TC18 titanium alloy with good corrosion resistance and preparation method thereof

Abstract

The application discloses a TC18 titanium alloy with good corrosion resistance and a preparation method thereof, and relates to the technical field of titanium alloy materials. The application aims at solving the problem of poor corrosion resistance of the existing as-cast TC18 titanium alloy. The titanium alloy comprises the following components in percentage by mass: Zr 2.0-6.0%, Al 4.5-6.5%, V 4.0-5.5%, Mo 4.0-5.5%, Cr 0.5-1.5%, Fe 0.5-1.5%, and the balance of Ti and inevitable impurities. The application adds Zr element, so that the Zr element forms a twin crystal in the titanium alloy, increases nucleation sites of a passivation film, generates a dense oxidation film mainly composed of ZrO2 and TiO2 on the surface of the alloy, and improves the corrosion resistance of the TC18 titanium alloy in a reducing acid and other corrosion environments. The application is used for the preparation of the titanium alloy.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy materials technology, specifically to a TC18 titanium alloy whose corrosion resistance is significantly improved by adding zirconium (Zr), and its preparation method. The addition of Zr improves the alloy microstructure and increases the passivation film thickness, resulting in higher corrosion resistance. Background Technology

[0002] Titanium alloys possess high specific strength, corrosion resistance, and good biocompatibility, making them widely used in aerospace, seawater desalination, offshore drilling, chemical, and medical fields. The corrosion resistance of titanium alloys is related not only to the service environment but also to their microstructure.

[0003] In acidic environments, hydrostatic pressure promotes the selective dissolution of the passivation film, affecting hydrogen evolution, absorption, and permeation in titanium alloys. It may also promote hydrogen entry into the microstructure of the titanium alloy. Hydrogen, by accelerating dislocation movement, incubates cracks, leading to instability in the passivation film and accelerating the corrosion process. Due to the presence of a natural oxide film on the surface of titanium alloys, primarily composed of titanium oxide, they exhibit excellent corrosion resistance in brine solutions.

[0004] Titanium alloys typically exhibit corrosion resistance in strongly oxidizing environments, such as dichromic acid, perchloric acid, and nitric acid, where the formation of a stable passivation film can be promoted. However, titanium alloys show relatively poor corrosion resistance in reducing acids such as sulfuric acid and hydrochloric acid, which can damage the passivation film and reduce their corrosion resistance. Therefore, appropriate and effective strategies must be adopted to improve the corrosion resistance of titanium alloys in reducing acid environments. The corrosion resistance of titanium alloys is also related to their microstructure.

[0005] Titanium alloys exhibit three typical microstructures: hexagonal close-packed structure (α), body-centered cubic structure (β), and α+β dual structure. The microstructure of titanium alloys can be controlled through heat treatment or the addition of alloying elements, and it also determines their corrosion resistance.

[0006] TC18 titanium alloy (typically composed of Ti-5Al-5Mo-5V-1Cr-1Fe) is a high-strength, high-toughness near-β-type titanium alloy widely used in important industrial fields such as aerospace and shipbuilding. However, existing cast TC18 titanium alloys sometimes fail to meet the requirements for long-term safe use in marine atmospheres, acidic media, or certain specific chemical environments, exhibiting poor corrosion resistance.

[0007] The main reasons for this are: firstly, TC18 titanium alloy is sensitive to reducing acids (such as sulfuric acid and hydrochloric acid), which can damage the natural oxide film on its surface; secondly, there is a lack of effective improvement methods for the complex composition of TC18 titanium alloy system in the existing technology.

[0008] In summary, the existing cast TC18 titanium alloy has the problem of poor corrosion resistance. Summary of the Invention

[0009] The purpose of this invention is to address the problem of poor corrosion resistance in existing cast TC18 titanium alloys. Therefore, it provides a TC18 titanium alloy with good corrosion resistance and its preparation method.

[0010] The technical solution of this invention is:

[0011] This invention provides a TC18 titanium alloy with good corrosion resistance. Its chemical composition, by mass percentage, includes: Zr 2.0-6.0%, Al 4.5-6.5%, V 4.0-5.5%, Mo 4.0-5.5%, Cr 0.5-1.5%, Fe 0.5-1.5%, with the balance being Ti and unavoidable impurities.

[0012] Preferably, the TC18 titanium alloy has the following mass percentage composition: Zr 2.0%, Al 5.0%, V 5.0%, Mo 5.0%, Cr 1.0%, Fe 1.0%, with the balance being Ti and unavoidable impurities.

[0013] Preferably, the TC18 titanium alloy has the following mass percentage composition: Zr 4.0%, Al 5.0%, V 5.0%, Mo 5.0%, Cr 1.0%, Fe 1.0%, with the balance being Ti and unavoidable impurities.

[0014] Preferably, the TC18 titanium alloy has the following mass percentage composition: Zr 6.0%, Al 5.0%, V 5.0%, Mo 5.0%, Cr 1.0%, Fe 1.0%, with the balance being Ti and unavoidable impurities.

[0015] Preferably, among the unavoidable impurities, H < 0.0125%, O < 0.13%, N < 0.05%, and C < 0.08%.

[0016] The present invention also provides a method for preparing TC18 titanium alloy with good corrosion resistance, the method comprising the following steps:

[0017] Step 1: Raw material preparation;

[0018] The ingredients are designed and formulated according to the required performance and cost of the target part.

[0019] The raw materials selected are aluminum sheets, vanadium blocks, iron blocks, zirconium blocks, chromium blocks, sponge titanium, and molybdenum.

[0020] Step Two: Raw Material Melting. The batching blocks obtained in Step One are subjected to five vacuum consumable melting processes to obtain ingots. Specifically, this includes: S1: Placing the pre-pressed raw material blocks into a crucible; S2: Vacuuming the furnace; S3: Introducing high-purity argon gas for two gas purging cycles; S4: Starting the medium-frequency power supply to begin melting; S5: Gradually increasing the current until complete melting, then cooling; S6: Tilting the crucible to turn the material over, repeating this process five times to obtain the ingots.

[0021] Step 3: Casting to obtain the target part;

[0022] Select a suitable mold according to the target part, pour the alloy melt obtained in step two into the preheated machining mold, and after it cools, the casting of the required size can be obtained.

[0023] Step 4: Surface post-treatment;

[0024] The riser of the casting obtained in step three is removed, and the surface is treated to obtain the target part.

[0025] Furthermore, in step S1, during the loading process, more raw material is loaded at the bottom of the crucible than at the bottom of the crucible, and the upper furnace charge is kept loose.

[0026] Furthermore, in step S4, the furnace charge is heated in the initial stage of melting until it begins to melt; after the furnace charge begins to melt, argon gas continues to be supplied, the melting power is increased and a reasonable melting rate is maintained.

[0027] Furthermore, the post-treatment of the casting surface described in step four is as follows: surface cleaning and surface polishing;

[0028] The surface cleaning process is as follows: ultrasonic cleaning is performed using anhydrous ethanol as the cleaning medium for 10 minutes.

[0029] Preferably, the surface polishing process is as follows: the sample is polished in sequence using SiC sandpaper of 240#, 400#, 800#, 1200# and 2000#, then ultrasonically cleaned with ethanol and distilled water for 120 seconds in sequence, and the surface moisture of the sample is dried using a dryer.

[0030] Compared with the prior art, the present invention has the following advantages:

[0031] 1. This invention improves the corrosion resistance of as-cast TC18 alloy through alloying. Specifically, it is reflected in:

[0032] (1) The present invention promotes the formation of passivation film by adding Zr element. X-ray photoelectron spectroscopy test shows that Zr element participates in the formation of oxides such as ZrO2, which together with titanium oxide form oxide film, improves the ability of this alloy to form passivation film in acid, and effectively reduces corrosion rate.

[0033] (2) In terms of microstructure, by adding Zr, a twin structure is formed in the alloy. At the same time, it provides a heterogeneous nucleation core for nucleation during the casting process and increases the nucleation sites of the passivation film.

[0034] Therefore, the corrosion resistance of alloyed as-cast TC18 titanium alloy is effectively improved by adding this element.

[0035] 2. This invention improves the microstructure of as-cast TC18 titanium alloy by using an alloying method, and finally obtains an as-cast TC18 titanium alloy with high corrosion resistance, so that the as-cast TC18 alloy has good corrosion resistance after molding.

[0036] 3. This invention prepares an alloyed TC18 titanium alloy with good corrosion resistance through vacuum arc remelting. The properties of this alloy were tested by static immersion corrosion testing. The results are as follows: In terms of corrosion resistance, the titanium alloy exhibits a minimum corrosion rate of 0.38 mm / year in a 5% (w / w) HCl solution at 25°C.

[0037] 4. This invention simplifies the production process of as-cast TC18 titanium alloy. It utilizes a vacuum arc remelting method, repeatedly melting five times to obtain a homogeneous alloy melt. This melt is then poured into a mold that meets the requirements of the target part. After casting, it cools and solidifies, the riser is removed, and a simple surface treatment is performed to form the final part. This simplifies the strength-enhancing processes of forging, rolling, and heat treatment, saving production costs and broadening the application scenarios of as-cast TC18 titanium alloy.

[0038] 5. This invention improves the corrosion resistance of as-cast TC18 titanium alloy by adding Zr. The addition of Zr promotes the formation of twinned structures in the alloy and increases the number of nucleation sites for the passivation film. At the same time, Zr can participate in the formation of the oxide film on the alloy surface, ensuring that a more stable passivation film can be formed on the alloy surface in acid.

[0039] In other words, adding Zr in a certain proportion can improve the corrosion resistance of as-cast TC18 titanium alloy. Attached Figure Description

[0040] Figure 1This is a transmission electron microscopy (TEM) diagram of the microstructure of the TC18-4Zr alloy in Embodiment 1 of the present invention; wherein, (a) is a bright-field image from a transmission electron microscope; and (b) is a selected area electron diffraction pattern.

[0041] Figure 2 These are surface microstructure and corrosion depth images of the TC18-4Zr alloy in Embodiment 1 of this invention after a 10-day static immersion test in 5 M HCl.

[0042] Figure 3 This is a graph showing the corrosion rate changes of cast TC18 titanium alloys with different alloying components in this invention after immersion in 5 M HCl for 10 days.

[0043] Figure 4 This is a graph showing the change in mass loss of cast TC18 titanium alloys with different alloying components after immersion in 5 M HCl for 10 days. Detailed Implementation

[0044] Specific Implementation Method 1: A TC18 titanium alloy with good corrosion resistance according to this embodiment is composed of the following mass percentages: Zr 2.0-6.0%, Al 4.5-6.5%, V 4.0-5.5%, Mo 4.0-5.5%, Cr 0.5-1.5%, Fe 0.5-1.5%, with the balance being Ti.

[0045] This embodiment tested the performance of the alloy using a static immersion corrosion test. The results are as follows: In terms of corrosion resistance, the titanium alloy exhibited a minimum corrosion rate of 0.38 mm / year in a 5% (w / w) HCl solution at 25°C. This represents a reduction of approximately 42% compared to the as-cast TC18 alloy. The corrosion depth was 0.002 mm, and the passivation film remained clean and intact without pitting corrosion, indicating excellent resistance to localized corrosion in a strong acid environment. Further surface composition analysis of the corroded sample revealed that the passivation film was primarily composed of Ti oxides, accompanied by Zr enrichment, forming a Ti–Zr composite oxide film structure. This composite film exhibits higher density and chemical stability, effectively hindering the penetration and diffusion of Cl⁻ in the corrosive medium, thereby significantly reducing the dissolution rate of the base metal. Simultaneously, electrochemical testing showed a significant increase in the passivation film resistance and a significant decrease in the corrosion current density, indicating lower corrosion kinetic activity and a more stable interface structure in the passivated state. When the film layer is locally damaged, the presence of Zr helps promote the rapid regeneration of the passivation film, thereby enhancing the material's self-healing ability. Based on the above performance characteristics, it can be inferred that under the same service environment conditions, this alloy has lower material loss and lower failure risk during long-term use, and can significantly extend its service life.

[0046] Specific Implementation Method 2: The TC18 titanium alloy with good corrosion resistance in this implementation method has the following mass percentages: Zr 2.0%, Al 5.0%, V 5.0%, Mo 5.0%, Cr 1.0%, Fe 1.0%, with the balance being Ti and unavoidable impurities.

[0047] Specific implementation method three: A TC18 titanium alloy with good corrosion resistance according to this implementation method is composed of the following elements in mass percentage: Zr 4.0%, Al 5.0%, V 5.0%, Mo 5.0%, Cr 1.0%, Fe 1.0%, with the balance being Ti and unavoidable impurities.

[0048] Specific Implementation Method 4: A TC18 titanium alloy with good corrosion resistance according to this embodiment is composed of the following elements in mass percentage: Zr 6.0%, Al 5.0%, V 5.0%, Mo 5.0%, Cr 1.0%, Fe 1.0%, with the balance being Ti and unavoidable impurities.

[0049] Since the corrosion performance of titanium alloys is highly sensitive to Zr content, the Zr-induced improvement in corrosion resistance is mainly attributed to the following modification effects: On the one hand, at the compositional level, Zr is uniformly distributed in the β matrix in solid solution form and preferentially participates in surface reactions during corrosion, promoting the formation of Zr-containing composite oxides; on the other hand, at the microstructure level, the introduction of Zr helps improve the uniformity of the microstructure and reduce micro-region compositional segregation, thereby reducing local electrochemical inhomogeneity; furthermore, at the surface film structure level, Zr participates in the construction of Ti-Zr composite passivation films, transforming the film layer from a single TiO2 structure to a TiO2-ZrO2 composite structure. This composite film exhibits higher density, stability, and resistance to Cl. - This enhances the erosion resistance, thereby significantly improving the thermodynamic stability and resistance to damage of the passivation film.

[0050] Current research mainly focuses on adding 10–40% Zr to industrial pure titanium, or modifying some mature grades with 1–6% Zr. However, these studies are mostly aimed at low-alloy or single-phase systems, and their mechanisms of action and applicable ranges differ significantly from those of high-alloy β-titanium alloys. This invention, based on the TC18 high-alloy system, is the first to systematically study the role of low-content Zr (1-5%) in multi-component β-titanium alloys. The study found that within this composition range, Zr not only stably dissolves in the matrix but also significantly optimizes the microstructure uniformity and interfacial chemical behavior without disrupting the original phase structure. Specifically, this invention discovered that when the Zr content is 4%, a twinned structure appears in the alloy. The presence of twinned structures increases the nucleation sites for the passivation film, thereby increasing the thickness of the passivation film and achieving synergistic optimization of the passivation film structure and electrochemical performance, thus obtaining optimal corrosion resistance. This mechanism has not yet been revealed in existing technologies.

[0051] Therefore, the 1-5% Zr addition range defined in this invention is not a simple repetition of existing technologies, but a key window range determined by composition-structure-property synergistic design in a specific alloy system, and has clear innovation and practical value.

[0052] This invention first determines the elemental ratio for 100g button ingots, then places the material in a crucible, closes the furnace door, evacuates the furnace, introduces argon gas into the furnace for cleaning, starts the power supply to begin melting, and after the material is completely melted, it is turned over, and this process is repeated five times to finally obtain a uniformly composed ingot.

[0053] In the actual preparation process, Cr will volatilize during melting. Argon gas is used as a protective gas to remove impurities and suppress Cr volatilization. Mo is a refractory element, and it has not melted when all other elements have melted. At this time, the current is increased to promote the melting of Mo until all elements have melted, and then the current is reduced. To ensure uniform composition, the melting process is repeated five times, and the current used each time is improved based on the previous melting.

[0054] Specific Implementation Method 5: The preparation method of TC18 titanium alloy with good corrosion resistance according to this embodiment includes the following steps:

[0055] Step 1: Raw material preparation;

[0056] The ingredients are designed and formulated according to the required performance and cost of the target part.

[0057] The raw materials selected are aluminum sheets, vanadium blocks, iron blocks, zirconium blocks, chromium blocks, sponge titanium, and molybdenum.

[0058] Step Two: Raw Material Smelting;

[0059] Step 21: Perform five vacuum self-consumption melting processes on the batching blocks obtained in Step 1 to obtain ingots;

[0060] Step 22: The alloyed TC18 titanium alloy is melted in a vacuum induction melting furnace to obtain a uniformly composed ingot;

[0061] Step 3: Casting to obtain the target part;

[0062] Select a suitable mold according to the target part, pour the alloy melt obtained in step two into the preheated machining mold, and after it cools, the casting of the required size can be obtained.

[0063] Step 4: Surface post-treatment;

[0064] The riser of the casting obtained in step three is removed, and the surface is treated to obtain the target part.

[0065] This embodiment utilizes a vacuum arc remelting method to prepare an alloyed TC18 titanium alloy with good corrosion resistance. The alloy is composed of the following elements by mass percentage: Zr 2-6.0%, Al 4.5-6.5%, V 4.0-5.5%, Mo 4.0-5.5%, Cr 0.5-1.5%, Fe 0.5-1.5%, with the balance being Ti and unavoidable impurities. The alloy's properties were tested using a static immersion corrosion test. The results are as follows:

[0066] In terms of corrosion resistance, the titanium alloy has a minimum corrosion rate of 0.38 mm / year in a 5% HCl solution at 25°C.

[0067] Specific Implementation Method Six: In step two of this implementation method, the smelting of TC18 titanium alloy includes the following steps:

[0068] Step S1: First, put the pre-pressed raw material blocks into the crucible;

[0069] Step S2: After loading the raw material blocks into the crucible, close the furnace door and evacuate the furnace.

[0070] Step S3: High-purity argon gas is introduced into the furnace for two gas purging processes;

[0071] Step S4: After cleaning, start the medium frequency power supply to begin melting;

[0072] Step S5: Gradually increase the current until it is completely melted into a liquid state, and after 5 minutes, gradually decrease the current and wait for it to cool down;

[0073] Step S6: After cooling, tilt the crucible to turn the material over until five repeated melting processes are completed, finally obtaining an ingot with uniform composition.

[0074] Specific Implementation Method Seven: In step S1 of this implementation method, during the charging process, the raw material is filled to a greater extent than the bottom of the crucible, and the upper furnace charge is kept loose. Other components and connections are the same as in Specific Implementation Method Six.

[0075] Specific Implementation Method Eight: In step S4 of this implementation method, the furnace charge is slowly heated in the initial stage of melting until it begins to melt; after the furnace charge begins to melt, argon gas is continuously supplied, the melting power is increased, and a reasonable melting rate is maintained. Other components and connections are the same as in Specific Implementation Method Seven.

[0076] Specific Implementation Method Nine: The post-treatment of the casting surface described in step four of this implementation method is as follows: surface cleaning and surface polishing. Other components and connections are the same as in Specific Implementation Method Eight.

[0077] Specific Implementation Method Ten: The surface cleaning process in this implementation method is as follows: ultrasonic cleaning is performed using anhydrous ethanol as the cleaning medium, and the cleaning time is 10 minutes. Other components and connections are the same as in Specific Implementation Method Nine.

[0078] Specific Implementation Method Eleven: The surface polishing process in this implementation method is as follows: The sample is polished sequentially using SiC sandpaper of grades 240#, 400#, 800#, 1200#, and 2000#, then ultrasonically cleaned with ethanol and distilled water for 120 seconds, and the surface moisture of the sample is dried using a dryer. Other components and connections are the same as in Specific Implementation Method Ten.

[0079] Example 1:

[0080] The as-cast alloyed TC18 titanium alloy of this embodiment is composed of the following elements by mass percentage: Zr 2.0%, Al 5.0%, V 5.0%, Mo 5.0%, Cr 1.0%, Fe 1.0%, with the balance being Ti and unavoidable impurities. Specifically, it includes the following steps:

[0081] Step 1: Raw material preparation;

[0082] Based on the required performance and cost of the target part, the raw materials are formulated according to the design composition TC18-2Zr. Aluminum sheets, vanadium blocks, iron blocks, zirconium blocks, chromium blocks, sponge titanium, and molybdenum raw materials are selected for the formulation.

[0083] Step Two: Raw Material Smelting;

[0084] The raw material blocks obtained in step one are subjected to five vacuum arc remelting processes to obtain ingots. When melting the alloyed TC18 titanium alloy using a vacuum induction melting furnace, the pre-pressed raw material blocks are first placed into the crucible. During loading, more raw material should be placed at the bottom of the crucible, while the upper part of the furnace charge should be kept loose to accelerate the melting speed and prevent material jamming during the melting process. After the furnace charge is loaded into the crucible, the furnace door is closed and the furnace is evacuated. To reduce the oxygen content in the melting chamber, high-purity argon gas is introduced into the furnace for purging. After purging, the medium-frequency power supply is started to begin melting. In the initial stage of melting, the furnace charge should be heated at a low power until it begins to melt. After the furnace charge begins to melt, argon gas is continued to be introduced, and the melting power is increased to maintain a reasonable melting speed. After complete melting, the crucible is tilted to turn the charge over until five repeated melting processes are completed, finally obtaining an ingot with uniform composition.

[0085] Step 3: Casting to obtain the target part;

[0086] Select a suitable mold based on the target part, pour the alloy melt obtained in step two into a preheated machining mold, and obtain the casting of the required size after it cools.

[0087] Step 4: Surface post-treatment;

[0088] The riser of the casting obtained in step three is removed, and the surface is treated to obtain the target part.

[0089] Further, the surface treatment of the casting in step four consists of surface cleaning, surface grinding, and surface sandblasting. The surface cleaning process is as follows: ultrasonic cleaning is performed using anhydrous ethanol as the cleaning medium for 10 minutes. The surface grinding process is as follows: the sample is successively ground with SiC sandpaper of 240#, 400#, 800#, 1200#, and 2000#, and then ultrasonically cleaned with ethanol and distilled water for 120 seconds. The sample surface moisture is then dried using a dryer.

[0090] Its corrosion resistance was tested, and the results are as follows: In terms of corrosion resistance, the corrosion rate of the titanium alloy in a 5 MHCl solution at 25℃ is 0.56 mm / year.

[0091] Example 2:

[0092] The difference between this embodiment and Embodiment 1 is that the as-cast alloyed TC18 titanium alloy in this embodiment is composed of the following elements by mass percentage: Zr 4.0%, Al 5.0%, V 5.0%, Mo 5.0%, Cr 1.0%, Fe 1.0%, with the balance being Ti and unavoidable impurities.

[0093] The test results are as follows: In terms of corrosion resistance, the corrosion rate of the titanium alloy in a 5 M HCl solution at 25°C is 0.38 mm / year.

[0094] Example 3:

[0095] The difference between this embodiment and Embodiment 1 is that the as-cast alloyed TC18 titanium alloy in this embodiment is composed of the following elements by mass percentage: Zr 6.0%, Al 5.0%, V 5.0%, Mo 5.0%, Cr 1.0%, Fe 1.0%, with the balance being Ti and unavoidable impurities.

[0096] The test results are as follows: In terms of corrosion resistance, the corrosion rate of the titanium alloy in a 5 M HCl solution at 25°C is 0.74 mm / year.

[0097] Comparative Example 1:

[0098] The as-cast TC18 titanium alloy of this comparative example is composed of the following elements by mass percentage: Al 5.0%, V 5.0%, Mo 5.0%, Cr 1.0%, Fe 1.0%, with the balance being Ti, and unavoidable impurity elements. The preparation method of the as-cast TC18 titanium alloy of this comparative example includes the following steps:

[0099] Step 1: Select aluminum sheets, vanadium blocks, iron blocks, chromium blocks, sponge titanium, and molybdenum raw materials for batching according to the design composition of the target product;

[0100] Prepare the ingredients and place them in a crucible in preparation for smelting;

[0101] Step 2: Perform five vacuum arc remelting processes on the smelting material from Step 1 to obtain a TC18 ingot with uniform texture.

[0102] Step 3: The ingot obtained in Step 2 is cut according to Step 4 in Example 1, and the surface is polished and cleaned to obtain the test part. The test results are as follows: In terms of corrosion resistance, the corrosion rate of the titanium alloy in 5 M HCl solution at 25℃ is 0.64 mm / year.

[0103] The corrosion performance of the alloyed as-cast TC18 titanium alloys of Examples 1 to 3 of the present invention, and the as-cast TC18 titanium alloy of Comparative Example 1, was tested and analyzed. The specific process is as follows:

[0104] The results of experiments in Examples 1 to 3 and Comparative Example 1 were subjected to corrosion resistance tests in accordance with JBT7901-2023:

[0105] The titanium alloy obtained in the experiment was used to make static immersion samples with dimensions (length × width × height) of 10mm × 10mm × 10mm. Three samples were cut from each titanium alloy ingot to ensure the repeatability of the experiment.

[0106] The sample surface was treated as follows: The statically immersed sample was polished in sequence with SiC sandpaper of 240#, 400#, 800#, 1200# and 2000#, then ultrasonically cleaned with ethanol and distilled water for 120s in sequence, and the surface moisture of the sample was dried with a dryer.

[0107] After completing the pre-experiment preparation, the samples were immersed in containers containing 100ml of natural gas filling test solution to meet the minimum solution volume to sample area ratio requirement (0.20ml / mm²), and the exposed area of ​​each sample was calculated independently based on its geometric dimensions.

[0108] During the 10-day immersion period, statically immersed samples were removed every two days and sequentially washed with ethanol and distilled water to remove corrosion products. After drying, the samples were weighed. Three parallel samples were selected each time to ensure repeatability, and the average value was taken. The corrosion rate R was calculated using the following formula. corr :

[0109]

[0110] Where m represents the mass of the sample before the test, in g; This represents the mass of the sample after testing, in units of... t represents the static immersion corrosion test time, in hours; A represents the area of ​​the sample exposed in the test solution, in cm². 2 ; as well as This represents the density of the sample being tested, expressed in g / cm³. 2 The result is as follows Figure 3 As shown.

[0111] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make other changes within the spirit of the invention and apply it to fields not mentioned in the invention. Of course, all such changes made in accordance with the spirit of the invention should be included within the scope of protection claimed by the invention.

Claims

1. A TC18 titanium alloy with good corrosion resistance, characterized in that: Its chemical composition by mass percentage includes: Zr 2.0-6.0%, Al 4.5-6.5%, V 4.0-5.5%, Mo 4.0-5.5%, Cr 0.5-1.5%, Fe 0.5-1.5%, with the balance being Ti and unavoidable impurities.

2. The TC18 titanium alloy with good corrosion resistance according to claim 1, characterized in that: The mass percentage of TC18 titanium alloy is: Zr 2.0%, Al 5.0%, V 5.0%, Mo 5.0%, Cr 1.0%, Fe 1.0%, with the balance being Ti and unavoidable impurities.

3. The TC18 titanium alloy with good corrosion resistance according to claim 1, characterized in that: The mass percentage of TC18 titanium alloy is: Zr 4.0%, Al 5.0%, V 5.0%, Mo 5.0%, Cr 1.0%, Fe 1.0%, with the balance being Ti and unavoidable impurities.

4. The TC18 titanium alloy with good corrosion resistance according to claim 1, characterized in that: The mass percentage of TC18 titanium alloy is: Zr 6.0%, Al 5.0%, V 5.0%, Mo 5.0%, Cr 1.0%, Fe 1.0%, with the balance being Ti and unavoidable impurities.

5. A TC18 titanium alloy with good corrosion resistance according to any one of claims 1-4, characterized in that: The unavoidable impurities are H < 0.0125%, O < 0.13%, N < 0.05%, and C < 0.08%.

6. A method for preparing the TC18 titanium alloy with good corrosion resistance as described in claim 5, characterized in that: The method includes the following steps: Step 1: Raw material preparation; The ingredients are designed and formulated according to the required performance and cost of the target part. The raw materials selected are aluminum sheets, vanadium blocks, iron blocks, zirconium blocks, chromium blocks, sponge titanium, and molybdenum. Step Two: Raw Material Melting. The batching blocks obtained in Step One are subjected to five vacuum consumable melting processes to obtain ingots. Specifically, this includes: S1: Placing the pre-pressed raw material blocks into a crucible; S2: Vacuuming the furnace; S3: Introducing high-purity argon gas for two gas purging cycles; S4: Starting the medium-frequency power supply to begin melting; S5: Gradually increasing the current until complete melting, then cooling; S6: Tilting the crucible to turn the material over, repeating this process five times to obtain the ingots. Step 3: Casting to obtain the target part; Select a suitable mold according to the target part, pour the alloy melt obtained in step two into the preheated machining mold, and after it cools, the casting of the required size can be obtained. Step 4: Surface post-treatment; The riser of the casting obtained in step three is removed, and the surface is treated to obtain the target part.

7. The method according to claim 6, characterized in that: In step S1, during the loading process, more raw material is loaded at the bottom of the crucible than at the bottom of the crucible, and the upper furnace charge is kept loose.

8. The method according to claim 7, characterized in that: In step S4, the furnace charge is heated in the early stage of melting until it begins to melt; after the furnace charge begins to melt, argon gas continues to be supplied, the melting power is increased and a reasonable melting rate is maintained.

9. The method according to claim 8, characterized in that: The post-treatment of the casting surface described in step four is as follows: surface cleaning and surface polishing; The surface cleaning process is as follows: ultrasonic cleaning is performed using anhydrous ethanol as the cleaning medium for 10 minutes.

10. The method according to claim 9, characterized in that: The surface polishing process is as follows: the sample is polished in sequence with SiC sandpaper of 240#, 400#, 800#, 1200# and 2000#, then ultrasonically cleaned with ethanol and distilled water for 120s in sequence, and the surface moisture of the sample is dried with a dryer.

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