Titanium alloy resistant to high-temperature nitric acid corrosion and preparation method thereof

Abstract

The application relates to a high-temperature nitric acid corrosion-resistant titanium alloy and a preparation method thereof, and belongs to the field of spent fuel reprocessing materials. The alloy is composed of the following elements in percentage by mass: 0.02-0.08wt.% of palladium, 0-7wt.% of aluminum, and the balance of titanium and inevitable impurities. By controlling the addition of the high-corrosion-resistant noble metal Pd element and the low-cost Al element, the titanium alloy with stable corrosion resistance in a spent fuel reprocessing nitric acid solution is prepared, the application cost is reduced, and the technical difficulties of the current titanium alloy for spent fuel reprocessing in corrosion resistance and application cost are solved. In addition, the application further provides a preparation method of the high-temperature nitric acid corrosion-resistant titanium alloy. The high-temperature nitric acid corrosion-resistant titanium alloy formula is scientific and reasonable, the preparation method is simple and easy, the high-temperature nitric acid corrosion-resistant titanium alloy shows good mechanical properties and corrosion resistance in a high-temperature nitric acid environment, and is worth popularizing and using.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of spent fuel reprocessing materials, and particularly relates to a high-temperature nitric acid corrosion-resistant titanium alloy and a preparation method thereof. BACKGROUND

[0002] High-concentration nitric acid is used to dissolve spent fuel in the spent fuel reprocessing process, and meanwhile, high temperature and strong radioactivity are accompanied, so the reliability of the related equipment materials is extremely high.

[0003] In view of the special requirements of the equipment materials of the acid treatment system in the reprocessing, Japan has developed a Ti-5Ta binary corrosion-resistant titanium alloy, which can work in the simulated medium environment of the reprocessing dissolver and evaporator for a long time. In China, Ti35 alloy is developed on the basis of the Ti-5Ta alloy, and has been applied to a 50-ton pilot plant for reprocessing. However, the price of the Ti35 alloy is extremely high (about 3 million yuan per ton), which greatly limits its wide application in the spent fuel reprocessing plant. Meanwhile, since a certain amount of Ta (melting point 2996℃) is added in the Ti35 alloy, the alloy smelting difficulty is significantly increased.

[0004] Alloying is one of the important methods for improving the corrosion resistance and mechanical properties of titanium alloys. Platinum group metal elements (such as Pd, Pt, Ru, etc.) as important corrosion-resistant elements can significantly improve the corrosion resistance of pure titanium or titanium alloys with a small amount of addition. At the same time, Al is an alpha phase stabilizing element, which has a solid solution strengthening effect and can significantly improve the heat resistance of titanium alloys. When the content of Al in the alloy is less than 7wt.%, with the increase of the content of Al, the strength of the alloy is improved, the plasticity is basically unchanged, and the corrosion resistance is good; but when the content of Al in the alloy is more than 7wt.%, brittle Ti3Al will appear in the alloy structure, and the plasticity and corrosion resistance are significantly reduced. It is well known that the chemical stability of Al oxide-Al2O3 is high, and it has excellent high-temperature oxidation resistance in high-temperature environment.

[0005] In view of this, the application adds a certain amount of Al and Pd to obtain a titanium alloy with excellent corrosion resistance and mechanical properties. SUMMARY

[0006] In view of the above deficiencies in the prior art, the purpose of the application is to provide a high-temperature nitric acid corrosion-resistant titanium alloy. The high-temperature nitric acid corrosion-resistant titanium alloy prepared by the application has high-temperature nitric acid corrosion resistance and good mechanical properties.

[0007] To achieve the above purpose, the technical scheme adopted by the application is as follows:

[0008] A high-temperature nitric acid corrosion-resistant titanium alloy comprises the following raw materials in mass percentage: 0.02-0.08wt.% of Pd, 0-7wt.% of Al, and the balance of titanium.

[0009] In one or more embodiments, the high-temperature nitric acid corrosion resistant titanium alloy comprises the following raw materials by mass percentage:

[0010] Palladium 0.04-0.06wt.%, aluminum 0-6wt.%, and the balance being titanium.

[0011] In one preferred embodiment, the high-temperature nitric acid corrosion resistant titanium alloy comprises the following raw materials by mass percentage:

[0012] Palladium 0.04wt.%, aluminum 4wt.%, and the balance being titanium.

[0013] In one or more embodiments, the high-temperature nitric acid corrosion resistant titanium alloy has the following unavoidable impurity element content requirements: H < 0.015wt.%, O < 0.13wt.%, N < 0.05wt.%, and C < 0.08wt.%.

[0014] The present application also provides a production process for the high-temperature nitric acid corrosion resistant titanium alloy, which is performed according to the following steps:

[0015] S1: Material preparation: respectively weigh palladium, aluminum and titanium, and dry and preheat each raw material for standby;

[0016] S2: Smelting: sequentially place the raw materials in step S1 into a smelting furnace for melting;

[0017] S3: Casting: cast the treated melt in step S2 to obtain the high-temperature nitric acid corrosion resistant titanium alloy.

[0018] The production process for the high-temperature nitric acid corrosion resistant titanium alloy described above, wherein:

[0019] The smelting temperature in step S2 is 1650-1700°C;

[0020] The vacuum degree for smelting in step S2 is 5x10 -3 Pa-6x10 -3 Pa;

[0021] The number of times for improving smelting in step S2 is 5-7 times;

[0022] The discharge temperature in step S3 is set to 30-40°C;

[0023] The present application has the following beneficial effects:

[0024] The application improves the high-temperature nitric acid corrosion resistance and mechanical properties of the titanium alloy by adding Pd and Al elements in different proportions, and develops a material suitable for spent fuel reprocessing equipment. The titanium alloy prepared by controlling the addition of high-corrosion-resistant noble metal Pd element and low-cost Al element forms a passivation film in the nitric acid solution of spent fuel reprocessing, has stable corrosion resistance, reduces the application cost, and solves the problem of corrosion resistance and application cost of the titanium alloy for spent fuel reprocessing. The high-temperature nitric acid corrosion resistant titanium alloy has uniform structure and no obvious defects, and can be used in as-cast state or processed into equipment in any spent fuel reprocessing environment by processes such as forging, rolling and drawing. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The potentiodynamic polarization curve of the titanium alloy prepared in example 1-4 of the application in 100℃, V 5+ , Cr 6+ , Ce 4+ concentrated nitric acid solution electrochemical corrosion test;

[0026] Figure 2 The Vickers hardness diagram of the titanium alloy prepared in example 1-4 of the application at room temperature.

[0027] Figure 3 The morphology diagram of the titanium alloy prepared in example 3 of the application after being soaked in 100℃, V 5+ , Cr 6+ , Ce 4+ concentrated nitric acid solution for 120h. DETAILED DESCRIPTION

[0028] The application will be further described in detail through examples and drawings.

[0029] Example 1

[0030] The embodiment discloses a high-temperature nitric acid corrosion resistant alloy, and the weight percentage of each component is as follows: 0.04wt.% Pd, unavoidable impurity element content requirements: H<0.015wt.%、O<0.13wt.%、N<0.05wt.%、C<0.08wt.% and the balance is Ti.

[0031] A production process of a high-temperature nitric acid corrosion resistant titanium alloy, comprising the following steps:

[0032] S1: material preparation: respectively weigh the palladium and titanium according to the proportion, dry and preheat each raw material, and reserve;

[0033] S2: smelting: put the raw materials in step S1 into a smelting furnace in sequence and melt; the smelting temperature is set to 1650℃, and the vacuum degree of smelting is to 5×10 -3Pa, alloy ingot smelting 5 times;

[0034] S3: Casting: the melt treated in step S2 is cast to obtain a high-temperature nitric acid corrosion resistant titanium alloy; wherein the temperature at which the alloy is discharged is set to 30 DEG C.

[0035] By Figure 1 The potentiodynamic polarization curve results of the electrochemical corrosion test show that the high-temperature nitric acid corrosion resistant titanium alloy in this embodiment 1 has a clear passivation zone, and the passivation current density is 2.71 x 10 -5 A / cm 2 , showing good high-temperature corrosion resistance. By Figure 2 The Vickers hardness results at room temperature show that the high-temperature nitric acid corrosion resistant titanium alloy in this embodiment 1 has a Vickers hardness of 150 HV1, and has excellent mechanical properties.

[0036] Embodiment 2

[0037] This embodiment discloses a high-temperature nitric acid corrosion resistant alloy, the weight percentage of each component is: 0.04wt.% Pd, 2wt.% Al, the content requirements of inevitable impurity elements are: H < 0.015wt.%, O < 0.13wt.%, N < 0.05wt.%, C < 0.08wt.%, and the balance is Ti.

[0038] A production process of a high-temperature nitric acid corrosion resistant titanium alloy, comprising the following steps:

[0039] S1: Preparation: Pd, Al and Ti are weighed according to the proportion respectively, and each raw material is dried and preheated for standby;

[0040] S2: Smelting: the raw materials in step S1 are sequentially put into a smelting furnace for melting; the smelting temperature is set to 1650 DEG C, and the vacuum degree of smelting is to 5 x 10 -3 Pa, alloy ingot smelting 5 times;

[0041] S3: Casting: the melt treated in step S2 is cast to obtain a high-temperature nitric acid corrosion resistant titanium alloy; wherein the temperature at which the alloy is discharged is set to 30 DEG C.

[0042] By Figure 1 The potentiodynamic polarization curve results of the electrochemical corrosion test show that the high-temperature nitric acid corrosion resistant titanium alloy in this embodiment 2 has a clear passivation zone, and the passivation current density is 1.799 x 10 -5 A / cm 2 , showing good high-temperature corrosion resistance. By Figure 2 The Vickers hardness results at room temperature show that the high-temperature nitric acid corrosion resistant titanium alloy in this embodiment 2 has a Vickers hardness of 220 HV1, and has excellent mechanical properties.

[0043] Example 3

[0044] This embodiment discloses a high-temperature nitric acid corrosion resistant alloy, the weight percentages of its components are: 0.04 wt.% Pd, 4 wt.% Al, and the unavoidable impurity element content requirements are: H < 0.015 wt.%, O < 0.13 wt.%, N < 0.05 wt.%, C < 0.08 wt.%, with the balance being Ti.

[0045] A production process for a high-temperature nitric acid corrosion resistant titanium alloy includes the following steps:

[0046] S1: Material preparation: Weigh palladium, aluminum and titanium separately according to the proportions, and dry and preheat each raw material for later use;

[0047] S2: Smelting: The raw materials from step S1 are sequentially placed into a smelting furnace for melting; the smelting temperature is set to 1650℃, and the vacuum degree of smelting is set to 5×10⁻⁶. -3 Pa, alloy ingot smelted 5 times;

[0048] S3: Casting: Cast the melt processed in step S2 to obtain a high-temperature nitric acid corrosion resistant titanium alloy; wherein the furnace exit temperature is set to 30℃.

[0049] Depend on Figure 1 The electrodynamic polarization curves of the electrochemical corrosion test show that the high-temperature nitric acid corrosion-resistant titanium alloy in Example 3 has a significant passivation zone, with a passivation current density of 1.434 × 10⁻⁶ at a passivation potential of 1.25 V. -5 A / cm 2 It exhibits good high-temperature corrosion resistance. Figure 2 The Vickers hardness results at room temperature show that the high-temperature nitric acid corrosion-resistant titanium alloy in Example 3 has a Vickers hardness of 239 HV1, exhibiting excellent mechanical properties. The morphology of the alloy prepared in Example 3 after corrosion is shown in the figure below. Figure 3 As shown, the surface has no obvious corrosion pits, indicating that it has excellent corrosion resistance.

[0050] Example 4

[0051] This embodiment discloses a high-temperature nitric acid corrosion resistant alloy, the weight percentage of each component is: 0.04 wt.% Pd, 6 wt.% Al, and the unavoidable impurity element content requirements are: H < 0.015 wt.%, O < 0.13 wt.%, N < 0.05 wt.%, C < 0.08 wt.%, with the balance being Ti.

[0052] A production process for a high-temperature nitric acid corrosion resistant titanium alloy includes the following steps:

[0053] S1: Material preparation: Weigh palladium, aluminum and titanium separately according to the proportions, and dry and preheat each raw material for later use;

[0054] S2: Smelting: The raw materials from step S1 are sequentially placed into a smelting furnace for melting; the smelting temperature is set to 1650℃, and the vacuum degree of smelting is set to 5×10⁻⁶. -3 Pa alloy ingots were smelted 5 times;

[0055] S3: Casting: Cast the melt processed in step S2 to obtain a high-temperature nitric acid corrosion resistant titanium alloy; wherein the furnace exit temperature is set to 30℃.

[0056] Depend on Figure 1 The electrodynamic polarization curves of the electrochemical corrosion test show that the high-temperature nitric acid corrosion-resistant titanium alloy in Example 4 has a significant passivation zone, with a passivation current density of 1.659 × 10⁻⁶ at a passivation potential of 1.25 V. -5 A / cm 2 It exhibits good high-temperature corrosion resistance. Figure 2 The Vickers hardness results at room temperature show that the Vickers hardness of the high-temperature nitric acid corrosion resistant titanium alloy in Example 4 is 278HV1, which indicates that it has excellent mechanical properties.

[0057] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive technical essence shall still fall within the protection scope of the present invention.

Claims

1. A titanium alloy resistant to high-temperature nitric acid corrosion, characterized in that, This titanium alloy is prepared from the following raw materials by mass percentage: palladium 0.04 wt.%, aluminum 2-6 wt.%, with the balance being titanium; when palladium is 0.04 wt.% and aluminum is 2 wt.%, the passivation current density of this titanium alloy at a passivation potential of 1.25V is 1.799 × 10⁻⁶. -5 A / cm 2 The Vickers hardness is 220 HV1; when palladium is 0.04 wt.% and aluminum is 4 wt.%, the passivation current density of this titanium alloy at a passivation potential of 1.25 V is 1.434 × 10⁻⁶. -5 A / cm 2 The Vickers hardness is 239 HV1; when palladium is 0.04 wt.% and aluminum is 6 wt.%, the passivation current density of this titanium alloy at a passivation potential of 1.25 V is 1.659 × 10⁻⁶. -5 A / cm 2 With a Vickers hardness of 278HV1, this titanium alloy is used as a spent fuel reprocessing material. The preparation method of this titanium alloy includes the following steps: S1: Material preparation: Weigh palladium, aluminum and titanium separately, and dry and preheat each raw material for later use; S2: Smelting: The raw materials in step S1 are sequentially placed into a smelting furnace for melting at a smelting temperature of 1650℃-1700℃. S3: Casting: Cast the melt processed in step S2 to obtain a high-temperature nitric acid corrosion resistant titanium alloy, and set the furnace temperature to 30℃-40℃.

2. The titanium alloy resistant to high-temperature nitric acid corrosion according to claim 1, characterized in that, The unavoidable impurity element content requirements for this titanium alloy are: H < 0.015 wt.%, O < 0.13 wt.%, N < 0.05 wt.%, C < 0.08 wt.%.

3. The titanium alloy resistant to high-temperature nitric acid corrosion according to claim 1, characterized in that, The vacuum degree of smelting in step S2 is reduced to 5 × 10⁻⁶. -3 Pa-6×10 -3 Pa.

4. The titanium alloy resistant to high-temperature nitric acid corrosion according to claim 1, characterized in that, In step S2, the number of smelting operations is increased to 5-7 times.

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