Preparation method of anti-ablation refractory high-entropy alloy composite coating

Abstract

The application discloses a preparation method of an anti-ablation refractory high-entropy alloy composite coating, and the method comprises the following steps: mixing WMoTaNbX alloy powder and Cu according to a predetermined mass ratio to form mixed powder; according to a target thickness of the coating, the mixed powder is weighed and prepared; after the substrate is subjected to sand blasting treatment, a SiC transition layer is prepared on the surface by chemical vapor deposition, and an anti-ablation coating is prepared by thermal spraying; the mixed powder is put into a plasma thermal spraying powder feeder, a base layer is formed on the SiC transition layer of the substrate by plasma spraying, the current and voltage are adjusted, and the base layer is subjected to plasma spraying to form the coating with the target thickness.

Description

Technical Field

[0001] This invention relates to the field of refractory high-entropy alloy composite materials, and particularly to a method for preparing a refractory high-entropy alloy composite coating. Background Technology

[0002] Spacecraft operate under harsh conditions, and without effective thermal protection using ultra-high temperature materials, they cannot complete their necessary flight operations. Carbon-based materials (C / C composites or graphite matrices) are widely used in hot-end components of aerospace equipment. However, carbon undergoes ablation at temperatures up to 2000°C, under high pressure, and at high speeds, severely impacting its service life. Therefore, it is necessary to prepare an ablation-resistant refractory alloy coating on the carbon-based surface. Existing copper infiltration techniques for tungsten alloy skeletons mostly involve high-temperature sintering of the tungsten skeleton followed by infiltration of molten copper. While the process is mature, it suffers from high porosity, and its performance is heavily influenced by the skeleton structure. Subsequently, techniques such as mechanical alloying and spark plasma sintering (SPS) were employed to optimize tungsten powder particle size and sintering parameters, shortening the preparation cycle and improving material uniformity. Currently, a transition layer is prepared by chemical vapor deposition followed by thermal spraying to prepare an ablation-resistant coating. This process is complex and time-consuming, with a single preparation time exceeding 10 hours. The addition of Re and HfC improves the ablation resistance of the W-Cu alloy. After ablation, the mass ablation rate of W-Cu is 0.595 mg / s, and the mass ablation rate of W-Re-HfC-Cu is 0.335 mg / s.

[0003] Chemical vapor deposition (CVD) is a time-consuming process that requires the introduction of hydrogen gas into the furnace (for protective reduction), posing a safety hazard. If a transition layer is needed, the CVD cycle is even longer. Spark plasma sintering (SPS) presents several challenges: 1) In terms of the fabrication process, the small mold size and micron- to nanometer-sized powder particles lead to uneven powder distribution, affecting density; 2) Rapid heating (100-500°C / min) results in a large temperature gradient at the coating / substrate interface (local temperature difference > 200°C), combined with differences in thermal expansion coefficients (> 2 × 10⁻⁶). -6 / K), brittle coatings crack due to thermal stress concentration; interfacial microcracks are prone to occur; 3) the skin effect of high-frequency pulsed current enriches the surface current of poorly conductive coatings (such as Al2O3), preferential migration of grain boundaries leads to abnormal grain growth (size deviation > 30%), metal-ceramic composite coatings are not synchronously densified due to conductive phase permeation network; resulting in non-uniform structure: the most important problem with magnetron sputtering preparation of coatings is that the coating thickness is very thin, generally around 3μm, which is far from meeting the requirements for ablation resistance.

[0004] The information disclosed in the background section is only for enhancing the understanding of the background of this invention, and therefore may contain information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] This invention provides a method for preparing a refractory high-entropy alloy coating and the coating itself. Using plasma thermal spraying technology, a SiC transition layer and a tungsten alloy coating are simultaneously prepared on the surface of C / C composite materials or heat-resistant steel. The process is simple and has a short cycle time. Compared with coatings prepared by spark plasma method, the thermally sprayed coating is simpler, faster, and lower cost, and can be used to prepare large areas. Compared with existing tungsten-copper infiltrated materials, the sweating mechanism is incorporated into the coating preparation, and the refractory alloy powder is directly mixed with Cu powder before plasma spraying.

[0006] A method for preparing a refractory high-entropy alloy coating includes:

[0007] Prepare a mixed powder by mixing WMoTaNbX alloy powder and Cu according to a predetermined mass fraction, where X = Ti, Zr and V; weigh the mixed powder according to the target coating thickness for later use.

[0008] After the substrate is sandblasted, a SiC transition layer is prepared on the surface by CVD.

[0009] The mixed powder is placed in a plasma thermal spray powder feeder and plasma sprayed onto the SiC transition layer of the substrate to form a base layer. The current and voltage are adjusted to form a coating of the target thickness.

[0010] In the method for preparing a refractory high-entropy alloy coating, during plasma spraying, the power of the plasma thermal spraying powder feeder is 15-40KW; the powder feeding rate is 18g / s; the argon flow rate is 30-45L / min; the hydrogen flow rate is 3.0-8.5L / min; the spraying distance is 90mm; the spray gun moving speed is 200mm / s; the spray gun scanning speed is 5mm / s; and the coating is cooled to room temperature by air cooling.

[0011] In the method for preparing a refractory high-entropy alloy coating, the thickness of the SiC transition layer is 10-50 μm, and the target thickness is 200-500 μm.

[0012] In the method for preparing a refractory high-entropy alloy coating, the particle size of the WMoTaNbX alloy powder is 15-45 μm, and the particle size of the Cu powder is 20-60 μm.

[0013] In the method for preparing a refractory high-entropy alloy coating, a predetermined mass fraction component is used to make the mass fraction of Cu in the coating 5-30%.

[0014] In the method for preparing a refractory high-entropy alloy coating, the mixture is mixed in a V-type mixer with a rotation speed of 50-120 r / min and a ball milling time of 4-10 h.

[0015] In the method for preparing a refractory high-entropy alloy coating, the substrate is a C / C substrate or a heat-resistant steel substrate.

[0016] A refractory high-entropy alloy coating, prepared by the method described above.

[0017] In the aforementioned refractory high-entropy alloy coating, the porosity of the refractory high-entropy alloy coating is ≤5%.

[0018] In the aforementioned refractory high-entropy alloy coating, the interlayer bonding strength of the refractory high-entropy alloy coating is ≥50 MPa.

[0019] Compared with existing technologies, this invention has the following advantages: This invention improves the high-temperature ablation resistance of existing refractory alloy coatings, solves problems such as numerous process steps and long preparation cycles, and is easily industrialized. Thermal spraying is formed by the stacking and collision of molten or semi-molten microparticles, resulting in a certain porosity in the plasma-sprayed coating. Sometimes, due to suboptimal process parameters, powder treatment, and substrate pretreatment, the prepared coating contains a large number of pores. These pores cause uneven performance across the coating and a decrease in overall mechanical properties. The layered structure of the coating may result in weaker bonding than laser cladding and uneven microstructure, leading to performance differences between coatings. The SiC transition layer reduces the impact of thermal matching differences in the coating. Furthermore, the copper melts and volatilizes during high-temperature use, achieving a self-cooling effect, thus providing excellent high-temperature ablation resistance and resistance to airflow erosion. Attached Figure Description

[0020] Various other advantages and benefits of the present invention will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0021] In the attached diagram:

[0022] Figure 1 This is a flowchart of the present invention;

[0023] Figure 2 The macroscopic morphology of C / C / SiC / WMoTaNb-20%wt.Cu before ablation;

[0024] Figure 3XRD pattern of C / C / SiC / WMoTaNb-20%wt.Cu before ablation;

[0025] Figure 4 SEM and EDS images of C / C / SiC / WMoTaNb-20%wt.Cu before ablation;

[0026] Figure 5 Microstructure of the C / C / SiC / WMoTaNb-20%wt.Cu coating before ablation: Figure 5 (a) and (b) surfaces in the middle; Figure 5 Sections (c) and (d) in the middle;

[0027] Figure 6 Microscopic morphology of different cross-sections of WMoTaNbTi-20%wt.Cu after ablation: Figure 6 (a) Transition region in the middle, Figure 6 (b) Central area, Figure 6 (c) edge region.

[0028] The present invention will be further explained below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0029] The following will refer to the appendix. Figures 1 to 6 Specific embodiments of the invention will be described in more detail below. While specific embodiments of the invention are shown in the accompanying drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the invention and to fully convey the scope of the invention to those skilled in the art.

[0030] It should be noted that certain terms are used in the specification and claims to refer to specific components. Those skilled in the art will understand that different terms may be used to refer to the same component. This specification and claims do not distinguish components based on differences in terminology, but rather on differences in function. The terms "comprising" or "including" used throughout the specification and claims are open-ended and should be interpreted as "comprising but not limited to." The following descriptions are preferred embodiments for carrying out the invention; however, these descriptions are for the purpose of understanding the general principles of the specification and are not intended to limit the scope of the invention. The scope of protection of this invention is determined by the appended claims.

[0031] To facilitate understanding of the embodiments of the present invention, further explanations and descriptions will be provided below with reference to the accompanying drawings and specific embodiments. The accompanying drawings do not constitute a limitation on the embodiments of the present invention.

[0032] like Figure 1As shown, "refractory" mainly refers to the fact that its core components are composed of metallic elements with extremely high melting points (usually ≥ 2200°C). The preparation method of refractory high-entropy alloy coatings includes the following steps:

[0033] Prepare a mixed powder by mixing WMoTaNbX alloy powder and Cu according to a predetermined mass fraction, where X = Ti, Zr and V; weigh the mixed powder according to the target coating thickness for later use.

[0034] After the substrate is sandblasted, a SiC transition layer is prepared on the surface by CVD.

[0035] The mixed powder is placed in a plasma thermal spraying powder feeder and plasma sprayed onto the SiC transition layer of the substrate to form a base coat. The current and voltage are adjusted to form a coating of the target thickness. Further, by adjusting the voltage and current to control the power between 15-40 kW, plasma spraying is performed on the base coat to form a coating of the target thickness.

[0036] In a preferred embodiment of the method for preparing a refractory high-entropy alloy coating, during plasma spraying, the power of the plasma thermal spraying powder feeder is 15-40KW; the powder feeding rate is 18g / s; the argon flow rate is 30-45L / min; the hydrogen flow rate is 3.0-8.5L / min; the spraying distance is 90mm; the spray gun moving speed is 200mm / s; the spray gun scanning speed is 5mm / s; and the coating is cooled to room temperature by air cooling.

[0037] In a preferred embodiment of the method for preparing a refractory high-entropy alloy coating, the thickness of the SiC transition layer is 10-50 μm, and the target thickness is 200-500 μm.

[0038] In a preferred embodiment of the method for preparing a refractory high-entropy alloy coating, the WMoTaNbX alloy powder has a particle size of 15-45 μm, and the Cu powder has a particle size of 20-60 μm.

[0039] In a preferred embodiment of the method for preparing a refractory high-entropy alloy coating, a predetermined mass fraction component is used such that the mass fraction of Cu in the coating is 5-30%.

[0040] In a preferred embodiment of the method for preparing a refractory high-entropy alloy coating, the mixture is mixed in a V-type mixer with a rotation speed of 50-120 r / min and a ball milling time of 4-10 h.

[0041] In a preferred embodiment of the method for preparing a refractory high-entropy alloy coating, the substrate is a C / C substrate or a heat-resistant steel substrate.

[0042] In a preferred embodiment of a refractory high-entropy alloy coating, it is prepared via the method described above.

[0043] In a preferred embodiment of a refractory high-entropy alloy coating, the interlayer bonding strength of the refractory high-entropy alloy coating is ≥50MPa.

[0044] In a preferred embodiment of a refractory high-entropy alloy coating, the interlayer ablation rate of the refractory high-entropy alloy coating is ≤0.05mm / s.

[0045] In one embodiment, Example 1: High Cu content coating

[0046] 1. Raw material preparation

[0047] Matrix: C / C composite material (100×100×10 mm)

[0048] Mixed powder:

[0049] WMoTaNb alloy powder (particle size 25μm): 70wt%

[0050] Cu powder (particle size 45μm): 30wt%

[0051] Powder mixing process: V-type mixer, rotation speed 85 r / min, ball milling time 6 h.

[0052] 2. Matrix Pretreatment

[0053] Sandblasting: Brown corundum abrasive (120 mesh), surface roughness Ra=3.5μm

[0054] SiC transition layer:

[0055] CVD process: CH3SiCl3 / H2 atmosphere, temperature 1100℃, deposition time 2h

[0056] Thickness: 20μm (measured value)

[0057] 3. Plasma spraying

[0058] Parameters are built into the underlying functional layer.

[0059] Power 15 kW 35 kW

[0060] Powder feeding rate 12 g / s 15 g / s

[0061] Argon flow rate 35 L / min 40 L / min

[0062] Hydrogen flow rate: 5.0 L / min - 7.5 L / min

[0063] Spraying distance 90 mm 90 mm

[0064] Spray gun movement speed 180 mm / s

[0065] Spray gun scanning speed 7 mm / s 7 mm / s

[0066] Coating structure:

[0067] Substrate thickness: 50 μm

[0068] Total thickness of functional layer: 243μm (applied in 8 coats)

[0069] 4. Cooling: Argon gas is used to cool to room temperature (cooling rate 50℃ / s).

[0070] 5. Performance Testing

[0071] Interlayer bond strength 58 MPa

[0072] Ablation rate at 2500℃: 0.041 mm / s

[0073] Example 2: Medium Cu content coating (comprehensive performance type)

[0074] 1. Key Adjustments

[0075] Alloy composition: WMoTaNb

[0076] Mixture ratio: Alloy powder:Cu powder = 80:20 wt%

[0077] Cu particle size: 30μm (to improve flowability)

[0078] 2. Matrix treatment

[0079] SiC transition layer thickness: 20 μm (CVD temperature 1200℃)

[0080] 3. Spraying parameter optimization

[0081] Parameter values

[0082] Power 20 kW

[0083] Powder delivery rate: 13.5g / s

[0084] Hydrogen flow rate: 5.5 L / min

[0085] Spraying distance 100 mm

[0086] Functional layer thickness: 326μm (applied in 7 coats)

[0087] 4. Coating performance

[0088] Interlayer bond strength 67MPa

[0089] Ablation rate at 2500℃: 0.046 mm / s

[0090] Example 3: Coating with low to medium Cu content

[0091] 1. Raw material adjustment

[0092] Mixed powder: WMoTaNb alloy powder (particle size 35 μm): Cu powder (particle size 55 μm) = 90:10 wt%

[0093] Powder mixing process: rotation speed 85 r / min, ball milling time 6 h

[0094] 2. Matrix treatment

[0095] SiC transition layer thickness: 20 μm (CVD temperature 1200℃)

[0096] 3. Optimization of spraying parameters

[0097] Parameter values

[0098] 25 kW power

[0099] Powder delivery rate 14g / s

[0100] Hydrogen flow rate 6 L / min

[0101] Spraying distance 100 mm

[0102] Functional layer thickness: 357μm (applied in 6 coats)

[0103] 4. Performance Results

[0104] Interlayer bond strength 70MPa

[0105] Ablation rate at 2500℃: 0.049 mm / s

[0106] Example 4: Cu-free coating (high temperature stable type)

[0107] 1. Raw material adjustment

[0108] Mixed powder: WMoTaNb alloy powder (particle size 35 μm)

[0109] Powder mixing process: rotation speed 85 r / min, ball milling time 6 h

[0110] 2. Matrix treatment

[0111] SiC transition layer thickness: 20 μm (CVD temperature 1200℃)

[0112] 3. Optimization of spraying parameters

[0113] Parameter values

[0114] 25 kW power

[0115] Powder feeding rate: 14.5 g / s

[0116] Hydrogen flow rate 6 L / min

[0117] Spraying distance 100 mm

[0118] The functional layer is 376 μm thick (applied in 5 coats).

[0119] 4. Performance Results

[0120] Interlayer bond strength 78MPa

[0121] Ablation rate at 2500℃: 0.063 mm / s

[0122] Counterexample: WMoTaNbTi + 20%Cu

[0123] 1. Raw material adjustment

[0124] Mixed powder: WMoTaNbTi alloy powder (particle size 35 μm): Cu powder (particle size 55 μm) = 80:20 wt%

[0125] Powder mixing process: rotation speed 85 r / min, ball milling time 6 h

[0126] 2. Matrix treatment

[0127] SiC transition layer thickness: 20 μm (CVD temperature 1200℃)

[0128] 3. Optimization of spraying parameters

[0129] Parameter values

[0130] Power 20 kW

[0131] Powder feeding rate: 13.5 g / s

[0132] Hydrogen flow rate: 5.5 L / min

[0133] Spraying distance 100 mm

[0134] Functional layer thickness: 349 μm (applied in 5 coats)

[0135] 4. Performance Results

[0136] Interlayer bond strength 95MPa

[0137] Ablation rate at 2500℃: 0.081 mm / s

[0138] Comparison of the effects of all the examples above

[0139] Taking Example 4 as an example, although it can serve as an embodiment, its ablation rate at 2500℃ is 0.063 mm / s, which is excessively high. During the high-temperature ablation process, the coating melts and volatilizes, accumulating towards the ablation edge under the scouring of the airflow and flame, resulting in a low linear ablation rate. The counterexample is even more extreme, with an ablation rate reaching 0.081 mm / s. Even with an interlayer bonding strength as high as 95 MPa, it is clearly impossible to balance both interlayer bonding strength and ablation rate at 2500℃.

[0140] Therefore, after comprehensive comparison, WMoTaNb+20%Cu, i.e., Example 2, is the best, possessing an interlayer bonding strength of 67 MPa, while having an ablation rate of 0.046 mm / s, lower than 0.05 mm / s, achieving a good balance between ablation rate at 2500℃ and interlayer bonding strength. The WMoTaNb composite coating with added 20% Cu exhibits high bonding strength with the substrate, reducing the sensitivity to coating detachment under high-temperature service environments. Furthermore, it melts and evaporates under the action of a sweating mechanism, producing a heat sink effect that removes heat, significantly reducing the internal temperature of the material. Accompanying the formation of microporous channels, these high-temperature gases escape from the interior of the material to the exterior through the pores. When they escape to the material surface, they form a relatively cool gas layer on the hot surface. This gas barrier prevents external high-temperature airflow from directly impacting the material surface, further protecting the substrate.

[0141] Industrialization advantages:

[0142] Simplified process: CVD + spraying completed in one step vs. traditional copper infiltration + sintering (saving 2 steps);

[0143] Cost comparison: 850 / m² (this invention) vs 1400 / m² (spark plasma sintering).

[0144] Although embodiments of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific embodiments and application fields described above. The specific embodiments described above are merely illustrative and instructive, and not restrictive. Those skilled in the art can make many other forms based on the guidance of this specification and without departing from the scope of protection of the claims of the present invention, and all of these are within the scope of protection of the present invention.

Claims

1. A method for preparing an ablation-resistant refractory high-entropy alloy composite coating, characterized in that, Includes the following steps: Prepare a mixed powder by mixing WMoTaNbX alloy powder with Cu according to a predetermined mass fraction, where X = Ti, Zr and V; weigh the mixed powder according to the target thickness of the coating for later use. After the substrate is sandblasted, a SiC transition layer is prepared on the surface by CVD. The mixed powder is placed in a plasma thermal spray powder feeder and plasma sprayed onto the SiC transition layer of the substrate to form a base layer. The current and voltage are adjusted to form a coating of the target thickness.

2. The method for preparing a refractory high-entropy alloy coating according to claim 1, characterized in that, Preferably, in plasma spraying, the power of the plasma thermal spraying powder feeder is 15-40KW; the powder feeding rate is 18g / s; the argon flow rate is 30-45L / min; the hydrogen flow rate is 3.0-8.5L / min; the spraying distance is 90mm; the spray gun moving speed is 200mm / s; the spray gun scanning speed is 5mm / s; and it is cooled to room temperature by air cooling.

3. The method for preparing a refractory high-entropy alloy coating according to claim 2, characterized in that, The thickness of the SiC transition layer is 10-50 μm, and the target thickness is 200-500 μm.

4. The method for preparing a refractory high-entropy alloy coating according to claim 1, characterized in that, The WMoTaNbX alloy powder has a particle size of 15-45 μm, and the Cu powder has a particle size of 20-60 μm.

5. The method for preparing a refractory high-entropy alloy coating according to claim 1, characterized in that, The predetermined mass fraction components result in a Cu mass fraction of 3-35% in the coating.

6. The method for preparing a refractory high-entropy alloy coating according to claim 1, characterized in that, Mix in a V-type mixer with a speed of 50-120 r / min and a ball milling time of 4-10 h.

7. The method for preparing a refractory high-entropy alloy coating according to claim 1, characterized in that, The substrate is a C / C substrate or a heat-resistant steel substrate.

8. A refractory high-entropy alloy coating, characterized in that, It is prepared by the method described in any one of claims 1-7.

9. The refractory high-entropy alloy coating according to claim 8, characterized in that, The porosity of the refractory high-entropy alloy coating is ≤5%.

10. The refractory high-entropy alloy coating according to claim 8, characterized in that, The interlayer bonding strength of the refractory high-entropy alloy coating is ≥50 MPa.

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