W-Re alloy with an anti-ablation composite coating on its surface and a method for preparing an anti-ablation composite coating on the surface of W-Re alloy.

Abstract

The invention relates to a W-Re alloy with an anti-ablation composite coating on its surface and a method for preparing the anti-ablation composite coating on the surface of the W-Re alloy. The method involves sequentially depositing a tungsten oxide layer and a high-entropy alloy coating on the surface of the alloy substrate from the inside out. The high-entropy alloy coating is (WMoNbTaHf)Cx, and x = 1–3 wt%. This invention improves the brittleness of the tungsten oxide coating on the surface of the W-Re alloy and increases the ablation resistance temperature of the anti-ablation coating.

Description

Technical Field

[0001] This invention relates to the technical field of W-Re alloy anti-ablation composite coating, specifically to a W-Re alloy with an anti-ablation composite coating on its surface and a method for preparing an anti-ablation composite coating on the surface of a W-Re alloy. Background Technology

[0002] As advanced aircraft Mach numbers increase and high-thrust rockets improve specific impulse, the service temperature of hot-end components rises, placing increasingly higher demands on the ablation resistance of refractory materials. W-Re alloy (tungsten-rhenium alloy), a solid solution-strengthened alloy with W (tungsten) as the matrix and Re (rhenium) as the component, is widely used in aerospace hot-end components due to its excellent high-temperature performance and physical properties. To improve the ablation resistance of W-Re, sintering, embedding, and plasma spraying methods are often used to prepare ablation-resistant composite coatings (such as tungsten oxide coatings, silicides, aluminides, carbides, borides, etc.) on its surface.

[0003] However, as the service temperature of hot-end components increases to 2200℃ or even 3000℃, the applicant discovered in their research that under extreme high-temperature conditions of 3000℃, the tungsten oxide coating on the surface of the tungsten-rhenium alloy exhibits poor adhesion and brittle cracking. Under the scouring of high-temperature, high-speed airflow, the ablation-resistant composite coating undergoes brittle cracking and peels off, failing. Even coating the tungsten oxide coating with a ceramic layer cannot improve its brittleness; that is, the overall ablation-resistant composite coating exhibits brittleness. Summary of the Invention

[0004] To address the issues of poor adhesion and brittle cracking of tungsten oxide coatings on the surface of tungsten-rhenium alloys in existing technologies, this invention provides a W-Re alloy with an anti-ablation composite coating on its surface and a method for preparing the anti-ablation composite coating on the surface of the W-Re alloy. This improves the brittleness of the tungsten oxide coating on the W-Re alloy surface and increases the ablation resistance temperature of the anti-ablation composite coating.

[0005] To achieve the above objectives, the specific solution adopted by the present invention is as follows: a W-Re alloy with an anti-ablation composite coating on its surface, wherein a tungsten oxide layer and a high-entropy alloy coating are sequentially disposed on the surface of the alloy substrate from the inside to the outside, the high-entropy alloy coating being (WMoNbTaHf)Cx, and x = 1~3wt%.

[0006] As an optimized solution for the W-Re alloy with an anti-ablation composite coating on the surface mentioned above, the thickness of the tungsten oxide layer is 30-80 μm.

[0007] As another optimized option for the W-Re alloy with an anti-ablation composite coating on its surface, the thickness of the high-entropy alloy coating is 50-100 μm.

[0008] A method for preparing an ablation-resistant composite coating on the surface of a W-Re alloy involves treating the surface of the alloy substrate and forming a tungsten oxide layer on its surface using micro-arc oxidation.

[0009] Polish the tungsten oxide layer;

[0010] 20wt%-50wt% of tungsten powder, 10wt%-30wt% of molybdenum powder, 5wt%-20wt% of niobium powder, 10wt%-30wt% of tantalum powder, 1wt%-20wt% of hafnium powder and 1wt%-3wt% of carbon powder are mixed to obtain a uniform powder, and the mixed powder is sprayed onto the surface of tungsten oxide layer to form a high-entropy alloy coating.

[0011] An optimized approach to the aforementioned method for preparing an ablation-resistant composite coating on the surface of a W-Re alloy is as follows: The process of forming a tungsten oxide layer on the W-Re alloy surface using micro-arc oxidation involves using the W-Re alloy as the anode and stainless steel as the cathode. The W-Re alloy and stainless steel are placed in a Na2SiO3 electrolyte at a temperature of 5-80℃ for micro-arc oxidation. The process parameters for micro-arc oxidation are: voltage 400-600V, current density 1-10A / dm³. 2 .

[0012] As another optimized method for preparing an ablation-resistant composite coating on the surface of the aforementioned W-Re alloy, the pH of the Na2SiO3 electrolyte is 12-14.

[0013] As another optimization of the above-mentioned method for preparing an ablation-resistant composite coating on the surface of W-Re alloy, the grinding depth of the tungsten oxide layer is 5-10 μm.

[0014] As another optimized method for preparing an ablation-resistant composite coating on the surface of the aforementioned W-Re alloy, the particle size of tungsten, molybdenum, niobium, tantalum and hafnium powders is 50-100 nm, and the particle size of carbon powder is 100-200 nm.

[0015] As an alternative optimization of the above-mentioned method for preparing an ablation-resistant composite coating on the surface of a W-Re alloy, the mixed powder is sprayed onto the surface of the tungsten oxide layer by high-speed plasma thermal spraying.

[0016] As another optimized method for preparing an ablation-resistant composite coating on the surface of the aforementioned W-Re alloy, the process parameters of the high-speed plasma thermal spraying method are: flame velocity of 500-1200 m / s and mixed powder spraying velocity of 200-700 m / s.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] This invention provides a W-Re alloy with an anti-ablation composite coating on its surface and a method for preparing the anti-ablation composite coating on the surface of the W-Re alloy. The anti-ablation composite coating includes a tungsten oxide layer and a high-entropy alloy coating sequentially disposed from the inside to the outside of the alloy substrate surface. Specifically, the alloy substrate surface is subjected to micro-arc oxidation to instantly and in-situ grow a firmly bonded tungsten oxide layer. A (WMoNbTaHf)Cx high-entropy alloy coating is sprayed onto the tungsten oxide layer, filling the micropores within the tungsten oxide layer. Simultaneously, the tungsten oxide, as a second phase particle, strengthens the hardness and adhesion of the high-entropy alloy coating, improving the coating adhesion and thus alleviating the brittleness problem of the tungsten oxide layer, improving the stability of the high-entropy alloy coating, and increasing the service life and service temperature of the anti-ablation composite coating. The addition of C to the high-entropy alloy coating preferentially reacts with Hf to form an HfC reinforcing phase, further improving the ablation resistance temperature of the anti-ablation composite coating. Detailed Implementation

[0019] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. Parts not described or disclosed in detail in the following embodiments of the present invention should be understood as prior art known or should be known by those skilled in the art, such as how to prepare alloy matrix, etc.

[0020] Example 1

[0021] A W-Re alloy with an anti-ablation composite coating is disclosed. From the inside out, a tungsten oxide layer and a high-entropy alloy coating are sequentially deposited on the surface of the alloy substrate. The thickness of the tungsten oxide layer is 30-80 μm; the thickness of the high-entropy alloy coating is 50-100 μm, and the high-entropy alloy coating is (WMoNbTaHf)Cx, where x = 1-3 wt%. A firmly bonded tungsten oxide layer is grown in situ on the alloy substrate surface, and the high-entropy alloy coating is sprayed onto the surface of the tungsten oxide layer, filling the micropores within the tungsten oxide layer. The tungsten oxide, acting as a second phase particle, strengthens the hardness and adhesion of the high-entropy alloy coating, improving the coating's adhesion and thus mitigating the brittleness of the tungsten oxide layer. Simultaneously, it enhances the stability of the high-entropy alloy coating. The synergistic strengthening effect of the tungsten oxide layer and the high-entropy alloy coating effectively improves the ablation resistance of the W-Re alloy. Furthermore, the C atoms in the high-entropy alloy coating preferentially react with Hf to form an HfC ceramic reinforcing phase, increasing the ablation temperature and density of the anti-ablation composite coating.

[0022] Example 2

[0023] A method for preparing an ablation-resistant composite coating on the surface of a W-Re alloy involves using micro-arc oxidation to form a tungsten oxide layer on the alloy substrate surface, followed by high-entropy alloy coating sprayed onto the tungsten oxide layer using high-speed plasma spraying. Specifically, micro-arc oxidation refers to enhancing the anodic reaction by utilizing arc discharge on top of anodic oxidation, thereby forming a high-quality tungsten oxide layer on the alloy substrate surface. The tungsten oxide layer grows in situ on the alloy substrate surface and has a strong adhesion to the alloy substrate. High-speed plasma spraying uses an ion arc as a heat source to heat the high-entropy alloy powder to a semi-molten state and spray it onto the tungsten oxide layer at high speed, forming a firmly adhered high-entropy alloy coating. Tungsten oxide, as a second-phase ion, strengthens the interfacial strength between the alloy substrate and the high-entropy alloy coating, improving the adhesion of the ablation-resistant composite coating and thus mitigating the brittleness problem of the tungsten oxide coating.

[0024] Specifically, the following steps are included:

[0025] The alloy substrate surface is treated by mechanical polishing and alcohol cleaning to remove surface impurities. Then, a tungsten oxide layer is formed on its surface using micro-arc oxidation. Specifically, W-Re alloy is used as the anode, and stainless steel is selected as the cathode. The W-Re alloy and stainless steel are placed in a Na2SiO3 electrolyte at a temperature of 5-80℃ and a pH of 12-14 for micro-arc oxidation. The process parameters for micro-arc oxidation are: voltage 400-600V, current density 1-10A / dm³. 2 The micro-arc oxidation time is 10-60 min. After the micro-arc oxidation is completed, the W-Re alloy is taken out of the electrolyte and rinsed with clean water to remove residual electrolyte and impurities.

[0026] The tungsten oxide layer is polished to a depth of 5-10 μm to remove the porous structure on the surface of the tungsten oxide layer. After polishing, the surface of the tungsten oxide layer is wiped with alcohol.

[0027] 20wt%-50wt% of tungsten powder, 10wt%-30wt% of molybdenum powder, 5wt%-20wt% of niobium powder, 10wt%-30wt% of tantalum powder, 1wt%-20wt% of hafnium powder, and 1wt%-3wt% of carbon powder are mixed to obtain a uniform powder. The particle size of the tungsten, molybdenum, niobium, tantalum, and hafnium powders is 50-100 nm, and the particle size of the carbon powder is 100-200 nm. The tungsten, molybdenum, niobium, tantalum, hafnium, and carbon powders are mixed uniformly using a mechanical ball milling method to obtain a mixed powder. The mixed powder is then sprayed onto the surface of a tungsten oxide layer to form... The high-entropy alloy coating is formed by spraying mixed powder onto the surface of a tungsten oxide layer using a high-speed plasma thermal spraying method. The process parameters of the high-speed plasma thermal spraying method are: flame velocity of 500-1200 m / s, mixed powder spraying velocity of 200-700 m / s, and spraying time of 10-30 min. The mixed powder is melted by high-temperature plasma to form a hot slurry that is sprayed onto the surface of the tungsten oxide layer, forming (WMoNbTaHf)Cx (x = 1-3 wt%) on its surface. After spraying, the high-entropy alloy coating is cooled.

[0028] In this embodiment, a method for preparing an ablation-resistant composite coating on a W-Re alloy surface includes the following steps:

[0029] The surface of an alloy substrate with dimensions of φ40×10mm was mechanically polished and cleaned with alcohol. Then, the treated alloy substrate was used as the anode and stainless steel as the cathode, and the electrodes were placed in a Na2SiO3 electrolyte with a pH of 12. The electrolyte temperature was adjusted to 40℃, the voltage to 400V, and the current density to 5A / dm³. 2 The micro-arc oxidation time was 40 min, forming a 60 μm thick tungsten oxide layer on the surface of the alloy substrate; the micro-arc oxidized alloy substrate was removed from the electrolyte and rinsed clean with water.

[0030] The tungsten oxide layer was polished to a depth of 5μm, and then wiped with alcohol.

[0031] The 80nm tungsten powder (50wt%), molybdenum powder (30wt%), niobium powder (5wt%), tantalum powder (10wt%), hafnium powder (2wt%), and 80nm carbon powder (3wt%) were mixed evenly by mechanical ball milling to form a mixed powder. The mixed powder was placed in a spray gun, and the flame velocity was adjusted to 800m / s and the mixed powder spraying velocity was adjusted to 500m / s. After spraying for 20 minutes, a (WMoNbTaHf)Cx (x=1~3wt%) high-entropy alloy coating with a thickness of 80μm was formed on the surface of the tungsten oxide layer.

[0032] After spraying, the high-entropy alloy coating is cooled. The tungsten oxide layer and the high-entropy alloy coating form an ablation-resistant composite coating, the properties of which are shown in Table 1.

[0033] Example 3

[0034] A method for preparing an ablation-resistant composite coating on a W-Re alloy surface includes the following steps:

[0035] The surface of an alloy substrate with dimensions of φ40×10mm was mechanically polished and cleaned with alcohol. Then, the treated alloy substrate was used as the anode and stainless steel as the cathode, and the electrodes were placed in a Na2SiO3 electrolyte with a pH of 14. The electrolyte temperature was adjusted to 45℃, the voltage to 500V, and the current density to 8A / dm³. 2 The micro-arc oxidation time was 40 min, forming an 80 μm thick tungsten oxide layer on the surface of the alloy substrate. The micro-arc oxidized alloy substrate was then removed from the electrolyte and rinsed with clean water.

[0036] The tungsten oxide layer was polished to a depth of 5μm, and then wiped with alcohol.

[0037] The tungsten powder (20 wt%), molybdenum powder (10 wt%), niobium powder (20 wt%), tantalum powder (30 wt%), hafnium powder (20 wt%), and 80 nm carbon powder (1 wt%) were mixed uniformly using a mechanical ball milling method. The mixed powder was placed in a spray gun, and the flame velocity was adjusted to 800 m / s and the mixed powder spraying velocity was adjusted to 500 m / s. After spraying for 16 min, a (WMoNbTaHf)Cx (x = 1~3 wt%) high-entropy alloy coating with a thickness of 60 μm was formed on the surface of the tungsten oxide layer.

[0038] After spraying, the high-entropy alloy coating is cooled. The tungsten oxide layer and the high-entropy alloy coating form an ablation-resistant composite coating, the properties of which are shown in Table 1.

[0039] Example 4

[0040] A method for preparing an ablation-resistant composite coating on a W-Re alloy surface includes the following steps:

[0041] The surface of an alloy substrate with dimensions of φ30×5mm was mechanically polished and cleaned with alcohol. Then, the treated alloy substrate was used as the anode and stainless steel as the cathode, and the electrodes were placed in a Na2SiO3 electrolyte with a pH of 14. The electrolyte temperature was adjusted to 40℃, the voltage to 450V, and the current density to 8A / dm³. 2 The micro-arc oxidation time was 45 min, forming a 60 μm thick tungsten oxide layer on the surface of the alloy substrate; the micro-arc oxidized alloy substrate was removed from the electrolyte and rinsed with clean water.

[0042] The tungsten oxide layer was polished to a depth of 5μm, and then wiped with alcohol.

[0043] The 80nm tungsten powder (50wt%), molybdenum powder (30wt%), niobium powder (5wt%), tantalum powder (10wt%), hafnium powder (2wt%), and 80nm carbon powder (3wt%) were mixed evenly by mechanical ball milling to form a mixed powder. The mixed powder was placed in a spray gun, and the flame velocity was adjusted to 900m / s and the mixed powder spraying velocity was adjusted to 600m / s. After spraying for 10 minutes, a 50μm thick (WMoNbTaHf)Cx (x=1~3wt%) high-entropy alloy coating was formed on the surface of the tungsten oxide layer.

[0044] After spraying, the high-entropy alloy coating is cooled. The tungsten oxide layer and the high-entropy alloy coating form an ablation-resistant composite coating, the properties of which are shown in Table 1.

[0045] Example 5

[0046] A method for preparing an ablation-resistant composite coating on a W-Re alloy surface includes the following steps:

[0047] The surface of an alloy substrate with dimensions of φ30×5mm was mechanically polished and cleaned with alcohol. Then, the treated alloy substrate was used as the anode and stainless steel as the cathode, and the electrodes were placed in a Na2SiO3 electrolyte with a pH of 13. The electrolyte temperature was adjusted to 40℃, the voltage to 400V, and the current density to 8A / dm³. 2 The micro-arc oxidation time was 40 min, forming a tungsten oxide layer with a thickness of 50 μm on the surface of the alloy substrate; the micro-arc oxidized alloy substrate was removed from the electrolyte and rinsed with clean water.

[0048] The tungsten oxide layer was polished to a depth of 5μm, and then wiped with alcohol.

[0049] The 80nm tungsten powder (50wt%), molybdenum powder (30wt%), niobium powder (5wt%), tantalum powder (10wt%), hafnium powder (2wt%), and 80nm carbon powder (3wt%) were mixed evenly by mechanical ball milling to form a mixed powder. The mixed powder was placed in a spray gun, and the flame velocity was adjusted to 900m / s and the mixed powder spraying velocity was adjusted to 600m / s. After spraying for 20min, a 60μm thick (WMoNbTaHf)Cx (x=1~3wt%) high-entropy alloy coating was formed on the surface of the tungsten oxide layer.

[0050] After spraying, the high-entropy alloy coating is cooled. The tungsten oxide layer and the high-entropy alloy coating form an ablation-resistant composite coating, the properties of which are shown in Table 1.

[0051] Table 1 Performance parameters of the ablation-resistant composite coatings in Examples 2-5

[0052] Comparative Example

[0053] The surface of an alloy substrate with dimensions of φ30×5mm was mechanically polished and cleaned with alcohol. Then, the treated alloy substrate was used as the anode and stainless steel as the cathode, and the electrodes were placed in a Na2SiO3 electrolyte with a pH of 13. The electrolyte temperature was adjusted to 40℃, the voltage to 400V, and the current density to 8A / dm³. 2 The micro-arc oxidation time was 40 min, forming a tungsten oxide layer with a thickness of 50 μm on the surface of the alloy substrate. The alloy substrate after micro-arc oxidation was removed from the electrolyte and rinsed with clean water. The adhesion strength of the anti-ablation composite coating was 43 MPa. It was easily peeled off under high-speed airflow and exhibited brittleness.

[0054] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an ablation-resistant composite coating on the surface of a W-Re alloy, characterized in that: The surface of the alloy substrate is treated, and a tungsten oxide layer is formed on its surface using micro-arc oxidation; The tungsten oxide layer is polished; the polishing depth of the tungsten oxide layer is 5-10 μm. A uniform powder is prepared by mixing 20wt% - 50wt% tungsten powder, 10wt% - 30wt% molybdenum powder, 5wt% - 20wt% niobium powder, 10wt% - 30wt% tantalum powder, 1wt% - 20wt% hafnium powder, and 1wt% - 3wt% carbon powder. The mixed powder is then sprayed onto the surface of a tungsten oxide layer to form a high-entropy alloy coating. The mixed powder is then sprayed onto the surface of the tungsten oxide layer using a high-speed plasma thermal spraying method. The process parameters for the high-speed plasma thermal spraying method are: flame velocity of 500-1200 m / s and spray velocity of the mixed powder of 200-700 m / s. The ablation-resistant composite coating consists of a tungsten oxide layer and a high-entropy alloy coating sequentially disposed from the inside to the outside on the surface of the alloy substrate. The high-entropy alloy coating is (WMoNbTaHf)Cx, and x = 1~3wt%.

2. The method for preparing an ablation-resistant composite coating on a W-Re alloy surface as described in claim 1, characterized in that: The process of forming a tungsten oxide layer on the surface of W-Re alloy using micro-arc oxidation involves using the W-Re alloy as the anode and stainless steel as the cathode. The W-Re alloy and stainless steel are placed in a Na2SiO3 electrolyte at a temperature of 5-80℃ for micro-arc oxidation. The process parameters for micro-arc oxidation are: voltage 400-600V and current density 1-10A / dm³. 2 .

3. The method for preparing an ablation-resistant composite coating on a W-Re alloy surface as described in claim 2, characterized in that: The pH of the Na2SiO3 electrolyte is 12-14.

4. The method for preparing an ablation-resistant composite coating on a W-Re alloy surface as described in claim 1, characterized in that: The particle size of tungsten, molybdenum, niobium, tantalum and hafnium powders is 50-100 nm, and the particle size of carbon powder is 100-200 nm.

5. The method for preparing an ablation-resistant composite coating on a W-Re alloy surface as described in claim 1, characterized in that: The thickness of the tungsten oxide layer is 30-80 μm.

6. The method for preparing an ablation-resistant composite coating on a W-Re alloy surface as described in claim 1, characterized in that: The thickness of the high-entropy alloy coating is 50-100 μm.

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