A method of inhibiting the formation of an oxide film on a zirconium alloy during high temperature gas nitriding

Abstract

The application discloses a method for inhibiting the generation of an oxide film of a zirconium alloy in a high-temperature gas nitriding process, and belongs to the field of artificial joint ball head surface modification. High-purity iron beads are used as a deoxidizer in the high-temperature gas nitriding process to inhibit the generation of an oxide film on the surface of the zirconium alloy, and X-ray diffraction is used to analyze the phase of the surface coating. The high-purity iron beads used as the deoxidizer can effectively inhibit the generation of the oxide film on the surface of the zirconium alloy, the prepared ZrN coating is more pure, the impurity phase is reduced, the thickness of the coating reaches 5-8 microns, the hardness of the prepared ZrN coating reaches 600-850 HV through Vickers microhardness testing, and the hardness of the ZrN coating prepared without using the high-purity iron beads as the deoxidizer is improved by 20-40%. The friction and wear test in a SBF simulated body fluid is used to simulate the internal service environment of the artificial joint in the human body, and the average friction coefficient is reduced by 10-25% after the deoxidization of the high-purity iron beads, and the biological tribological performance is significantly improved.

Description

Technical Field

[0001] This invention relates to the field of artificial joint ball head surface modification technology, and in particular to a method for inhibiting oxide film formation in zirconium alloys during high-temperature gas nitriding. Background Technology

[0002] With the increasing aging of society, the number of patients with joint diseases is increasing year by year. Joint replacement surgery is an important means of treating joint diseases, and research on the most important artificial joint head material in joint replacement surgery is of great significance.

[0003] In clinical applications, traditional Co-Cr-Mo alloy joints release metal ions Co and Cr after implantation into the human body. During long-term use, the release of these metal ions causes the artificial joint to loosen due to bone resorption, resulting in pain and even causing patients to lose their vision and hearing.

[0004] Zirconium alloys possess high strength, low elastic modulus, high corrosion resistance, and good biocompatibility, making them ideal materials for joint implants. However, zirconium and its alloys exhibit poor wear resistance and a high coefficient of friction. High-temperature gas nitriding, a surface coating technique, is used to prepare a ZrN thin film coating on the surface of zirconium alloys to improve their wear resistance and reduce the coefficient of friction, thereby enhancing the performance of zirconium alloys as joint implant materials and extending the lifespan of the joint.

[0005] Because zirconium alloys have a strong affinity for oxygen, oxygen elements diffuse into the zirconium alloy matrix during high-temperature gas nitriding, forming zirconium oxide impurities such as ZrO2 films. This severely affects the surface morphology and performance of the ZrN film coating. Oxygen accounts for approximately 21% of air, and high-purity nitrogen contains approximately 3 × 10⁻⁶ ppm. -6 In high-temperature gas nitriding processes, the influence of oxygen (volume fraction) on the preparation of pure ZrN thin film coatings is unavoidable, making it urgent to design a method for preparing pure ZrN thin film coatings on zirconium alloy substrates. This invention aims to solve this problem and provide a possibility for reducing the experimental influence of oxygen in a series of studies requiring high-temperature gas nitriding. Summary of the Invention

[0006] Technical problems to be solved:

[0007] To address the shortcomings of existing high-temperature gas nitriding techniques for preparing ZrN thin film coatings on zirconium alloys, this application solves the problems of easy oxidation interference in zirconium alloys prepared by high-temperature gas nitriding and the poor biotribological properties of ZrN thin film coatings prepared by existing high-temperature gas nitriding methods on zirconium alloys. It provides a method for suppressing oxide film formation on zirconium alloys during high-temperature gas nitriding. This method involves introducing high-purity nitrogen gas into a high-temperature vacuum tube furnace. At a certain temperature, the nitrogen gas decomposes to generate nitrogen atoms, which then diffuse into the zirconium alloy surface to form a nitriding layer. However, air contains approximately 21% oxygen, and high-purity nitrogen contains approximately 3 × 10⁻⁶ nitrogen atoms. -6 O2 (volume fraction) will also decompose to generate oxygen atoms at a certain temperature. At lower temperatures (below 600℃), the diffusion coefficient of oxygen is greater than that of nitrogen. During the heating process, oxygen preferentially diffuses to the surface of zirconium alloy to form a dense oxide film, which hinders the diffusion of nitrogen into the interior of zirconium alloy. This results in a thin, discontinuous and dense ZrN thin film coating. Therefore, this application introduces high-purity iron beads as a deoxidizer in the high-temperature gas nitriding process to suppress the formation of oxide film in the bonded gold during the high-temperature gas nitriding process.

[0008] Technical solution:

[0009] To achieve the above objectives, this application provides the following technical solution:

[0010] A method for suppressing oxide film formation in zirconium alloys during high-temperature gas nitriding includes the following steps:

[0011] Step 1, Polishing: The zirconium alloy is machined into round pieces of the appropriate size, using 180... #- 7000 # After grinding the zirconium alloy surface with SiC sandpaper, polish the zirconium alloy surface until it reaches a mirror finish. Then, ultrasonically clean it for 20 minutes and dry it for later use.

[0012] Step 2: Place the zirconium alloy processed in Step 1 onto the corundum sheet, place the corundum sheet horizontally in the vacuum tube furnace, and seal both ends of the tube furnace.

[0013] Step 3: Before heating, introduce high-purity nitrogen into the tube furnace for five minutes, then perform a vacuum process. The vacuum level must be 0.1-1.3 × 10⁻⁶. -5 bar, repeat the vacuuming operation three times;

[0014] Step 4: Open the valves at both ends of the tubular furnace and introduce 20-100 sccm of flowing high-purity nitrogen into the tubular furnace;

[0015] Step 5: Start heating at a rate of 5-10℃ / min to 900-1400℃, and hold for 2-10 hours;

[0016] Step 6: Cool down to room temperature to complete the nitriding treatment of the zirconium alloy.

[0017] Furthermore, in the second step, high-purity iron beads are selected as deoxidizers. The diameter of the high-purity iron beads is selected in the range of 1-5mm according to the change of nitrogen gas flow rate parameters. The size of the high-purity iron beads varies according to the gas flow rate and temperature parameters.

[0018] Furthermore, in the second step, the alumina crucible has dimensions of 100×30×10mm, and the high-purity iron beads are arranged in a wavy pattern inside the crucible to increase the adsorption area.

[0019] Furthermore, in the second step, the alumina crucible is placed 2-10 cm directly in front of the zirconium alloy.

[0020] Furthermore, in the third step, the vacuum level needs to reach 1.3 × 10⁻⁶. -5 The high-purity nitrogen gas has a purity of 99.999%.

[0021] Furthermore, in the fourth step, the flow rate of the high-purity nitrogen gas is set to 50 sccm.

[0022] Furthermore, in the fifth step, the heating rate is 5℃ / min, the temperature is raised to 1000-1100℃, and then held for 2 hours.

[0023] Furthermore, in the sixth step, the cooling rate is 5°C / min.

[0024] Furthermore, the zirconium alloy used is industrial-grade Zr702 (R60702).

[0025] Furthermore, 30g of high-purity iron beads with a diameter of 1mm are added, and the zirconium alloy is placed 2cm behind the alumina crucible.

[0026] Explanation of the principle: External absorption deoxidation is a highly efficient solid-state deoxidation technology. Although the tubular furnace has been evacuated multiple times before operation, complete deoxidation cannot be achieved in the actual process. High-purity nitrogen is the main source of impurities throughout the process. It is worth noting that at lower temperatures (below 600℃), the diffusion coefficient of oxygen is greater than that of nitrogen, while at higher temperatures (above 600℃), the diffusion coefficient of nitrogen is greater than that of oxygen. At 800℃, the diffusion coefficient of nitrogen begins to be much greater than that of oxygen. Therefore, high-purity iron beads are used as deoxidizers because in the temperature range of 900-1400℃, when Zr702 alloy and iron beads coexist in a closed system, oxygen will preferentially migrate to the high-purity iron beads, achieving the goal of solid-state deoxidation.

[0027] Beneficial effects:

[0028] This application provides a method for suppressing oxide film formation on zirconium alloys during high-temperature gas nitriding, which has the following beneficial effects:

[0029] 1. After deoxidation using high-purity iron beads, the hardness of the ZrN coating increases by 20-40%, the average coefficient of friction decreases by 10-25%, and its biotribological properties are significantly improved.

[0030] 2. Currently, there is no simple and feasible method to suppress the formation of surface oxide film during high-temperature gas nitriding of zirconium alloys. Compared with the existing high-temperature gas nitriding technology for preparing ZrN thin film coatings, this invention has the effect of suppressing oxide film formation during high-temperature gas nitriding.

[0031] 3. Reduce the impact of oxide film on nitriding effect during preparation to prepare a purer ZrN thin film coating;

[0032] 4. Using high-purity iron beads as a deoxidizer is cost-effective and efficient. Iron has a high melting point, meeting the temperature requirements for high-temperature gas nitriding. The XRD main diffraction peak pattern of a zirconium alloy after high-purity iron beads were used in high-temperature gas nitriding at 1000℃ for 2 hours is shown below. Figure 4 As shown, the analysis revealed that oxygen atoms were successfully adsorbed on the surface, accompanied by the formation of new phases of Fe2O3 and Fe3O4. This confirms that the high-purity iron beads effectively participate in deoxidation and have an excellent deoxidation effect.

[0033] 5. Compared with other technologies for preparing ZrN thin film coatings on alloy surfaces, high-temperature vacuum tube furnaces are cheaper, have lower equipment investment costs, can process larger samples, and can be mass-produced, resulting in high production efficiency. Attached Figure Description

[0034] Figure 1 The following are process diagrams of embodiments of this application, wherein (a) is a process diagram of Embodiment 1 and Embodiment 3; and (b) is a process diagram of Embodiment 2 and Embodiment 4.

[0035] Figure 2 The XRD main diffraction peak patterns obtained from tests in Examples 1-4 of this application are shown below.

[0036] Figure 3 This is a line graph showing the change in friction coefficient obtained from tests in Examples 1-4 of this application;

[0037] Figure 4 The image shows the main XRD diffraction peaks obtained after deoxidation of high-purity iron beads at 1000℃ in this application. Detailed Implementation

[0038] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0039] Example 1:

[0040] A method for suppressing oxide film formation in zirconium alloys during high-temperature gas nitriding includes the following steps:

[0041] Step 1, Polishing: Select zirconium alloy Zr702 (R60702), process the zirconium alloy into round pieces of the appropriate size, and use 180... #- 7000 # After grinding the zirconium alloy surface with SiC sandpaper, polish the zirconium alloy surface until it reaches a mirror finish. Then, ultrasonically clean it for 20 minutes and dry it for later use.

[0042] Step 2: Place the zirconium alloy processed in Step 1 onto the corundum sheet, place the corundum sheet horizontally in the vacuum tube furnace, and seal both ends of the tube furnace.

[0043] Step 3: Before heating, introduce high-purity nitrogen into the tubular furnace for five minutes, then perform a vacuum process. The high-purity nitrogen should have a purity of 99.999%, and the vacuum level should reach 1.3 × 10⁻⁶. -5 bar, repeat the vacuuming operation three times;

[0044] Step 4: Open the valves at both ends of the tubular furnace and introduce 50 sccm of flowing high-purity nitrogen into the tubular furnace to prevent accidents caused by the sealing inside the tube under high temperature conditions.

[0045] Step 5: Start heating to 1000℃ at a rate of 5℃ / min and hold for 2 hours;

[0046] Step 6: Cool the zirconium alloy to room temperature at a cooling rate of 5℃ / min to complete the nitriding treatment.

[0047] Figure 1 (a) is a schematic diagram of the high-temperature gas nitriding process for preparing ZrN thin film coatings without the addition of iron beads.

[0048] Example 2:

[0049] A method for suppressing oxide film formation in zirconium alloys during high-temperature gas nitriding includes the following steps:

[0050] Step 1, Polishing: Select zirconium alloy Zr702 (R60702), process the zirconium alloy into round pieces of the appropriate size, and use 180... #- 7000 # After grinding the zirconium alloy surface with SiC sandpaper, polish the zirconium alloy surface until it reaches a mirror finish. Then, ultrasonically clean it for 20 minutes and dry it for later use.

[0051] Step 2: Place the zirconium alloy treated in step 1 on the corundum sheet, and place an alumina crucible horizontally on the corundum sheet. Place 30g of 1mm diameter high-purity iron beads in the 100×30×10mm alumina crucible, and then place the alumina crucible 2cm directly in front of the zirconium alloy. Arrange the high-purity iron beads in a wave-like pattern in the crucible to increase the adsorption area. Place the corundum sheet horizontally in the vacuum tube furnace and seal both ends of the tube furnace.

[0052] Step 3: Before heating, introduce high-purity nitrogen into the tubular furnace for five minutes, then perform a vacuum process. The high-purity nitrogen should have a purity of 99.999%, and the vacuum level should reach 1.3 × 10⁻⁶. -5 bar, repeat the vacuuming operation three times;

[0053] Step 4: Open the valves at both ends of the tubular furnace and introduce 50 sccm of flowing high-purity nitrogen into the tubular furnace to prevent accidents caused by the sealing inside the tube under high temperature conditions.

[0054] Step 5: Start heating to 1000℃ at a heating rate of 5℃ / min and hold for 2 hours; blow high-temperature, high-purity nitrogen gas over the iron beads. The very small amount of O2 in the tube furnace first reacts with Fe to generate iron oxides such as Fe3O4, and the oxygen is removed, thereby achieving the purpose of inhibiting the formation of oxide film on its surface.

[0055] Step 6: Cool the zirconium alloy to room temperature at a cooling rate of 5℃ / min to complete the nitriding treatment.

[0056] Figure 1 (b) is a schematic diagram of the high-temperature gas nitriding process for preparing ZrN thin film coatings with the addition of iron beads.

[0057] The surface phase composition of the ZrN thin film coatings prepared in Examples 1-2 was analyzed using a Bruker D8 Advance X-ray diffractometer. The obtained XRD main diffraction peak patterns are shown below. Figure 2 As shown; artificial joint materials undergo friction and wear during use in the human body environment, generating metal debris. Excessive metal debris can lead to inflammation and loosening. Therefore, SBF (Simulated Body Fluid) was selected as the friction lubricant, and a UMT-II micro-friction tester was used to test its biotribological properties. In the friction and wear test, the fixing fixture was referred to as the friction pair. A Φ10mm ZrO2 ceramic ball was selected as the upper friction pair, and a nitrided zirconium alloy was selected as the lower friction pair. The friction coefficient was analyzed to evaluate the biotribological properties of the ZrN thin film coating. The friction coefficients in Examples 1-2 are as follows: Figure 3 As shown in Table 1, hardness is one of the indicators for evaluating wear resistance. The microhardness of the ZrN thin film coating on the zirconium alloy surface was tested using an HV-1000 microhardness tester, and the specific values ​​are shown in Table 1.

[0058] Example 3:

[0059] A method for suppressing oxide film formation in zirconium alloys during high-temperature gas nitriding includes the following steps:

[0060] Step 1, Polishing: Select zirconium alloy Zr702 (R60702), process the zirconium alloy into round pieces of the appropriate size, and use 180... #- 7000 # After grinding the zirconium alloy surface with SiC sandpaper, polish the zirconium alloy surface until it reaches a mirror finish. Then, ultrasonically clean it for 20 minutes and dry it for later use.

[0061] Step 2: Place the zirconium alloy processed in Step 1 onto the corundum sheet, place the corundum sheet horizontally in the vacuum tube furnace, and seal both ends of the tube furnace.

[0062] Step 3: Before heating, introduce high-purity nitrogen into the tubular furnace for five minutes, then perform a vacuum process. The high-purity nitrogen should have a purity of 99.999%, and the vacuum level should reach 1.3 × 10⁻⁶. -5 bar, repeat the vacuuming operation three times;

[0063] Step 4: Open the valves at both ends of the tubular furnace and introduce 50 sccm of flowing high-purity nitrogen into the tubular furnace to prevent accidents caused by the sealing inside the tube under high temperature conditions.

[0064] Step 5: Start heating at a rate of 5℃ / min to 1100℃ and hold for 2 hours;

[0065] Step 6: Cool the zirconium alloy to room temperature at a cooling rate of 5℃ / min to complete the nitriding treatment.

[0066] Example 4:

[0067] A method for suppressing oxide film formation in zirconium alloys during high-temperature gas nitriding includes the following steps:

[0068] Step 1, Polishing: Select zirconium alloy Zr702 (R60702), process the zirconium alloy into round pieces of the appropriate size, and use 180... #- 7000 # After grinding the zirconium alloy surface with SiC sandpaper, polish the zirconium alloy surface until it reaches a mirror finish. Then, ultrasonically clean it for 20 minutes and dry it for later use.

[0069] Step 2: Place the zirconium alloy treated in step 1 on the corundum sheet, and place an alumina crucible horizontally on the corundum sheet. Place 30g of 1mm diameter high-purity iron beads in the 100×30×10mm alumina crucible, and then place the alumina crucible 2cm directly in front of the zirconium alloy. Arrange the high-purity iron beads in a wave-like pattern in the crucible to increase the adsorption area. Place the corundum sheet horizontally in the vacuum tube furnace and seal both ends of the tube furnace.

[0070] Step 3: Before heating, introduce high-purity nitrogen into the tubular furnace for five minutes, then perform a vacuum process. The high-purity nitrogen should have a purity of 99.999%, and the vacuum level should reach 1.3 × 10⁻⁶. -5 bar, repeat the vacuuming operation three times;

[0071] Step 4: Open the valves at both ends of the tubular furnace and introduce 50 sccm of flowing high-purity nitrogen into the tubular furnace to prevent accidents caused by the sealing inside the tube under high temperature conditions.

[0072] Step 5: Start heating to 1100℃ at a heating rate of 5℃ / min and hold for 2 hours; blow high-temperature, high-purity nitrogen gas over the iron beads. The very small amount of O2 in the tube furnace first reacts with Fe to generate iron oxides such as Fe3O4, and the oxygen is removed, thereby achieving the purpose of inhibiting the formation of oxide film on its surface.

[0073] Step 6: Cool the zirconium alloy to room temperature at a cooling rate of 5℃ / min to complete the nitriding treatment.

[0074] The surface phase composition of the ZrN thin film coatings prepared in Examples 3-4 was analyzed using a Bruker D8 Advance X-ray diffractometer. The obtained XRD main diffraction peak patterns are shown below. Figure 2 As shown; artificial joint materials undergo friction and wear during use in the human body environment, generating metal debris. Excessive metal debris can lead to inflammation and loosening. Therefore, SBF (Simulated Body Fluid) was selected as the friction lubricant, and a UMT-II micro-friction tester was used to test its biotribological properties. In the friction and wear test, the fixed fixture was used as the friction pair, a Φ10mm ZrO2 ceramic ball was used as the upper friction pair, and a nitrided zirconium alloy was used as the lower friction pair. The friction coefficient was analyzed to evaluate the biotribological properties of the ZrN thin film coating. The friction coefficients in Examples 3-4 are as follows. Figure 3 As shown in Table 1, hardness is one of the indicators for evaluating wear resistance. The microhardness of the ZrN thin film coating on the zirconium alloy surface was tested using an HV-1000 microhardness tester, and the specific values ​​are shown in Table 1.

[0075] Macroscopic observation and analysis revealed that the ZrN coatings prepared in Examples 1 and 3 were blackish-gray, while the ZrN prepared in Examples 2 and 4 were pale yellow, which is consistent with the description of the color of ZrN.

[0076] Table 1

[0077] As is Example 1 Example 2 Example 3 Example 4 Vickers hardness (HV) 227 524 640 592 809

[0078] Hardness is one of the indicators for evaluating wear resistance. A load of 10 N was applied, and the holding time was 10 s. Five test points were selected to measure the average hardness. The microhardness of Examples 1-2 and Examples 3-4 is shown in Table 1. Examples 1-2 were prepared by holding at 1000℃ for 2 h. The surface hardness of Example 2 was approximately 22.1% higher than that of Example 1. Examples 3-4 were prepared by holding at 1100℃ for 2 h. The surface hardness of Example 4 was approximately 36.6% higher than that of Example 3. The surface hardness of the samples prepared with added iron beads was significantly higher than that without added iron beads.

[0079] Examples 1-4 XRD main diffraction peak patterns are shown below. Figure 2 As shown, analysis revealed that the main phases in Examples 1 and 3 were ZrN and ZrO2, while the main phases in Examples 2 and 4 were ZrN and Zr3O. 1.05 The impurity peaks are significantly reduced and the generated product is an unsaturated oxide of zirconium. Therefore, adding high-purity iron beads for high-temperature gas nitriding can effectively deoxidize and greatly improve the purity of the ZrN coating. This is a significant improvement in the field of high-temperature gas nitriding and has good application prospects.

[0080] In the friction and wear test, the applied load was 10N, the distance traveled in a single reciprocating motion was 10mm, and the reciprocating time was 7200s. The changes in the friction coefficient in Examples 1-4 are as follows: Figure 3 As shown, the average friction coefficients of Examples 1 and 2 were 0.4672 and 0.407, respectively; the average friction coefficients of Examples 3 and 4 were 0.4929 and 0.4003, respectively. The average friction coefficients of the ZrN coating were reduced by 12.9% and 18.8% respectively by deoxidation with high-purity iron beads, and its biotribological properties were significantly improved.

[0081] The phase composition of the high-purity iron beads after deoxidation in Examples 1-2 was analyzed using a Bruker D8 Advance X-ray diffractometer. The obtained XRD main diffraction peak patterns are shown below. Figure 4 As shown in Table 1, after high-purity iron beads participated in the high-temperature gas nitriding deoxidation of zirconium alloy at 1000℃ for 2 hours, oxygen atoms were successfully adsorbed on the surface, accompanied by the formation of new Fe2O3 and Fe3O4 phases. This confirms that high-purity iron beads participated in the deoxidation process. Furthermore, combined with Table 1, Figure 2 , Figure 3 Data shows that using high-purity iron beads can not only effectively remove residual oxygen elements during the high-temperature gas nitriding process of zirconium alloys, but also significantly improve the biotribological properties of ZrN thin film coatings.

[0082] The embodiments proposed in this invention are preferred embodiments, but are not limited to the content described above. Those skilled in the art can easily replicate the above embodiments and further extend and modify them, but as long as they do not depart from the spirit of this invention, they are all within the protection scope of this invention.

Claims

1. A method for suppressing oxide film formation in zirconium alloys during high-temperature gas nitriding, characterized in that, The specific steps are as follows: Step 1, Polishing: The zirconium alloy is machined into round pieces of the appropriate size, using 180... #- 7000 # After grinding the zirconium alloy surface with SiC sandpaper, polish the zirconium alloy surface until it reaches a mirror finish. Then, ultrasonically clean it for 20 minutes and dry it for later use. Step 2: Place the zirconium alloy treated in Step 1 onto a corundum sheet, place the corundum sheet horizontally in a vacuum tube furnace, and seal both ends of the tube furnace; in Step 2, high-purity iron beads are used as deoxidizers. Place an alumina crucible horizontally on the corundum sheet, place the high-purity iron beads inside the alumina crucible, and then place the alumina crucible directly in front of the zirconium alloy. The diameter of the high-purity iron beads is in the range of 1-5mm, and the mass of the high-purity iron beads is controlled within the range of 20-50g. Step 3: Before heating, introduce high-purity nitrogen into the tube furnace for five minutes, then perform a vacuum process. The vacuum level must be 0.1-1.3 × 10⁻⁶. -5 bar, repeat the vacuuming operation three times; Step 4: Open the valves at both ends of the tubular furnace and introduce 20-100 sccm of flowing high-purity nitrogen into the tubular furnace; Step 5: Start heating at a rate of 5-10℃ / min to 900-1400℃, and hold for 2-10 hours; Step 6: Cool down to room temperature to complete the nitriding treatment of the zirconium alloy.

2. The method for suppressing oxide film formation in zirconium alloys during high-temperature gas nitriding according to claim 1, characterized in that: In the second step, the alumina crucible has dimensions of 100×30×10 mm, and the high-purity iron beads are arranged in a wavy pattern inside the crucible to increase the adsorption area.

3. The method for suppressing oxide film formation in zirconium alloys during high-temperature gas nitriding according to claim 2, characterized in that: In the second step, the alumina crucible is placed 2-10 cm directly in front of the zirconium alloy.

4. The method for suppressing oxide film formation in zirconium alloys during high-temperature gas nitriding according to claim 1, characterized in that: In the third step, the vacuum level needs to be 1.3 × 10⁻⁶. -5 The high-purity nitrogen gas has a purity of 99.999%.

5. The method for suppressing oxide film formation in zirconium alloys during high-temperature gas nitriding according to claim 1, characterized in that: In the fourth step, the flow rate of the high-purity nitrogen gas is set to 50 sccm.

6. The method for suppressing oxide film formation in zirconium alloys during high-temperature gas nitriding according to claim 1, characterized in that: In the fifth step, the heating rate is 5℃ / min, the temperature is raised to 1000-1100℃, and then held for 2 hours.

7. The method for suppressing oxide film formation in zirconium alloys during high-temperature gas nitriding according to claim 1, characterized in that: In the sixth step, the cooling rate is 5℃ / min.

8. The method for suppressing oxide film formation in zirconium alloys during high-temperature gas nitriding according to claim 1, characterized in that: The zirconium alloy is industrial grade Zr702, also known as R60702.

9. The method for suppressing oxide film formation in zirconium alloys during high-temperature gas nitriding according to claim 3, characterized in that: Add 30 g of high-purity iron beads with a diameter of 1 mm, and place the zirconium alloy 2 cm behind the alumina crucible.

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