An Hf-Ta-Si / (Hf,Zr)B2 layered composite ultrahigh-temperature protective coating and a preparation method thereof

Abstract

The application discloses an Hf-Ta-Si / (Hf,Zr)B2 layered composite ultrahigh-temperature protective coating which is composed of a TaSi2 bottom layer, a ceramic layer surface layer with (Hf,Zr)B2 ultrahigh-temperature ceramic as a main phase and a Ta5Si3 interface reaction layer located at the interface between the substrate and the TaSi2 bottom layer, and the interface between each layer is an in-situ reaction autogenous interface; the coating is obtained by prepositioning the slurry of raw material powder on the surface of a tantalum alloy, drying, and then vacuum reaction sintering in one step; the coating has excellent ultrahigh-temperature oxidation resistance, heat scouring resistance and thermal shock resistance, and can effectively protect the tantalum alloy material under the conditions of oxygen, heat scouring and strong thermal shock at 1000 DEG C to 1800 DEG C; the method can reduce the adverse effects of the melting and sintering process on the microstructure and mechanical properties of the tantalum alloy, avoid the problem of preparing the ultrahigh-temperature ceramic coating on the surface of a tantalum alloy with a complex shape, and has higher coating deposition efficiency and lower cost.

Description

Technical Field

[0001] This invention belongs to the field of high temperature protection technology, specifically relating to an Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating and its preparation method. Background Technology

[0002] Among refractory metals, tantalum alloys possess excellent properties such as high density, corrosion resistance, good machinability and weldability, and a low ductile-brittle transition temperature, leading to their widespread application in the aerospace and nuclear industries. Since the 1930s, countries like the United States and the Soviet Union have vigorously developed tantalum alloys, successfully using them as reinforcing structural materials for space nuclear propulsion systems, the combustion chamber of the Kinaga spacecraft, the nose cone of missiles (operating at around 2500℃), gas deflectors in rocket engine nozzles, the combustion chamber of Apollo rockets, and nozzles for liquid rocket nozzles. However, tantalum alloys have poor high-temperature oxidation resistance. Without any protective measures, they undergo slight oxidation above 200℃ and rapid oxidation failure under aerobic conditions above 500℃, exhibiting a "pesting" powdering phenomenon. This is because the Pilling-Beddingworth ratio (PBR) of Ta2O5, the main oxidation product of tantalum and its alloys, is 2.47. The oxide film will generate a lot of growth stress during the oxidation growth process. At the same time, Ta2O5 is loose, porous and brittle, and is very easy to crack and peel off under the action of growth stress or thermal stress, and cannot effectively protect the tantalum alloy matrix.

[0003] The most effective way to improve the high-temperature oxidation resistance of tantalum and its alloys is to apply a high-temperature protective coating. Suitable coating systems for tantalum and tantalum alloys include Mo-Si-X, Si-Cr-X, Ir, Hf-Ta, Al-X, and ZrB2. Overall, silicide coatings are the primary high-temperature protective coatings for tantalum-based alloys. A few researchers use iridium coatings for protection, but due to problems such as immature preparation processes, high cost, low emissivity, and insufficient bonding strength, silicide coatings remain the most important high-temperature protective coating for tantalum-based alloys. In a high-temperature oxygen-containing environment, silicide coatings form a continuous SiO2 glass protective film, which effectively prevents oxygen diffusion to the substrate. Furthermore, the SiO2 glass film has good fluidity at high temperatures, allowing it to promptly repair defects such as cracks and pores on the coating surface, exhibiting a certain degree of "self-healing" and continuously and effectively protecting the tantalum alloy substrate. However, as the service temperature of tantalum alloys further increases (>1750℃) and the service life further extends, existing silicide coatings can no longer meet the high-temperature protection requirements of tantalum alloys under extremely harsh environments: (1) When the ambient temperature is higher than the melting point of SiO2 (1710℃), the viscosity of the SiO2 glass protective film drops sharply, weakening its ability to block oxygen diffusion inward; (2) Above its melting point (1710℃), the protective effect is limited. When the operating temperature further increases to 1800℃, the vapor pressure of SiO at the silicide / SiO2 glass film interface exceeds one atmosphere, and the high-temperature protection capability of the SiO2 glass protective film is lost; (3) There is a large mismatch in the coefficients of thermal expansion among the substrate, coating, and oxide film. The silicide coating (~8×10 -6 K -1 The coefficient of thermal expansion of the tantalum-based alloy matrix is ​​5.6 × 10⁻⁶. -6 K -1 The difference is too large, and the coefficient of thermal expansion of glassy SiO2 (0.55×10) -6 K -1 The temperature is much lower than that of the substrate, making it highly susceptible to cracking induced by thermal stress accumulation under ultra-high temperature and strong thermal shock, thus accelerating the coating failure process. Elemental modification and ceramic particle modification of silicide coatings can improve their oxidation resistance to some extent in medium and low temperature environments, but they still cannot meet the requirements for use under ultra-high temperature conditions above 1700℃. Summary of the Invention

[0004] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing an Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating. This coating produces a structure similar to "sand-stone" concrete in a high-temperature oxidizing environment, exhibiting better high-temperature stability and higher high-temperature viscosity. It can effectively resist the erosion of high-temperature, high-speed airflow, thus demonstrating superior resistance to ultra-high temperature oxidation under ultra-high temperature (>1700℃) aerobic conditions. It also combines the good thermal erosion resistance and excellent thermal shock resistance of ultra-high temperature ceramics, providing effective protection for tantalum alloys under aerobic, thermal erosion, and strong thermal shock conditions at 1000℃~1800℃.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: an Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating, characterized in that the coating consists of a TaSi2 bottom layer, a ceramic top layer with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase, and a Ta5Si3 interface reaction layer located at the interface between the substrate and the TaSi2 bottom layer, and the interfaces between each layer are in-situ self-generated interfaces; the coating provides effective protection for tantalum alloy materials under oxygen, thermal erosion and strong thermal shock conditions at 1000℃~1800℃.

[0006] This invention constructs a layered composite ultra-high temperature protective coating of Hf-Ta-Si / (Hf,Zr)B2 on the surface of tantalum alloys. During ultra-high temperature oxidation, this coating forms a composite oxide film with high-melting-point oxides or silicates such as ZrO2, HfO2, ZrSiO4, and (Zr,Hf)SiO4 as the "skeleton" and Si-B-Ta glass as the filler. This composite oxide film with a "sand-stone" concrete structure can combine oxygen barrier properties and thermal erosion resistance. It not only makes up for the problems of rapid volatilization failure and insufficient oxygen barrier capacity of traditional silicide coatings under ultra-high temperature conditions (≥1800℃), but also effectively improves the coating's thermal erosion resistance and thermal shock resistance. This coating provides effective protection for tantalum alloy materials under oxygen, thermal erosion, and strong thermal shock conditions at 1000℃~1800℃, and its static oxidation resistance life at 1800℃ is not less than 1 hour, meeting the ultra-high temperature protection requirements of tantalum alloy high-temperature components in advanced orbital control rocket engines and hypersonic vehicles.

[0007] The aforementioned Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating is characterized in that the ceramic surface layer, with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase, is composed of (Hf,Zr)B2, (Hf,Zr)B, and (Zr,Hf)Si phases, wherein the atomic percentage content of Zr and Hf elements is not less than 45%; the (Hf,Zr)B2 ultra-high temperature ceramic main phase is generated in situ through a high-temperature interfacial reaction between ZrB2 and Hf elements. The oxidation resistance and erosion resistance of the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating of this invention are mainly borne by the ceramic surface layer with (Hf,Zr)B2 as the main phase. Therefore, by limiting the atomic percentage content of Zr and Hf elements, the sufficient content of (Hf,Zr)B2 ultra-high temperature ceramic is ensured, thereby guaranteeing the oxidation resistance and erosion resistance of the coating. Furthermore, since the oxidation rate of ultra-high temperature boride ceramics is faster than that of silicides, introducing an appropriate (Zr,Hf)Si phase into the ceramic surface layer can effectively reduce the high-temperature oxidation rate of the coating.

[0008] The aforementioned Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating is characterized by the following: the thickness of the Ta5Si3 interfacial reaction layer is 3μm to 8μm; the thickness of the TaSi2 underlayer is 30μm to 120μm; and the thickness of the ceramic layer with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase is 10μm to 50μm. This preferred thickness of each layer ensures the coating's high-temperature protective performance while preventing cracking and peeling under internal or thermal stress conditions.

[0009] The aforementioned Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating is characterized in that the coating is applied to the surface of a Ta10W or Ta12W tantalum alloy. By selecting a Ta10W or Ta12W tantalum alloy as the substrate, Ta element is provided for the Ta5Si3 interface reaction layer and the TaSi2 underlayer in the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating. Furthermore, this preferred tantalum alloy, when used as the substrate during the vacuum high-temperature melting preparation process and ultra-high temperature service of the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating, does not experience a significant decrease in mechanical properties, and its service temperature range is greater than the protection temperature range of the coating, making it suitable for the preparation method of this invention.

[0010] In addition, the present invention also discloses a method for preparing the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating as described above, characterized in that it is prepared by a one-step vacuum reaction sintering method.

[0011] The above method is characterized by comprising the following steps:

[0012] Step 1: Surface pretreatment of tantalum alloy: grinding, sandblasting, pickling and degreasing are performed in sequence;

[0013] Step 2: Place Si powder, Hf powder, ZrB2 ceramic particles and dispersant in a ball mill for high-energy ball milling to obtain a composite suspension slurry;

[0014] Step 3: The composite suspension slurry obtained in Step 2 is pre-placed on the surface of the tantalum alloy that underwent surface pretreatment in Step 1. After drying, a pre-placed layer is obtained on the tantalum alloy surface. Then, the tantalum alloy with the pre-placed layer is placed in a vacuum sintering furnace at a vacuum degree of 1.0 × 10⁻⁶. -3 Pa ~ 7.0 × 10 -2 Under the condition of Pa, high-temperature melting was carried out, and after furnace cooling, Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating was prepared on the surface of tantalum alloy.

[0015] This invention involves preparing a composite suspension slurry from silicon powder, hafnium powder, zirconium boride ceramic particles, and a dispersant for the preparation of silicide ceramic phases. This slurry is then pre-placed on a pretreated tantalum alloy surface, followed by drying and a one-step vacuum reaction sintering method to obtain an Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating. This invention uses a one-step vacuum reaction sintering method to prepare the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating on the tantalum alloy surface. The interfaces between the tantalum alloy substrate / Ta5Si3 interface reaction layer / TaSi2 bottom layer / (Hf,Zr)B2 ultra-high temperature ceramic layers are all in-situ self-generated interfaces during the vacuum high-temperature sintering process of the coating. Compared to artificial interfaces, these interfaces exhibit better interlayer bonding, which is beneficial for improving the coating's resistance to cracking and spalling under thermal erosion or strong thermal shock conditions. This results in the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating possessing excellent thermal shock resistance. Meanwhile, since ZrB2 and (Hf,Zr)B2 are both ultra-high temperature ceramics with very high sintering temperatures, this invention employs a one-step vacuum reaction sintering method. This method utilizes the (Hf,Zr)B2, (Hf,Zr)B, and (Zr,Hf)Si ceramic phases formed by the chemical reaction of Si, Hf, and ZrB2 under vacuum and high-temperature conditions. This avoids the adverse effects of excessively high sintering temperatures on the tantalum alloy substrate, ensuring the quality of the coating. Furthermore, the one-step vacuum reaction sintering method avoids grain growth in the tantalum alloy matrix during multiple melting processes, reducing the adverse effects on the microstructure and mechanical properties of the tantalum alloy matrix.

[0016] The above method is characterized in that, in step one, the sandblasting process uses corundum sand or zirconium oxide sand, the sandblasting pressure is 0.4 MPa to 0.8 MPa, and the time is 3 min to 8 min; the acid pickling process uses an acid solution composed of concentrated nitric acid (64% to 69% by mass) and hydrofluoric acid (38% to 48% by mass) mixed in a volume ratio of 1:3 to 5, and the pickling time is 2 min to 5 min. The above-mentioned preferred sandblasting process can effectively remove impurities and oxide scale from the surface of tantalum alloys and increase the surface roughness of the tantalum alloy substrate. Tantalum alloys have good acid resistance and will passivate in the acid solution. By controlling the ratio of the strong acid hydrofluoric acid and the strong oxidizing nitric acid, the situation where the tantalum alloy cannot obtain a clean surface due to the formation of a passivation film during the pickling process is effectively avoided. Therefore, the above pretreatment process is beneficial for further removing the oxygen-absorbing layer on the surface of the tantalum alloy and enhancing the surface roughness of the tantalum alloy, thereby making it more conducive to the formation of a good interfacial bond between the coating and the tantalum alloy substrate.

[0017] The above method is characterized in that, in step two, the particle size of both the Si powder and Hf powder is less than 30 μm, and their mass purity is not less than 99%, and the mass content of Si powder in the Si powder, Hf powder, and ZrB2 ceramic particles is not less than 50%; the particle size of the ZrB2 ceramic particles is less than 20 μm, and their mass purity is not less than 99%. This preferred particle size of the Si powder and Hf powder is beneficial for promoting the silanization reaction between Si and the metallic element Hf, as well as between the Si powder and the tantalum alloy matrix, during vacuum high-temperature sintering. By limiting the mass purity of the powders, the introduction of impurity elements is reduced, thereby reducing the impact of impurity elements on the high-temperature protective performance of the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating. Simultaneously, by limiting the mass content of Si powder to not less than 50%, the continuity and density of the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating are improved, thereby enhancing the coating's oxidation resistance.

[0018] The above method is characterized in that, in step two, the ball milling speed is 300 r / min to 500 r / min, the time is 4 h to 48 h, the ball-to-material ratio is 3:1, the dispersant is a mixture of varnish and ethyl acetate in a volume ratio of 1:2 to 8, and the volume of the dispersant is 6 to 12 times the total mass of Si powder, Hf powder, and ZrB2 ceramic particles, wherein the unit of volume is mL and the unit of mass is g. This invention significantly reduces the "sinking" phenomenon of high-density Hf particles in the composite suspension slurry by optimizing the dispersant ratio to control the dispersant viscosity. Combined with ball milling, Si powder, Hf powder, and ZrB2 ceramic particles are evenly distributed in the dispersant, resulting in a uniformly mixed composite suspension slurry without significantly changing the particle size of the metal powder. This ensures the slurry's spraying and dipping performance and improves the uniformity of the coating. Furthermore, by controlling the drying and vacuum high-temperature melting processes, the mass transfer and chemical reaction processes on the tantalum alloy surface during vacuum melting are regulated, forming an Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating on the tantalum alloy surface.

[0019] The above method is characterized in that, in step three, the composite suspension slurry is uniformly pre-placed on the surface of the pre-treated tantalum alloy by dip coating or pneumatic spraying, and the spraying pressure of pneumatic spraying is 0.4MPa~0.6MPa, and the spraying distance is 10cm~30cm; the drying temperature is 80℃~220℃, and the time is 8h~24h; the specific process of high-temperature melting is as follows: first, the temperature is raised to 700℃~900℃ at a rate of 10℃ / min~30℃ / min and held for 30min~60min, and then the temperature is raised to 1350℃~1650℃ at a rate of 10℃ / min~15℃ / min and held for 30min~90min. This invention effectively prevents significant deviations between the composition of the pre-placed layer on the tantalum alloy substrate surface and the composition of the slurry due to differences in particle density in the atomized composite suspension slurry by controlling the spraying air pressure and spraying distance of the pneumatic spraying. The above-mentioned preferred drying process significantly reduces the content of varnish in the pre-placed layer, thereby reducing the adverse effects of excessively high vacuum inside the vacuum sintering furnace on the high-temperature heating process caused by varnish volatilization during vacuum high-temperature melting. The above-mentioned preferred vacuum melting process can ensure sufficient reaction between Si element and metal Hf powder in the coating, between the coating and the alloy substrate, and between the bottom layer and the top layer, while avoiding the problem of low content of antioxidant Si element in the coating due to excessive reaction between the coating and the substrate. At the same time, it significantly reduces the adverse effects of dispersants in the coating on the coating quality.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] 1. Compared with the most commonly used silicide coatings for tantalum alloys, the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating of the present invention forms a glassy oxide film of Ta-Si-BO glass on its surface under ultra-high temperature oxidation conditions. Compared with the SiO2 glass film and Si-BO glass film formed by oxidation of traditional silicide coatings, it has better high-temperature stability and higher high-temperature viscosity. It has a stronger oxygen barrier effect under ultra-high temperature (>1700℃) conditions and has superior resistance to ultra-high temperature oxidation.

[0022] 2. For the most commonly used silicide coatings for tantalum alloys, the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating of the present invention can generate a composite oxide film with high melting point oxides or silicate particles as the "skeleton" and Ta-Si-BO glass as the filler in a high-temperature oxidation environment. This oxide film has a structure similar to "sand-stone" concrete, which can effectively resist the erosion of high temperature and high-speed airflow. Moreover, its anti-stripping performance under strong thermal shock conditions is better than that of a single amorphous oxide film, and it has superior thermal erosion resistance and thermal shock resistance.

[0023] 3. Compared with single ultra-high temperature boride ceramic coatings prepared by thermal spraying, CVD, etc., this invention utilizes the chemical reaction of Si, Hf and ZrB2 under vacuum and high temperature conditions to form a composite ceramic surface layer with (Hf,Zr)B2 as the main component and containing (Hf,Zr)B and (Zr,Hf)Si ceramic phases. This results in the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating having better ultra-high temperature oxidation resistance and erosion resistance. At the same time, due to the presence of the (Zr,Hf)Si ceramic phase, the high-temperature oxidation rate of the ceramic surface layer in the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating is lower than that of ultra-high temperature ceramics.

[0024] 4. This invention employs a one-step vacuum reaction sintering method to prepare a layered composite ultra-high temperature protective coating of Hf-Ta-Si / (Hf,Zr)B2 on the surface of tantalum alloy. The interfaces formed between the layers are in-situ self-generated interfaces with good interlayer bonding, effectively avoiding interface cracking and peeling of the coating under thermal erosion or strong thermal shock conditions. Compared with the preparation of ultra-high temperature ceramic coatings directly on the surface of silicide coatings by methods such as thermal spraying, it has superior thermal shock resistance. In addition, the one-step sintering process of this invention reduces the adverse effects of the melting process on the microstructure and mechanical properties of the tantalum alloy matrix compared with the multiple melting process.

[0025] 5. This invention uses a vacuum high-temperature melting process to prepare a layered composite ultra-high temperature protective coating of Hf-Ta-Si / (Hf,Zr)B2 on the surface of tantalum alloy. This avoids the problem that conventional thermal spraying or electron beam physical vapor deposition processes are difficult to prepare ultra-high temperature ceramic coatings on the surface of complex-shaped tantalum alloy components. Moreover, it has higher coating deposition efficiency and lower cost compared with traditional chemical vapor deposition methods.

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0027] Figure 1 The XRD pattern of the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating prepared in Example 1 of this invention.

[0028] Figure 2 The image shows the surface morphology of the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating prepared in Example 1 of this invention.

[0029] Figure 3 The image shows the cross-sectional morphology of the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating prepared in Example 1 of this invention.

[0030] Figure 4 The image shows the surface morphology of the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating prepared in Example 1 of this invention after oxidation at 1700℃ for 5 hours in an atmospheric environment.

[0031] Figure 5 The image shows the cross-sectional morphology of the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating prepared in Example 2 of this invention after oxidation at 1800℃ for 30 min. Detailed Implementation

[0032] Example 1

[0033] The Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating of this embodiment consists of a 120μm thick TaSi2 base layer, a 25μm thick ceramic top layer with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase, and a 3μm thick Ta5Si3 interface reaction layer located at the interface between the substrate and the TaSi2 base layer. The interfaces between each layer are in-situ self-generated interfaces. The ceramic top layer with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase is composed of (Hf,Zr)B2, (Hf,Zr)B, and (Zr,Hf)Si phases, wherein the atomic percentage of Zr and Hf elements is 46%. The (Hf,Zr)B2 ultra-high temperature ceramic main phase is generated in-situ through a high-temperature interface reaction between ZrB2 and Hf elements. The coating provides effective protection for Ta12W tantalum alloy under oxygen, thermal erosion, and strong thermal shock conditions at 1000℃~1800℃.

[0034] The Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating in this embodiment is prepared by a one-step vacuum reaction sintering method, which includes the following steps:

[0035] Step 1: Surface pretreatment of Ta12W tantalum alloy: grinding, sandblasting, pickling, and degreasing are performed sequentially; the sandblasting uses corundum sand, the pressure is 0.4 MPa, and the time is 3 minutes; the pickling uses an acid solution composed of 64% concentrated nitric acid and 48% hydrofluoric acid in a 1:4 volume ratio, and the pickling time is 2 minutes.

[0036] Step 2: Si powder, Hf powder, ZrB2 ceramic particles, and a dispersant are placed in a ball mill for high-energy ball milling to obtain a composite suspension slurry. The particle size of the Si powder and Hf powder is less than 30 μm, and the mass purity is not less than 99.5%. The mass content of Si powder in the Si powder, Hf powder, and ZrB2 ceramic particles is 60%. The particle size of the ZrB2 ceramic particles is less than 10 μm, and the mass purity is 99.5%. The ball milling speed is 340 r / min, the time is 8 h, and the ball-to-particle ratio is 3:1. The dispersant is a mixture of varnish and ethyl acetate in a volume ratio of 1:4, and the volume of the dispersant is 12 times the total mass of the Si powder, Hf powder, and ZrB2 ceramic particles. The unit of volume is mL, and the unit of mass is g.

[0037] Step three involves using pneumatic spraying to pre-apply the composite suspension slurry obtained in step two to the surface of the pre-treated Ta12W tantalum alloy from step one. The spraying pressure is 0.4 MPa, the spraying distance is 30 cm, and after drying at 200°C for 8 hours, a pre-formed layer is obtained on the Ta12W tantalum alloy surface. The Ta12W tantalum alloy with the pre-formed layer is then placed in a vacuum sintering furnace at a vacuum degree of 7.0 × 10⁻⁶. -2 Under the condition of Pa, high-temperature sintering was carried out, and after furnace cooling, Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating was prepared on the surface of Ta12W tantalum alloy; the specific process of the high-temperature sintering was as follows: first, the temperature was raised to 800℃ at a rate of 10℃ / min and held for 30min, and then the temperature was raised to 1450℃ at a rate of 10℃ / min and held for 90min.

[0038] Figure 1 The XRD pattern of the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating prepared in this embodiment is shown below. Figure 1 It can be seen that the surface of the coating is composed of (Hf,Zr)B2, (Hf,Zr)B, and (Zr,Hf)Si phases.

[0039] Figure 2 The image shows the surface morphology of the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating prepared in Example 1 of this invention. Figure 2 It can be seen that the coating surface exhibits typical characteristics of vacuum reactive sintering coatings, with the relatively flat strip-shaped areas being (Zr,Hf)Si phase and the relatively rough areas being (Hf,Zr)B2 phase.

[0040] Figure 3 This is a cross-sectional morphology image of the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating prepared in this embodiment. Figure 3 As can be seen, the coating exhibits a distinct layered structure. The top layer is primarily composed of ultra-high temperature ceramic, the bottom layer is TaSi2, and the interfacial reaction layer at the interface between the bottom layer and the substrate is Ta5Si3.

[0041] Figure 4 The image shows the surface morphology of the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating prepared in Example 1 of this invention after oxidation at 1700℃ for 5 hours in an atmospheric environment. Figure 4 It can be seen that the coating forms a continuous protective oxide film on the surface after oxidation, without blistering or cracking. The oxide film formed after oxidation exhibits obvious "sand and gravel concrete" structural characteristics, and the coating demonstrates good high-temperature protection performance.

[0042] Example 2

[0043] The Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating of this embodiment consists of a 30μm thick TaSi2 base layer, a 50μm thick ceramic top layer with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase, and an 8μm thick Ta5Si3 interface reaction layer located at the interface between the substrate and the TaSi2 base layer. The interfaces between each layer are in-situ self-generated interfaces. The ceramic top layer with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase is composed of (Hf,Zr)B2, (Hf,Zr)B, and (Zr,Hf)Si phases, wherein the atomic percentage of Zr and Hf elements is 48%. The (Hf,Zr)B2 ultra-high temperature ceramic main phase is generated in-situ through the high-temperature interface reaction between ZrB2 and Hf elements. The coating provides effective protection for Ta10W tantalum alloy under oxygen, thermal erosion, and strong thermal shock conditions at 1000℃~1800℃.

[0044] The Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating in this embodiment is prepared by a one-step vacuum reaction sintering method, which includes the following steps:

[0045] Step 1: Surface pretreatment of Ta10W tantalum alloy: grinding, sandblasting, pickling and degreasing are performed in sequence at 84MPa for 4 minutes; the pickling acid solution is a mixture of 69% concentrated nitric acid and 40% hydrofluoric acid in a volume ratio of 1:5, and the pickling time is 4 minutes.

[0046] Step 2: Si powder, Hf powder, ZrB2 ceramic particles, and a dispersant are placed in a ball mill for high-energy ball milling to obtain a composite suspension slurry. The particle size of the Si powder and Hf powder is less than 30 μm, and the mass purity is not less than 99%. The mass content of Si powder in the Si powder, Hf powder, and ZrB2 ceramic particles is 65%. The particle size of the ZrB2 ceramic particles is less than 10 μm, and the mass purity is 99%. The ball milling speed is 300 r / min, the time is 6 h, and the ball-to-particle ratio is 3:1. The dispersant is a mixture of varnish and ethyl acetate in a volume ratio of 1:8, and the volume of the dispersant is 9 times the total mass of the Si powder, Hf powder, and ZrB2 ceramic particles. The unit of volume is mL, and the unit of mass is g.

[0047] Step 3 involves using pneumatic spraying to pre-apply the composite suspension slurry obtained in Step 2 onto the surface of the pre-treated Ta10W tantalum alloy from Step 1. The spraying pressure is 0.6 MPa, the spraying distance is 10 cm, and after drying at 150°C for 10 hours, a pre-formed layer is obtained on the Ta10W tantalum alloy surface. The Ta10W tantalum alloy with the pre-formed layer is then placed in a vacuum sintering furnace at a vacuum degree of 1.0 × 10⁻⁶. -3Under the condition of Pa, high-temperature sintering was carried out, and after furnace cooling, Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating was prepared on the surface of Ta10W tantalum alloy; the specific process of the high-temperature sintering was as follows: first, the temperature was raised to 700℃ at a rate of 20℃ / min and held for 60min, and then the temperature was raised to 1350℃ at a rate of 12℃ / min and held for 60min.

[0048] Figure 5 The image shows the cross-sectional morphology of the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating prepared in this embodiment after oxidation at 1800℃ for 30 min. Figure 5 It can be seen that the coating forms a continuous protective oxide film on the surface after oxidation, without blistering or cracking. The oxide film formed after oxidation exhibits obvious "sand and gravel concrete" structural characteristics, thus demonstrating good high-temperature protection performance.

[0049] Example 3

[0050] The Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating of this embodiment consists of a 90μm thick TaSi2 base layer, a 10μm thick ceramic top layer with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase, and a 5μm thick Ta5Si3 interface reaction layer located at the interface between the substrate and the TaSi2 base layer. The interfaces between each layer are in-situ self-generated interfaces. The ceramic top layer with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase is composed of (Hf,Zr)B2, (Hf,Zr)B, and (Zr,Hf)Si phases, wherein the atomic percentage of Zr and Hf elements is 49%. The (Hf,Zr)B2 ultra-high temperature ceramic main phase is generated in-situ through the high-temperature interface reaction between ZrB2 and Hf elements. The coating provides effective protection for Ta12W tantalum alloy under oxygen, thermal erosion, and strong thermal shock conditions at 1000℃~1800℃.

[0051] The Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating in this embodiment is prepared by a one-step vacuum reaction sintering method, which includes the following steps:

[0052] Step 1: Surface pretreatment of Ta12W tantalum alloy: grinding, sandblasting, pickling, and degreasing are performed sequentially; the sandblasting uses corundum sand, the sandblasting pressure is 0.6 MPa, and the time is 8 min; the pickling uses an acid solution composed of 68% concentrated nitric acid and 42% hydrofluoric acid in a 1:3 volume ratio, and the pickling time is 5 min.

[0053] Step 2: Si powder, Hf powder, ZrB2 ceramic particles, and a dispersant are placed in a ball mill for high-energy ball milling to obtain a composite suspension slurry. The particle size of the Si powder and Hf powder is less than 30 μm, and the mass purity is not less than 99%. The mass content of Si powder in the Si powder, Hf powder, and ZrB2 ceramic particles is 55%. The particle size of the ZrB2 ceramic particles is less than 10 μm, and the mass purity is 99%. The ball milling speed is 500 r / min, the time is 4 h, and the ball-to-particle ratio is 3:1. The dispersant is a mixture of varnish and ethyl acetate in a volume ratio of 1:2, and the volume of the dispersant is 6 times the total mass of the Si powder, Hf powder, and ZrB2 ceramic particles. The unit of volume is mL, and the unit of mass is g.

[0054] Step 3: The composite suspension slurry obtained in Step 2 is pre-placed on the surface of the Ta12W tantalum alloy that underwent surface pretreatment in Step 1 using pneumatic spraying. The spraying pressure is 0.5 MPa, the spraying distance is 20 cm, and after drying at 80℃ for 24 h, a pre-formed layer is obtained on the surface of the Ta12W tantalum alloy. Then, the Ta12W tantalum alloy with the pre-formed layer is placed in a vacuum sintering furnace at a vacuum degree of 2.0 × 10⁻⁶. -2 Under the condition of Pa, high-temperature sintering was carried out, and after furnace cooling, a layered composite ultra-high temperature protective coating of Hf-Ta-Si / (Hf,Zr)B2 was prepared on the surface of Ta12W tantalum alloy. The specific process of the high-temperature sintering was as follows: first, the temperature was raised to 900℃ at a rate of 30℃ / min and held for 45min, and then the temperature was raised to 1650℃ at a rate of 15℃ / min and held for 30min.

[0055] Testing showed that the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating prepared in this embodiment did not fail after being oxidized at an atmospheric temperature of 1800℃ for 2 hours.

[0056] Example 4

[0057] The Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating of this embodiment consists of a 60μm thick TaSi2 base layer, a 40μm thick ceramic top layer with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase, and a 6μm thick Ta5Si3 interface reaction layer located at the interface between the substrate and the TaSi2 base layer. The interfaces between each layer are in-situ self-generated interfaces. The ceramic top layer with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase is composed of (Hf,Zr)B2, (Hf,Zr)B, and (Zr,Hf)Si phases, wherein the atomic percentage of Zr and Hf elements is 50%. The (Hf,Zr)B2 ultra-high temperature ceramic main phase is generated in-situ through a high-temperature interface reaction between ZrB2 and Hf elements. The coating provides effective protection for Ta10W tantalum alloy under oxygen, thermal erosion, and strong thermal shock conditions at 1000℃~1800℃.

[0058] The Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating in this embodiment is prepared by a one-step vacuum reaction sintering method, which includes the following steps:

[0059] Step 1: Surface pretreatment of Ta10W tantalum alloy: Grinding, sandblasting, pickling, and degreasing are performed sequentially. The sandblasting uses corundum abrasive, with a pressure of 0.5 MPa and a time of 6 minutes. The pickling solution is a mixture of 65% concentrated nitric acid and 38% hydrofluoric acid at a volume ratio of 1:3.5, and the pickling time is 3 minutes.

[0060] Step 2: Si powder, Hf powder, ZrB2 ceramic particles, and a dispersant are placed in a ball mill for high-energy ball milling to obtain a composite suspension slurry. The particle size of the Si powder and Hf powder is less than 30 μm, and the mass purity is not less than 99%. The mass content of Si powder in the Si powder, Hf powder, and ZrB2 ceramic particles is 70%. The particle size of the ZrB2 ceramic particles is less than 10 μm, and the mass purity is 99%. The ball milling speed is 400 r / min, the time is 5 h, and the ball-to-particle ratio is 3:1. The dispersant is a mixture of varnish and ethyl acetate in a volume ratio of 1:7, and the volume of the dispersant is 7 times the total mass of the Si powder, Hf powder, and ZrB2 ceramic particles. The unit of volume is mL, and the unit of mass is g.

[0061] Step 3 involves using pneumatic spraying to pre-apply the composite suspension slurry obtained in Step 2 onto the surface of the pre-treated Ta10W tantalum alloy from Step 1. The spraying pressure is 0.6 MPa, the spraying distance is 15 cm, and after drying at 120°C for 20 hours, a pre-formed layer is formed on the Ta10W tantalum alloy surface. The Ta10W tantalum alloy with the pre-formed layer is then placed in a vacuum sintering furnace at a vacuum degree of 5.0 × 10⁻⁶. -3 Under the condition of Pa, high-temperature sintering was carried out, and after furnace cooling, Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating was prepared on the surface of Ta10W tantalum alloy; the specific process of the high-temperature sintering was as follows: first, the temperature was raised to 850℃ at a rate of 12℃ / min and held for 50min, and then the temperature was raised to 1400℃ at a rate of 12℃ / min and held for 45min.

[0062] Testing showed that the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating prepared in this embodiment did not fail after 200 thermal shocks at 1800℃ in an atmospheric environment.

[0063] Example 5

[0064] The Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating of this embodiment consists of a 115μm thick TaSi2 base layer, a 40μm thick ceramic top layer with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase, and a 7μm thick Ta5Si3 interface reaction layer located at the interface between the substrate and the TaSi2 base layer. The interfaces between each layer are in-situ self-generated interfaces. The ceramic top layer with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase is composed of (Hf,Zr)B2, (Hf,Zr)B, and (Zr,Hf)Si phases, wherein the atomic percentage of Zr and Hf elements is 45%. The (Hf,Zr)B2 ultra-high temperature ceramic main phase is generated in-situ through a high-temperature interface reaction between ZrB2 and Hf elements. The coating provides effective protection for Ta12W tantalum alloy under oxygen, thermal erosion, and strong thermal shock conditions at 1000℃~1800℃.

[0065] The Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating in this embodiment is prepared by a one-step vacuum reaction sintering method, which includes the following steps:

[0066] Step 1: Surface pretreatment of Ta12W tantalum alloy: grinding, sandblasting, pickling, and degreasing are performed sequentially; the sandblasting uses corundum sand, the pressure is 0.4 MPa, and the time is 3 min; the pickling uses an acid solution composed of 69% concentrated nitric acid and 45% hydrofluoric acid in a 1:5 volume ratio, and the pickling time is 2 min.

[0067] Step 2: Si powder, Hf powder, ZrB2 ceramic particles, and a dispersant are placed in a ball mill for high-energy ball milling to obtain a composite suspension slurry. The particle size of the Si powder and Hf powder is less than 20 μm, and the mass purity is not less than 99%. The mass content of Si powder in the Si powder, Hf powder, and ZrB2 ceramic particles is 54%. The particle size of the ZrB2 ceramic particles is less than 20 μm, and the mass purity is 99%. The ball milling speed is 360 r / min, the time is 4 h, and the ball-to-particle ratio is 3:1. The dispersant is a mixture of varnish and ethyl acetate in a volume ratio of 1:6, and the volume of the dispersant is 9 times the total mass of the Si powder, Hf powder, and ZrB2 ceramic particles. The unit of volume is mL, and the unit of mass is g.

[0068] Step 3: The composite suspension slurry obtained in Step 2 is pre-coated onto the surface of the Ta12W tantalum alloy after surface pretreatment in Step 1 using a dip-coating method. After drying at 110℃ for 12 hours, a pre-coated layer is obtained on the surface of the Ta12W tantalum alloy. Then, the Ta12W tantalum alloy with the pre-coated layer is placed in a vacuum sintering furnace at a vacuum degree of 4.0×10⁻⁶. -2 Under the condition of Pa, high-temperature sintering was carried out, and after furnace cooling, a layered composite ultra-high temperature protective coating of Hf-Ta-Si / (Hf,Zr)B2 was prepared on the surface of Ta12W tantalum alloy. The specific process of the high-temperature sintering was as follows: first, the temperature was raised to 900℃ at a rate of 15℃ / min and held for 30min, and then the temperature was raised to 1550℃ at a rate of 15℃ / min and held for 60min.

[0069] Testing showed that the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating prepared in this embodiment did not fail after 400 thermal shocks at 1800℃ in an atmospheric environment.

[0070] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A layered composite ultra-high temperature protective coating of Hf-Ta-Si / (Hf,Zr)B2, characterized in that, The coating consists of a TaSi2 substrate, a ceramic top layer with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase, and a Ta5Si3 interface reaction layer located at the interface between the substrate and the TaSi2 substrate. The interfaces between the layers are in-situ self-generated interfaces. The coating is prepared by a one-step vacuum reaction sintering method. The coating provides effective protection for tantalum alloy materials under oxygen, thermal erosion, and strong thermal shock conditions at 1000℃~1800℃.

2. The Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating according to claim 1, characterized in that, The ceramic layer with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase is composed of (Hf,Zr)B2, (Hf,Zr)B and (Zr,Hf)Si phases, wherein the atomic percentage of Zr and Hf elements is not less than 45%; the (Hf,Zr)B2 ultra-high temperature ceramic main phase is generated in situ through high-temperature interfacial reaction between ZrB2 and Hf elements.

3. The Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating according to claim 1, characterized in that, The thickness of the Ta5Si3 interface reaction layer is 3μm~8μm, the thickness of the TaSi2 bottom layer is 30μm~120μm, and the thickness of the ceramic surface layer with (Hf,Zr)B2 ultra-high temperature ceramic as the main phase is 10μm~50μm.

4. The Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating according to claim 1, characterized in that, The coating is applied to the surface of Ta10W or Ta12W tantalum alloy.

5. A method for preparing the Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating as described in any one of claims 1 to 4, characterized in that, The method includes the following steps: Step 1: Surface pretreatment of tantalum alloy: grinding, sandblasting, pickling and degreasing are performed in sequence; Step 2: Place Si powder, Hf powder, ZrB2 ceramic particles and dispersant in a ball mill for high-energy ball milling to obtain a composite suspension slurry; Step 3: The composite suspension slurry obtained in Step 2 is pre-placed on the surface of the tantalum alloy that underwent surface pretreatment in Step 1. After drying, a pre-placed layer is obtained on the tantalum alloy surface. Then, the tantalum alloy with the pre-placed layer is placed in a vacuum sintering furnace at a vacuum degree of 1.0 × 10⁻⁶. -3 Pa ~ 7.0 × 10 -2 Under the condition of Pa, high-temperature melting was carried out, and after furnace cooling, Hf-Ta-Si / (Hf,Zr)B2 layered composite ultra-high temperature protective coating was prepared on the surface of tantalum alloy.

6. The method according to claim 5, characterized in that, The sand used in step one is corundum sand or zirconium oxide sand. The sandblasting pressure is 0.4MPa~0.8MPa and the time is 3min~8min. The acid solution used in the pickling is a mixture of concentrated nitric acid with a mass concentration of 64%~69% and hydrofluoric acid with a mass concentration of 38%~48% in a volume ratio of 1:3~5. The pickling time is 2min~5min.

7. The method according to claim 5, characterized in that, In step two, the particle size of Si powder and Hf powder is less than 30 μm, and the mass purity is not less than 99%, and the mass content of Si powder in Si powder, Hf powder and ZrB2 ceramic particles is not less than 50%; the particle size of ZrB2 ceramic particles is less than 20 μm, and the mass purity is not less than 99%.

8. The method according to claim 5, characterized in that, In step two, the ball milling speed is 300 r / min to 500 r / min, the time is 4 h to 48 h, the ball-to-material ratio is 3:1, and the dispersant is a mixture of varnish and ethyl acetate in a volume ratio of 1:2 to 8. The volume of the dispersant is 6 to 12 times the total mass of Si powder, Hf powder, and ZrB2 ceramic particles. The unit of volume is mL and the unit of mass is g.

9. The method according to claim 5, characterized in that, In step three, the composite suspension slurry is uniformly pre-placed on the surface of the pretreated tantalum alloy using dip coating or pneumatic spraying. The spraying pressure for pneumatic spraying is 0.4MPa~0.6MPa, and the spraying distance is 10cm~30cm. The drying temperature is 80℃~220℃, and the time is 8h~24h. The specific process of high-temperature melting is as follows: first, the temperature is raised to 700℃~900℃ at a rate of 10℃ / min~30℃ / min and held for 30min~60min, and then the temperature is raised to 1350℃~1650℃ at a rate of 10℃ / min~15℃ / min and held for 30min~90min.

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