A method for making a tungsten-rhenium alloy having an ablative-resistant composite coating

Abstract

A method for preparing a tungsten-rhenium alloy with an ablation-resistant composite coating is disclosed, relating to the field of tungsten-rhenium alloy surface coating technology. The coating comprises a transition layer and an HfCN layer distributed sequentially from the inside to the outside of the alloy material surface. The transition layer is a structure consisting of a tungsten mesh and an HfC phase embedded within the tungsten mesh, exhibiting both mechanical interlocking and metallurgical bonding. This invention yields a thin, dense ablation-resistant composite coating with high bonding strength to the substrate, and uniform nitrogen penetration.

Description

Technical Field

[0001] This invention relates to the field of tungsten-rhenium alloy surface coating technology, specifically to an ablation-resistant composite coating and a method for preparing tungsten-rhenium alloy with an ablation-resistant composite coating. Background Technology

[0002] Tungsten-rhenium alloys (W-Re alloys) possess high melting points, excellent high-temperature strength, and good thermal shock resistance, making them widely used in extreme heat flow components such as rocket engine nozzles, nuclear fusion divertors, and nose cones of hypersonic vehicles. However, these components often operate in extreme environments involving ultra-high temperatures, strong erosion, and oxidative ablation. The alloy surface undergoes rapid ablation due to high-temperature gas flow and chemical corrosion, severely reducing its service life and reliability. Therefore, it is crucial to prepare high-performance ablation-resistant coatings on the surface of tungsten-rhenium alloys to enhance the components' resistance to extreme environments.

[0003] Currently, hafnium carbonitride (HfCN) coatings combine the advantages of both hafnium carbide (HfC) and hafnium nitride (HfN), possessing ultra-high melting point, high hardness, excellent chemical stability, and superior ablation resistance, making them ideal materials for ultra-high temperature ablation-resistant coatings. The current methods for preparing HfCN coatings typically involve high-energy ball milling of hafnium powder or HfC powder in nitrogen or ammonia gas to synthesize HfCN powder, which is then plasma-sprayed onto a substrate to form HfCN powder. Alternatively, HfC and HfN powders can be mixed to form a hybrid powder, which is then laid on the substrate surface and sintered to ultimately form an HfCN coating. However, when preparing HfCN coatings on tungsten-rhenium alloy surfaces using these methods, the adhesion between the coating and the substrate is poor, and the thermal compatibility is also poor. Summary of the Invention

[0004] To address the issues of poor adhesion and thermal compatibility between HfCN coatings and tungsten-rhenium alloy substrates in existing technologies, this invention provides an ablation-resistant composite coating and a method for preparing a tungsten-rhenium alloy with the ablation-resistant composite coating. The resulting ablation-resistant composite coating is thin and dense, exhibits high adhesion strength to the substrate, and allows for uniform nitrogen penetration.

[0005] To achieve the above objectives, the specific solution adopted by the present invention is as follows: an anti-ablation composite coating, comprising a transition layer and an HfCN layer distributed sequentially from the inside to the outside of the alloy material surface, wherein the transition layer is a structure in which mechanical interlocking and metallurgical bonding coexist, formed by a tungsten mesh and the HfC phase embedded in the tungsten mesh.

[0006] As an optimized solution for the above-mentioned ablation-resistant composite coating: the HfCN layer is formed by plasma sintering of HfC powder into an HfC layer, and then by laser pulse nitriding to form the HfC layer.

[0007] As another optimization of the above-mentioned ablation-resistant composite coating, the thickness of the HfCN layer is 1-20 μm.

[0008] As another optimized solution for the above-mentioned ablation-resistant composite coating: the diameter of the tungsten wire in the tungsten mesh is 50-200μm, and the mesh diameter is 100-500μm.

[0009] A method for preparing a tungsten-rhenium alloy with an ablation-resistant composite coating involves sequentially laying a tungsten mesh and HfC powder from the inside out of the alloy material, and then using plasma sintering to form a transition layer and an HfC layer from the inside out. The transition layer is a structure in which mechanical interlocking and metallurgical bonding coexist between the tungsten mesh and the HfC phase embedded in the tungsten mesh. In a nitrogen atmosphere, the HfC layer is subjected to laser pulse nitriding to form an HfCN layer. The tungsten-rhenium alloy is obtained by cooling to room temperature.

[0010] As an optimized method for preparing the above-mentioned tungsten-rhenium alloy with an anti-ablation composite coating, the parameters for plasma sintering are: sintering temperature of 1600~1800℃, heating rate of 50~100℃ / min, sintering pressure of 30~50MPa, and sintering time of 10~15min.

[0011] As another optimized method for preparing the aforementioned tungsten-rhenium alloy with an anti-ablation composite coating, the parameters for laser pulse nitriding are as follows: laser power of 100~500W, pulse width of 50~200ns, pulse frequency of 10~100kHz, scanning speed of 50~500mm / s, spot diameter of 50~200μm, overlap rate of 30~60%, nitrogen pressure of 0.1~0.5MPa, and gas flow rate of 5~20L / min.

[0012] As another optimized method for preparing the above-mentioned tungsten-rhenium alloy with an ablation-resistant composite coating: after laser nitriding, the HfCN layer is kept at 1000~1200℃ for 1~2h.

[0013] As another optimized method for preparing the above-mentioned tungsten-rhenium alloy with an anti-ablation composite coating, the particle size of the HfC powder is 100nm~5μm.

[0014] A tungsten-rhenium alloy with an ablation-resistant composite coating was prepared using the above-described method.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention provides an ablation-resistant composite coating and a method for preparing a tungsten-rhenium alloy with the ablation-resistant composite coating. After laying a tungsten mesh and HfC powder on the surface of the alloy material, plasma sintering is performed to obtain a transition layer and an HfC layer. Then, laser pulse nitriding is performed on the HfC layer to obtain an HfCN layer, i.e., the tungsten mesh is introduced and the HfC phase is embedded within the tungsten mesh, forming a structure where mechanical interlocking and metallurgical bonding coexist. Simultaneously, atomic-scale metallurgical bonding is achieved through spark plasma sintering. The transition layer effectively buffers thermal stress, increasing the interfacial bonding strength to over 100 MPa, and exhibits no peeling after multiple thermal shocks. Nitrogen atoms in the HfCN layer completely and uniformly penetrate the entire thickness of the HfC layer.

[0016] 2. The HfCN layer obtained by this invention has strong hybridization bonds and a high oxidation energy barrier mechanism, that is, the competitive absorption of adjacent N to O inhibits the adsorption of Hf to O; at the same time, the obtained HfCN layer has excellent ablation resistance, with a linear ablation rate of only 0.6 μm / s. Attached Figure Description

[0017] Figure 1 These are SEM images of the cross-section of the HfCN coating prepared according to the present invention, wherein (a) is the SEM image of the cross-section of the HfCN coating, (b) is the surface scan result of element Hf, (c) is the surface scan result of element N, and (d) is the surface scan result of element C. Detailed Implementation

[0018] 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.

[0019] An ablation-resistant composite coating comprises a transition layer and an HfCN layer sequentially distributed from the inside out on the surface of an alloy material. The transition layer is a structure consisting of a tungsten mesh and HfC phase embedded within the tungsten mesh, exhibiting both mechanical interlocking and metallurgical bonding. The diameter of the tungsten wires in the tungsten mesh is 50-200 μm, and the mesh aperture diameter is 100-500 μm. The thickness of the HfCN layer is 1-20 μm. The HfC ceramic phase embedded in the pores of the tungsten mesh forms an interpenetrating network structure, while atomic-scale metallurgical bonding is achieved through spark plasma sintering. The gradient transition layer effectively buffers thermal stress, increasing the interfacial bonding strength to over 100 MPa, and exhibits no peeling after multiple thermal shocks. The intermediate layer of the tungsten mesh not only alleviates thermal stress, but its high-strength tungsten wire skeleton also effectively prevents the mechanical erosion and ablation of the coating by high-temperature, high-speed airflow. Even when microcracks appear locally in the coating, the tungsten mesh can prevent the cracks from propagating into the substrate, providing a "crack arrest" function and significantly improving the damage tolerance of the coating.

[0020] This invention also provides a method for preparing a tungsten-rhenium alloy with an ablation-resistant composite coating, comprising the following steps: An alloy material, which is tungsten-rhenium alloy powder or tungsten-rhenium alloy matrix, is placed inside a graphite mold. A tungsten mesh and HfC powder are then laid on the alloy material from the inside out. The tungsten wire diameter of the tungsten mesh is 50-200μm and the mesh size is 100-500μm. The purity of the HfC powder is ≥99.9% and the particle size is 100nm-5μm.

[0021] The filled mold is placed in a spark plasma sintering (SPCS) apparatus and plasma sintered under vacuum or argon protection to form a transition layer and an HfC layer. The plasma sintering parameters are: sintering temperature 1600~1800℃, heating rate 50~100℃ / min, sintering pressure 30~50MPa, and sintering time 10~15min. After sintering, the mold is cooled to room temperature in the furnace to obtain a composite preform. If tungsten-rhenium alloy powder is used, it forms a dense tungsten-rhenium alloy matrix after sintering. The transition layer is a structure consisting of a tungsten mesh and HfC phase embedded in the tungsten mesh, with both mechanical interlocking and metallurgical bonding. The surface is a continuous and dense HfC layer.

[0022] The composite preform was placed in the atmosphere-protected chamber of a laser processing platform. After evacuation, high-purity nitrogen gas was introduced, maintaining a nitrogen pressure of 0.1–0.5 MPa and a gas flow rate of 5–20 L / min. Laser pulse nitriding was then performed on the HfC layer to form an HfCN layer with a thickness of 1–20 μm. During laser pulse nitriding, nitrogen molecules dissociate into highly reactive nitrogen atoms, which diffuse into the HfC coating, replacing some of the C atoms in the non-metallic sublattice to form an HfCN solid solution ceramic phase. The parameters for laser pulse nitriding were: laser power 100–500 W, pulse width 50–200 ns, pulse frequency 10–100 kHz, scanning speed 50–500 mm / s, spot diameter 50–200 μm, and overlap rate 30–60%. After laser nitriding, the HfCN layer was held at 1000–1200 °C for 1–2 h. After laser pulse nitriding is completed, nitrogen gas flow is maintained for protection, and the material is allowed to cool naturally to room temperature to obtain a tungsten-rhenium alloy. Laser pulse heating limits the heat-affected zone to the coating and shallow surface areas, keeping the tungsten-rhenium matrix at room temperature or low temperature, thus preventing grain growth, recrystallization, or performance degradation in the W-Re alloy.

[0023] The ablation-resistant composite coating prepared by the above method can control the thickness of the HfCN layer and the C / N atomic ratio, so that the atomic ratio is C: 15%-30% and N: 30%-45%.

[0024] Example 1

[0025] A method for preparing a tungsten-rhenium alloy with an ablation-resistant composite coating includes the following steps: S1. Place a W-25Re alloy matrix (block structure) into a graphite mold, and then lay a tungsten mesh and HfC powder in sequence. The tungsten mesh has a tungsten wire diameter of 100μm and a mesh size of 200μm. The HfC powder has a purity of ≥99.9% and a particle size of 500nm.

[0026] S2. The filled mold is placed in a spark plasma sintering apparatus and plasma sintering is carried out under vacuum or argon protection. The plasma sintering parameters are: sintering temperature of 1700℃, heating rate of 80℃ / min, sintering pressure of 40MPa, and sintering time of 12min. After sintering, the mold is cooled to room temperature in the furnace to obtain a composite green body.

[0027] S3. The composite preform was placed in the atmosphere protection chamber of the laser processing platform. After evacuation, high-purity nitrogen gas was introduced, maintaining a nitrogen pressure of 0.3 MPa and a gas flow rate of 15 L / min. Laser pulse nitriding of the HfC layer was performed using a 1064 nm fiber pulsed laser. The laser pulse nitriding parameters were: laser power 300 W, pulse width 100 ns, pulse frequency 50 kHz, scanning speed 200 mm / s, spot diameter 100 μm, and overlap rate 40%. The HfCN layer was heated to 1100 °C and held at that temperature for 1.5 h. After laser pulse nitriding was completed, nitrogen gas flow protection was maintained, and the mixture was allowed to cool naturally to room temperature to obtain the W-Re alloy.

[0028] In this embodiment, the thickness of the HfCN layer in the ablation-resistant composite coating is 2.5 μm, with a C atomic ratio of 25% and a N atomic ratio of 39%. The interfacial bonding strength is 105 MPa. Oxyacetylene ablation (4 MW / m) 2 The ablation rate of the 180s line is 0.6 μm / s.

[0029] Example 2

[0030] A method for preparing a tungsten-rhenium alloy with an ablation-resistant composite coating includes the following steps: S1. Place W-10Re alloy powder in a graphite mold, and then lay tungsten mesh and HfC powder in sequence. The tungsten mesh has a tungsten wire diameter of 150μm and a mesh size of 300μm. The HfC powder has a purity of ≥99.9% and a particle size of 1μm.

[0031] S2. The filled mold is placed in a spark plasma sintering apparatus and plasma sintering is carried out under vacuum or argon protection. The plasma sintering parameters are: sintering temperature of 1650℃, heating rate of 80℃ / min, sintering pressure of 35MPa, and sintering time of 15min. After sintering, the mold is cooled to room temperature in the furnace to obtain a composite green body.

[0032] S3. The composite preform was placed in the atmosphere protection chamber of the laser processing platform. After evacuation, high-purity nitrogen gas was introduced, maintaining a nitrogen pressure of 0.25 MPa and a gas flow rate of 15 L / min. A 1064 nm fiber pulsed laser was used to perform laser pulse nitriding on the HfC layer. The laser pulse nitriding parameters were: laser power 250 W, pulse width 150 ns, pulse frequency 30 kHz, scanning speed 150 mm / s, spot diameter 100 μm, and overlap rate 40%. The HfCN layer was heated to 1100 °C and held at that temperature for 1.5 h. After laser pulse nitriding was completed, nitrogen gas flow protection was maintained, and the mixture was allowed to cool naturally to room temperature to obtain the W-Re alloy.

[0033] In this embodiment, the thickness of the HfCN layer in the ablation-resistant composite coating is 3.5 μm, with a C atomic ratio of 20% and a N atomic ratio of 42%. The interfacial bonding strength is 34 MPa. Oxyacetylene ablation (4 MW / m) 2 The ablation rate of the 180s line is 0.5 μm / s.

[0034] Example 3

[0035] A method for preparing a tungsten-rhenium alloy with an ablation-resistant composite coating includes the following steps: S1. Place W-25Re alloy powder in a graphite mold, and then lay tungsten mesh and HfC powder in sequence. The tungsten mesh has a tungsten wire diameter of 50μm and a mesh size of 100μm. The HfC powder has a purity of ≥99.9% and a particle size of 100nm.

[0036] S2. The filled mold is placed in a spark plasma sintering apparatus and plasma sintering is carried out under vacuum or argon protection. The plasma sintering parameters are: sintering temperature of 1600℃, heating rate of 50℃ / min, sintering pressure of 30MPa, and sintering time of 10min. After sintering, the mold is cooled to room temperature in the furnace to obtain a composite green body.

[0037] S3. The composite preform was placed in the atmosphere protection chamber of the laser processing platform. After evacuation, high-purity nitrogen gas was introduced, maintaining a nitrogen pressure of 0.1 MPa and a gas flow rate of 5 L / min. Laser pulse nitriding of the HfC layer was performed using a 1064 nm fiber pulsed laser. The laser pulse nitriding parameters were: laser power 100 W, pulse width 50 ns, pulse frequency 10 kHz, scanning speed 50 mm / s, spot diameter 50 μm, and overlap rate 30%. The HfCN layer was heated to 1000 °C and held at that temperature for 1 hour. After laser pulse nitriding was completed, nitrogen gas flow protection was maintained, and the mixture was allowed to cool naturally to room temperature to obtain the W-Re alloy.

[0038] In this embodiment, the thickness of the HfCN layer in the ablation-resistant composite coating is 7.8 μm, with a C atomic ratio of 20% and a N atomic ratio of 42%. The interfacial bonding strength is 39 MPa. Oxyacetylene ablation (4 MW / m) 2 The ablation rate of the 180s line is 0.41 μm / s.

[0039] Example 4

[0040] A method for preparing a tungsten-rhenium alloy with an ablation-resistant composite coating includes the following steps: S1. Place W-10Re alloy powder in a graphite mold, and then lay tungsten mesh and HfC powder in sequence. The tungsten mesh has a tungsten wire diameter of 200μm and a mesh size of 500μm. The HfC powder has a purity of ≥99.9% and a particle size of 5μm.

[0041] S2. The filled mold is placed in a spark plasma sintering apparatus and plasma sintering is carried out under vacuum or argon protection. The plasma sintering parameters are: sintering temperature of 1800℃, heating rate of 100℃ / min, sintering pressure of 50MPa, and sintering time of 15min. After sintering, the mold is cooled to room temperature in the furnace to obtain a composite green body.

[0042] S3. The composite preform was placed in the atmosphere-protected chamber of the laser processing platform. After evacuation, high-purity nitrogen was introduced, maintaining a nitrogen pressure of 0.5 MPa and a gas flow rate of 20 L / min. A 1064 nm fiber pulsed laser was used to perform laser pulse nitriding on the HfC layer. The laser pulse nitriding parameters were: laser power 500 W, pulse width 200 ns, pulse frequency 100 kHz, scanning speed 500 mm / s, spot diameter 200 μm, and overlap rate 60%. The HfCN layer was heated to 1200 °C and held at that temperature for 2 hours. After laser pulse nitriding was completed, the nitrogen flow protection was maintained, and the mixture was allowed to cool naturally to room temperature to obtain the W-Re alloy.

[0043] In this embodiment, the thickness of the HfCN layer in the ablation-resistant composite coating is 15 μm, with a C atomic ratio of 24% and a N atomic ratio of 40%. The interfacial bonding strength is 45 MPa. Oxyacetylene ablation (4 MW / m) 2 The ablation rate of the 180s line is 0.13 μm / s.

[0044] Table 1 shows the performance of the ablation-resistant composite coatings obtained in Examples 1-2.

[0045] 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. An ablation-resistant composite coating, characterized in that: It includes a transition layer and an HfCN layer that are distributed sequentially from the inside to the outside of the alloy material surface. The transition layer is a structure in which mechanical interlocking and metallurgical bonding coexist, formed by a tungsten mesh and the HfC phase embedded in the tungsten mesh.

2. The ablation-resistant composite coating as described in claim 1, characterized in that: The HfCN layer is formed by plasma sintering of HfC powder into an HfC layer, and then by laser pulse nitriding to nitrid the HfC layer.

3. The ablation-resistant composite coating as described in claim 1, characterized in that: The thickness of the HfCN layer is 1-20 μm.

4. The ablation-resistant composite coating as described in claim 1, characterized in that: The tungsten wires in the tungsten mesh have a diameter of 50-200 μm, and the mesh opening diameter is 100-500 μm.

5. A method for preparing a tungsten-rhenium alloy with an ablation-resistant composite coating, characterized in that: A tungsten mesh and HfC powder are sequentially laid on the alloy material from the inside out, and plasma sintering is used to form a transition layer and an HfC layer from the inside out. The transition layer is a structure in which mechanical interlocking and metallurgical bonding coexist between the tungsten mesh and the HfC phase embedded in the tungsten mesh. In a nitrogen atmosphere, the HfC layer is subjected to laser pulse nitriding to form an HfCN layer. After cooling to room temperature, a tungsten-rhenium alloy is obtained.

6. The method for preparing a tungsten-rhenium alloy with an ablation-resistant composite coating as described in claim 5, characterized in that: The parameters for plasma sintering are: sintering temperature of 1600~1800℃, heating rate of 50~100℃ / min, sintering pressure of 30~50MPa, and sintering time of 10~15min.

7. The method for preparing a tungsten-rhenium alloy with an ablation-resistant composite coating as described in claim 5, characterized in that: The parameters for laser pulsed nitriding are as follows: laser power 100~500W, pulse width 50~200ns, pulse frequency 10~100kHz, scanning speed 50~500mm / s, spot diameter 50~200μm, overlap rate 30~60%, nitrogen pressure 0.1~0.5MPa, and gas flow rate 5~20L / min.

8. The method for preparing a tungsten-rhenium alloy with an ablation-resistant composite coating as described in claim 5, characterized in that: After laser nitriding, the HfCN layer is kept at 1000~1200℃ for 1~2 hours.

9. The method for preparing a tungsten-rhenium alloy with an ablation-resistant composite coating as described in claim 5, characterized in that: The particle size of the HfC powder is 100 nm to 5 μm.

10. A tungsten-rhenium alloy with an ablation-resistant composite coating, characterized in that: It is prepared by the preparation method described in any one of claims 5-9.

Images