S3: A wearable layer is prepared on the surface of the flame-retardant layer using flame spraying technology. The wearable layer uses NiCrAl.Be powder.

[0094] Example 3

[0095] Except for the preparation of a flame-resistant and wear-resistant composite coating on the sample spraying surface of the titanium alloy substrate according to the following steps, the rest is the same as in Example 1.

[0096] S1: A flame-retardant layer is prepared on the sample spraying surface using plasma spraying technology. The flame-retardant layer uses Cr powder.

[0097] S2: A heat insulation layer is prepared on the surface of the flame-retardant layer using plasma spraying technology, and the heat insulation layer uses 8YSZ powder.

[0098] S3: A wearable layer is prepared on the surface of the heat insulation layer using flame spraying technology. The wearable layer uses NiCrAl.Be powder.

[0099] Example 4

[0100] Except for the preparation of a flame-resistant and wear-resistant composite coating on the sample spraying surface of the titanium alloy substrate according to the following steps, the rest is the same as in Example 1.

[0101] S1: A flame-retardant layer is prepared on the sample spraying surface using plasma spraying technology. The flame-retardant layer uses Cr powder.

[0102] S2: A wearable layer is prepared on the surface of the flame-retardant layer using flame spraying technology. The wearable layer uses NiCrAl.Be powder.

[0103] Examples 5 to 9

[0104] Except for adjusting the material of the flame-retardant layer according to Table 2, everything else is the same as in Example 1.

[0105] Examples 10 to 11

[0106] Except for adjusting the thickness of the flame-retardant layer according to Table 2, everything else is the same as in Example 1.

[0107] Comparative Example 1

[0108] The titanium alloy substrate TC11 was treated with the same pretreatment steps as in Example 1, and the resulting sample was used as a test specimen.

[0109] Comparative Example 2

[0110] Except for obtaining the existing flame-retardant coating on the sample spraying surface of the titanium alloy substrate according to the following steps, the rest is the same as in Example 1.

[0111] S1: An adhesive layer was prepared on the sample spraying surface using plasma spraying technology. The adhesive layer used NiCrAl alloy powder.

[0112] S2: A heat insulation layer is prepared on the surface of the adhesive layer using plasma spraying technology. The heat insulation layer uses 8YSZ.

[0113] S3: A wearable layer is prepared on the surface of the heat insulation layer using flame spraying technology. The wearable layer uses NiCrAl.Be powder.

[0114] The relevant parameters for each embodiment and comparative example are shown in Tables 2 and 3.

[0115] Table 2

[0116]

[0117] Note: In Table 2, " / " indicates that the corresponding substance or parameter does not exist. The data on critical pressure increase and ignition temperature increase are the increase values ​​compared to the titanium alloy matrix of Comparative Example 1.

[0118] Table 3

[0119]

[0120] Referring to Tables 2 and 3, from Examples 1 to 11, and Comparative Examples 1 and 2, it can be seen that the flame-retardant and wear-resistant composite coating within the scope of this application can improve the flame-retardant performance of the titanium alloy substrate. Simultaneously, it possesses excellent mechanical properties, such as bonding performance, surface hardness, thermal shock resistance, and bending resistance, meeting the requirements for aero-engine use. Compared to Comparative Example 1, the critical pressure and ignition temperature are increased. The critical pressure increase is ≥0.16 MPa, with a maximum increase of 0.56 MPa, representing an increase of more than four times; the ignition temperature increase is not less than 102.96℃. This demonstrates that the flame-retardant and wear-resistant composite coating of this application can significantly improve the combustion performance of the titanium alloy substrate. Compared to the existing flame-retardant coating in Comparative Example 2, the samples in this application have higher critical pressure, ignition temperature, and bonding strength, as well as higher surface hardness. The surface hardness value meets the requirements of the aviation industry national standard HB 5486-1991, ensuring the wear resistance of the surface layer. Furthermore, in the thermal shock test, the number of water cooling cycles at 600°C is greater, and no warping or peeling occurs when bending at 90°, and no cracks appear in the surface layer. This indicates that the flame-retardant wear-resistant composite coating of this application has higher flame resistance and better mechanical properties.

[0121] As can be seen from Examples 1 to 4, the fire-resistant and wear-resistant composite coatings with different structures provided in this application, when applied to the surface of the titanium alloy substrate, can increase the critical pressure and ignition temperature, indicating that they are beneficial to improving the fire resistance of the titanium alloy substrate.

[0122] As can be seen from Examples 1, 5 to 11, selecting a coating with a value of f within the range of this application as a flame-retardant layer can increase the critical pressure and ignition temperature, indicating that it is beneficial to improve the flame-retardant performance of the titanium alloy substrate.

[0123] Figure 5 The critical pressure comparison diagrams of different structures of flame-retardant abrasive composite coatings in Examples 1 to 4, Comparative Examples 1 and 2 are shown. Figure 5 It can be seen that the critical pressure of the flame-retardant wear-resistant composite coating within the scope of this application is significantly higher than that of the titanium alloy substrate and existing flame-retardant coatings.

[0124] Figure 6 Here is a scanning electron microscope image of the flame-retardant and wear-resistant composite coating sample from Example 1, as shown below. Figure 6 As shown, the surface of the titanium alloy substrate 10 is sequentially provided with an adhesive layer 23, a flame-retardant layer 21, a heat insulation layer 24, and a wearable layer 22. It can be seen that the flame-retardant and wearable composite coating prepared in Example 1 has good interfacial bonding between the layers and a uniform distribution of the structure of each layer.

[0125] Figure 7 The ignition temperature curve of the flame-retardant abrasive composite coating sample in Example 1 is shown. Figure 7It can be seen that the flame-retardant and wear-resistant composite coating sample of Example 1 has a high ignition temperature of 835.7℃.

[0126] It should be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0127] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0128] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for determining a flame-retardant and wear-resistant composite coating, comprising the following steps: The flame-retardant and wear-resistant composite coating consists of an adhesive layer, a flame-retardant layer, a heat-insulating layer, and a wear-resistant layer sequentially disposed on the surface of the titanium alloy substrate; the material of the flame-retardant layer is selected from Cr. m Ni n Alloy, 0≤n≤100, m=100-n; the material of the adhesive layer is selected from NiCrAl, NiCrAlY, NiAl or TiCrAl; the material of the heat insulation layer is selected from ZrO2-xY2O3, Al2O3, cBN or SiC, 6≤x≤8; based on the combustion threshold factor, the characteristic parameters affecting the combustion of the coating material are determined, and the expression of the combustion threshold factor is: ； Where f represents the combustion threshold factor, h represents the coating thickness, D represents the oxygen diffusion resistance coefficient, K represents the oxygen adsorption rate on the coating surface, and Kc represents the coating reaction coefficient. The characteristic parameters include at least one of the following: coating thickness h, oxygen diffusion resistance coefficient D, oxygen adsorption rate K on the coating surface, and coating reaction coefficient Kc. The measured values ​​of characteristic parameters of multiple candidate coating materials are obtained and substituted into the expression of the combustion threshold factor to obtain f. The candidate coating materials with f ranging from 1.25 to 2.28 are determined as the flame-retardant layer materials.

2. The determination method according to claim 1, wherein, The material of the wearable layer is selected from metal-based bentonite composite powder, metal-based graphite alloy powder, or aluminum-silicon powder.

3. The determination method according to claim 1, wherein, The titanium alloy matrix includes TC11, TC4, TC17, Ti40, Ti14, TC25G, or Ti2AlNb.

4. The determination method according to claim 1, wherein, The thickness of the flame-retardant layer is 70μm to 130μm, and the thickness of the wear-resistant layer is not less than 600μm.

5. The determination method according to claim 1, wherein, The thickness of the adhesive layer is 70 μm to 130 μm; the thickness of the thermal insulation layer is 150 μm to 250 μm.

6. A flame-retardant abrasive composite coating, determined by the method for determining a flame-retardant abrasive composite coating according to any one of claims 1 to 5.

7. The flame-retardant and wear-resistant composite coating according to claim 6, wherein, The flame-retardant layer is prepared by plasma spraying technology, and the wear-resistant layer is prepared by flame spraying technology.

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