A refractory alloy surface oxidation-resistant coating and a preparation method and application thereof

Abstract

The application belongs to the technical field of oxidation-resistant coating and specifically relates to a refractory alloy surface oxidation-resistant coating and a preparation method and application thereof, wherein the refractory alloy surface comprises a primer layer, an intermediate layer and a surface layer which are sequentially stacked, and the silicon content in the intermediate layer is greater than that in the primer layer and the surface layer. By referring to the design concept of high-entropy alloy, multi-component refractory metals Ta, W, Zr, Hf and Ti with high-entropy effect are introduced into the silicide coating to construct a refractory high-entropy silicide coating, so as to increase the microstructure thermal stability of the silicide coating and improve the temperature resistance thereof by means of the coupling effect of multi-principal component alloying. A secondary slurry melting and sintering process which is simple in process and low in cost is used, and by adjusting the composition of the coating slurry, the gradient distribution of Si component is realized by means of the Si internal diffusion phenomenon in the melting and sintering process.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of oxidation-resistant coating, and particularly relates to a refractory alloy surface oxidation-resistant coating and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of aerospace and nuclear industries, the demand for super-high-temperature structural materials is also increasing. Among them, refractory metal-based alloys (such as niobium alloys, tantalum alloys, tungsten alloys, molybdenum alloys, etc.) are widely used due to their excellent high-temperature mechanical properties. However, refractory alloys have poor high-temperature oxidation resistance, and catastrophic "powdering" oxidation often occurs when oxidized at 500-800 ℃. Therefore, it is necessary to prepare an oxidation-resistant coating on the surface to ensure its safe service.

[0003] Among the many oxidation-resistant coating systems, silicide coatings are the most widely used coating system on the surface of refractory alloys. However, the oxidation resistance of single silicide coatings is insufficient, and active elements are generally added for modification. Common active elements include Al, Cr, Ti, B, Ge, Zr, Hf, and rare earth elements (Y, Ce), etc. These modifying elements either change the selective oxidation activity of Si or oxidize to form a composite oxide film coexisting with SiO2, which not only inhibits the "pesting" oxidation phenomenon in the medium temperature zone of silicide, but also improves the fluidity and adhesion of the SiO2 film at high temperatures, and improves the oxygen resistance. However, in the prior art, the heat resistance of the silicide coating modified by active elements is not high. For example, the working temperature of Si-Cr-Ti or Si-Cr-Fe silicide coating system is generally not higher than 1400 ℃. In order to reduce the wall temperature of the thrust chamber to a working temperature that the coating can withstand, a combination of fuel liquid film / radiation cooling mode is used in design, and the propellant flow of this part of cooling accounts for about 30%-40% of the fuel, so further improving the heat resistance of the silicide coating to reduce the consumption of propellant has important scientific significance and engineering value.

[0004] In addition, in the actual application process of the oxidation-resistant coating, its high-temperature resistance (temperature resistance), thermal shock / thermal fatigue resistance (heat resistance) need to be investigated. The main principle of silicide oxidation resistance is that after SiO2 is generated, a complete and dense layer is formed on the surface to inhibit the inward penetration of oxygen. The failure of silicide coating is the result of the combined action of kinetic factors such as liquid phase volatilization in the form of gas, high-temperature creep of oxide particles, and thermodynamic factors such as high temperature and low oxygen pressure. In the engine operating environment, the oxygen partial pressure is generally higher than the critical oxygen partial pressure of SiO generation, so the volatilization of high-temperature SiO and SiO2 is an important factor for the failure of the coating. SUMMARY

[0005] The present application aims to provide a refractory alloy surface oxidation-resistant coating and a preparation method and application thereof, so as to overcome the shortcomings of the prior art, and the prepared oxidation-resistant coating has excellent heat resistance.

[0006] The overall inventive concept adopted by the present application is: by referring to the design concept of high-entropy alloy, introducing multi-component refractory metals with high-entropy effect, i.e., Ta, W, Zr, Hf, Ti, into the silicide coating to construct a refractory high-entropy silicide coating, increasing the microstructure thermal stability of the silicide coating and improving its temperature resistance by means of the coupling effect of multi-principal-element alloying. A simple process and low-cost secondary slurry melting process is used, and by adjusting the composition of the coating slurry, the gradient distribution of Si component is realized by using the Si internal diffusion phenomenon in the melting process.

[0007] The refractory alloy surface oxidation-resistant coating is a high-entropy silicide gradient oxidation-resistant coating, which comprises a primer layer, an intermediate layer and a surface layer stacked in sequence, and the silicon content in the intermediate layer is greater than that in the primer layer and the surface layer. The atomic percentage of Si in the thickness direction of the coating increases from 30-45% to 50-65% and then decreases to 35-50% away from the refractory alloy part, that is, it presents a gradient distribution of low in the middle and high on the outside. Since the melting point of the low silicide is higher than that of the high silicide, the temperature resistance of the low silicide is superior to that of the high silicide. In addition, since the Si content in the surface layer is low, the surface generates a composite oxidation film composed of oxide ceramic phases (such as TiO2, ZrO2, HfO2, etc.) and glassy silicon oxide (SiO2) when oxidized, which can improve the density and oxygen diffusion resistance of the oxidation film. At the same time, the presence of the oxide ceramic phase can also play a "pinning effect" on the SiO2 glass phase, reducing the high-temperature volatilization of SiO2, and thus improving the oxidation resistance of the coating. The intermediate layer provides a silicon source for the continuous generation of SiO2 to maintain its oxygen resistance. The primer layer reduces the thermal physical property difference between the coating and the substrate alloy, and improves the thermal shock resistance of the coating.

[0008] In order to achieve the above-mentioned purpose, the technical scheme of the present application is:

[0009] In the first aspect, the present application provides a refractory alloy surface oxidation-resistant coating, which comprises a primer layer, an intermediate layer and a surface layer stacked in sequence, and the silicon content in the intermediate layer is greater than that in the primer layer and the surface layer.

[0010] In some other embodiments, the atomic percentage of silicon in the primer layer is 30-45%, the atomic percentage of silicon in the intermediate layer is 50-65%, and the atomic percentage of silicon in the surface layer is 35-50%.

[0011] In the second aspect, the present application provides a preparation method of the refractory alloy surface oxidation-resistant coating of the first aspect, comprising the following steps:

[0012] (1) taking Ta, W, Zr, Hf and Ti elemental metal powders as raw materials, synthesizing a TaWZrHfTi supersaturated solid solution state alloy powder;

[0013] (2) mixing the TaWZrHfTi supersaturated solid solution state alloy powder with Si powder to obtain coating powder I, mixing the coating powder I with a binder to obtain coating slurry I;

[0014] (3) coating the coating slurry I on a refractory alloy piece, and performing first-time sintering to obtain a coated alloy piece I;

[0015] (4) mixing the TaWZrHfTi supersaturated solid solution state alloy powder with Si powder to obtain coating powder II, mixing the coating powder II with a binder to obtain coating slurry II;

[0016] (5) coating the coating slurry II on the coated alloy piece I, and performing second-time sintering to obtain a coated alloy piece II, wherein the surface coating of the refractory alloy piece in the coated alloy piece II is a refractory alloy surface oxidation-resistant coating.

[0017] In some other embodiments, in the step (1), the raw material composition of the TaWZrHfTi supersaturated solid solution state alloy powder is as follows in terms of atomic percentage: Ta = 15-25%, W = 15-25%, Zr = 15-25%, Hf = 15-25%, and Ti = 15-30%.

[0018] Alternatively, the particle size of the Ta, W, Zr, Hf and Ti elemental metal powders is 20-100 µm, and the purity of each is greater than 99.5%.

[0019] In some other embodiments, in the step (1), the preparation method of the TaWZrHfTi supersaturated solid solution state alloy powder is mechanical alloying, and the mechanical alloying is as follows: uniformly mixing the raw material Ta, W, Zr, Hf and Ti elemental metal powders with a solvent, ultrasonic dispersion, vacuum pumping, then ball milling under protection of a protective gas, and drying to obtain the TaWZrHfTi supersaturated solid solution state alloy powder.

[0020] Preferably, the solvent is anhydrous ethanol.

[0021] The ultrasonic dispersion time is 5-10 min.

[0022] The vacuum pumping is to a pressure of less than 10 Pa.

[0023] The protective gas is nitrogen, argon or helium.

[0024] The protective gas is filled to 1 atm.

[0025] The ball milling treatment is that the rotation speed is 300-400 r / min, and the ball milling time is 10-30 h.

[0026] The drying is vacuum drying, the drying time is 12-24 h, and the drying temperature is 60-80 ℃.

[0027] In some other embodiments, in the step (2), the mixing molar ratio of the TaWZrHfTi supersaturated solid solution state alloy powder and the Si powder is 1:(2-2.5); and the mixing mass ratio of the coating powder I and the binder is (1-2.5) g:1 mL.

[0028] Or, in the step (3), the first sintering is under vacuum condition, the sintering temperature is 1400-1500 ℃, the vacuum degree is ≥1.0×10 -2 Pa, and the sintering time is 20-40 min.

[0029] In some other embodiments, in the step (4), the mixing molar ratio of the TaWZrHfTi supersaturated solid solution state alloy powder and the Si powder is 1:(0.9-1.5); and the mixing mass ratio of the coating powder II and the binder is (1-2.5) g:1 mL.

[0030] Or, in the step (5), the second sintering is under vacuum condition, the sintering temperature is 1450-1550 ℃, the vacuum degree is ≥1.0×10 -2 Pa, and the sintering time is 20-40 min.

[0031] In some other embodiments, in the step (2), the mixing time of the TaWZrHfTi supersaturated solid solution state alloy powder and the Si powder is 5-10 h; and the mixing time of the coating powder I and the binder is 1-2 h.

[0032] Or, in the step (4), the mixing time of the TaWZrHfTi supersaturated solid solution state alloy powder and the Si powder is 5-10 h; and the mixing time of the coating powder II and the binder is 1-2 h.

[0033] In some other embodiments, in the step (3), before the coating slurry I is coated on the refractory alloy part, the step further comprises pretreating the refractory alloy part, and the pretreating is polishing the surface of the refractory alloy part to expose the metallic luster, ultrasonic cleaning in alcohol, and then drying.

[0034] Or, in the step (5), before the coating slurry II is coated on the coating alloy part I, the step further comprises pretreating the coating alloy part I, and the pretreating is ultrasonic cleaning in alcohol, and then drying.

[0035] Or, in the step (3) or step (5), the ultrasonic cleaning time is 15-25 min, and the drying temperature is 45-55 DEG C, and the time is 10-15 min.

[0036] In a third aspect, the application provides the use of the refractory alloy surface oxidation-resistant coating in the preparation of a refractory metal-based alloy.

[0037] The beneficial effects of the application are:

[0038] 1. The application draws on the design concept of high-entropy alloy, and proposes to introduce multi-component refractory metals Ta, W, Zr, Hf and Ti with high-entropy effect into the silicide coating to construct a refractory high-entropy silicide coating. With the coupling effect of multi-principal element alloying, the microstructure thermal stability of the silicide coating is increased, and the temperature resistance is improved.

[0039] 2. The method of the application uses a simple and low-cost secondary slurry melting process. By adjusting the composition of the coating slurry, the Si component is distributed in a gradient of low outside and high inside by using the Si internal diffusion phenomenon in the melting process.

[0040] 3. The refractory alloy surface oxidation-resistant coating prepared by the application is a high-entropy silicide gradient oxidation-resistant coating, which includes a refractory alloy surface including a primer layer, an intermediate layer and a surface layer stacked in turn. The silicon content in the intermediate layer is greater than that in the primer layer and the surface layer. The Si atomic percentage content increases from 30-45% to 50-65% and then decreases to 35-50% in the thickness direction of the coating away from the refractory alloy piece, that is, it presents a gradient distribution of low outside and high inside.

[0041] 4. The refractory alloy surface oxidation-resistant coating prepared by the application has excellent oxidation resistance and can effectively protect the refractory alloy piece at 1700 DEG C. For example, after 1600 DEG C oxidation for 10 h, the unit area weight of the coating reaches 15-18 mg / cm 2 . BRIEF DESCRIPTION OF DRAWINGS

[0042] The drawings accompanying the specification of the application form a part of the application and serve to provide further understanding of the application, and the exemplary embodiments of the application and their descriptions serve to explain the application, and do not constitute an improper limitation on the application.

[0043] Figure 1 The process flow chart of the preparation method of the refractory alloy surface oxidation-resistant coating in Example 1 of the application;

[0044] Figure 2 The cross-sectional backscattered image of the refractory alloy surface oxidation-resistant coating in Example 1 of the application;

[0045] Figure 3 Figure 1 is a diagram showing the gradient of Si content in the cross-section of the refractory alloy surface oxidation-resistant coating in Example 1 along the thickness direction;

[0046] Figure 4 Figure 2 is a secondary electron image of the surface of the refractory alloy surface oxidation-resistant coating in Example 1 after oxidation at 1600 ℃ for 10 h;

[0047] Figure 5 Figure 3 is a backscattered image of the cross-section of the refractory alloy surface oxidation-resistant coating in Example 1 after oxidation at 1600 ℃ for 10 h. DETAILED DESCRIPTION

[0048] Example 1

[0049] A preparation method of a refractory alloy surface oxidation-resistant coating, a process flow chart thereof is shown as Figure 1 The method comprises the following steps:

[0050] (1) Synthesis of TaWZrHfTi supersaturated solid solution alloy powder: taking Ta, W, Zr, Hf and Ti elemental metal powders as raw materials, the particle size of each metal powder is 50-100 µm, and the purity is greater than 99.5%, and the atomic percentage is as follows: Ta=15%, W=15%, Zr=20%, Hf=20%, Ti=30%, and the TaWZrHfTi supersaturated solid solution alloy powder is synthesized by mechanical alloying method, specifically comprising the following steps:

[0051] The raw material Ta, W, Zr, Hf and Ti elemental metal powders are placed in a stainless steel ball mill tank containing a process control agent (absolute ethanol), ultrasonic oscillation dispersion for 10 min, then placed in a vacuum glove box, vacuumed to below 10 Pa, then sealed the stainless steel ball mill tank after filling protective gas (such as argon) to 1 atm, then taken out from the glove box and installed in a ball mill for ball milling treatment (rotation speed is 300 r / min, ball milling time is 30 h), then the milled powder is placed in a vacuum drying box at 80℃ for 12 h to obtain the TaWZrHfTi supersaturated solid solution alloy powder;

[0052] (2) Preparation of coating slurry I: the TaWZrHfTi supersaturated solid solution alloy powder and Si powder are mixed in a mixer at a molar ratio of 1:2.1 for 6 h to obtain coating powder I; the coating powder I and the binder (PVB) are stirred in a magnetic stirrer at a mass ratio of 1.5 g / ml for 1 h to obtain the coating slurry I;

[0053] (3) First melting and sintering: polish the surface of the refractory alloy NbMoTaWTi high-entropy alloy (20Nb-20Mo-20Ta-20W-20Ti) substrate to expose the metal luster, ultrasonic clean in alcohol for 20 min, dry at 50 ℃ for 10 min, and obtain the treated refractory alloy piece; coat the coating slurry I on the surface of the treated refractory alloy piece by dipping or brushing; dry the coated sample in a drying oven at 80 ℃ for 12 h; and sinter the dried sample in a vacuum high-temperature furnace, wherein the sintering temperature is 1400 ℃, the vacuum degree is better than 1.0×10 -2 Pa, and the sintering time is 40 min, to obtain the coating alloy piece I;

[0054] (4) Preparation of coating slurry II: mix the TaWZrHfTi supersaturated solid solution alloy powder and Si powder in a mixer at a molar ratio of 1:1 for 6 h to obtain coating powder II; and mix the coating powder II and the binder (PVB) in a magnetic stirrer at a mass ratio of 1.8 g / ml for 1 h to obtain the coating slurry II;

[0055] (5) Second melting and sintering: ultrasonic clean the coating alloy piece I in alcohol for 20 min, dry at 50 ℃ for 10 min, and obtain the treated coating alloy piece I; coat the coating slurry II on the surface of the treated coating alloy piece I by dipping or brushing; dry in a drying oven at 80 ℃ for 12 h; and sinter the dried sample in a vacuum high-temperature furnace, wherein the sintering temperature is 1450 ℃, the vacuum degree is 1.0×10 -2 Pa, and the sintering time is 40 min, to obtain the coating alloy piece II; and the surface of the coating alloy piece II is a high-entropy silicide gradient oxidation-resistant coating.

[0056] It is tested that the atomic percentage of Si in the high-entropy silicide gradient oxidation-resistant coating on the surface of the refractory alloy along the direction away from the refractory alloy piece (i.e. from inside to outside) in the thickness direction is 42% in the base layer, 64% in the middle layer, and 37% in the surface layer.

[0057] The cross-sectional structure of the refractory alloy surface oxidation-resistant coating is characterized, Figure 2 which is the cross-sectional backscattered image of the high-entropy silicide gradient oxidation-resistant coating on the surface of the refractory alloy in Example 1. It can be seen from Figure 2 that the coating has a clear gradient structure: the surface layer structure is loose and has large pores; the middle layer is denser, and some bright gray particle phases are scattered on the gray matrix; and the base layer is dense and continuous, and is metallurgically combined with the matrix alloy.

[0058] The Si content of the cross-sectional structure of the high-entropy silicide gradient oxidation-resistant coating on the surface of the refractory alloy is characterized.Figure 3 A graph of the Si content variation gradient along the thickness direction of the cross section of the refractory alloy surface oxidation-resistant coating in Example 1 is shown in Figure 2. Figure 3 It can be seen that the surface layer of the coating is a low-silicon silicide, the intermediate layer is a high-silicon silicide, and the base layer is a low-silicon silicide.

[0059] The surface of the refractory alloy surface oxidation-resistant coating after oxidation was characterized. Figure 4 A secondary electron image of the surface of the refractory alloy surface oxidation-resistant coating in Example 1 after oxidation at 1600 ℃ for 10 h is shown in Figure 3. Figure 4 It can be seen that a dense glassy silicon oxide film is formed on the surface of the coating, which can block the diffusion of oxygen into the interior of the coating; the metal oxides are uniformly distributed and embedded in the silicon oxide film, which can play a role as a skeleton, and the composite oxide film formed has excellent temperature resistance and ablation resistance.

[0060] Figure 5 A backscattered image of the cross section of the refractory alloy surface oxidation-resistant coating in Example 1 after oxidation at 1600 ℃ for 10 h is shown in Figure 4. Figure 5 It can be seen that the coating after oxidation also has a three-layer structure corresponding to the original base layer, intermediate layer and surface layer structure of the refractory alloy surface before high-temperature treatment, but the surface layer after oxidation is composed of white granular grains and black structures wrapped in each other, and the structure is relatively dense without obvious pores and cracks; compared with before high-temperature oxidation treatment, the thickness of the intermediate layer increases significantly.

[0061] After testing, the weight gain per unit area of the coating after oxidation at 1600 ℃ for 10 h is about 15 mg / cm 2 , and the thickness of the generated surface layer is 20 μm.

[0062] Example 2

[0063] A method for preparing a refractory alloy surface oxidation-resistant coating, comprising the following steps:

[0064] (1) Synthesis of TaWZrHfTi supersaturated solid solution alloy powder: taking Ta, W, Zr, Hf and Ti elemental metal powders as raw materials, the particle size of each metal powder is 50-100 μm, and the purity is greater than 99.5%, according to the following atomic percentage, Ta=18%, W=18%, Zr=18%, Hf=20%, Ti=26%, the TaWZrHfTi supersaturated solid solution alloy powder is synthesized by mechanical alloying method, specifically, comprising the following steps:

[0065] The raw materials Ta, W, Zr, Hf, Ti elemental metal powders are placed in a stainless steel ball mill tank containing a process control agent (anhydrous ethanol), ultrasonic vibration dispersed for 10 min, then placed in a vacuum glove box, vacuumed to below 10 Pa, then filled with a protective gas (such as argon) to 1 atm, then the stainless steel ball mill tank is sealed, then taken out of the glove box and installed in a ball mill for ball milling treatment (rotation speed is 350 r / min, ball milling time is 25 h), then the ball-milled powder is placed in a vacuum drying oven at 80°C for 18 h to obtain a TaWZrHfTi supersaturated solid solution alloy powder;

[0066] (2) Preparation of coating slurry I: the TaWZrHfTi supersaturated solid solution alloy powder and Si powder are mixed in a molar ratio of 1:2.3 in a mixer for 8 h to obtain a coating powder I; the coating powder I and a binder (PVB) are stirred in a magnetic stirrer in a mass ratio of 2 g / ml for 1.5 h to obtain a coating slurry I;

[0067] (3) First melting and sintering: the refractory alloy niobium tungsten alloy Nb521 (Nb-5W-2Mo-1Zr) workpiece surface is polished to expose the metal luster, ultrasonic cleaned in alcohol for 20 min, dried at 50°C for 10 min to obtain a treated refractory alloy piece; the coating slurry I is coated on the surface of the treated refractory alloy piece by dipping or brushing; the coated coating sample is placed in a drying oven at 100°C for 10 h; the dried coating sample is placed in a vacuum high-temperature furnace for sintering, wherein the sintering temperature is 1450°C, the vacuum degree is better than 1.0×10 -2 Pa, and the sintering time is 30 min to obtain a coating alloy piece I;

[0068] (4) Preparation of coating slurry II: the TaWZrHfTi supersaturated solid solution alloy powder and Si powder are mixed in a molar ratio of 1:1.3 in a mixer for 6 h to obtain a coating powder II; the coating powder II and a binder (PVB) are stirred in a magnetic stirrer in a mass ratio of 2.5 g / ml for 1.5 h to obtain a coating slurry II;

[0069] (5) Second melting and sintering: the coating alloy piece I is ultrasonic cleaned in alcohol for 20 min, dried at 50°C for 10 min to obtain a treated coating alloy piece I; the coating slurry II is coated on the surface of the treated coating alloy piece I by dipping or brushing; placed in a drying oven at 100°C for 10 h; the dried coating sample is placed in a vacuum high-temperature furnace for sintering, wherein the sintering temperature is 1500°C, the vacuum degree is 1.0×10 -2Pa, sintering time is 30 min, to obtain coated alloy part II; the surface of the coated alloy part II is high-entropy silicide gradient oxidation-resistant coating; it is tested that the atomic percentage content of Si in the refractory alloy surface high-entropy silicide gradient oxidation-resistant coating in the thickness direction away from the refractory alloy part (i.e. from inside to outside) is 37% in the primer layer, 62% in the middle layer and 43% in the surface layer.

[0070] It is tested that the unit area weight gain of the refractory alloy surface oxidation-resistant coating after 1600 ℃ oxidation for 10 h is about 18 mg / cm 2 , indicating that it has good oxidation resistance.

[0071] Example 3

[0072] A method for preparing a refractory alloy surface oxidation-resistant coating, comprising the following steps:

[0073] (1) Synthesis of TaWZrHfTi supersaturated solid solution alloy powder: taking Ta, W, Zr, Hf and Ti elemental metal powders as raw materials, the particle size of each metal powder is 50-100 µm, and the purity is greater than 99.5%, according to the following atomic percentage, Ta=17%, W=17%, Zr=20%, Hf=20%, Ti=26%, the TaWZrHfTi supersaturated solid solution alloy powder is synthesized by mechanical alloying method, specifically including the following steps:

[0074] The raw material Ta, W, Zr, Hf and Ti elemental metal powders are placed in a stainless steel ball mill pot containing a process control agent (absolute ethanol), ultrasonic oscillation dispersion for 10 min, then placed in a vacuum glove box, vacuumed to below 10 Pa, then sealed the stainless steel ball mill pot after filling protective gas (such as argon) to 1 atmosphere, then taken out from the glove box and installed in a ball mill for ball milling treatment (rotation speed is 400 r / min, ball milling time is 20 h), then the milled powder is placed in a vacuum drying box for drying at 60℃ for 24 h, to obtain TaWZrHfTi supersaturated solid solution alloy powder;

[0075] (2) Preparation of coating slurry I: the TaWZrHfTi supersaturated solid solution alloy powder and Si powder are placed in a mixer according to the molar ratio of 1:2.5 for mixing for 10 h to obtain coating powder I; the coating powder I and the binder (PVB) are stirred in a magnetic stirrer according to the mass ratio of 1.5 g / ml for 2 h to obtain coating slurry I;

[0076] (3) First melting and sintering: polish the surface of the refractory alloy tantalum-tungsten alloy (Ta10W) workpiece to expose the metal luster, ultrasonic cleaning in alcohol for 20 min, 50 ℃ drying for 10 min, to obtain the treated refractory alloy piece; coating slurry I is coated on the surface of the treated refractory alloy piece by dipping or brushing method; the coated sample is placed in a drying oven at 120 ℃ for 8 h; the dried coating sample is placed in a vacuum high-temperature furnace for sintering, wherein the sintering temperature is 1500 ℃, the vacuum degree is better than 1.0×10 -2 Pa, and the sintering time is 20 min, to obtain a coating alloy piece I;

[0077] (4) Preparation of coating slurry II: mix TaWZrHfTi supersaturated solid solution alloy powder and Si powder in a mixer for 10 h at a molar ratio of 1:1.5 to obtain coating powder II; mix the coating powder II and the binder (PVB) in a magnetic stirrer for 2 h at a mass ratio of 2.0 g / ml to obtain the coating slurry II;

[0078] (5) Second melting and sintering: the coating alloy piece I is ultrasonic cleaned in alcohol for 20 min, 50 ℃ drying for 10 min, to obtain the treated coating alloy piece I; coating slurry II is coated on the surface of the treated coating alloy piece I by dipping or brushing method; it is placed in a drying oven at 120 ℃ for 8 h; the dried coating sample is placed in a vacuum high-temperature furnace for sintering, wherein the sintering temperature is 1550 ℃, the vacuum degree is 1.0×10 -2 Pa, and the sintering time is 20 min, to obtain a coating alloy piece II; the surface of the coating alloy piece II is a high-entropy silicide gradient oxidation-resistant coating; it is tested that the atomic percentage of Si in the refractory alloy surface high-entropy silicide gradient oxidation-resistant coating in the thickness direction away from the refractory alloy piece (i.e. from inside to outside) is 38% in the base layer, 63% in the middle layer, and 42% in the surface layer.

[0079] It is tested that after 1700 ℃ oxidation for 5 h, the unit area weight gain of the refractory alloy surface oxidation-resistant coating is about 16 mg / cm 2 , which has good oxidation resistance.

[0080] Comparative Example 1

[0081] Different from Example 1, steps (2)-(5) are omitted, and only step (1) is performed, i.e. only the TaWZrHfTi supersaturated solid solution alloy powder is mixed with the binder and coated on the refractory alloy piece, and then subjected to first sintering.

[0082] It is tested that after 1600 ℃ oxidation for 10 h, the coating and the alloy substrate are completely oxidized and destroyed.

[0083] The present application focuses on high temperature oxidation resistance performance, mainly by the unit area weight to measure the oxidation resistance performance of the coating. From examples 1-3 and comparative example 1, the preparation method of the oxidation resistant coating on the surface of the refractory alloy can realize the gradient distribution of Si composition from low outside to high inside by adjusting the composition of the coating slurry and using the Si internal diffusion phenomenon in the melting process. It can provide effective protection for refractory alloy parts at 1700 ℃, for example, after 1600 ℃ oxidation for 10 h, the unit area weight of the coating reaches 15~18 mg / cm 2 .

[0084] The above examples are only used to explain the technical solutions provided by the present application, and cannot limit the present application. Any simple modification, equivalent change and modification made according to the technical essence of the present application to the above examples all fall within the protection scope of the technical solutions of the present application.

Claims

1. A method of producing a surface oxidation resistant coating of a refractory alloy, characterized by, The refractory alloy surface comprises a primer layer, an intermediate layer and a surface layer which are stacked in sequence, and the silicon content in the intermediate layer is greater than that in the primer layer and the surface layer; The preparation method of the refractory alloy surface oxidation-resistant coating comprises the following steps: (1) Taking Ta, W, Zr, Hf and Ti elemental metal powders as raw materials, a TaWZrHfTi supersaturated solid solution alloy powder is synthesized; (2) The TaWZrHfTi supersaturated solid solution alloy powder is mixed with Si powder to obtain coating powder I, and the coating powder I is mixed with a binder to obtain coating slurry I; (3) The coating slurry I is coated on a refractory alloy part, and after first sintering, a coating alloy part I is obtained; (4) The TaWZrHfTi supersaturated solid solution alloy powder is mixed with Si powder to obtain coating powder II, and the coating powder II is mixed with a binder to obtain coating slurry II; (5) The coating slurry II is coated on the coating alloy part I, and after second sintering, a coating alloy part II is obtained, and the surface coating of the refractory alloy part in the coating alloy part II is the refractory alloy surface oxidation-resistant coating; In the step (2), the mixing molar ratio of the TaWZrHfTi supersaturated solid solution alloy powder and the Si powder is 1:(2-2.5); In the step (4), the mixing molar ratio of the TaWZrHfTi supersaturated solid solution alloy powder and the Si powder is 1:(0.9-1.5).

2. The method of claim 1, wherein the refractory alloy surface oxidation resistant coating is prepared by a process comprising: The silicon atom percentage content in the primer layer is 30-45%, the silicon atom percentage content in the intermediate layer is 50-65%, and the silicon atom percentage content in the surface layer is 35-50%.

3. The method of claim 1, wherein the refractory alloy surface oxidation resistant coating is prepared by a process comprising: In the step (1), the raw material composition of the TaWZrHfTi supersaturated solid solution alloy powder is as follows according to the atomic percentage: Ta=15-25%, W=15-25%, Zr=15-25%, Hf=15-25%, and Ti=15-30%.

4. The method of claim 1, wherein the refractory alloy surface oxidation resistant coating is prepared by, In the step (1), the particle size of the Ta, W, Zr, Hf and Ti elemental metal powders is 20-100 µm, and the purity is greater than 99.5%.

5. The method of claim 1, wherein the refractory alloy surface oxidation resistant coating is prepared by, In the step (1), the preparation method of the TaWZrHfTi supersaturated solid solution alloy powder is a mechanical alloying method, and the mechanical alloying method is as follows: the raw material Ta, W, Zr, Hf and Ti elemental metal powders are uniformly mixed with a solvent, ultrasonic dispersion is performed, vacuum is drawn, then protective gas is filled, ball milling treatment is performed, and drying is performed to obtain the TaWZrHfTi supersaturated solid solution alloy powder; The solvent is anhydrous ethanol; The ultrasonic dispersion time is 5-10 min; The vacuum drawing is to draw vacuum to below 10 Pa; The protective gas is nitrogen, argon or helium; The protective gas filling is to fill protective gas to 1 atm; The ball milling treatment is performed at a rotation speed of 300-400 r / min for 10-30 h; The drying is vacuum drying, the drying time is 12-24 h, and the drying temperature is 60-80 ℃.

6. The method of claim 1, wherein the refractory alloy surface oxidation resistant coating is prepared by, In the step (2), the mixing mass ratio of the coating powder I and the binder is (1-2.5) g:1 mL.

7. The method of claim 1, wherein the refractory alloy surface oxidation resistant coating is prepared by, In the step (3), the first sintering is under vacuum condition, the sintering temperature is 1400-1500 ℃, the vacuum degree is ≥1.0×10 -2 Pa, and the sintering time is 20-40 min.

8. The method of claim 1, wherein the refractory alloy surface oxidation resistant coating is prepared by, In the step (4), the mixing mass ratio of the coating powder II and the binder is (1-2.5) g:1 mL.

9. The method of claim 1, wherein the refractory alloy surface oxidation resistant coating is prepared by, In the step (5), the second sintering is under vacuum condition, the sintering temperature is 1450-1550 ℃, the vacuum degree is ≥1.0×10 -2 Pa, and the sintering time is 20-40 min.

10. The method of claim 1, wherein In the step (2), the mixing time of the TaWZrHfTi supersaturated solid solution alloy powder and the Si powder is 5-10 h; and the mixing time of the coating powder I and the binder is 1-2 h.

11. The method of claim 1, wherein the refractory alloy surface oxidation resistant coating is prepared by, In the step (4), the mixing time of the TaWZrHfTi supersaturated solid solution alloy powder and the Si powder is 5-10 h; and the mixing time of the coating powder II and the binder is 1-2 h.

12. The method of claim 1, wherein the refractory alloy surface oxidation resistant coating is prepared by, In the step (3), before the coating slurry I is coated on the refractory alloy part, the step further comprises pretreating the refractory alloy part, wherein the pretreatment is polishing the surface of the refractory alloy part to expose the metal luster, ultrasonic cleaning the refractory alloy part in alcohol, and then drying.

13. The method of claim 1, wherein the refractory alloy surface oxidation resistant coating is prepared by, In the step (5), before the coating slurry II is coated on the coating alloy part I, the step further comprises pretreating the coating alloy part I, wherein the pretreatment is ultrasonic cleaning the coating alloy part I in alcohol, and then drying.

14. The method of claim 12, wherein the refractory alloy surface oxidation resistant coating is prepared by, In the step (3), the ultrasonic cleaning time is 15-25 min, and the drying temperature is 45-55℃, and the drying time is 10-15 min.

15. The method of claim 13, wherein the refractory alloy surface oxidation resistant coating is prepared by a process comprising: In the step (5), the ultrasonic cleaning time is 15-25 min, and the drying temperature is 45-55℃, and the drying time is 10-15 min.

16. Use of the refractory alloy surface oxidation-resistant coating prepared by the method of any one of claims 1-15 in preparation of a refractory metal-based alloy.

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