CN114657525B - FeCrAl/Ta alloy coating and preparation method thereof - Google Patents

Abstract

The invention discloses a FeCrAl/Ta alloy coating and a preparation method thereof, comprising a Ta transition layer and a FeCrAl layer deposited on its surface; the chemical composition of the FeCrAl coating is Fe:Cr:Al, and the atomic percentage is 79:10:11at%. . The FeCrAl/Ta alloy coating was prepared on the polished zirconium alloy substrate by magnetron sputtering. By controlling the deposition sequence of the Ta target and the FeCrAl alloy target, a Ta transition layer was deposited between the FeCrAl coating and the zirconium alloy substrate. The surface of the intermediate transition layer prepared by the method is smooth and has few defects, which has little influence on the structure of the upper coating, and the interface of the double-layer coating is clear and stable, which is beneficial to the bonding performance of the film-base interface, and the obtained film has uniform composition and compact structure; The addition of can effectively improve the service correlation of FeCrAl coating.

Description

A kind of FeCrAl/Ta alloy coating and preparation method thereof

technical field

The invention relates to the field of metal surface modification, in particular to a FeCrAl/Ta alloy coating and a preparation method thereof.

Background technique

FeCrAl alloy is widely used in aerospace, military industry, nuclear reactor and other fields due to its excellent high temperature oxidation resistance and mechanical properties. During the high temperature oxidation process, the Cr and Al elements in the alloy can quickly form a dense Cr ₂ O ₃ and Al ₂ O ₃ oxide layer on the surface of the sample, which hinders the further erosion of oxygen elements to the inside, showing excellent resistance to high temperature oxidation performance. Compared with the current zirconium alloy cladding materials, the oxidation kinetic rate constant of FeCrAl alloy is reduced by 3 to 5 orders of magnitude, while maintaining good high temperature mechanical properties. Therefore, it is listed as a candidate material for reactor accident-tolerant fuel zirconium alloy cladding coating.

The surface modification of the active Zr alloy is to prepare a layer of anti-oxidation and corrosion-resistant protective coating on the surface of the cladding, which can realize the physical isolation between the zirconium cladding and the coolant without changing the structural design of the reactor, and improve its performance. Accident fault tolerance is the most realistic and feasible solution to improve the service safety of nuclear cladding in the short term.

However, the FeCrAl coating is directly deposited on the surface of the Zr alloy. Since the Fe-Zr eutectic temperature is only 928°C, when a dehydration accident occurs, the cladding temperature can reach 1200°C. During the high-temperature water vapor oxidation process, the coating Severe interdiffusion will occur with matrix elements. In the interdiffusion zone, a large number of cavities will be formed due to the dissolution of Fe-Zr eutectic and the Kirkendall effect, which will seriously deteriorate the mechanical properties of the matrix and the bonding of the film-base interface, and even cause matrix deformation and coating peeling off.

Contents of the invention

Aiming at the problems existing in the prior art, the invention provides a FeCrAl/Ta alloy coating and a preparation method thereof. The prepared FeCrAl/Ta coating has a uniform and compact microstructure and excellent high-temperature oxidation resistance.

The present invention is achieved through the following technical solutions:

A FeCrAl/Ta alloy coating, comprising a Ta transition layer and a FeCrAl layer deposited on its surface;

The grains of the FeCrAl layer and the Ta transition layer are nano columnar crystals, the size of the nano columnar crystals is 50-80nm, and the thickness of the Ta layer is 20-200nm.

Preferably, the atomic percentage of each element in the FeCrAl layer is: Cr: 10-20 at.%, Al: 11 at.%, and the rest is Fe.

Preferably, the thickness of the FeCrAl layer is 2.3±0.2 μm.

A kind of preparation method of FeCrAl/Ta coating system, comprises the following steps:

Step 1, grinding, cleaning and vacuum etching the alloy substrate;

Step 2, using magnetron sputtering to sequentially sputter-deposit a Ta transition layer and a FeCrAl layer on the alloy substrate obtained in step 1, and cool to room temperature to obtain a FeCrAl/Ta alloy coating;

The Ta target is sputtered by radio frequency power, the sputtering power is 100W, and the deposition time of the Ta transition layer is 332s-3320s.

Preferably, the grinding and cleaning method of the alloy matrix described in step 1 is as follows:

The alloy substrate is ground and polished with sandpaper, and the polished alloy substrate is ultrasonically cleaned and dried.

Preferably, the method of described vacuum etching is as follows:

The cleaned alloy substrate was sent into the magnetron sputtering coating chamber, and then etched after vacuuming. The etching power was 200W, and the etching time was 5min.

Preferably, the method for depositing the Ta transition layer and the FeCrAl layer sequentially in step 2 is as follows:

The Ta target is firstly sputtered by radio frequency power source to deposit the Ta transition layer, and then two FeCrAl alloy targets are used for double target co-sputtering by DC power source.

Preferably, the purity of the Ta target is 99.99wt.%, the sputtering power is 100W, the deposition pressure is set at 0.3Pa, the deposition temperature is room temperature, and the rotation speed of the substrate is 15r/min.

Preferably, the alloy matrix is zirconium alloy, steel matrix or titanium alloy.

Compared with the prior art, the present invention has the following beneficial technical effects:

A FeCrAl/Ta alloy coating, due to the low solubility of pure metal Ta in Zr alloy, the interdiffusion coefficient with Zr matrix is low, and the thermal expansion coefficient is similar to that of FeCrAl alloy coating, the intermediate transition layer should be selected as much as possible Materials with larger atomic size, because materials with larger atomic size have higher diffusion activation energy, and the replacement compatibility between atomic sizes is small, which can hinder the interdiffusion between elements, Ta has a larger atomic size, Its morphology is nano-columnar crystal, and its structure is dense and uniform. It can be used as the preferred material for the intermediate transition layer between FeCrAl coating and Zr alloy matrix. Ta as the intermediate transition layer can improve the service performance of FeCrAl coating.

The preparation method of the FeCrAl/Ta alloy coating provided by the present invention alternately sputters the pure metal Ta target and the FeCrAl alloy target by magnetron sputtering, the deposited coating interface is obvious, and the deposition rate is fast; the working gas argon gas is sputtered out The scattering effect of the atoms is weak, and the deposition efficiency and the adhesion of the film are further improved. Therefore, the deposited film is uniform and dense, with few defects, high purity and strong adhesion. The present invention deposits a transition layer between the FeCrAl coating and the Zr alloy substrate by controlling the deposition sequence of the pure metal Ta target and the FeCrAl alloy target. The intermediate transition layer prepared by the method has a smooth surface and few defects, and is convenient for depositing the upper layer coating. The influence of the structure of the upper coating is small, and the interface of the double-layer coating is clear and stable, which is convenient for subsequent research on the characteristics and laws of the interface. The FeCrAl alloy target uses a DC power of 200W, and the pure metal Ta target uses a radio frequency power supply of 100W.

Finally, the finished product is naturally cooled to room temperature in a vacuum coating chamber to avoid debonding and breaking of the film from the substrate due to the difference in thermal expansion coefficient between the film and the substrate, and to prevent oxidation of the film.

Description of drawings

Fig. 1 is the SEM surface photograph of the FeCrAl/Ta alloy coating of the present invention and the element distribution diagram of the EDS surface scan.

Fig. 2 is the SEM photograph of the FeCrAl/Ta alloy coating section of the present invention.

Fig. 3 is a low-magnification cross-sectional TEM photo of the FeCrAl/Ta alloy coating of the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings, which are explanations rather than limitations of the present invention.

A FeCrAl/Ta alloy coating, comprising a Ta transition layer and a FeCrAl layer deposited on its surface; the Ta transition layer is pure metal Ta, and the atomic percentages of each element in the FeCrAl layer are, Cr:10-20at.%, Al:11at .%, the rest is Fe; the crystal grains of the Ta transition layer and the FeCrAl layer are nano columnar crystals, the columnar crystal size is 50-80nm, the thickness of Ta is 20-200nm, and the thickness of FeCrAl alloy coating is 2.3±0.2μm.

Fig. 1 has shown FeCrAl/Ta coating system SEM surface picture of the present invention and surface EDS scanning element distribution figure; Fig. 2 has shown FeCrAl/Ta coating system SEM section picture of the present invention; Fig. 3 has shown FeCrAl/Ta coating system of the present invention Low-resolution TEM cross-sectional images of the Ta coating system. According to the FeCrAl/Ta coating system of the present invention, the internal alloy elements are evenly distributed, and the crystal grains are nano columnar crystals. The FeCrAl/Ta coating system of the invention has a uniform and dense structure and excellent oxidation resistance.

A preparation method of FeCrAl/Ta alloy coating, comprising the following steps:

Step 1: Grinding and polishing the alloy substrate to remove the oxide layer on its surface.

The polishing and grinding method is as follows: the zirconium alloy substrate is ground using the "cross" grinding method, and the 600, 1000, 1500, and 2000-mesh sandpaper is sequentially ground, and then polished on a polishing machine, and the remaining surfaces are sequentially ground with 600, 1000, and 1500-mesh sandpaper , Grinding off the surface oxide layer until there are no scratches on the surface.

The alloy matrix is zirconium alloy, steel matrix or titanium alloy.

Step 2: Ultrasonic cleaning is performed on the alloy matrix after grinding and polishing in step 1.

Specifically, take the single-sided polished alloy substrate, ultrasonically clean it in acetone and ethanol for 10 minutes, and dry it to ensure that the surface of the substrate is clean and free from stains and dust. Matrix binding force.

Step 3: Etching the alloy matrix obtained in step 2 under vacuum conditions to remove impurities on the surface of the alloy matrix.

Specifically, the alloy substrate was glued to the substrate with conductive adhesive and sent into the coating chamber, the vacuum degree of the back was evacuated to below 4.0×10 ^-4 Pa, the etching power was 200W, and the etching time was 5 minutes.

Step 4: The Ta transition layer and the FeCrAl layer are successively sputter-deposited on the alloy substrate by magnetron sputtering, and after successively sputter-depositing to a preset thickness, cooling to room temperature to obtain a FeCrAl/Ta alloy coating.

Specifically, the ultrasonically cleaned alloy substrate is fixed on the base plate, and automatically sent into the magnetron sputtering coating chamber by automatic machinery, and vacuumed until the vacuum degree of the background is below 4.0×10 ^-4 Pa.

Ta target and FeCrAl alloy target are used to deposit Ta transition layer and FeCrAl layer on the alloy substrate in sequence, sputtering to a preset thickness. Due to the temperature rise during the deposition process, in order to ensure that the internal stress of the sample is small and prevent the sample from being oxidized in the air , the substrate is taken out after cooling to room temperature in a high-vacuum coating chamber to obtain a FeCrAl/Ta alloy coating.

The purity of the FeCrAl alloy target is 99.9wt.%. The atomic percentage of each element in the FeCrAl layer is Cr: 10-20 at.%, Al: 11 at.%, and the rest is Fe. The FeCrAl alloy target is sputtered by a DC power supply with a power of 200W.

Ta target purity 99.99wt.% is sputtered by radio frequency power supply, power 100W, deposition pressure is set at 0.3Pa, deposition temperature is at room temperature, substrate rotation speed is 15r/min, and the deposition preparation starts when the vacuum degree is below 4.0×10 ^-4 Pa. The deposition time of the Ta intermediate transition layer is 332s-3320s, the deposition time of the FeCrAl coating is 10800s, the thickness of the final Ta intermediate transition layer is 20-200nm, and the thickness of the FeCrAl coating is 2.3±0.2μm.

The principle of depositing a coating on the surface of a substrate by magnetron sputtering is: the Ar ⁺ ionized by Ar gas accelerates to bombard the surface of the cathode target under the action of an electric field, so that the target atoms sputtered by the target are deposited on the substrate, and the sputtered atoms are deposited on the substrate. Under the action of electric field and magnetic field, secondary electrons are bound in the plasma region close to the target surface, which increases the probability of collision with Ar, thus ionizes more Ar ⁺ , and achieves a higher deposition rate. After the deposition, the substrate is fully cooled in the high-vacuum coating chamber and taken out to prevent debonding, cracking, and oxidation of high-temperature air caused by the difference in thermal expansion coefficient between the substrate and the film material. Finally, a FeCrAl/Ta coating system with an intermediate transition layer Ta is deposited.

Example 1

Step 1: Grinding and polishing the zirconium alloy substrate with sandpaper.

Step 2: ultrasonically clean the single-side polished zirconium alloy substrate in acetone and ethanol for 10 min, and dry with a hair dryer.

Step 3: Fix the zirconium alloy base on the substrate, and then mechanically and automatically send it into the vacuum coating chamber. Before deposition, the vacuum degree of the background should be lower than 4.0×10 ^-4 Pa, and etch for 5 minutes, and the etching power is 200W .

Step 4: The Ta transition layer and the FeCrAl layer are successively sputter-deposited on the zirconium alloy substrate by magnetron sputtering, after successively sputter-depositing to a preset thickness, cooling to room temperature to obtain a FeCrAl/Ta alloy coating.

Among them, the purity of the FeCrAl alloy target is 99.9wt.%, the atomic percentage of Fe:Cr:Al is 79:10:11at.%, and it is sputtered with a DC power supply of 200W. The purity of the Ta target is 99.9wt.%, and a radio frequency power supply of 100W is used. Sputtering, deposition pressure 0.3Pa, deposition temperature at room temperature, substrate rotation speed 15r/min, Ta transition layer deposition time 1660s, FeCrAl coating deposition time 10800s, the thickness of the final Ta transition layer was 100±20nm, FeCrAl The coating thickness is 2.3±0.2 μm.

Step 5: After the deposition, the zirconium alloy substrate is taken out after natural cooling in a high-vacuum sputtering chamber for 4 hours to obtain a FeCrAl/Ta coating system.

The prepared FeCrAl/Ta coating system was characterized by microstructure and oxidation performance. The EDS element distribution data showed that the atomic percentage of Fe:Cr:Al was 79:10:11at.%, and the crystal grains were nano-columnar crystals, which had excellent high temperature oxidation resistance.

Example 2

Step 1: Sandpaper and polish the steel substrate.

Step 2: Ultrasonic clean the steel substrate polished on one side in acetone and ethanol for 10 min, and dry it with a hair dryer.

Step 3: Fix the steel substrate on the substrate, and then mechanically and automatically send it into the vacuum coating chamber. Before deposition, the vacuum degree of the background should be lower than 4.0×10 ^-4 Pa, and etch for 5 minutes, and the etching power is 200W.

Step 4: The Ta transition layer and the FeCrAl layer are successively sputter-deposited on the steel substrate by magnetron sputtering, and after successively sputter-depositing to a preset thickness, cooling to room temperature to obtain a FeCrAl/Ta alloy coating.

Among them, the purity of the FeCrAl alloy target is 99.9wt.%, the atomic percentage of Fe:Cr:Al is 74:15:11at.%, and it is sputtered with a DC power supply of 200W. The purity of the Ta target is 99.9wt.%, and a radio frequency power supply of 100W is used. Sputtering, the deposition pressure is 0.3Pa, the deposition temperature is room temperature, the substrate rotation speed is 15r/min, the Ta intermediate transition layer deposition time is 332s, the FeCrAl coating deposition time is 10800s, the thickness of the final Ta transition layer is 20nm, FeCrAl coating The layer thickness was 2.3±0.2 μm.

Step 5: After the deposition, the steel substrate was naturally cooled in a high-vacuum sputtering chamber for 4 hours and then taken out to obtain a FeCrAl/Ta coating system.

The prepared FeCrAl/Ta coating system was characterized by microstructure and oxidation performance. The EDS element distribution data showed that the atomic percentage of Fe:Cr:Al was 74:15:11at.%, and the crystal grains were nano-columnar crystals, which had excellent high temperature oxidation resistance.

Example 3

Step 1: Sandpaper the titanium alloy substrate and polish it.

Step 2: ultrasonically clean the titanium alloy substrate polished on one side in acetone and ethanol for 10 min, and dry it with a hair dryer.

Step 3: Fix the steel substrate on the substrate, and then mechanically and automatically send it into the vacuum coating chamber. Before deposition, the vacuum degree of the background should be lower than 4.0×10 ^-4 Pa, and etch for 5 minutes, and the etching power is 200W.

Step 4: The Ta transition layer and the FeCrAl layer are successively sputter-deposited on the titanium alloy substrate by magnetron sputtering, and after successively sputter-depositing to a preset thickness, cooling to room temperature to obtain a FeCrAl/Ta alloy coating.

Among them, the purity of the FeCrAl alloy target is 99.9wt.%, the atomic percentage of Fe:Cr:Al is 69:20:11at.%, and the sputtering is performed with a DC power supply of 200W. The purity of the Ta target is 99.9wt.%, and the RF power supply is 100W. Sputtering, the deposition pressure is 0.3Pa, the deposition temperature is room temperature, the substrate rotation speed is 15r/min, the Ta intermediate transition layer deposition time is 3320s, the FeCrAl coating deposition time is 10800s, the thickness of the final Ta transition layer is 200nm, FeCrAl coating The layer thickness was 2.3±0.2 μm.

Step 5: After the deposition, the titanium alloy substrate was naturally cooled in a high-vacuum sputtering chamber for 4 hours and then taken out to obtain a FeCrAl/Ta coating system.

The prepared FeCrAl/Ta coating system was characterized by microstructure and oxidation performance. The EDS element distribution data showed that the atomic percentage of Fe:Cr:Al was 69:20:10 at.%, and the crystal grains were nano-columnar crystals, which had excellent high temperature oxidation resistance.

The above content is only to illustrate the technical ideas of the present invention, and cannot limit the protection scope of the present invention. Any changes made on the basis of the technical solutions according to the technical ideas proposed in the present invention shall fall within the scope of the claims of the present invention. within the scope of protection.

Claims (5)

1. The FeCrAl/Ta alloy coating is characterized by comprising a Ta transition layer and a FeCrAl layer deposited on the surface of the Ta transition layer;

the crystal grains of the FeCrAl layer and the Ta transition layer are nano columnar crystals, the size of the nano columnar crystals is 50-80 nm, and the thickness of the Ta layer is 20-200 nm;

the FeCrAl layer comprises the following elements in atomic percent: 10-20: 20 at% of Cr, 11at% of Al and the balance of Fe;

the preparation method of the FeCrAl/Ta coating comprises the following steps:

step 1, grinding, cleaning and vacuum etching are carried out on a zirconium alloy matrix;

step 2, sputtering and depositing a Ta transition layer and a FeCrAl layer on the zirconium alloy substrate obtained in the step 1 in sequence by adopting a magnetron sputtering mode, and cooling to room temperature to obtain a FeCrAl/Ta alloy coating;

the method for sequentially sputtering and depositing the Ta transition layer and the FeCrAl layer comprises the following steps:

firstly, carrying out Ta transition layer deposition on a Ta target by adopting radio frequency power sputtering, and then carrying out double-target co-sputtering on two FeCrAl alloy targets by adopting a direct current power supply;

the Ta target adopts a radio frequency power supply to carry out sputtering, the sputtering power is 100W, the deposition time of the Ta transition layer is 332s-3320s, and the FeCrAl alloy target adopts a direct current power of 200W.

2. A FeCrAl/Ta alloy coating according to claim 1, wherein the FeCrAl layer has a thickness of 2.3±0.2 μm.

3. A FeCrAl/Ta alloy coating according to claim 1, wherein the method of grinding and cleaning the zirconium alloy substrate in step 1 is as follows:

and grinding and polishing the zirconium alloy matrix by sand paper, and ultrasonically cleaning and drying the polished zirconium alloy matrix.

4. A FeCrAl/Ta alloy coating according to claim 1, characterized in that the vacuum etching method is as follows:

and (3) conveying the cleaned zirconium alloy substrate into a magnetron sputtering coating chamber, and carrying out etching after vacuumizing, wherein the etching power is 200W, and the etching time is 5min.

5. The FeCrAl/Ta alloy coating of claim 1, wherein the Ta target has a purity of 99.99 wt%, a sputtering power of 100W, a deposition gas pressure setting of 0.3Pa, a deposition temperature of room temperature, and a substrate speed of 15r/min.

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