Novel high-strength corrosion-resistant medium-entropy alloy for petrochemical equipment field and preparation method thereof

Abstract

The application discloses a new high-strength corrosion-resistant medium-entropy alloy for the field of petrochemical equipment and a preparation method thereof. a Cr b V c W d , the atomic mass percentage of each element satisfies 22%<=a<=24%, 45%<=b<=49%, 22%<=c<=24%, 3%<=d<=11%, and a+b+c+d=100%; the medium-entropy alloy is prepared by a preparation method of vacuum arc melting combined with directional solidification, the compressive strength of the obtained medium-entropy alloy reaches 1766 MPa, the plastic strain is more than 100%, the oxidation rate constant k is 0.522 after the medium-entropy alloy is placed in an air environment at 650 DEG C for 48 hours, and the medium-entropy alloy is far superior to traditional alloy materials for petrochemical equipment; the medium-entropy alloy can be widely used in reactors, heat exchangers, conveying pipelines and other key equipment in the petrochemical industry, and has a good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of medium-entropy alloy materials technology, specifically to a novel high-strength, corrosion-resistant medium-entropy alloy for use in petrochemical equipment and its preparation method. Background Technology

[0002] Petrochemical equipment often faces the combined effects of high temperature, high pressure, and highly corrosive media (such as hydrochloric acid, hydrogen sulfide, and acidic impurities in crude oil) during operation, placing stringent demands on the mechanical properties and corrosion resistance of materials. While traditional materials used in petrochemical equipment, such as stainless steel and nickel-based alloys, possess a certain degree of corrosion resistance, they still suffer from insufficient strength and corrosion failure under extreme operating conditions. This leads to shortened equipment lifespan, increased maintenance costs, and even safety accidents.

[0003] Medium-entropy alloys, as a novel type of multi-principal-element alloy, form a simple solid solution structure through the synergistic effect of multiple elements, exhibiting characteristics such as high strength, high hardness, excellent corrosion resistance, and thermal stability, providing a new direction for solving the performance bottlenecks of traditional materials. However, the application of existing medium-entropy alloys in the petrochemical equipment field still has many shortcomings: some medium-entropy alloys, although having high strength, have poor plasticity, making it difficult to meet the processing and forming requirements of equipment; some alloys with good corrosion resistance have low strength and cannot withstand high-pressure conditions; at the same time, medium-entropy alloys prepared by simple arc melting have problems such as coarse grains and uneven microstructure, further affecting the stability of their overall performance.

[0004] Therefore, developing a medium-entropy alloy material that combines high strength, good plasticity, and excellent corrosion resistance, and optimizing its preparation process to enable it to adapt to the harsh service environment of petrochemical equipment, has important engineering application value and practical significance. Summary of the Invention

[0005] To address the problem of existing alloy materials used in petrochemical equipment having difficulty in balancing strength and corrosion resistance, as well as poor service stability, this invention provides a novel high-strength, corrosion-resistant, medium-entropy alloy and its preparation method.

[0006] This invention employs a preparation process combining vacuum arc melting and directional solidification to produce a medium-entropy alloy with a compressive strength of 1766 MPa and a plastic strain exceeding 100%. It is suitable for manufacturing key equipment (reactors, heat exchangers, pipelines, etc.) under high temperature, high pressure, and strong corrosion conditions in the petrochemical industry, and has broad prospects for industrial application.

[0007] The technical solution of the present invention is as follows: A medium-entropy alloy, chemical formula: Fe a Cr b V c W d ; The atomic mass percentages of each element satisfy the following conditions: 22%≤a≤24%, 45%≤b≤49%, 22%≤c≤24%, 3%≤d≤11%; and a+b+c+d=100%.

[0008] Preferably, a medium-entropy alloy, chemical formula: Fe a Cr b V c W d ; The atomic mass percentages of each element satisfy the following conditions: a=23%, b=47%, c=23%, d=7%; this can be represented as Fe. 23 Cr 47 V 23 W7.

[0009] The purity of Fe, Cr, V, and W are all higher than 99.9%, and the raw material form is... Cylindrical particles or blocky elemental metals of 3-5 mm are used to ensure the accuracy and uniformity of the composition during the smelting process.

[0010] The method for preparing the medium-entropy alloy of the present invention includes: S1. Weigh out the Fe, Cr, V, and W elemental raw materials according to the atomic mass percentage of each element, and set aside for later use; Specifically, considering the element loss during the smelting process, each raw material is weighed at 103% of its nominal mass to ensure that the final alloy composition meets the design requirements; S2. Place the raw materials prepared in S1 into the water-cooled copper crucible of the electric arc melting furnace in order of increasing melting point (Fe, Cr, V, W) from bottom to top. Evacuate the furnace and introduce high-purity argon as a protective gas to remove residual oxygen before alloy melting. The melting current is 400~500A, and the melting is repeated 7 times, with each melting time being 60~80 seconds, to obtain an alloy ingot. Specific procedures: Place the raw materials prepared in S1 into the water-cooled copper crucible of the electric arc melting furnace in order of increasing melting point (Fe, Cr, V, W), from bottom to top, and evacuate to 5×10⁻⁶. -4 Pa, high-purity argon gas (purity ≥99.99wt%) at 60Pa is introduced as a protective gas. First, the titanium block is melted to remove residual oxygen in the furnace, and then the alloy is melted. The melting current is 400~500A, and the melting is repeated 7 times. Each melting time is 60~80 seconds. The ingot is turned over before each melting to ensure that the alloy composition is uniform and a button-shaped alloy ingot is obtained. S3. The alloy ingot obtained in S2 is processed into a metal rod. First, it is polished with sandpaper, then ultrasonically cleaned in anhydrous ethanol, and dried for later use. Specific operation: The alloy ingot is processed into a metal rod with a diameter of 8mm by wire cutting. First, the surface oxide scale and cutting marks are removed by polishing with 1200 grit sandpaper. Then, it is placed in anhydrous ethanol and ultrasonically cleaned for 15 minutes at 300W and 25~30℃ to remove surface oil and impurities. After drying, it is ready for use. S4. Place the metal rod prepared in S3 into an alumina ceramic crucible, put it into a vacuum directional solidification furnace, evacuate the furnace, introduce high-purity argon gas, heat to 1200℃, hold for 1.5h, and cool to room temperature with the furnace to complete the preparation of the medium-entropy alloy. Specific procedure: Place the metal rod prepared in S3 into the alumina ceramic crucible (ensuring the metal rod is in close contact with the inner wall of the crucible), place it in a vacuum directional solidification furnace, and evacuate to 2×10⁻⁶. -3 Pa, introduce 50 Pa of high-purity argon gas, heat to 1200℃, hold for 1.5 h (to make the metal rod composition uniform), and cool to room temperature with the furnace to complete the preparation of the medium-entropy alloy.

[0011] The medium-entropy alloy described in this invention can be used in the manufacture of key equipment in the petrochemical field.

[0012] The beneficial effects of this invention are: I. Scientific and rational composition design: The high content of Cr (45%~49% atomic percentage) can form a dense and stable Cr2O3 passivation film on the alloy surface, effectively resisting the erosion of corrosive media and significantly improving the corrosion resistance of the alloy; W and V have large atomic radii, and their addition forms a significant lattice distortion effect, achieving solid solution strengthening, while promoting the formation of high-strength BCC phase and improving the second phase strengthening effect; Fe, as the matrix element, ensures that the alloy has good plasticity and processing performance. The synergistic effect of each element makes the alloy have both high strength and excellent corrosion resistance.

[0013] II. Optimization of the preparation process: Vacuum arc melting was repeatedly melted 7 times, which effectively ensured the uniformity of the alloy composition and avoided compositional segregation; the application of directional solidification technology enabled the alloy to form a columnar dendritic structure with a single direction, reducing transverse grain boundaries and preventing the rapid propagation of cracks along transverse grain boundaries during stretching. At the same time, it refined the grains, increased the grain boundary content, enhanced the grain boundary strengthening effect, and further improved the strength and plasticity of the alloy.

[0014] III. Excellent comprehensive performance: The entropy alloy of this invention has a compressive strength exceeding 1766MPa and an elongation of 100%. After being placed in an air environment at 650℃ for 48 hours, the oxidation rate constant k is 0.522, which is far superior to the alloy materials used in traditional petrochemical equipment. At the same time, the preparation method is simple to operate, has high stability, and controllable production costs, making it suitable for large-scale industrial production. Attached Figure Description

[0015] Figure 1 Fe23 Cr 47 V 23 XRD pattern of W7 medium entropy alloy material.

[0016] Figure 2 Fe 23 Cr 47 V 23 Compressive stress-strain curve of W7 medium-entropy alloy material.

[0017] Figure 3 Fe 23 Cr 47 V 23 Oxidation kinetics curve of W7 medium entropy alloy material at 650℃. Detailed Implementation

[0018] The present invention is further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0019] Example 1

[0020] A novel high-strength, corrosion-resistant, medium-entropy alloy for use in petrochemical equipment, with atomic percentages of: 24% iron, 49% chromium, 24% vanadium, and 3% tungsten.

[0021] The preparation method is as follows: S1. Weigh the Fe, Cr, V, and W elemental raw materials according to the stated atomic percentages. Considering element loss during the smelting process, weigh each raw material at 103% of its nominal mass to ensure that the final alloy composition meets the design requirements. The actual weighing amounts are: Fe 12.4g, Cr 25.2g, V 12.4g, and W 1.5g.

[0022] S2. Place the raw materials into the water-cooled copper crucible of the electric arc melting furnace from bottom to top, in order of increasing melting point (Fe, Cr, V, W), and evacuate to 5 × 10⁻⁶. -4 After Pa, 60 Pa of high-purity argon gas (purity ≥99.99wt%) is introduced as a protective gas. First, 51.5g of titanium block is melted to remove residual oxygen in the furnace, and then alloy melting is carried out. The melting current is 400A, and the melting time is 60 seconds each time. The melting is repeated 7 times. Before each melting, the ingot is turned over to ensure that the alloy composition is uniform and a button-shaped alloy ingot is obtained. S3. The alloy ingot is processed into a metal rod with a diameter of 8mm by wire cutting. First, the surface oxide scale and cutting marks are removed by polishing with 1200 grit sandpaper. Then, it is placed in anhydrous ethanol and ultrasonically cleaned for 15 minutes at 300W power and 25-30℃ to remove surface oil and impurities. After drying, it is ready for use. S4. Place the cleaned metal rod into the alumina ceramic crucible, ensuring the metal rod is in close contact with the inner wall of the crucible, and place them together into a vacuum directional solidification furnace. Evacuate the furnace to 2×10⁻⁶. -3 After passing through a Pa pressure, high-purity argon gas at 50 Pa is introduced, and the mixture is heated to 1200℃ for 1.5 hours. The temperature is then maintained for 1.5 hours to ensure uniform composition of the metal rod. Finally, the metal rod is cooled to room temperature in the furnace, thus completing the preparation of the medium-entropy alloy.

[0023] Example 2

[0024] A novel high-strength, corrosion-resistant, medium-entropy alloy for use in petrochemical equipment, with atomic percentages of: 23% iron, 47% chromium, 23% vanadium, and 7% tungsten.

[0025] The preparation method is as follows: S1. Weigh the Fe, Cr, V, and W elemental raw materials according to the stated atomic percentages. Considering element loss during the smelting process, weigh each raw material at 103% of its nominal mass to ensure that the final alloy composition meets the design requirements. The actual weighing amounts are: Fe 11.8g, Cr 24.3g, V 11.8g, and W 3.6g.

[0026] S2. Place the raw materials into the water-cooled copper crucible of the electric arc melting furnace from bottom to top, in order of increasing melting point (Fe, Cr, V, W), and evacuate to 5 × 10⁻⁶. -4 After Pa, 60 Pa of high-purity argon gas (purity ≥99.99wt%) is introduced as a protective gas. First, 51.5g of titanium block is melted to remove residual oxygen in the furnace, and then alloy melting is carried out. The melting current is 450A, and the melting time is 70 seconds each time. The melting is repeated 7 times. Before each melting, the ingot is turned over to ensure that the alloy composition is uniform and a button-shaped alloy ingot is obtained. S3. The alloy ingot is processed into a metal rod with a diameter of 8mm by wire cutting. First, the surface oxide scale and cutting marks are removed by polishing with 1200 grit sandpaper. Then, it is placed in anhydrous ethanol and ultrasonically cleaned for 15 minutes at 300W power and 25-30℃ to remove surface oil and impurities. After drying, it is ready for use. S4. Place the cleaned metal rod into the alumina ceramic crucible, ensuring the metal rod is in close contact with the inner wall of the crucible, and place them together into a vacuum directional solidification furnace. Evacuate the furnace to 2×10⁻⁶. -3 After passing through a Pa pressure, high-purity argon gas at 50 Pa is introduced, and the mixture is heated to 1200℃ for 1.5 hours. The temperature is then maintained for 1.5 hours to ensure uniform composition of the metal rod. Finally, the metal rod is cooled to room temperature in the furnace, thus completing the preparation of the medium-entropy alloy.

[0027] Example 3

[0028] A novel high-strength, corrosion-resistant, medium-entropy alloy for use in petrochemical equipment, with atomic percentages of: 22% iron, 45% chromium, 22% vanadium, and 11% tungsten.

[0029] The preparation method is as follows: S1. Weigh the Fe, Cr, V, and W elemental raw materials according to the stated atomic percentages. Considering element loss during the smelting process, weigh each raw material at 103% of its nominal mass to ensure that the final alloy composition meets the design requirements. The actual weighing amounts are: Fe 11.4g, Cr 23.1g, V 11.4g, and W 5.6g.

[0030] S2. Place the raw materials into the water-cooled copper crucible of the electric arc melting furnace from bottom to top, in order of increasing melting point (Fe, Cr, V, W), and evacuate to 5 × 10⁻⁶. -4 After Pa, 60 Pa of high-purity argon gas (purity ≥99.99wt%) is introduced as a protective gas. First, 51.5g of titanium block is melted to remove residual oxygen in the furnace, and then alloy melting is carried out. The melting current is 500A, and the melting time is 80 seconds each time. The melting is repeated 7 times. Before each melting, the ingot is turned over to ensure that the alloy composition is uniform and a button-shaped alloy ingot is obtained. S3. The alloy ingot is processed into a metal rod with a diameter of 8mm by wire cutting. First, the surface oxide scale and cutting marks are removed by polishing with 1200 grit sandpaper. Then, it is placed in anhydrous ethanol and ultrasonically cleaned for 15 minutes at 300W power and 25-30℃ to remove surface oil and impurities. After drying, it is ready for use. S4. Place the cleaned metal rod into the alumina ceramic crucible, ensuring the metal rod is in close contact with the inner wall of the crucible, and place them together into a vacuum directional solidification furnace. Evacuate the furnace to 2×10⁻⁶. -3 After passing through a Pa pressure, high-purity argon gas at 50 Pa is introduced, and the mixture is heated to 1200℃ for 1.5 hours. The temperature is then maintained for 1.5 hours to ensure uniform composition of the metal rod. Finally, the metal rod is cooled to room temperature in the furnace, thus completing the preparation of the medium-entropy alloy.

[0031] Experimental Example 1

[0032] The novel high-strength, corrosion-resistant, medium-entropy alloy material Fe obtained in Example 2 for use in the petrochemical equipment field 23 Cr 47 V 23 W7 was cut using an electrical discharge wire cutting machine to obtain medium-entropy alloy samples for testing. XRD was used to analyze the obtained Fe, a novel high-strength, corrosion-resistant medium-entropy alloy material for petrochemical equipment. 23 Cr 47 V 23 W7 is used for phase analysis, such as Figure 1 As shown. By Figure 1 As can be seen from the XRD analysis results, this novel high-strength, corrosion-resistant, medium-entropy alloy material Fe, used in petrochemical equipment, demonstrates its superior performance. 23 Cr 47 V 23 W7 contains two phases: BCC and sigma.

[0033] Experimental Example 2

[0034] The novel high-strength, corrosion-resistant, medium-entropy alloy material Fe prepared in Example 2 for use in petrochemical equipment was tested using a universal testing machine. 23 Cr 47 V 23 W7 was used to perform compression performance tests, and the results are as follows: Figure 2 As shown.

[0035] Depend on Figure 2 The test results show that the new high-strength, corrosion-resistant, medium-entropy alloy material Fe, used in petrochemical equipment, is effective. 23 Cr 47 V 23 The ultimate compressive strength of W7 is 1766 MPa, and the compressive plastic strain exceeds 100%, indicating that this new high-strength, corrosion-resistant, medium-entropy alloy material for use in petrochemical equipment has excellent plasticity and high strength.

[0036] Experimental Example 3

[0037] The novel high-strength, corrosion-resistant, medium-entropy alloy material Fe obtained in Example 2 for use in the petrochemical equipment field 23 Cr 47 V 23 After W7 was placed in an air environment at 650℃ for 48 hours, its antioxidant performance was tested, and the results were as follows: Figure 3 As shown.

[0038] Depend on Figure 3 It can be seen that the oxidation rate constant k of the new high-strength corrosion-resistant medium-entropy alloy material used in the petrochemical equipment field is 0.522, indicating that the new high-strength corrosion-resistant medium-entropy alloy material used in the petrochemical equipment field has excellent oxidation resistance.

[0039] P91 steel, commonly used in traditional petrochemical equipment, was selected as a comparison. Its compressive strength is 585 MPa, and its oxidation constant k is 0.704 in an air environment at 650℃.

[0040] In summary, the medium-entropy alloy prepared by this invention has superior compressive strength and corrosion resistance compared to traditional petrochemical equipment, fully meeting the processing and service requirements of petrochemical equipment. It has significant advantages in high strength and corrosion resistance, and can effectively solve the problem of insufficient performance of traditional materials under harsh petrochemical conditions.

Claims

1. A medium-entropy alloy, characterized in that, Chemical formula: Fe a Cr b V c W d ; The atomic mass percentages of each element satisfy the following conditions: 22%≤a≤24%, 45%≤b≤49%, 22%≤c≤24%, 3%≤d≤11%; and a+b+c+d=100%.

2. The medium-entropy alloy as described in claim 1, characterized in that, Chemical formula: Fe a Cr b V c W d ; The atomic mass percentages of each element satisfy the following: a=23%, b=47%, c=23%, d=7%; represented as Fe. 23 Cr 47 V 23 W7.

3. The medium-entropy alloy as described in claim 1 or 2, characterized in that, The purity of Fe, Cr, V, and W are all higher than 99.9%, and the raw material form is... Cylindrical particles or blocky elemental metals of 3-5 mm.

4. The method for preparing the medium-entropy alloy as described in claim 1, characterized in that, The preparation method includes: S1. Weigh out the Fe, Cr, V, and W elemental raw materials according to the atomic mass percentage of each element, and set aside for later use; S2. Place the raw materials prepared in S1 into the water-cooled copper crucible of the electric arc melting furnace from bottom to top in order of melting point from low to high. Evacuate the furnace and introduce high-purity argon as a protective gas to remove residual oxygen in the furnace before alloy melting. The melting current is 400~500A, and the melting is repeated 7 times, with each melting time being 60~80 seconds, to obtain an alloy ingot. S3. The alloy ingot obtained in S2 is processed into a metal rod. First, it is polished with sandpaper, then ultrasonically cleaned in anhydrous ethanol, and dried for later use. S4. Place the metal rod prepared in S3 into an alumina ceramic crucible, put it into a vacuum directional solidification furnace, evacuate the furnace, introduce high-purity argon gas, heat to 1200℃, hold for 1.5h, and cool to room temperature with the furnace to complete the preparation of the medium-entropy alloy.

5. The preparation method according to claim 4, characterized in that, The S2 operation is as follows: Place the raw materials prepared in S1 into the water-cooled copper crucible of the electric arc melting furnace in order of increasing melting point from bottom to top, and evacuate to 5×10. -4 Pa, high-purity argon gas of 60 Pa is introduced as a protective gas, titanium blocks are first melted to remove residual oxygen in the furnace, and then alloy melting is carried out; the melting current is 400~500A; the melting is repeated 7 times, each melting time is 60~80 seconds, and the ingot is turned over before each melting to ensure that the alloy composition is uniform, and a button-shaped alloy ingot is obtained.

6. The preparation method according to claim 4, characterized in that, The S4 procedure is as follows: Place the metal rod prepared in S3 into the alumina ceramic crucible, ensuring that the metal rod is in close contact with the inner wall of the crucible. Place it in a vacuum directional solidification furnace and evacuate to a vacuum level of 2×10⁻⁶. -3 Pa, introduce 50 Pa of high-purity argon gas, heat to 1200℃, hold for 1.5 h to make the metal rod composition uniform, and then cool to room temperature with the furnace to complete the preparation of the medium-entropy alloy.

7. The application of the medium-entropy alloy as described in claim 1 in the manufacturing of key equipment in the petrochemical field.

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