Hf-ta-mo-si multicomponent ultrahigh-temperature oxidation-resistant coating and preparation method thereof

Abstract

The application discloses a kind of Hf-Ta-Mo-Si multivariate ultra-high temperature oxidation-resistant coating, by Hf-rich surface layer, TaSi2 intermediate layer and Ta5Si3 interface reaction bottom layer, and the interface between each layer is in-situ self-birth interface;The preparation method of the coating is: one, the surface pretreatment of tantalum alloy;Two, hafnium powder, molybdenum powder and silicon powder are uniformly mixed with dispersant ball milling to obtain composite suspension slurry;Three, the composite suspension slurry is prepositioned on the surface of the tantalum alloy after surface pretreatment and dried to high-temperature melting and sintering.The coating of the application has better high-temperature stability and excellent thermal shock resistance and thermal shock resistance, and provides effective protection for tantalum alloy materials under the condition of oxygen strong thermal shock at 1000-1900 DEG C;The preparation method of the application is easy to realize the thickness control of coating, can be coated on the surface of special-shaped hot end part and inner surface, and is suitable for the ultra-high temperature protection of advanced orbit control rocket engine and hypersonic vehicle tantalum alloy high-temperature parts.

Description

Technical Field

[0001] This invention belongs to the field of ultra-high temperature protection technology, specifically relating to an Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating and its preparation method. Background Technology

[0002] Tantalum alloys, due to their excellent high-temperature strength and toughness as well as good machinability, can be used as ultra-high temperature hot-end components for next-generation high-specific-impulse, attitude control and orbital control rocket engines, and hypersonic vehicles. However, tantalum alloys face oxidation resistance challenges in ultra-high temperature oxidizing environments. Because of their high oxygen affinity and solubility, they readily absorb oxygen at room temperature and undergo severe oxidation far below their service temperature. Without any protective measures, slight oxidation occurs at service temperatures above 200°C, and rapid oxidation failure occurs under aerobic conditions above 500°C, resulting in "pesting" powdering. Therefore, to ensure the high-temperature mechanical properties and service life of tantalum alloy high-temperature components, an ultra-high temperature protective coating must be applied.

[0003] Currently, silicide coatings are the primary high-temperature protective coating for tantalum-based alloys. Under high-temperature oxidation conditions, silicide coatings generate a SiO2 glass protective film through the selective oxidation of Si, thus providing protection to the substrate and exhibiting good resistance to high-temperature oxidation (1000℃~1700℃). However, with the development of the aerospace industry, new-generation high-specific-impulse attitude and orbital control rocket engines and hypersonic vehicles have placed more stringent service requirements on high-temperature anti-oxidation coatings for tantalum alloys. Traditional silicide coatings, due to their inherent limitations, can no longer meet the high-temperature protection requirements of tantalum alloy high-temperature components. When the service temperature of the silicide coating exceeds 1700℃, the high-temperature generated SiO2 glass protective film softens and cannot effectively resist the erosion of high-temperature, high-speed airflow. 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 SiO2 glass protective film loses its high-temperature protective capability. On the other hand, silicide coatings have poor toughness and a significant mismatch in thermal expansion coefficients with tantalum alloys and their alloys, inevitably leading to through-cracks during thermal cycling and accelerating the high-temperature oxidation process of tantalum-based alloys. Besides silicide ceramics, borides of group IVB metals possess high melting points, good chemical stability, and high-temperature mechanical properties, exhibiting optimal resistance to high-temperature oxidation at 1500℃. This makes them promising for applications in ultra-high temperature fields and one of the potential high-temperature protective coating materials for tantalum alloys. However, the oxidation control steps and the resulting composite oxide film structure of ultra-high temperature boride ceramics differ significantly across different temperature ranges. When the temperature rises to around 1200℃, the B2O3 glass film softens, its viscosity decreases, and its oxygen-blocking effect is limited. When the oxidation temperature further increases to the volatilization temperature of B2O3, i.e., 1500℃, B2O3 volatilizes severely, resulting in an excessively rapid oxidation rate of boride ceramics at high temperatures. Furthermore, the thermal expansion coefficients of boride ceramics and tantalum alloys are mismatched, making them prone to cracking and spalling during thermal cycling. Moreover, the melting point of boride ceramics is as high as about 3000℃. Even with the addition of flux and the use of hot pressing sintering process, the preparation temperature of boride bulk materials is only about 2000℃. The excessively high sintering preparation temperature also limits its application in tantalum alloys.

[0004] In summary, traditional silicide coatings and single ultra-high temperature ceramic coatings are no longer sufficient to meet the ultra-high temperature protection requirements of tantalum alloy high-temperature components for next-generation high specific impulse orbital control rocket engines and hypersonic vehicles. Summary of the Invention

[0005] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing an Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating. This Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating has a multi-layer structure composed of an Hf-rich surface layer, a TaSi2 intermediate layer, and a Ta5Si3 interface reaction underlayer. The elements in each layer are gradient-distributed, and the interfaces between each layer are in-situ self-generated interfaces, exhibiting good interlayer bonding performance. It possesses better high-temperature stability and excellent resistance to thermal erosion and thermal shock, providing effective protection for tantalum alloy materials under strong aerobic thermal shock conditions of 1000℃~1900℃.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: an Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating, characterized in that the coating is composed of an Hf-rich surface layer, a TaSi2 intermediate layer and a Ta5Si3 interface reaction bottom layer, and the interfaces between each layer are in-situ self-generated interfaces; the Hf-rich surface layer is composed of the following components by mass percentage: Hf 20%~35%, Ta 8%~15%, Mo 10%~30%, Si 40%~62%, with the balance being W and unavoidable impurities, and the coating provides effective protection for tantalum alloy materials under strong aerobic thermal shock conditions of 1000℃~1900℃.

[0007] The Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating formed in situ on the surface of tantalum alloy material in this invention has a multi-layer structure. The Si, Ta, Hf, and Mo elements in each layer are distributed in a gradient, and the interfaces between each layer are all in situ self-generated interfaces with good bonding performance. This gives the Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating excellent thermal shock resistance, providing effective protection for tantalum alloy material under strong aerobic thermal shock conditions of 1000℃~1900℃, and a static anti-oxidation life of not less than 2 hours at 1800℃.

[0008] The aforementioned Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating is characterized in that the phases of the Hf-rich surface layer are composed of MoSi2, TaSi2, Hf2Si, and elemental Si. In this invention, the outermost Hf-rich surface layer of the Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating forms a multi-phase composite structure composed of MoSi2, TaSi2, Hf2Si, and elemental Si. This ensures that the coating can form a Ta-Si-O ternary glass protective film under ultra-high temperature and oxygen conditions, and also ensures that the coating surface, due to its high Hf content, can form high-melting-point oxides or silicate "skeletons" such as HfO2 and HfSiO4. This, in turn, guarantees that the coating possesses both excellent ultra-high temperature anti-oxidation properties and excellent thermal shock resistance.

[0009] The aforementioned Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating is characterized by the following: the thickness of the Hf-rich surface layer is 15μm~40μm, the thickness of the TaSi2 intermediate layer is 30μm~120μm, and the thickness of the Ta5Si3 interfacial reaction substrate is 5μm~20μm. This preferred coating thickness ensures the high-temperature protective performance of the coating while preventing cracking and peeling under internal or thermal stress conditions, and also prevents rapid degradation of the coating due to Si diffusion to the substrate side under ultra-high temperature conditions.

[0010] The aforementioned Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating is characterized in that the coating is applied to the surface of a Ta10W or Ta12W tantalum alloy. By preferably using a Ta10W or Ta12W tantalum alloy as the substrate, Ta elements are provided for the in-situ self-generated Ta5Si3 interface reaction underlayer and TaSi2 intermediate layer in the Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating. Simultaneously, since the vacuum reaction firing temperature and protection target temperature of the Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating are both high, the mechanical properties of the aforementioned preferred tantalum alloy as the substrate will not significantly decrease during the vacuum high-temperature melting preparation process and ultra-high temperature service.

[0011] In addition, the present invention also discloses a method for preparing the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating as described above, characterized in that the method includes the following steps:

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

[0013] Step 2: Mix hafnium powder, molybdenum powder and silicon powder evenly to obtain a mixed powder. Then, place the dispersant and the mixed powder in a ball mill and ball mill them evenly 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 sintering was carried out, and after furnace cooling, an Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating was prepared on the surface of the tantalum alloy.

[0015] This invention involves preparing a composite suspension slurry from hafnium powder, molybdenum powder, and silicon powder (used to prepare silicide ceramic phases) and a dispersant. This slurry is then pre-placed on a surface-pretreated tantalum alloy, followed by drying and vacuum reaction sintering to obtain an Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating. This invention utilizes a vacuum reaction sintering method to prepare the Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating on the tantalum alloy surface. Both the anti-oxidation phase and the coating structure are formed in situ during the vacuum high-temperature reaction process. The interfaces between the tantalum alloy substrate / Ta5Si3 interface reaction bottom layer / TaSi2 intermediate layer / Hf-rich surface layer are all in-situ self-generated interfaces, ensuring good compatibility and interfacial bonding performance between the coating and the substrate.

[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 1 min to 4 min; the acid pickling process uses an acid solution composed of concentrated nitric acid (65% to 68% by mass) and hydrofluoric acid (40% to 60% by mass) mixed in a volume ratio of 1:2.5 to 4, and the pickling time is 1 min to 6 min. The above-mentioned preferred sandblasting process parameters can effectively remove impurities and oxide scale from the surface of the tantalum alloy substrate and increase the surface roughness of the tantalum alloy substrate. Since tantalum alloy has good acid resistance, it will passivate in the acid solution. By controlling the ratio of strong acid hydrofluoric acid and strong oxidizing nitric acid in the acid solution, 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 surface pretreatment process is beneficial for further removing the oxygen-absorbing layer on the surface of the tantalum alloy, while enhancing the surface roughness of the tantalum alloy, thus 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 the hafnium powder, molybdenum powder, and silicon powder mentioned in step two all have a particle size of less than 20 μm, a purity of not less than 99%, and a silicon powder content of not less than 50% in the mixed powder. This preferred combination of hafnium powder, molybdenum powder, and silicon powder, along with their preferred particle size, facilitates the silanization reaction between Si and the metallic elements Hf, Mo, and the tantalum alloy matrix during vacuum high-temperature melting. By limiting the purity of the powders, the introduction of impurity elements is reduced, thereby decreasing the impact of impurity elements on the high-temperature protective performance of the Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating. The preferred silicon powder content of not less than 50% in the mixed powder improves the continuity and density of the Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating and its preparation method, thus enhancing the coating's anti-oxidation performance.

[0018] The above method is characterized in that, in step two, the ball milling speed is 340 r / min to 600 r / min, the time is 4 h to 48 h, the ball-to-powder ratio is 4:1, and the dispersant is a mixture of varnish and ethyl acetate in a volume ratio of 1:4 to 10, with the volume of the dispersant being 5 to 10 times the mass of the mixed powder. Here, volume is measured in mL and mass in g. This invention optimizes the dispersant ratio to control its viscosity, which facilitates the uniform distribution of hafnium powder, molybdenum powder, and silicon powder in the dispersant. This significantly reduces the "sinking" phenomenon of high-density Hf and Mo particles in the composite suspension slurry. Combined with the ball milling process, the powder particles are further refined to obtain a uniformly mixed composite suspension slurry, ensuring the spraying and dipping performance of the composite suspension slurry and improving 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 are regulated during vacuum melting, forming an Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation 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 0.3MPa~0.5MPa, and the spraying distance is 10cm~30cm; the drying temperature is 60℃~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~90min, and then the temperature is raised to 1400℃~1600℃ at a rate of 10℃ / min~15℃ / min and held for 45min~90min. This invention effectively prevents significant deviations between the composition of the pre-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-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 high-temperature melting process can ensure sufficient reaction between Si element and metal (Hf, Mo) powder in the coating, and between the coating and the alloy substrate, 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 to the most commonly used silicide coatings and single ultra-high temperature boride ceramic coatings for tantalum alloys, the Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating of this invention forms a Ta-Si-O glassy oxide film on its surface under ultra-high temperature oxidation conditions. Compared to the SiO2 glass film and Si-BO glass film formed by the oxidation of traditional silicide coatings, it has better high-temperature stability and higher high-temperature viscosity. Under ultra-high temperature (>1700℃) conditions, it has a stronger oxygen barrier effect and superior resistance to ultra-high temperature oxidation, thus significantly improving the oxidation resistance of tantalum alloys in ultra-high temperature environments. Experiments have shown that the Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating did not undergo oxidation failure after oxidation in static air at 1800℃ for 5 hours, and is expected to meet the ultra-high temperature protection requirements of tantalum alloy high-temperature components in advanced orbital control rocket engines and hypersonic vehicles.

[0022] 2. Compared to the most commonly used silicide coatings for tantalum alloys, the Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating of this invention utilizes the chemical reaction between Si, Hf, Mo and the tantalum alloy substrate under vacuum and high temperature conditions to form a multi-layer structure consisting of an Hf-rich surface layer, a TaSi2 intermediate layer and a Ta5Si3 interface reaction bottom layer. The elements between each layer are distributed in a gradient, and the interlayer interfaces are all in-situ self-generated interfaces, resulting in good interlayer bonding performance. This effectively avoids interface cracking and peeling of the coating under thermal erosion or strong thermal shock conditions, giving the Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating excellent thermal erosion resistance and thermal shock resistance. At the same time, the Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating of this invention can generate a composite oxide film with high-melting-point oxides or silicate particles as the "skeleton" and Ta-Si-O 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, and its anti-peeling performance under strong thermal shock conditions is better than that of a single amorphous oxide film.

[0023] 3. This invention prepares an Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating on the surface of tantalum alloy by high-temperature sintering under vacuum conditions. The preparation method is simple and the coating thickness can be easily controlled. More importantly, the high-temperature sintering method is not limited by the shape of the hot-end component and can be applied to the surface and inner surface of irregularly shaped hot-end components, thereby overcoming the "line-of-sight effect" of PVD and laser cladding methods. In addition, the Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating prepared by this invention by high-temperature sintering has a smooth coating surface and achieves metallurgical bonding between the coating and the substrate.

[0024] 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

[0025] Figure 1 The image shows the XRD pattern of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating prepared in Example 1 of this invention.

[0026] Figure 2 The surface morphology photograph of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating prepared in Example 1 of the present invention.

[0027] Figure 3 This is a cross-sectional morphology image of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating prepared in Example 1 of the present invention.

[0028] Figure 4 The cross-sectional elemental distribution diagram is shown for the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating prepared in Example 1 of this invention.

[0029] Figure 5 The image shows the surface morphology of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating prepared in Example 1 of this invention after oxidation at 1700℃ for 3 hours in an atmospheric environment.

[0030] Figure 6 The cross-sectional morphology of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating prepared in Example 2 of the present invention after oxidation at 1700℃ for 4 hours is shown. Detailed Implementation

[0031] Example 1

[0032] The Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating of this embodiment consists of a 15μm thick Hf-rich surface layer, a 120μm thick TaSi2 intermediate layer, and a 10μm thick Ta5Si3 interface reaction bottom layer. The interfaces between each layer are in-situ self-generated interfaces. The Hf-rich surface layer is composed of the following components by mass percentage: Hf 26%, Ta 12%, Mo 10%, Si 52%, with the balance being W and unavoidable impurities. The phases consist of MoSi2, TaSi2, Hf2Si, and elemental Si. The Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating is applied to the surface of Ta12W tantalum alloy. This coating provides effective protection for Ta12W tantalum alloy under strong aerobic thermal shock conditions at 1000℃~1900℃.

[0033] The preparation method of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating in this embodiment includes the following steps:

[0034] 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 0.4 MPa, and the time is 4 min; the pickling uses an acid solution composed of 65% concentrated nitric acid and 46% hydrofluoric acid in a 1:3 volume ratio, and the pickling time is 3 min.

[0035] Step 2: Mix hafnium powder, molybdenum powder, and silicon powder evenly to obtain a mixed powder. Then, place the dispersant and the mixed powder in a ball mill and ball mill evenly to obtain a composite suspension slurry. The particle size of the hafnium powder, molybdenum powder, and silicon powder is all less than 10 μm, and the mass purity is not less than 99.5%. The mass content of silicon powder in the mixed powder is 60%. The ball milling speed is 340 r / min, the time is 48 h, and the ball-to-powder ratio is 4:1. The dispersant is a mixture of varnish and ethyl acetate in a volume ratio of 1:8, and the volume of the dispersant is 10 times the mass of the mixed powder. The unit of volume is mL, and the unit of mass is g.

[0036] 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 0.4 MPa and the spraying distance is 10 cm. After drying, 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 1.0 × 10⁻⁶. -3 Under the condition of Pa, high-temperature sintering was carried out, and after furnace cooling, an Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating was prepared on the surface of Ta12W tantalum alloy; the drying temperature was 60℃ and the time was 12h; the specific process of high-temperature sintering was as follows: first, the temperature was raised to 900℃ at a rate of 10℃ / min and held for 30min, and then the temperature was raised to 1500℃ at a rate of 15℃ / min and held for 60min.

[0037] Figure 1 The XRD pattern of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating prepared in this embodiment is shown below. Figure 1 It can be seen that the surface of the coating is composed of MoSi2, TaSi2, Hf2Si and Si elemental phases.

[0038] Figure 2 These are surface morphology images of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating prepared in this embodiment. Figure 2 It can be seen that the coating surface exhibits typical characteristics of a vacuum reactive melting coating, with obvious undulations on the coating surface.

[0039] Figure 3This is a cross-sectional morphology image of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating prepared in this embodiment. Figure 4 This is a cross-sectional elemental distribution diagram of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating prepared in this embodiment, combined with coating 3 and... Figure 4 It can be seen that the coating exhibits a distinct layered structure, with Hf element enriched on the surface. Combined with the quantitative analysis results of energy dispersive spectroscopy, the middle layer of the coating is TaSi2, and the bottom layer of the interface reaction is Ta5Si3.

[0040] Figure 5 The image shows the surface morphology of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating prepared in this embodiment after oxidation at 1700℃ for 3 hours in an atmospheric environment. Figure 5 It can be seen that the coating forms a continuous protective oxide film on the surface after oxidation. The oxide film formed after oxidation exhibits obvious "sand and gravel concrete" structural characteristics, thus the coating shows good high-temperature protection performance.

[0041] Example 2

[0042] The Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating of this embodiment consists of a 40μm thick Hf-rich surface layer, a 100μm thick TaSi2 intermediate layer, and a 20μm thick Ta5Si3 interface reaction underlayer. The interfaces between each layer are in-situ self-generated interfaces. The Hf-rich surface layer is composed of the following components by mass percentage: Hf 35%, Ta 8%, Mo 17%, Si 40%, with the balance being W and unavoidable impurities. The phases consist of MoSi2, TaSi2, Hf2Si, and elemental Si. The Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating is applied to the surface of Ta10W tantalum alloy. This coating provides effective protection for Ta10W tantalum alloy under strong aerobic thermal shock conditions at 1000℃~1900℃.

[0043] The preparation method of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating in this embodiment includes the following steps:

[0044] Step 1: Surface pretreatment of Ta10W tantalum alloy: Grinding, sandblasting, pickling, and degreasing are performed sequentially. The sandblasting uses zirconium oxide sand at a pressure of 0.8 MPa for 1 minute. The pickling solution is a mixture of 67% concentrated nitric acid and 40% hydrofluoric acid at a volume ratio of 1:2.5, and the pickling time is 6 minutes.

[0045] Step 2: Mix hafnium powder, molybdenum powder, and silicon powder evenly to obtain a mixed powder. Then, place the dispersant and the mixed powder in a ball mill and ball mill evenly to obtain a composite suspension slurry. The particle size of the hafnium powder, molybdenum powder, and silicon powder is all less than 20 μm, and the mass purity is not less than 99.5%. The mass content of silicon powder in the mixed powder is 54%. The ball milling speed is 600 r / min, the time is 4 h, and the ball-to-powder ratio is 4:1. The dispersant is a mixture of varnish and ethyl acetate in a volume ratio of 1:4, and the volume of the dispersant is 5 times the mass of the mixed powder. The unit of volume is mL, and the unit of mass is g.

[0046] Step 3: The composite suspension slurry obtained in Step 2 is pre-placed on the surface of the Ta10W tantalum alloy after surface pretreatment in Step 1 using pneumatic spraying. The spraying pressure is 0.3 MPa and the spraying distance is 30 cm. After drying, a pre-layer is formed on the surface of the Ta10W tantalum alloy. Then, the Ta10W tantalum alloy with the pre-layer is 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, an Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating was prepared on the surface of Ta10W tantalum alloy; the drying temperature was 220℃ and the time was 8h; the specific process of high-temperature sintering was as follows: first, the temperature was raised to 750℃ at a rate of 30℃ / min and held for 90min, and then the temperature was raised to 1400℃ at a rate of 12℃ / min and held for 90min.

[0047] Figure 6 The image shows the cross-sectional morphology of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating prepared in this embodiment after oxidation at 1700℃ for 4 hours. Figure 6 It can be seen that a continuous protective oxide film is formed on the surface of the coating after oxidation. The oxide film formed after the coating oxidation exhibits obvious "sand and gravel concrete" structural characteristics, thus the coating shows good high-temperature protection performance.

[0048] Example 3

[0049] The Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating of this embodiment consists of a 30μm thick Hf-rich surface layer, a 30μm thick TaSi2 intermediate layer, and a 5μm thick Ta5Si3 interface reaction underlayer. The interfaces between each layer are in-situ self-generated interfaces. The Hf-rich surface layer is composed of the following components by mass percentage: Hf 20%, Ta 15%, Mo 12%, Si 53%, with the balance being W and unavoidable impurities. The phases consist of MoSi2, TaSi2, Hf2Si, and elemental Si. The Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating is applied to the surface of Ta12W tantalum alloy. This coating provides effective protection for Ta12W tantalum alloy under strong aerobic thermal shock conditions of 1000℃~1900℃.

[0050] The preparation method of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating in this embodiment includes the following steps:

[0051] 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 3 min; the pickling uses an acid solution composed of 68% concentrated nitric acid and 60% hydrofluoric acid in a 1:4 volume ratio, and the pickling time is 1 min.

[0052] Step 2: Mix hafnium powder, molybdenum powder, and silicon powder evenly to obtain a mixed powder. Then, place the dispersant and the mixed powder in a ball mill and ball mill evenly to obtain a composite suspension slurry. The particle size of the hafnium powder, molybdenum powder, and silicon powder is all less than 5 μm, and the purity is not less than 99.9%. The mass content of silicon powder in the mixed powder is 65%. The ball milling speed is 500 r / min, the time is 24 h, and the ball-to-powder ratio is 4:1. The dispersant is a mixture of varnish and ethyl acetate at a volume ratio of 1:10, and the volume of the dispersant is 8 times the mass of the mixed powder. The unit of volume is mL, and the unit of mass is g.

[0053] 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 and the spraying distance is 20 cm. After drying, 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 7.0 × 10⁻⁶. -3Under the condition of Pa, high-temperature sintering was carried out, and after furnace cooling, an Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating was prepared on the surface of Ta12W tantalum alloy; the drying temperature was 120℃ and the time was 24h; the specific process of high-temperature sintering was as follows: first, the temperature was raised to 700℃ at a rate of 15℃ / min and held for 60min, and then the temperature was raised to 1600℃ at a rate of 10℃ / min and held for 45min.

[0054] Testing showed that the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating prepared in this embodiment did not undergo oxidation failure after being oxidized at 1800℃ in an atmospheric environment for 2 hours.

[0055] Example 4

[0056] The Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating of this embodiment consists of a 30μm thick Hf-rich surface layer, a 110μm thick TaSi2 intermediate layer, and a 13μm thick Ta5Si3 interface reaction bottom layer. The interfaces between each layer are in-situ self-generated interfaces. The Hf-rich surface layer is composed of the following components by mass percentage: Hf 20%, Ta 8%, Mo 10%, Si 62%, with the balance being W and unavoidable impurities. The phases consist of MoSi2, TaSi2, Hf2Si, and elemental Si. The Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating is applied to the surface of Ta10W tantalum alloy. This coating provides effective protection for Ta10W tantalum alloy under strong aerobic thermal shock conditions of 1000℃~1900℃.

[0057] The preparation method of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating in this embodiment includes the following steps:

[0058] Step 1: Surface pretreatment of Ta10W tantalum alloy: Grinding, sandblasting, pickling, and degreasing are performed sequentially. The sandblasting uses zirconium oxide abrasive at a pressure of 0.5 MPa for 2 minutes. The pickling solution is a mixture of 65% concentrated nitric acid and 54% hydrofluoric acid at a volume ratio of 1:3.5, and the pickling time is 4 minutes.

[0059] Step 2: Mix hafnium powder, molybdenum powder, and silicon powder evenly to obtain a mixed powder. Then, place the dispersant and the mixed powder in a ball mill and ball mill until evenly mixed to obtain a composite suspension slurry. The particle size of the hafnium powder, molybdenum powder, and silicon powder is all less than 10 μm, and the mass purity is not less than 99.8%. The mass content of silicon powder in the mixed powder is 55%. The ball milling speed is 450 r / min, the time is 36 h, and the ball-to-powder ratio is 4:1. The dispersant is a mixture of varnish and ethyl acetate in a volume ratio of 1:6, and the volume of the dispersant is 6 times the mass of the mixed powder. The unit of volume is mL, and the unit of mass is g.

[0060] Step 3: The composite suspension slurry obtained in Step 2 is pre-coated onto the surface of the Ta10W tantalum alloy that underwent surface pretreatment in Step 1 using a dip-coating method. After drying, a pre-coated layer is formed on the surface of the Ta10W tantalum alloy. Then, the Ta10W tantalum alloy with the pre-coated layer is placed in a vacuum sintering furnace at a vacuum degree of 4.0 × 10⁻⁶. -3 Under the condition of Pa, high-temperature sintering was carried out, and after furnace cooling, an Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating was prepared on the surface of Ta10W tantalum alloy; the drying temperature was 80℃ and the time was 12h; the specific process of high-temperature sintering was as follows: first, the temperature was raised to 800℃ at a rate of 20℃ / min and held for 45min, and then the temperature was raised to 1550℃ at a rate of 12℃ / min and held for 80min.

[0061] Testing showed that the Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating prepared in this embodiment did not undergo oxidation failure after 500 thermal shocks at 1800℃ in an atmospheric environment.

[0062] Example 5

[0063] The Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating of this embodiment consists of a 34μm thick Hf-rich surface layer, a 66μm thick TaSi2 intermediate layer, and a 13μm thick Ta5Si3 interface reaction bottom layer. The interfaces between each layer are in-situ self-generated interfaces. The Hf-rich surface layer is composed of the following components by mass percentage: Hf 20%, Ta 8%, Mo 30%, Si 42%, with the balance being W and unavoidable impurities. The phases consist of MoSi2, TaSi2, Hf2Si, and elemental Si. The Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating is applied to the surface of Ta12W tantalum alloy. This coating provides effective protection for Ta12W tantalum alloy under strong aerobic thermal shock conditions of 1000℃~1900℃.

[0064] The preparation method of the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating in this embodiment includes the following steps:

[0065] 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 0.7 MPa, and the time is 3 min; the pickling uses an acid solution composed of 68% concentrated nitric acid and 58% hydrofluoric acid in a 1:3 volume ratio, and the pickling time is 5 min.

[0066] Step 2: Mix hafnium powder, molybdenum powder, and silicon powder evenly to obtain a mixed powder. Then, place the dispersant and the mixed powder in a ball mill and ball mill evenly to obtain a composite suspension slurry. The particle size of the hafnium powder, molybdenum powder, and silicon powder is all less than 20 μm, and the purity of each is not less than 99.8%. The mass content of silicon powder in the mixed powder is 52%. The ball milling speed is 400 r / min, the time is 40 h, and the ball-to-powder ratio is 4:1. The dispersant is a mixture of varnish and ethyl acetate in a volume ratio of 1:5, and the volume of the dispersant is 7 times the mass of the mixed powder. The unit of volume is mL, and the unit of mass is g.

[0067] 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 0.4 MPa and the spraying distance is 25 cm. After drying, 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 5.0 × 10⁻⁶. -3 Under the condition of Pa, high-temperature sintering was carried out, and after furnace cooling, an Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating was prepared on the surface of Ta12W tantalum alloy; the drying temperature was 170℃ and the time was 15h; the specific process of high-temperature sintering was as follows: first, the temperature was raised to 850℃ at a rate of 25℃ / min and held for 55min, and then the temperature was raised to 1450℃ at a rate of 14℃ / min and held for 70min.

[0068] Testing showed that the Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating prepared in this embodiment did not undergo oxidation failure after being oxidized at 1900℃ in an atmospheric environment for 0.5 hours.

[0069] 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 multi-element ultra-high temperature antioxidant coating of Hf-Ta-Mo-Si, characterized in that, The coating consists of an Hf-rich top layer, a TaSi2 intermediate layer, and a Ta5Si3 interface reaction bottom layer, with all interfaces between the layers being in-situ self-generated interfaces. The Hf-rich top layer is composed of the following components by mass percentage: Hf 20%~35%, Ta 8%~15%, Mo 10%~30%, Si 40%~62%, with the balance being unavoidable impurities. The phases of the Hf-rich top layer consist of MoSi2, TaSi2, Hf2Si, and elemental Si. The coating provides effective protection for tantalum alloy materials under strong aerobic thermal shock conditions at 1000℃~1900℃.

2. The Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating according to claim 1, characterized in that, The thickness of the Hf-rich surface layer is 15μm~40μm, the thickness of the TaSi2 intermediate layer is 30μm~120μm, and the thickness of the Ta5Si3 interface reaction bottom layer is 5μm~20μm.

3. The Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating according to claim 1, characterized in that, The coating is applied to the surface of Ta10W or Ta12W tantalum alloy.

4. A method for preparing the Hf-Ta-Mo-Si multi-element ultra-high temperature antioxidant coating as described in any one of claims 1 to 3, 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: Mix hafnium powder, molybdenum powder and silicon powder evenly to obtain a mixed powder. Then, place the dispersant and the mixed powder in a ball mill and ball mill them evenly 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 sintering was carried out, and after furnace cooling, an Hf-Ta-Mo-Si multi-element ultra-high temperature anti-oxidation coating was prepared on the surface of the tantalum alloy.

5. The method according to claim 4, characterized in that, In step one, the sandblasting process uses corundum sand or zirconium oxide sand, and the sandblasting pressure is 0.4MPa~0.8MPa, and the time is 1min~4min. The acid pickling process uses a solution of concentrated nitric acid with a mass concentration of 65%~68% and hydrofluoric acid with a mass concentration of 40%~60% mixed at a volume ratio of 1:2.5~4, and the pickling time is 1min~6min.

6. The method according to claim 4, characterized in that, In step two, the particle size of hafnium powder, molybdenum powder and silicon powder are all less than 20 μm, the mass purity is not less than 99%, and the mass content of silicon powder in the mixed powder is not less than 50%.

7. The method according to claim 4, characterized in that, In step two, the ball milling speed is 340 r / min to 600 r / min, the time is 4 h to 48 h, the ball-to-material ratio is 4:1, and the dispersant is a mixture of varnish and ethyl acetate in a volume ratio of 1:4 to 10, with the volume of the dispersant being 5 to 10 times the mass of the mixed powder. The unit of volume is mL, and the unit of mass is g.

8. The method according to claim 4, 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 0.3MPa~0.5MPa, and the spraying distance is 10cm~30cm. The drying temperature is 60℃~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~90min, and then the temperature is raised to 1400℃~1600℃ at a rate of 10℃ / min~15℃ / min and held for 45min~90min.

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