CN108585897B - Refractory metal high-temperature oxidation-resistant Si-Mo-YSZ coating and preparation method thereof - Google Patents

Abstract

The invention relates to a high-temperature oxidation-resistant Si-Mo-YSZ ceramic coating on the surface of a refractory metal material and a preparation method thereof. The coating raw materials include, in mass percentage, Si45%-65%, Mo25%-40%, YSZ 2%-15%, and additives 2%-8%. In the present invention, the coating material is first made into slurry, and the slurry is coated on the surface of the refractory metal, and the coating is prepared by sintering at 1370° C. to 1530° C. for 20 minutes to 90 minutes. In the invention, by rationally allocating coating components and matching the thermal expansion coefficient of the refractory metal matrix, the coating can quickly form a ZrSiO ₄ ‑ZrO ₂ ‑SiO ₂ composite oxide film during use, effectively reducing the oxygen diffusion coefficient of the coating, and realizing various Refractory metal materials are used for long-term oxidation resistance at high temperatures above 1700 °C. The invention has simple process, low cost, good thermal matching between the coating and the substrate, and can effectively improve the high-temperature oxidation resistance of the refractory metal.

Description

A kind of refractory metal high temperature oxidation resistant Si-Mo-YSZ coating and preparation method thereof

technical field

The invention belongs to the technical field of high-temperature oxidation-resistant coating preparation, in particular to a high-temperature oxidation-resistant Si-Mo-YSZ coating for refractory metal materials and a preparation method thereof.

Background technique

Refractory metals and their alloys have the advantages of high high temperature strength, good processing plasticity, and strong resistance to liquid metal corrosion. and other high temperature applications. However, due to the high oxygen affinity and high solubility of refractory metals, their high-temperature oxidation resistance is extremely poor. When they are far below the service temperature (about 700 °C), severe oxidation occurs and high-temperature mechanical properties drop sharply, which limits their high-temperature performance. Engineering applications in aerobic environments. At present, anti-oxidation coating is the most effective way to solve the high temperature oxidation protection of refractory metals and their alloys.

At present, refractory metal high temperature anti-oxidation coatings include aluminide coatings, precious metal coatings, boride coatings and silicide coatings. Among them, aluminide coatings represented by Al-Cr-Si, Al-Si and Al-Sn are widely used in the aerospace field, with excellent creep, fatigue properties and low temperature oxidation resistance, but the operating temperature is generally No more than 1500°C; precious metal coatings represented by Ir and Pt have the characteristics of high melting point, good chemical inertness, low oxygen permeability, etc., and the protection temperature can reach 2200°C, but there are extremely high prices, high technical thresholds, and special equipment required. , low emissivity of the coating and other bottlenecks; boride coatings represented by ZrB ₂ and HfB ₂ have the potential for ultra-high temperature protection, but currently they can only be used for short-term protection in s and are generally single-use, It cannot be used for long-term protection in h, and there are problems such as mismatch with the thermal expansion coefficient of the refractory metal matrix and poor thermal shock performance. Silicide coating is currently the most widely used and most studied high-temperature anti-oxidation coating for refractory metals. Its anti-oxidation mechanism is mainly to form a high-temperature self-healing SiO ₂ glass film with low oxygen diffusion rate. Since the melting point of the SiO ₂ oxide film is only 1600°C (quartz type) ~ 1710°C (cristobalite type), it is difficult to be used in a higher temperature service environment, so a lot of coating modification research has been carried out at home and abroad for different research and development goals. _The selection principle, introduction form and addition ratio of modified elements will directly change the coating structure, phase structure matching, thermal expansion coefficient, high temperature oxidation resistance and other comprehensive properties. It is a complex system engineering. The research on basic data, oxidation theory, and protective mechanism is still in the exploratory stage, so there are still few silicide coating systems that have been publicly reported using temperatures over 1700 °C.

With the rapid development of technology, the performance requirements of high temperature anti-oxidation coatings for refractory metals are gradually increasing. It is urgent to enrich the high-temperature anti-oxidation coating systems that can be used at temperatures of 1700 °C and above to meet the needs of different application environments.

SUMMARY OF THE INVENTION

Aiming at the problem that the protection temperature of the current refractory metal high temperature anti-oxidation coating is relatively low, the purpose of the present invention is to provide a refractory metal Si-Mo-YSZ coating with simple preparation process, low cost and excellent ultra-high temperature oxidation resistance. The invention provides a layer and a preparation process thereof, and solves the problem of oxidation protection of a refractory metal matrix in an ultra-high temperature environment above 1700°C.

The present invention is a refractory metal ultra-high temperature oxidation-resistant Si-Mo-YSZ coating, and the raw materials used in the coating include the following components in mass percent:

Si powder 45%-65%, preferably 49-59%, more preferably 54-59%;

Mo 25% to 40%, preferably 25 to 35%, more preferably 25 to 31%;

YSZ 2%-15%, preferably 8-12%, more preferably 9.5-10.5%; still more preferably 10%;

Additives 2% to 8%, preferably 3 to 7.5%, more preferably 3 to 6%;

The additive is selected from at least one of SiO ₂ powder, NH ₄ F powder, and PVB powder. As a preferred solution, the additive is composed of at least two of SiO ₂ powder, NH ₄ F powder, and PVB powder.

Wherein YSZ is yttria-stabilized zirconia, and the addition amount of yttrium oxide is 3%-10%. It is preferably 8%.

A preparation method of a refractory metal ultra-high temperature oxidation-resistant Si-Mo-YSZ coating of the present invention comprises the following steps:

step one

Allocate Si powder, Mo powder, YSZ powder and additives according to the design composition; mix them evenly and make slurry; obtain spare materials;

Step 2

Taking the refractory metal with clean and dry surface as the base, coating a layer of spare material on the surface of the base; drying to obtain the base with spare material;

Step 3

The substrate with the spare material obtained in step 2 is placed in a sintering furnace, sintered at 1370°C to 1530°C under a protective atmosphere, kept warm, and cooled to obtain a refractory metal ultra-high temperature oxidation-resistant Si-Mo-YSZ coating.

As a preferred solution, the present invention provides a method for preparing a refractory metal ultra-high temperature oxidation-resistant Si-Mo-YSZ coating. In step 1, Si powder, Mo powder, YSZ powder, and additives are taken as raw materials according to the design composition. ; Use alcohol solution as ball milling medium, control the mass ratio of raw materials and grinding balls to be 1:5~10, control the ball milling speed to be 200r/min~400r/min; ball mill for 5h~15h to obtain spare materials. As a further preferred solution, the mass ratio of the raw material to the ball milling medium is 2:1 to 2:5. The ball milling medium is preferably ethanol.

The present invention is a preparation method of a refractory metal ultra-high temperature oxidation-resistant Si-Mo-YSZ coating. In step 1, the average particle size of the Si powder is 0.5-5 μm, preferably 0.5-3 μm, and the Mo powder is The average particle size of the body is 2 μm to 10 μm, the average particle size of the YSZ powder is 0.1 to 3 μm, preferably 0.1 to 0.5 μm, and the average particle size of the other additives is 0.1 to 10 μm. The purity of Si powder, Mo powder and YSZ powder is not less than 98%.

As a preferred solution, a method for preparing a refractory metal ultra-high temperature oxidation-resistant Si-Mo-YSZ coating of the present invention, in step 2, the refractory metal with a clean and dry surface is prepared by the following scheme: The substrate is polished, after pickling and alkali washing, ultrasonically cleaned in alcohol, and dried in a drying box to obtain a refractory metal with a clean and dry surface.

As a preferred solution, a method for preparing a refractory metal ultra-high temperature oxidation-resistant Si-Mo-YSZ coating of the present invention, in step 2, the refractory metal is selected from Mo, Mo-based alloys, Ta, Ta-based alloys, Nb, Nb Base alloy, one of W and W base alloys.

As a preferred solution, a method for preparing a refractory metal ultra-high temperature oxidation-resistant Si-Mo-YSZ coating of the present invention, in step 2, the standby material obtained in step 1 is evenly coated on the surface by dipping and/or spraying The surface of the refractory metal is cleaned and dried to form a coating with a thickness of 120 μm to 300 μm, and then placed in an oven to be dried at 70 to 200° C. for 20 to 120 minutes; the substrate with the spare material is obtained.

As a preferred solution, a method for preparing a refractory metal ultra-high temperature anti-oxidation Si-Mo-YSZ coating of the present invention, in step 3, the substrate with the spare material obtained in step 2 is placed in a sintering furnace, and under a protective atmosphere, Heat up to 1370℃～1530℃ at a heating rate of 5℃/min～50℃/min, keep for 20min～90min and then cool down with the furnace, after cooling, Si-Mo-YSZ with a thickness of 80μm～200μm is obtained on the surface of the refractory metal material High temperature oxidation resistant coating.

In step 3, the protective atmosphere is selected from at least one of argon, helium, and nitrogen.

The high-temperature anti-oxidation Si-Mo-YSZ coating designed and prepared by the present invention has a static anti-oxidation life at 1725 DEG C of 6-15 hours.

As a preferred solution, a method for preparing a refractory metal ultra-high temperature anti-oxidation Si-Mo-YSZ coating of the present invention, in order to further improve the performance, after the third step is completed, a silicon infiltration process can be used. _The silicon infiltration process is as follows: the coated refractory metal sample is placed in a crucible containing an infiltrating material, sealed, and then placed in a vacuum sintering furnace. _3. It is composed of 15%-25% Si and 5-15% NH ₄ F. The coating sample can be prepared by keeping the temperature at 1100 ℃～1300 ℃ for 2-6 hours under argon protective atmosphere and then cooling with the furnace.

After optimization, the high temperature anti-oxidation Si-Mo-YSZ coating designed and prepared by the present invention has a static anti-oxidation life of 22.3 hours at 1725°C and 10-12 hours at 1800°C. It is subjected to a cyclic oxidation test at room temperature -1800 ℃, and its life span is 214 cycles.

Principle of the Invention

The coating of the invention adopts three main raw materials, Si powder, Mo powder and ultrafine YSZ powder, and is supplemented by one or more additives in _NH4F , PVB and _SiO2 , and is sintered by high temperature in-situ reaction to react. (1) to (5) A coating outer layer containing MoSi ₂ , ZrSi ₂ , and SiO ₂ as main phases is formed. Among them, NH ₄ F is used as a reaction activator to promote the in-situ reaction at high temperature; PVB is used as a binder to promote the formation of the coating embryo, which is beneficial to the thickening of the coating; SiO ₂ is used to adjust the thermal expansion coefficient of the coating.

3Si(l)+5Mo(s)=Mo ₅ Si ₃ (s) (1)

2Si(l)+Mo(s)=MoSi ₂ (s) (2)

7Si(l)+Mo ₅ Si ₃ (s)=5MoSi ₂ (s) (3)

Si(l)+ZrO ₂ (s)=ZrSi(s)+SiO ₂ (s) (4)

Si(l)+ZrSi(s)=ZrSi ₂ (s) (5)

The use of ultra-fine YSZ powder instead of coarse YSZ powder is mainly based on the larger surface contact area of the ultra-fine powder, which can promote the in-situ reaction at high temperature, and is conducive to the formation of a ZrSi ₂ phase that better matches the MoSi ₂ main phase. The internal stress of the coating can be reduced, and on the other hand, the ZrSi ₂ phase with fine grains is formed in the grain boundary region of the larger MoSi ₂ phase, which makes the coating more dense. ZrSi ₂ exists in the MoSi ₂ grain boundary region, which can block the grain boundary (the channel through which high-temperature oxygen quickly enters the interior of the coating), which is beneficial to improve the high-temperature oxygen permeation resistance of the coating, thereby improving the high-temperature oxidation resistance of the coating to a certain extent. The introduction of Y element is beneficial to the grain refinement of the coating on the one hand; on the other hand, it is beneficial to inhibit the volume expansion caused by the high and low temperature phase transition of ZrO ₂ , which is beneficial to improve the high temperature protection performance of the coating.

During the ultra-high temperature oxidation process higher than 1700℃, the refractory metal matrix Si-Mo-YSZ coating reacts (6)～(10) to rapidly form a composite oxide film of ZrSiO ₄ +ZrO ₂ +SiO ₂ , due to ZrSiO ₄ The melting points of ZrO ₂ and ZrO ₂ are 2550℃ and 2715℃, respectively, which is higher than the melting point of SiO ₂ by _1670-1710 ℃, which is beneficial to improve the temperature resistance of the oxide film. The viscosity is increased, the SiO ₂ volatilization rate is reduced, the erosion resistance of the oxide film is improved, and the ultra-high temperature oxidation resistance of the composite oxide film is improved.

5MoSi ₂ (s)+7O ₂ (g)=Mo ₅ Si ₃ (s)+7SiO ₂ (l) (6)

2Mo ₅ Si ₃ (s)+21O ₂ (g)=10MoO ₃ (g)+6SiO ₂ (l) (7)

2MoSi ₂ +7O ₂ (g)=2MoO ₃ (g)+4SiO ₂ (l) (8)

ZrSi ₂ (s)+3O ₂ (g)=ZrSiO ₄ (s)+SiO ₂ (l) (9)

ZrSiO ₄ (s)=ZrO ₂ (s)+SiO ₂ (l) (10)

Advantages and Benefits of the Invention

1. In the present invention, an appropriate amount of Mo, Si and YSZ are used as the main formulation of the coating, and the outer layer is Y-modified MoSi ₂ +ZrSi ₂ +SiO ₂ and the inner layer is MSi ₂ + by a simple slurry reaction sintering method. The composite coating of M ₅ Si ₃ (M refers to the element of refractory metal and its alloy substrate), and the thermal expansion coefficient of the coating can be adjusted according to the thermal expansion coefficient of the refractory metal alloy substrate, so as to achieve compatibility with common refractory metals and The good matching of its alloys greatly reduces all kinds of defects caused by thermal stress. The coating can rapidly form a ZrO ₂ +ZrSiO ₄ +SiO ₂ composite oxide film with high viscosity and low evaporation rate in an ultra-high temperature oxidation environment. Compared with the prior art, the product of the present invention has excellent anti-oxidation performance at ultra-high temperature. After optimization, the static anti-oxidation life at 1725°C is more than 22h, and the static anti-oxidation life at 1800°C is more than 10h.

2. The present invention adopts the slurry sintering method to prepare the coating. Compared with the prior art, the preparation method of the present invention does not need to use relatively expensive equipment such as plasma spraying, magnetron sputtering, chemical vapor deposition, etc., the preparation process is simple, the production cost is low, and it is suitable for difficult objects with different shapes and sizes. The molten metal base material, and the coating raw materials are commonly used industrial finished raw materials, and the price is relatively low.

Description of drawings:

Figure 1 shows the cross-sectional morphology and surface scanning analysis of the original coating of TZM molybdenum alloy Si-Mo-YSZ

Figure 2 shows the cross-sectional morphology and surface scanning analysis of TZM molybdenum alloy Si-Mo-YSZ coating after high temperature oxidation at 1725℃ for 8h

Fig.3 Cross-sectional morphology of Ta-10W alloy Si-Mo-YSZ original coating and its line scan analysis: (a) cross-sectional morphology of original coating; (b) coating line scan analysis results

Fig.4 Oxidation kinetics curve of Ta-10W alloy Si-Mo-YSZ coating at 1800℃: (a) Macromorphology comparison and oxidation weight gain of Ta-10W alloy coated and uncoated after oxidation; (b) Fitting plot of the square of the oxidative weight gain of the coating versus time

Fig.5 Cross-sectional and surface topography of Ta-10W alloy Si-Mo-YSZ coating after oxidation at 1800℃ for 10h: (a) cross-sectional topography; (b) surface topography

It can be seen from Figure 1 that the TZM molybdenum alloy Si-Mo-YSZ composite coating can be divided into two layers, namely the outer layer of MoSi ₂ +ZrSi ₂ +SiO ₂ containing Y and the inner layer of pure MoSi ₂ .

It can be seen from Fig. 2 that after the TZM molybdenum alloy Si-Mo-YSZ coating is oxidized at a high temperature of 1725 °C, a Y-containing SiO ₂ oxide film with ZrO ₂ +ZrSiO ₄ high melting point particles dispersed on the surface is formed, and the coating structure evolves It is Y-containing ZrO ₂ +ZrSiO ₄ +SiO ₂ oxide layer-Y-containing MoSi ₂ +ZrSi ₂ +SiO ₂ coating outer layer-MoSi ₂ inner layer-Mo ₅ Si ₃ interface layer-Molybdenum alloy matrix.

It can be seen from Fig. 3 that the original coating structure of Ta-10W alloy Si-Mo-YSZ is Y-containing MoSi ₂ +ZrSi ₂ +SiO ₂ outer layer and TaSi ₂ +WSi ₂ inner layer.

It can be seen from Fig. 4 that the uncoated Ta-10W alloy was completely pulverized in the atmosphere at 1800 °C for only 6 minutes, with a weight gain of 1770.227 mg cm ^-2 , while the Si-Mo-YSZ coating was The layered Ta-10W alloy did not fail after being oxidized for 10 h in the same environment, the weight gain was only 6.729 mg cm ^-2 , and the oxidation weight gain rate K _p was 4.378 mg ² cm ^-4 h ^-1 .

It can be seen from Figure 5 that the Ta-10W alloy Si-Mo-YSZ coating formed a composite oxide film with a thickness of 68 microns after being oxidized at 1800 °C for 10 h, with fine micro-cracks visible on the surface layer, and the coating structure evolved into Y-containing ZrO ₂ +ZrSiO ₄ +SiO ₂ oxide layer-Y-containing MoSi ₂ +ZrSi ₂ +SiO ₂ coating outer layer-TaSi ₂ +WSi ₂ inner layer-Ta ₅ Si ₃ +W ₅ Si ₃ interface layer- Tantalum-tungsten alloy matrix .

Detailed ways:

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

Example 1

(1) Substrate pretreatment: Select TZM molybdenum alloy as the substrate, polish with sandpaper until the surface is smooth and flat, then carry out pickling and alkali cleaning treatment, then ultrasonically clean in alcohol, and dry in a drying box.

( ₂ ) Slurry preparation: Proportion according to the mass fraction of 58.5% Si powder, 29% Mo powder and 9.5% YSZ powder, the average particle sizes of the three are 1 μm, 3 μm and 100 nm respectively; 2μm NH ₄ F powder and 5μm PVB powder are used as additives, and the mass fraction ratios are 0.5%, 2% and 0.5% respectively; the purity of the six powders is not less than 99%. Put the prepared coating raw materials into the ball milling tank, the ball milling medium is ethanol, the ball-to-material ratio is 8:1, the rotation speed is 300r/min, and the ball milling time is 10h.

(3) Evenly coating the slurry and drying: The slurry described in (2) is evenly coated on the surface of the molybdenum alloy substrate after drying in (1) by spraying, and a thickness of about 140 μm is formed on the surface. The coated embryos were then dried in a drying oven at 110 °C for 1 h.

(4) Vacuum sintering: Put the coated molybdenum alloy sample in (3) into a vacuum sintering furnace, and under argon protection, the temperature is raised to 1450 ℃ at a heating rate of 10 ℃/min for sintering, and the temperature is kept for 60 minutes. Then cool down with the furnace, and take out the sample after cooling.

(5) Silicon infiltration treatment: The prepared coated sample is placed in a crucible containing an infiltrating material, sealed and placed in a vacuum furnace. The infiltrating material is composed of 53% by mass Al ₂ O ₃ , 25% Si and The composition of 12% NH ₄ F was kept at 1150 ℃ for 4 hours under argon protective atmosphere, and then cooled in the furnace. After cooling, a Si-Mo-YSZ high-temperature anti-oxidation coating with a thickness of 120 μm was obtained on the surface of the molybdenum alloy. The cross-sectional morphology of the original coating and its surface scanning analysis are shown in Figure 1.

(6) The ultra-high temperature anti-oxidation Si-Mo-YSZ coating sample of molybdenum alloy prepared in the embodiment is subjected to a static anti-oxidation test at 1725 ℃, and its static anti-oxidation life is 22.3h. The cross-sectional morphology and surface scanning analysis of the coating after oxidation at 1725 °C for 8 h are shown in Figure 2.

Example 2

(1) Substrate pretreatment: Select TZM molybdenum alloy as the substrate, polish with sandpaper until the surface is smooth and flat, then carry out pickling and alkali cleaning treatment, then ultrasonically clean in alcohol, and dry in a drying box.

(2) Slurry preparation: Proportion according to the mass fraction of 54% Si powder, ₂₅ % Mo powder and 15% YSZ powder, the average particle sizes of the three are 1 μm, 3 μm and 100 nm respectively; The 2μm NH ₄ F powder was used as an additive, and the mass fraction ratios were 0.5% and 5.5%, respectively; the purity of the five powders was not less than 99%. Put the prepared coating raw materials into the ball milling tank, the ball milling medium is ethanol, the ball-to-material ratio is 5:1, the rotation speed is 350r/min, and the ball milling time is 7h.

(3) uniformly coating the slurry and drying: the slurry described in (2) is evenly coated on the surface of the molybdenum alloy substrate after drying in (1) by spraying, and a thickness of about 170 μm is formed on the surface. The coated embryos were then dried in a drying oven at 200 °C for 0.5 h.

(4) Vacuum sintering: Put the coated molybdenum alloy sample in (3) into a vacuum sintering furnace, and under argon protection, the temperature is raised to 1400 ℃ at a heating rate of 30 ℃/min for sintering, and the temperature is kept for 90 minutes. After cooling in the furnace, a Si-Mo-YSZ high-temperature anti-oxidation coating with a thickness of 120 μm was obtained on the surface of the molybdenum alloy after cooling, and the samples were taken out.

(5) The ultra-high temperature anti-oxidation Si-Mo-YSZ coating sample of molybdenum alloy prepared in the example was subjected to a static anti-oxidation test at 1725 ℃, and its static anti-oxidation life was 11.2 hours.

Example 3

(1) Substrate pretreatment: select Ta-10W alloy as the substrate, polish with sandpaper until the surface is smooth and flat, then carry out pickling and alkali cleaning, then ultrasonically clean in alcohol, and dry in a drying box .

( ₂ ) Slurry preparation: Proportion according to the mass fraction of 56% Si powder, 30% Mo powder and 10% YSZ powder, the average particle sizes of the three are 1 μm, 2 μm and 200 nm respectively; The 5 μm PVB powder is used as an additive, and the mass fraction ratio is 3% and 1% respectively; the purity of the five powders is not less than 99%. Put the prepared coating raw materials into the ball milling tank, the ball milling medium is ethanol, the ball-to-material ratio is 10:1, the rotation speed is 400r/min, and the ball milling time is 6h.

(3) Evenly coating the slurry and drying: The slurry described in (2) was evenly coated on the surface of the Ta-10W alloy substrate after drying in (1) by spraying, and the thickness was 180 μm on the surface. The coating was then placed in a vacuum drying oven at 100 °C for vacuum drying for 1 h.

(4) Vacuum sintering: Put the coated Ta-10W alloy sample in (3) into a vacuum sintering furnace, and sinter it at a heating rate of 10°C/min to 1450°C under argon protection. After holding for 60 min, the temperature was lowered with the furnace, and the sample was taken out after cooling.

(5) Silicon infiltration treatment: The prepared coated sample is placed in a crucible containing an infiltration material, sealed and placed in a vacuum furnace. The infiltration material is composed of 70% by mass of Al ₂ O ₃ , 20% of Si and The Ta-W alloy Si-Mo-YSZ high temperature anti-oxidation coating sample was prepared by holding the temperature at 1200℃ for 5h under the protective atmosphere of argon gas, and then cooling down in the furnace. The coating thickness was about _154μm . The cross-sectional morphology and composition analysis of the original coating are shown in Figure 3.

(6) The Ta-10W alloy ultra-high temperature oxidation-resistant Si-Mo-YSZ coating sample prepared in the example was subjected to a static oxidation resistance test at 1800 °C, and the oxidation kinetics curve is shown in Figure 4; its static oxidation resistance life exceeds 10h It has not failed yet, and the cross-section and surface morphology of the coating after oxidation are shown in Figure 5; it was subjected to a cyclic oxidation test at room temperature -1800 °C, and the life span was 214 cycles.

Example 4

(1) Substrate pretreatment: Nb521 niobium alloy is selected as the substrate, polished with sandpaper until the surface is smooth and flat, and then subjected to acid washing and alkali washing treatment, then ultrasonically cleaned in alcohol, and dried in a drying box.

(2) Slurry preparation: Proportion according to the mass fraction of 49.5% Si powder, 40% Mo powder and ₅ % YSZ powder, the average particle sizes of the three are 3 μm, 5 μm and 500 nm respectively; The 10μm PVB powder was used as an additive, and the mass fraction ratios were 5% and 0.5%, respectively; the purity of the four powders was ≥99%. Put the prepared coating raw materials into the ball milling tank, the ball milling medium is ethanol, the ball-to-material ratio is 10:1, the rotation speed is 250r/min, and the ball milling time is 15h.

(3) Evenly coating the slurry and drying: The slurry described in (2) is evenly coated on the surface of the Nb521 niobium alloy substrate after drying in (1) by spraying, forming a thickness of about 150 μm on the surface. The coated embryos were then placed in a drying oven at 150 °C for 0.5 h.

(4) Vacuum sintering: put the coated Nb521 niobium alloy sample in (3) into a vacuum sintering furnace, and under argon protection, the temperature is raised to 1500 ℃ at a heating rate of 20 ℃/min for sintering, and the temperature is kept warm. After 40 minutes, the temperature was lowered in the furnace. After cooling, a Si-Mo-YSZ high-temperature anti-oxidation coating with a thickness of 100 μm was obtained on the surface of the Nb521 niobium alloy.

(5) The Nb521 niobium alloy ultra-high temperature anti-oxidation Si-Mo-YSZ coating sample prepared in the example was subjected to a static anti-oxidation test at 1725 ℃, and its static anti-oxidation life was 13.5h, and the protection life at 1800 ℃ was 4.1h .

The above descriptions are only some embodiments of the present invention, so the scope of implementation of the present invention cannot be limited based on this. That is, equivalent changes and modifications made according to the patent scope of the present invention and the contents of the description should still be covered by the present invention. within the range.

For the comparison of YSZ content, all the processes and raw materials are the same as in Example 1, but the ratio of Mo and YSZ has been adjusted. When Mo is 34% and YSZ is 4.5%, the Si-Mo-YS coating has a static high temperature resistance at 1725 ℃. The oxidation performance is 13.5h. When Mo is 34% and YSZ is 14.5%, the static high temperature oxidation resistance at 1725°C is 14.2h, which is quite different from 22.3h in Example 1.

Comparative Example 1:

(1) Substrate pretreatment: Select TZM molybdenum alloy as the substrate, polish with sandpaper until the surface is smooth and flat, then carry out pickling and alkali cleaning treatment, then ultrasonically clean in alcohol, and dry in a drying box.

( ₂ ) Slurry preparation: Proportion according to the mass fraction of 58.5% Si powder, 15% Mo powder and 25% YSZ powder, the average particle sizes of the three are 1 μm, 3 μm and 100 nm respectively; The 10μm PVB powder is used as an additive, and the mass fraction ratios are 1% and 0.5%, respectively; the purity of the five powders is not less than 99%. Put the prepared coating raw materials into the ball milling tank, the ball milling medium is ethanol, the ball-to-material ratio is 5:1, the rotation speed is 350r/min, and the ball milling time is 7h.

(3) Evenly coating the slurry and drying: The slurry described in (2) is evenly coated on the surface of the dried molybdenum alloy substrate in (1) by spraying, and a thickness of about 150 μm is formed on the surface. The coated embryos were then dried in a drying oven at 200 °C for 0.5 h.

(4) Vacuum sintering: Put the coated molybdenum alloy sample in (3) into a vacuum sintering furnace, and under argon protection, the temperature is raised to 1400 ℃ at a heating rate of 30 ℃/min for sintering, and the temperature is kept for 60 minutes. After cooling in the furnace, a Si-Mo-YSZ high-temperature anti-oxidation coating with a thickness of 100 μm was obtained on the surface of the molybdenum alloy after cooling, and the sample was taken out.

(5) The ultra-high temperature anti-oxidation Si-Mo-YSZ coating sample of molybdenum alloy prepared in the comparative example was subjected to static anti-oxidation test at 1725 ℃, and its static anti-oxidation life was about 0.4h.

Comparative Example 2:

(1) Substrate pretreatment: select Ta-10W alloy as the substrate, polish with sandpaper until the surface is smooth and flat, then carry out pickling and alkali cleaning, then ultrasonically clean in alcohol, and dry in a drying box .

(2) Slurry preparation: Proportion according to the mass fraction of 56% Si powder, ₁₀ % Mo powder and 30% YSZ powder, the average particle sizes of the three are 1 μm, 2 μm and 200 nm respectively; The 5 μm PVB powder is used as an additive, and the mass fraction ratio is 3% and 1% respectively; the purity of the five powders is not less than 99%. Put the prepared coating raw materials into the ball milling tank, the ball milling medium is ethanol, the ball-to-material ratio is 10:1, the rotation speed is 400r/min, and the ball milling time is 6h.

(3) Evenly coating the slurry and drying: The slurry described in (2) was evenly coated on the surface of the Ta-10W alloy substrate after drying in (1) by spraying, and the thickness was 180 μm on the surface. The coating was then placed in a vacuum drying oven at 100 °C for vacuum drying for 1 h.

(4) Vacuum sintering: Put the coated Ta-10W alloy sample in (3) into a vacuum sintering furnace, and sinter it at a heating rate of 10°C/min to 1450°C under argon protection. After holding for 60 min, the temperature was lowered with the furnace, and a sample with a thickness of 130 μm was obtained after cooling.

(5) The Ta-10W alloy ultra-high temperature oxidation-resistant Si-Mo-YSZ coating sample prepared in the example was subjected to a static oxidation resistance test at 1800 °C, and its static oxidation resistance life was 0.1 h.

Claims (6)

1. A refractory metal ultrahigh-temperature oxidation-resistant Si-Mo-YSZ coating is characterized in that: the coating comprises the following raw materials in percentage by mass:

54-59% of Si powder;

Mo 25~31%；

YSZ 9.5~10.5%；

3-6% of additives;

the additive is selected from SiO₂Powder, NH₄At least one of F powder and PVB powder;

the refractory metal ultrahigh-temperature oxidation-resistant Si-Mo-YSZ coating is prepared by the following steps:

step one

Distributing and taking Si powder, Mo powder, YSZ powder and additives according to a design group; mixing uniformly and preparing into slurry; obtaining a standby material;

step two

Taking refractory metal with clean and dry surface as a substrate, and coating a layer of standby material on the surface of the substrate; drying to obtain a matrix with standby materials;

step three

Placing the substrate with the spare materials obtained in the step two into a sintering furnace, sintering at 1370-1530 ℃ under protective atmosphere, preserving heat, and cooling to obtain a refractory metal ultrahigh-temperature oxidation-resistant Si-Mo-YSZ coating;

after the third step is finished, a pack siliconizing process is adopted; the pack siliconizing process comprises the following steps: placing the prepared refractory metal sample with the coating in a crucible containing a penetration material, sealing, and then placing in a vacuum sintering furnace, wherein the penetration material is made of Al with the mass percentage of 70%₂O₃20% Si and 10% NH₄And F, preserving the temperature at 1100-1300 ℃ for 2-6 h under the argon protective atmosphere, and then cooling along with the furnace to obtain the coating sample.

2. The refractory metal ultrahigh temperature oxidation resistant Si-Mo-YSZ coating according to claim 1, characterized in that: in the first step, Si powder, Mo powder, YSZ powder and additives are taken as raw materials according to the design group distribution; taking an alcoholic solution as a ball milling medium, and controlling the mass ratio of raw materials to milling balls to be 1: 5-10, and controlling the ball milling rotation speed to be 200 r/min-400 r/min; ball milling is carried out for 5-15 h, and a standby material is obtained.

3. The refractory metal ultrahigh temperature oxidation resistant Si-Mo-YSZ coating according to claim 1, characterized in that: in the first step, the average grain size of the Si powder is 0.5-5 μm, the average grain size of the Mo powder is 2-10 μm, the average grain size of the YSZ powder is 0.1-3 μm, and the average grain size of the additive is 0.1-10 μm.

4. The refractory metal ultrahigh temperature oxidation resistant Si-Mo-YSZ coating according to claim 1, characterized in that: in the second step, the refractory metal is selected from one of Mo, Mo-based alloy, Ta-based alloy, Nb-based alloy and W, W-based alloy.

5. The refractory metal ultrahigh temperature oxidation resistant Si-Mo-YSZ coating according to claim 1, characterized in that: step two, uniformly coating the standby material obtained in the step one on the surface of the clean and dry refractory metal by adopting a dip coating and/or spray coating mode to form a coating with the thickness of 120-300 mu m, and then drying the coating in an oven at the temperature of 70-200 ℃ for 20-120 min; obtaining the matrix with the standby material.

6. The refractory metal ultrahigh temperature oxidation resistant Si-Mo-YSZ coating according to claim 1, characterized in that: and step three, placing the substrate with the standby material obtained in the step two in a sintering furnace, heating to 1370-1530 ℃ at a heating rate of 5-50 ℃/min in a protective atmosphere, keeping the temperature for 20-90 min, cooling along with the furnace, and cooling to obtain a Si-Mo-YSZ high-temperature oxidation resistant coating with the thickness of 80-200 mu m on the surface of the refractory metal material.

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