CN116516291A - Cr-Si coating on surface of zirconium alloy for nuclear and preparation method thereof - Google Patents

Abstract

A Cr Si-based coating on the surface of a zirconium alloy for nuclear use is obtained by magnetron sputtering with a Cr target and a Si target, and the content of Si in the coating is controlled at 7.5 to 22.0 at.%. The Cr target and the The power drive of Si target is DC power supply and RF power supply respectively, among which the sputtering power of Cr target is 300W, and the power of Si target is 100~300W. In the present invention, the Cr-Si coating prepared on the surface of the zirconium alloy substrate has excellent high-temperature oxidation resistance. During the oxidation process, a Cr ₂ O ₃ /SiO ₂ double oxide layer is formed at the interface between the substrate and the coating, effectively delaying The failure of Cr ₂ O ₃ is eliminated, and the oxidation is carried out in a water vapor environment of 1200°C, and the oxidation weight gain is as low as 1.4mg/cm ² . At the same time, the mechanical properties of the coating are effectively improved through Si doping, and the hardness reaches 14.64GPa. Enhanced its wear resistance and antifriction performance.

Description

A kind of Cr-Si system coating on the surface of zirconium alloy for nuclear use and its preparation method

technical field

The invention relates to the technical field of alloy protective coating preparation, in particular to a Cr-Si coating on the surface of a nuclear zirconium alloy and a preparation method thereof.

Background technique

Nuclear fuel cladding is the first safety barrier of nuclear power plants. Zirconium alloy is the material of choice for nuclear fuel cladding due to its extremely low thermal neutron absorption cross section, good mechanical properties and corrosion resistance. However, in the Loss of Coolant Accident (LOCA), the zirconium alloy will react violently with high-temperature water vapor, causing the core to melt down, eventually causing hydrogen explosion and nuclear leakage, which poses a great safety hazard. Therefore, slowing or preventing the zirconium-water reaction by developing accident-tolerant fuel (ATF) is the key to improving the safety of nuclear reactors.

Surface modification of zirconium alloy can not only effectively improve the high temperature oxidation resistance of nuclear fuel cladding, but also retain the existing nuclear system and cladding tube production process, which is a relatively economical and efficient solution at present. The specific implementation method is to prepare a coating containing Si, Cr, and Al elements on the surface of the zirconium alloy, and generate corresponding oxides in a high-temperature water vapor environment to hinder or slow down the diffusion of O to the substrate, so as to improve the cladding of the zirconium alloy. Antioxidant purpose.

At present, the research on accident-tolerant coatings mainly revolves around ceramic coatings (MAX phase ceramic coatings, nitride coatings, carbide coatings, etc.) and metal coatings (FeCrAl coatings, Cr coatings, etc.). Among them, the metal Cr coating has a high thermal conductivity (94W/mK), excellent mechanical properties and corrosion resistance, and good compatibility with the production process of the zirconium alloy cladding tube, and Cr ₂ O ₃ will be generated during use. Oxide film, which reduces the oxidation rate of zirconium alloys, is considered to be the best choice for improving the fault tolerance of zirconium alloy cladding accidents in the short term. However, the maximum withstand temperature of Cr ₂ O ₃ in a high-temperature water vapor environment is 1042°C. When the temperature is too high, Cr ₂ O ₃ will form volatile CrO ₂ (OH) ₂ or Cr(OH) ₃ and fail . In addition, the interdiffusion between the Zr matrix and the Cr coating causes the eutectic reaction to occur at the coating interface in an environment above 1330 °C, which leads to the instability of the film-base interface and reduces the protective performance of the Cr coating.

Contents of the invention

The purpose of the present invention is to provide a Cr-Si coating on the surface of zirconium alloy for nuclear use.

Another object of the present invention is to provide a method for preparing the Cr-Si coating on the surface of the above-mentioned zirconium alloy for nuclear use. By doping Si atoms in the Cr coating, the prepared Cr-Si coating can effectively delay Cr ₂ O ₃ The failure of the oxide layer can effectively prevent the interdiffusion of Zr and Cr at the interface, and effectively improve the mechanical properties and wear resistance and friction reduction properties of the coating.

The object of the invention is achieved through the following technical solutions:

The present invention has following technical effect:

A Cr-Si coating on the surface of a nuclear zirconium alloy is characterized in that: the Cr-Si coating is made by magnetron sputtering with a Cr target and a Si target, and the content of Si in the coating is controlled at 7.5-22.0 at.%, the power drives of the Cr target and the Si target are DC power and RF power respectively, wherein the sputtering power of the Cr target is 300W, and the power of the Si target is 100-300W.

Further, during the magnetron sputtering process, the vacuum degree is 8×10 ^-4 Pa, the deposition temperature is 380-420°C, the substrate bias voltage is -40--60V, the deposition pressure is 0.3-0.5Pa, and the deposition time is 4～6h.

A method for preparing a Cr-Si coating on the surface of a zirconium alloy for nuclear use, which is characterized in that: by magnetron sputtering, a Cr target and a Si target are used to sputter-deposit a Si content of 7.5 to 7.5% on the surface of a zirconium alloy substrate. 22.0 at.% Cr-Si based coating.

Further, the power drives of the Cr target and the Si target are DC power and RF power respectively, wherein the sputtering power of the Cr target is 300W, and the power of the Si target is 100-300W.

Further, the vacuum degree of the magnetron sputtering is 8×10 ^-4 Pa, the deposition temperature is 380-420°C, the substrate bias voltage is -40--60V, the deposition pressure is 0.3-0.5Pa, and the deposition time is 4-420°C. 6h.

Preferably, the deposition temperature is 400°C, the substrate bias is -50V, the deposition pressure is 0.4Pa, and the deposition time is 5h.

Most specifically, a method for preparing a Cr-Si coating on the surface of a nuclear zirconium alloy is characterized in that, the steps are as follows:

①Zirconium alloy substrate pretreatment: use 100#, 400#, 1000#, 2000# SiC sandpaper to grind the surface of the Zry-4 alloy substrate in sequence, and then polish the Zry-4 alloy substrate with a particle size of 1.5 μm in turn solution, silicon dioxide suspension with a particle size of 0.06 μm for polishing, then ultrasonically clean with acetone and absolute ethanol for 10 minutes, and then blow dry for later use;

②Cr-Si coating preparation: The coating was prepared by magnetron sputtering, and the Cr target and the Si target were respectively driven by a direct current (DC) power supply and a radio frequency (RF) power supply, the vacuum was 8×10 ^-4 Pa, and the deposition temperature was 380 ～420℃, substrate bias voltage is -40～-60V, deposition pressure is 0.3～0.5Pa, deposition time is 4～6h; among them, the sputtering power of Cr target is fixed at 300W, and the sputtering power of Si target is 100～ 300W, the Si content of the coating is controlled between 7.5 and 22.0 at.%.

Beneficial effect:

In the present invention, the Cr-Si coating prepared on the surface of the zirconium alloy substrate has excellent high-temperature oxidation resistance. During the steam oxidation process at a higher temperature, a Cr ₂ O ₃ /SiO ₂ double oxide is formed at the interface between the substrate and the coating. layer, which effectively delays the failure of Cr ₂ O ₃ , and is oxidized in a water vapor environment at 1200°C, and the oxidation weight gain is as low as 1.4mg/cm ² . At the same time, the mechanical properties and hardness of the coating are effectively improved by Si doping. Reaching 14.64GPa, enhanced its wear resistance and friction reduction performance.

Description of drawings

Figure 1: Surface morphology and element content analysis of deposited CrSi-100W coating prepared by the present invention.

Fig. 2: A cross-sectional morphology diagram of the deposited CrSi-100W coating prepared by the present invention.

Figure 3: Surface morphology and element content analysis of the deposited CrSi-200W coating prepared by the present invention.

Fig. 4: A cross-sectional morphology diagram of the deposited CrSi-200W coating prepared by the present invention.

Figure 5: Surface morphology and element content analysis of the deposited CrSi-300W coating prepared by the present invention.

Fig. 6: A cross-sectional morphology diagram of the deposited CrSi-300W coating prepared by the present invention.

Figure 7: Comparison chart of high temperature oxidation weight gain of each coating.

Figure 8: Structural diagram of the double oxide layer formed after coating oxidation, in which (a) cross-sectional view; (b) EDS surface scan; (c) partial enlarged view; (d) high-resolution image and SAED image of area (d) ; (e) High-resolution image and SAED image of region (e).

Figure 9: Cross-sectional morphology and element distribution of CrSi-300W coating after oxidation in 1300°C/30min water vapor.

Detailed ways

The present invention is specifically described by the following examples. It is necessary to point out that the following examples are only used to further illustrate the present invention, and cannot be interpreted as limiting the protection scope of the present invention. Those skilled in the art can according to the above-mentioned description SUMMARY OF THE INVENTION Some non-essential improvements and adjustments are made to the present invention.

Example 1

A preparation method for nuclear zirconium alloy surface Cr-Si series coating, carried out as follows:

①Zirconium alloy substrate pretreatment: use 100#, 400#, 1000#, 2000# SiC sandpaper to grind the surface of the Zry-4 alloy substrate in sequence, and then polish the Zry-4 alloy substrate with a particle size of 1.5 μm in turn solution, silicon dioxide suspension with a particle size of 0.06 μm for polishing, then ultrasonically clean with acetone and absolute ethanol for 10 minutes, and then blow dry for later use;

②Cr-Si coating preparation: The coating was prepared by magnetron sputtering, and the Cr target and the Si target were respectively driven by a direct current (DC) power supply and a radio frequency (RF) power supply, the vacuum was 8×10 ^-4 Pa, and the deposition temperature was 400 ℃, the substrate bias is -50V, the deposition pressure is 0.4Pa, and the deposition time is 5h; among them, the sputtering power of the Cr target is fixed at 300W, the sputtering power of the Si target is 100W, and the Si content of the coating is 7.8at.% , Recorded as CrSi-100W.

Figure 1 shows the surface morphology and element content of the as-deposited CrSi-100W coating. It can be seen that the surface structure of the coating is compact without any defects such as cracks and holes, and the Si content in the coating is 7.8 at.%. Figure 2 is the cross-sectional morphology of the CrSi-200W coating. The coating is well combined with the Zry-4 alloy matrix, and the coating structure is dense and uniform, with a thickness of 11.4 μm.

Example 2

A preparation method for nuclear zirconium alloy surface Cr-Si series coating, carried out as follows:

①Zirconium alloy substrate pretreatment: use 100#, 400#, 1000#, 2000# SiC sandpaper to grind the surface of the Zry-4 alloy substrate in sequence, and then polish the Zry-4 alloy substrate with a particle size of 1.5 μm in turn solution, silicon dioxide suspension with a particle size of 0.06 μm for polishing, then ultrasonically clean with acetone and absolute ethanol for 10 minutes, and then blow dry for later use;

②Cr-Si coating preparation: The coating was prepared by magnetron sputtering, and the Cr target and the Si target were respectively driven by a direct current (DC) power supply and a radio frequency (RF) power supply, the vacuum was 8×10 ^-4 Pa, and the deposition temperature was 400 ℃, the substrate bias voltage is -50V, the deposition pressure is 0.4Pa, and the deposition time is 5h; among them, the sputtering power of the Cr target is fixed at 300W, the sputtering power of the Si target is 200W, and the Si content of the coating is controlled at 14.3at. %, denoted as CrSi-200W.

Figure 3 shows the surface morphology and element content of the deposited CrSi-200W coating. It can be seen that the surface structure of the coating is compact without any defects such as cracks and holes, and the Si content in the coating is 14.3 at.%. Figure 4 is the cross-sectional morphology of the CrSi-200W coating. It can be seen that the coating is well combined with the Zry-4 alloy matrix, and the coating structure is dense and uniform, with a thickness of 10.7 μm.

Example 3

A preparation method for nuclear zirconium alloy surface Cr-Si series coating, carried out as follows:

①Zirconium alloy substrate pretreatment: use 100#, 400#, 1000#, 2000# SiC sandpaper to grind the surface of the Zry-4 alloy substrate in sequence, and then polish the Zry-4 alloy substrate with a particle size of 1.5 μm in turn solution, silicon dioxide suspension with a particle size of 0.06 μm for polishing, then ultrasonically clean with acetone and absolute ethanol for 10 minutes, and then blow dry for later use;

②Cr-Si coating preparation: The coating was prepared by magnetron sputtering, and the Cr target and the Si target were respectively driven by a direct current (DC) power supply and a radio frequency (RF) power supply, the vacuum was 8×10 ^-4 Pa, and the deposition temperature was 400 ℃, the substrate bias is -50V, the deposition pressure is 0.4Pa, and the deposition time is 5h; among them, the sputtering power of the Cr target is fixed at 300W, the sputtering power of the Si target is 300W, and the Si content of the coating is controlled at 21.7at. %, denoted as CrSi-300W.

Figure 5 shows the surface morphology and element content of the as-deposited CrSi-300W coating. It can be seen that the surface structure of the coating is compact without any defects such as cracks and holes, and the Si content in the coating is 21.7 at.%. Figure 6 is the cross-sectional morphology of the CrSi-300W coating. It can be seen that the coating is well combined with the Zry-4 alloy substrate, and the coating structure is dense and uniform, with a thickness of 12.8 μm.

Performance Testing:

(1) Mechanical properties

Generally speaking, the higher the hardness of the material, the better its wear-reducing and wear-resisting performance, which is beneficial to improving the tribological performance of the zirconium composite cladding under normal working conditions. By doping Si atoms in the Cr coating, the hardness and elastic modulus of the coating are effectively improved, and the pure Cr coating on the zirconium alloy surface and the Cr-Si coating prepared in Examples 1-3 Hardness test, the results are shown in Table 1.

Table 1: Microhardness of as-deposited coatings

coating Cr CrSi-100W CrSi-200W CrSi-300W Si content(at.%) 0 7.8 14.3 21.7 Hardness (GPa) 3.11 5.73 8.62 14.64

It can be seen from Table 1 that the Cr-Si coating improves the hardness of the pure Cr coating. At the same time, the hardness of Cr-Si coating increases with the increase of Si content.

(2) High temperature oxidation resistance

By testing the Zry-4 alloy substrate and depositing Cr-Si coatings with different Si doping amounts on the surface of the Zry-4 alloy substrate by magnetron sputtering, the oxidation weight gain after treatment in a high-temperature water vapor environment at 1200°C for 30 minutes , the specific humidity is 90% at 50°C. The high-temperature oxidation resistance of each coating was tested. The results are shown in Figure 7. It can be seen that after steam oxidation of zirconium alloy without any coating protection at 1200°C for 30 minutes, The oxidation weight gain reached 29.9 mg/cm ² , while the oxidation weight gain of the Cr-Si coating (CrSi-100W) prepared in Example 1 was as low as 1.4 mg/cm ² , and the oxidation increased with the increase of Si content. The weight increases gradually, and the CrSi-200W and CrSi-300W are 2.2mg/cm ² and 4.6mg/cm ² respectively. As the subsequent oxidation time increases, the oxidation weight gain of each coating does not change significantly.

After the oxidation test, it was detected that the surface of CrSi-100W, CrSi-200W and CrSi-300W coatings all formed oxide layers, specifically Cr ₂ O ₃ /SiO ₂ double oxide layer structure, Cr ₂ O ₃ /SiO ₂ double oxide layer structure To delay the failure of Cr ₂ O ₃ , the structural analysis of CrSi-200W after oxidation shows that, as shown in Figure 8, where (a) is the cross-sectional view of the interface, it can be clearly seen that while the Cr ₂ O ₃ formed by oxidation , also generated SiO ₂ , forming a Cr ₂ O ₃ /SiO ₂ double oxide layer structure. (b) is the corresponding EDS surface scan. (c) is a partially enlarged image, (d) is a high-resolution image and SAED image of region (d) (Cr ₂ O ₃ ), (e) is a high-resolution image and SAED image of region (e) (SiO ₂ ). The elemental analysis corresponding to region (d) and region (e) is shown in Table 2.

Table 2: Elemental analysis corresponding to region (d) and region (e)

at.% o Si Cr Zr area (d) 70.3 0.2 29.2 0.3 area (e) 69.4 30.0 0.4 0.2

It can be seen from the above table that the elements in the area (d) are mainly O and Cr, while the elements in the area (e) are mainly O and Si. Due to the accuracy of the test, the accuracy of the specific gravity of the element analysis is limited, but combined with the overall analysis in Figure 8, it can be seen that , the main components of area (d) and area (d) are Cr ₂ O ₃ and SiO ₂ , and a small amount of Zr content proves that there is a slight diffusion, which is beneficial to the improvement of the bonding force between the coating and the substrate. The presence of amorphous SiO ₂ reduces the difference in thermal expansion coefficient between the CrSi residual layer and the Cr ₂ O ₃ oxide layer, thereby reducing the generation of internal stress and enhancing the stability of the coating.

(3) Interdiffusion properties of zirconium alloy and Cr-Si coating

After the CrSi-300W coating prepared in Example 3 was oxidized in 1300°C/30min water vapor (humidity at 50°C was 90%), its cross-sectional morphology and element distribution were detected, as shown in Figure 5, the oxidation treatment A continuous Zr-Si interdiffusion layer (Diffusion layer) is formed in situ between the final Cr-Si coating and the zirconium alloy interface. The surface is a CrSi residual layer (Residual layer), and the outermost surface is an oxide layer (Oxide layer). The thickness of each layer is shown in Table 3.

Table 3: Thickness of each layer after oxidation at 1300℃/30min (μm)

CrSi-100W CrSi-200W CrSi-300W Oxide layer 1.45 3.13 3.7 Residual layer 6.9 5.51 5.84 Cr-Si 5.6 5.8 8.3

At the same time, there is no Zr in the Cr-Si coating and no Cr in the zirconium alloy matrix. This shows that the continuous Zr-Si layer has a significant effect on hindering the interdiffusion of Zr and Cr.

In summary, the Cr-Si coating prepared on the surface of the Zry-4 alloy substrate by the method of the present invention forms a four-layer structure in the oxidation process, which is Cr ₂ O ₃ oxide layer, SiO ₂ oxidation layer from outside to inside. layer CrSi residual layer and Zr-Si interdiffusion layer.

Example 4

A preparation method for nuclear zirconium alloy surface Cr-Si series coating, carried out as follows:

①Zirconium alloy substrate pretreatment: use 100#, 400#, 1000#, 2000# SiC sandpaper to grind the surface of the Zry-4 alloy substrate in sequence, and then polish the Zry-4 alloy substrate with a particle size of 1.5 μm in turn solution, silicon dioxide suspension with a particle size of 0.06 μm for polishing, then ultrasonically clean with acetone and absolute ethanol for 10 minutes, and then blow dry for later use;

②Cr-Si coating preparation: The coating was prepared by magnetron sputtering, and the Cr target and the Si target were respectively driven by a direct current (DC) power supply and a radio frequency (RF) power supply, the vacuum was 8×10 ^-4 Pa, and the deposition temperature was 380 ℃, the substrate bias is -60V, the deposition pressure is 0.5Pa, and the deposition time is 4h; among them, the sputtering power of the Cr target is fixed at 300W, the sputtering power of the Si target is 200W, and the Si content of the coating is 16at.%.

Example 5

A preparation method for nuclear zirconium alloy surface Cr-Si series coating, carried out as follows:

①Zirconium alloy substrate pretreatment: use 100#, 400#, 1000#, 2000# SiC sandpaper to grind the surface of the Zry-4 alloy substrate in sequence, and then polish the Zry-4 alloy substrate with a particle size of 1.5 μm in turn solution, silicon dioxide suspension with a particle size of 0.06 μm for polishing, then ultrasonically clean with acetone and absolute ethanol for 10 minutes, and then blow dry for later use;

②Cr-Si coating preparation: The coating was prepared by magnetron sputtering, and the Cr target and the Si target were respectively driven by a direct current (DC) power supply and a radio frequency (RF) power supply. The vacuum was 8×10 ^-4 Pa, and the deposition temperature was 420 °C. ℃, the substrate bias is -40V, the deposition pressure is 0.3Pa, and the deposition time is 6h; among them, the sputtering power of the Cr target is fixed at 300W, the sputtering power of the Si target is 300W, and the Si content of the coating is 21.9at.% .

Claims (6)

1. A Cr-Si coating on the surface of a zirconium alloy for nuclear use, which is characterized in that: the Cr-Si coating is prepared by magnetron sputtering a Cr target and a Si target, wherein the content of Si in the coating is controlled to be 7.5-22.0 at%, the power supplies of the Cr target and the Si target are respectively a direct current power supply and a radio frequency power supply, the sputtering power of the Cr target is 300W, and the power of the Si target is 100-300W.

2. A Cr-Si based coating for a zirconium alloy surface for a core as claimed in claim 1, wherein: in the magnetron sputtering process, the vacuum degree is 8 multiplied by 10 ^-4 Pa, the deposition temperature is 380-420 ℃, the substrate bias voltage is-40 to-60V, the deposition air pressure is 0.3-0.5 Pa, and the deposition time is 4-6 h.

3. The preparation reverse of the Cr-Si coating on the surface of the zirconium alloy for the nuclear is characterized in that: the Cr-Si coating with Si content of 7.5-22.0 at.% is formed on the surface of the zirconium alloy substrate by magnetron sputtering with a Cr target and a Si target.

4. A reverse preparation of Cr-Si based coating on the surface of zirconium alloy for nuclear use as claimed in claim 3, wherein: the power drives of the Cr target and the Si target are respectively a direct current power supply and a radio frequency power supply, wherein the sputtering power of the Cr target is 300W, and the power of the Si target is 100-300W.

5. The reverse of the preparation of a cr—si based coating on a zirconium alloy surface for a core as claimed in claim 3 or 4, wherein: the vacuum degree of the magnetron sputtering is 8 multiplied by 10 ^-4 Pa, the deposition temperature is 380-420 ℃, the substrate bias voltage is-40 to-60V, the deposition air pressure is 0.3-0.5 Pa, and the deposition time is 4-6 h.

6. The preparation method of the Cr-Si coating on the surface of the zirconium alloy for the core is characterized by comprising the following steps:

(1) pretreatment of a zirconium alloy matrix: sequentially polishing the surface of a Zry-4 alloy matrix by using 100# SiC sand paper, 400# SiC sand paper, 1000# SiC sand paper and 2000# SiC sand paper, sequentially polishing the polished Zry-4 alloy matrix by using diamond polishing liquid with the granularity of 1.5 mu m and silica suspension with the granularity of 0.06 mu m, sequentially ultrasonically cleaning the polished Zry-4 alloy matrix by using acetone and absolute ethyl alcohol for 10min, and drying the polished Zry-4 alloy matrix for later use;

(2) preparing Cr-Si series coating: preparing a coating by magnetron sputtering, driving a Cr target and a Si target by a Direct Current (DC) power supply and a Radio Frequency (RF) power supply respectively, and performing vacuum of 8 multiplied by 10 ^-4 Pa, the deposition temperature is 380-420 ℃, the substrate bias voltage is-40 to-60V, the deposition air pressure is 0.3-0.5 Pa, and the deposition time is 4-6 h; wherein the sputtering power of the Cr target is fixed to 300W, the sputtering power of the Si target is 100-300W, and the Si content of the coating is 7.5-22.0 at%.