Low-expansion high-temperature alloy with good high-temperature performance and manufacturing method thereof

Abstract

The invention belongs to the related technical field of low-expansion high-temperature alloy manufacturing, and relates to a low-expansion high-temperature alloy with good high-temperature performance and a manufacturing method thereof. The alloy comprises the following components in percentage by weight: less than or equal to 0.030 percent of C, 6.00 to 10.00 percent of Cr, 35.00 to 40.00 percent of Ni, 6.00 to 7.00 percent of Al, 2.50 to 3.50 percent of Ti, 15.00 to 20.00 percent of Fe, 0.50 to 1.00 percent of Nb, 0.005 to 0.015 percent of B, less than or equal to 0.30 percent of Si, less than or equal to 0.30 percent of Mn, 0.80 to 1.50 percent of W, 1.80 to 2.50 percent of Mo, less than or equal to 0.30 percent of Cu, 0.01 to 0.04 percent of Zr, 0.005 to 0.015 percent of Y, less than or equal to 0.002 percent of S, less than or equal to 0.015 percent of P and the balance of Co and inevitable impurities. The alloy bar has excellent high-temperature oxidation resistance and low expansion performance.

Description

Technical Field

[0001] This invention belongs to the technical field of low-expansion high-temperature alloy manufacturing, and particularly relates to a low-expansion high-temperature alloy with excellent high-temperature strength and high-temperature oxidation resistance at operating temperatures above 750℃, and its manufacturing method. Background Technology

[0002] Low-expansion high-temperature alloys, with their high strength and low coefficient of expansion at high temperatures, are widely used in high-temperature resistant components in aerospace, aviation and energy fields, and have good resistance to thermal cycling.

[0003] In recent years, with the rapid development of my country's modern aviation, aerospace and energy industries, in order to further improve efficiency and reduce energy consumption, the technical parameters of various equipment have been greatly improved and the operating conditions have become more and more demanding. These have placed higher requirements on materials to have good high-temperature strength, high-temperature oxidation resistance and low expansion at higher operating temperatures.

[0004] GH783 alloy is a commonly used Co-Ni-Fe based precipitation-hardening low-expansion high-temperature alloy. It is strengthened at high temperatures by adding elements such as aluminum and niobium to precipitate γ′ phase and β-NiAl phase during aging. It has good strength, oxidation resistance and low expansion coefficient below 700℃. However, because this type of alloy has a low content of strengthening elements in order to achieve low expansion performance, its high-temperature strength is relatively low, which makes it unable to meet the requirements of harsh operating conditions such as higher operating temperatures.

[0005] Patent CN201310397115.4 describes a low-cost, low-expansion nickel-based alloy, the composition of which is shown in Table 1. This patent reduces costs and improves processability by decreasing the amount of precious metals and increasing the Fe content, while Mo and W increase strength, and high Cr content improves oxidation resistance. Simultaneously, the addition of rare earth elements improves grain boundary strength. This alloy has a low cost, a low coefficient of thermal expansion, excellent high-temperature strength, hot workability, and oxidation and corrosion resistance; however, its high coefficient of thermal expansion limits its application areas.

[0006] Patent CN201710262517.1 describes an oxidation-resistant, low-expansion high-temperature alloy, the composition of which is shown in Table 1. This patent achieves good high-temperature strength by combining precipitation strengthening and solid solution strengthening, and by adding a certain amount of iron to reduce the alloy's cost and improve its machinability (excluding cobalt). This alloy offers good cost-effectiveness, but its coefficient of thermal expansion is also relatively high, thus it cannot meet the stringent requirements of applications demanding comprehensive performance. Summary of the Invention

[0007] The purpose of this invention is to provide a low-expansion high-temperature alloy with good high-temperature strength and high-temperature oxidation resistance. This alloy can be used at temperatures above 750°C and its high-temperature strength is significantly better than that of GH783 alloy, thus ensuring the demand for high-temperature resistant, oxidation-resistant, and low-expansion alloy materials for equipment in my country's aviation, aerospace, and energy industries.

[0008] To achieve the above objectives, the technical solution of this invention is as follows:

[0009] The technical solution of this invention proposes a low-expansion high-temperature alloy with good high-temperature performance, with the following chemical composition (wt%): C: ≤0.030, Cr: 6.00~10.00, Ni: 35.00~40.00, Al: 6.00~7.00, Ti: 2.50~3.50, Fe: 15.00~20.00, Nb: 0.50~1.00, B: 0.005~0.015, Si: ≤0.30, Mn: ≤0.30, W: 0.80~1.50, Mo: 1.80~2.50, Cu: ≤0.30, Zr: 0.01~0.04, Y: 0.005~0.015, S: ≤0.002, P: ≤0.015, with the remainder being Co and unavoidable impurities.

[0010] Further preferred alloying elements (wt%): C: 0.010–0.020, Cr: 7.00–9.00, Ni: 37.00–39.00, Al: 6.30–6.80, Ti: 2.80–3.30, Fe: 17.00–19.00, Zr: 0.02–0.03, Y: 0.007–0.012.

[0011] The compositional design of this invention is mainly based on the following points: 1) Replacing Fe and Co with Ni, and Nb with Al and Ti, appropriately increasing the content of Ni, Al, and Ti, forms the γ′ phase to improve the high-temperature strength of the alloy, and also precipitates intragranular and grain boundary strengthening phases to improve the alloy's oxidation resistance and reduce grain boundary oxidation brittleness. 2) Increasing the content of W and Mo to improve the high-temperature strength and thermal stability of the alloy through solid solution strengthening. 3) Increasing Cr to improve the alloy's oxidation resistance. 4) Adding trace amounts of Zr and Y elements to purify the alloy's grain boundaries and improve its hot working plasticity. Therefore, this invention, through reasonable alloy composition design, obtains a low-expansion high-temperature alloy with good high-temperature strength and high-temperature oxidation resistance, ensuring the material needs of equipment in my country's aviation, aerospace, and energy industries.

[0012] Table 1 Comparison of main chemical components (wt%) of relevant grades, existing patents, and alloys of this invention

[0013] Patent number C Cr Ni Co Al Ti Fe GH783 ≤0.03 2.50～3.50 26.00～30.00 Remain 5.00～6.00 ≤0.40 24.00～27.00 CN201310397115.4 ≤0.10 14～18 Remain - 1.5～2.0 1.5～2.5 20～25 CN201710262517.1 ≥0.02 10～18 Remain - ≥1.2 ≥1.3 10.5～19 This invention ≤0.03 6.00～10.00 35.00～40.00 Remain 6.00～7.00 2.50～3.50 15.00～20.00 Nb(+Ta) B Si W Cu Mn Mo GH6783 2.50～3.50 0.003～0.012 ≤0.50 - ≤0.50 ≤0.50 - CN201310397115.4 0.5～2.0 ≤0.01 ≤1.0 0.5～2.0 ≤0.50 - 0.3～2 CN201710262517.1 - 0.002～0.02 0.1～0.8 0.2～4.0 ≤0.50 0.1～0.8 ≥3 This invention 0.50～1.00 0.005～0.015 ≤0.30 0.80～1.50 ≤0.30 ≤0.30 1.80～2.50

[0014] The reasons for selecting this chemical composition range in the alloy technology solution of this invention are as follows:

[0015] C: A strong austenite-forming element and an essential element for carbide formation in high-temperature alloys, it helps improve the strength of the alloy and plays a deoxidizing role in vacuum induction melting. When the C content is too high, it leads to a decrease in the alloy's ductility and toughness; therefore, the C content should be controlled at ≤0.030%.

[0016] Cr: An important element for improving corrosion resistance, and it also enhances the alloy's oxidation resistance. However, considering the requirement for a low coefficient of thermal expansion, the Cr content is controlled between 6.00% and 10.00%.

[0017] Ni: As a strong element for forming and expanding the austenite region, it can improve the stability of the austenite structure and enhance hot working properties. Excessive Ni content will increase the coefficient of thermal expansion; therefore, the preferred Ni content should be controlled between 35.00% and 40.00%.

[0018] Al is a high-temperature strengthening phase forming element. It can form γ′ phase with Nb and Ti to improve the high-temperature strength and stability of the alloy. It can also combine with Ni to form intragranular and grain boundary strengthening phases, improving the alloy's oxidation resistance and reducing grain boundary oxidation brittleness. Excessive Al content increases the difficulty of hot working of the alloy, so the Al content is controlled at 6.00-7.00%.

[0019] Ti is a high-temperature strengthening phase forming element that effectively improves the high-temperature strength and stability of the alloy. Excessive titanium content can generate harmful phases, leading to decreased alloy plasticity. Considering the requirement for a low coefficient of thermal expansion, the titanium content is controlled between 2.50% and 3.50%.

[0020] Fe can form an austenitic matrix together with Ni and Co. An appropriate amount of iron can significantly reduce alloy costs and ensure the alloy's coefficient of thermal expansion. Excessive iron content promotes the precipitation of harmful phases, leading to deterioration of alloy properties; therefore, the iron content should be controlled between 15.00% and 20.00%.

[0021] Niobium (Nb) is a high-temperature strengthening phase forming element that effectively improves the high-temperature strength and stability of alloys. Excessive niobium content can easily lead to segregation and deteriorate alloy properties; therefore, the niobium content is controlled between 0.50% and 1.00%.

[0022] B: Trace amounts of boron (B) in high-temperature alloys can strengthen grain boundaries, improve alloy plasticity, and enhance the alloy's high-temperature creep resistance. Excessive B content will deteriorate the alloy's hot workability; therefore, the B content should be controlled between 0.005% and 0.015%.

[0023] Si is a ferrite-forming element and can effectively act as a deoxidizer, which is beneficial for high-temperature oxidation resistance. However, excessive addition will degrade processing performance and toughness; therefore, the addition of Si should be controlled at ≤0.30%.

[0024] Mn is a weak austenitic element that plays a role in stabilizing austenite. Excessive Mn content will reduce the alloy's hot plasticity and oxidation resistance; therefore, the Mn content should be controlled to ≤0.30%.

[0025] S: This is an impurity element in steel. For the sake of thermoplasticity and corrosion resistance, the lower the content of this element, the better. Therefore, the sulfur content is controlled at ≤0.002%.

[0026] Phosphorus (P) is an impurity element in steel. Trace amounts of phosphorus can improve the high-temperature creep resistance and creep life of some high-temperature alloys. Excessive P content will exacerbate segregation and deteriorate the hot workability of the alloy; therefore, the P content should be controlled at ≤0.015%.

[0027] Cu: An element that improves corrosion resistance, but it is a harmful element in some high-temperature alloys. Excessive Cu content is detrimental to alloy strength and reduces hot workability; therefore, the Cu content should be controlled at ≤0.30%.

[0028] W: A strong carbide-forming element, it promotes the precipitation of grain boundary carbides, increases grain boundary strength, and also plays a role in solid solution strengthening, improving the high-temperature stability of the matrix. Excessive W content can lead to harmful effects and negatively impact thermoplasticity; therefore, the W content should be controlled between 0.80% and 1.50%.

[0029] Mo: An element that improves corrosion resistance, it dissolves into the matrix to provide solid solution strengthening. Excessive Mo content is detrimental to oxidation resistance; therefore, the Mo content is controlled between 1.80% and 2.50%.

[0030] Zr: Adding an appropriate amount of Zr can purify grain boundaries, reduce the segregation of harmful elements at grain boundaries, and improve the hot plasticity of the alloy. However, excessive Zr will lead to poor hot plasticity of the alloy, so the Zr content should be controlled between 0.01% and 0.04%.

[0031] Y: Trace amounts of Y can strengthen grain boundaries, improve alloy plasticity, and enhance the alloy's high-temperature creep resistance. However, excessive Y content can worsen the alloy's hot workability; therefore, the Y content should be controlled between 0.005% and 0.015%.

[0032] Co can form an austenitic matrix with elements such as Ni and Fe, which can improve the thermal strength, structural stability and oxidation resistance of alloys at high temperatures, and increase the Curie temperature of the alloys.

[0033] Based on the above chemical composition requirements, the alloy of the present invention is prepared using the following method: vacuum induction smelting → vacuum arc remelting → homogenization treatment → forging into finished products. More specifically, this method is as follows:

[0034] (1) Vacuum induction smelting:

[0035] The ingredients are prepared according to the chemical composition described in any one of claims 1-2; the vacuum degree during the smelting process is controlled at ≤3.0 Pa;

[0036] (2) Vacuum consumable remelting:

[0037] The surface of the induction electrode is ground clean to its original metal color. The melting rate is set at 2.5-4.5 kg / min, and the current is controlled at 3000-9000 A and the voltage at 18-28 V. The consumable ingot is demolded and air-cooled 60 minutes after the remelting is completed.

[0038] (3) Homogenization treatment:

[0039] After demolding, the consumable ingot is homogenized at a temperature of 1180–1280℃ for a time of ≥60h.

[0040] (4) Forged materials

[0041] The consumable ingot is ground to remove the surface oxide scale, and the forging heating temperature is 1080~1180℃, with a final forging temperature ≥900℃.

[0042] Furthermore, the specific process of vacuum induction smelting in step (1) is as follows: First, Ni, Co, Fe, W and Mo main materials are added during the melting period, and high vacuum and high power smelting is carried out. After the melt is cleared, refining is carried out. Al, Ti, Nb and Cr alloys are added in batches, melted and refined. Zr and Y are added at the end of the refining period. The refining power is controlled at 300-1200KW and the total refining time is ≥60min. Finally, the finished product sample is taken for composition analysis. After the chemical composition of the molten steel meets the internal control target requirements, the steel is tapped and the vacuum induction electrode is cast.

[0043] Furthermore, the casting temperature of the vacuum induction electrode is controlled at 1400–1500℃.

[0044] Furthermore, in step (4), the consumable ingot is upset twice on the forging machine, and the multiple upsets break the as-cast structure to improve the hot plasticity of the alloy. Finally, it is forged into forging bars of different diameters through multiple forgings.

[0045] The method described in this invention includes the following key steps:

[0046] (3) Vacuum induction smelting process:

[0047] The raw materials used should be clean and prepared according to the above chemical composition. The vacuum degree during the smelting process should be controlled at ≤3.0Pa. First, Ni, Co, Fe, W, Mo and other main materials are added during the melting period, and high-vacuum, high-power smelting is carried out. After the melt is clear, refining is carried out. Al, Ti, Nb, Cr and other alloys are added in batches, melted and refined. Zr and Y are added at the end of the refining period. The refining power is controlled at 300-1200KW, and the total refining time is ≥60min. Finally, a sample of the finished product is taken for composition analysis. After the chemical composition of the molten steel meets the control target requirements, the steel is tapped and the vacuum induction electrode is cast. The casting temperature of the vacuum induction electrode is controlled at 1400~1500℃.

[0048] (4) Vacuum consumable remelting process:

[0049] The surface of the induction electrode should be ground clean to its original metallic color, free from oxide scale and other contaminants. The melting rate should be set between 2.5-4.5 kg / min, with a current of 3000-9000 A and a voltage of 18-28 V. After remelting, the consumable ingot should be demolded and air-cooled 60 minutes later.

[0050] (5) Homogenization process:

[0051] After demolding, the consumable ingots are homogenized at a temperature of 1180–1280℃ for a time of ≥60h.

[0052] (6) Forging process

[0053] The consumable ingot is ground to remove the surface oxide scale, and then forged at a heating temperature of 1080-1180℃. The consumable ingot is upset twice on a forging machine. The multiple upsetting and drawing process breaks down the as-cast structure and improves the hot plasticity of the alloy. Finally, the ingot is drawn and forged into forging bars of different diameters at multiple forging processes, with a final forging temperature ≥900℃.

[0054] Beneficial technical effects:

[0055] Compared with the prior art, the present invention has outstanding features and significant advantages:

[0056] The high-temperature alloy rods prepared according to the chemical composition and production process provided by this invention have a service temperature above 750℃, and their high-temperature strength is significantly better than that of GH783 alloy. Furthermore, they exhibit excellent high-temperature oxidation resistance and low expansion performance above 750℃, which can guarantee the demand for high-temperature resistant, oxidation-resistant, and low-expansion alloy materials for equipment in my country's aviation, aerospace, and energy industries. Detailed Implementation

[0057] The technical solution of the present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are only used to describe the specific implementation of the present invention and are not intended to constitute any limitation on the scope of protection of the present invention.

[0058] Table 2 shows the chemical composition of the alloy examples of the present invention. Table 3 shows a performance comparison between the alloy examples of the present invention and the GH783 alloy. The high-temperature alloy bars prepared according to the chemical composition and production process provided by the present invention have a service temperature above 750℃, and their high-temperature strength is significantly better than that of the GH783 alloy. Furthermore, they exhibit excellent high-temperature oxidation resistance and low expansion properties above 750℃, which can meet the needs of my country's aviation, aerospace, and energy industries for high-temperature resistant, oxidation-resistant, and low-expansion alloy materials.

[0059] Table 2 Chemical composition (wt.%) of alloy examples of the present invention

[0060]

[0061]

[0062] Table 3 Comparison of the performance of the alloy examples of the present invention and GH783 alloy.

[0063]

[0064] Examples 1-8:

[0065] The manufacturing method according to embodiments 1 to 8 of the present invention includes the following steps:

[0066] 1. Vacuum induction smelting process:

[0067] The raw materials used should be clean and prepared according to the above chemical composition. The vacuum degree during the smelting process should be controlled at ≤3.0Pa. First, Ni, Co, Fe, W and Mo are added during the melting period for high vacuum and high power smelting. After the melt is clear, it is refined. Al, Ti, Nb and Cr alloys are added in batches, melted and refined. Zr and Y are added at the end of the refining process. The refining power is controlled at 300-1200KW and the total refining time is ≥60min. Finally, a sample of the finished product is taken for composition analysis. After the chemical composition of the molten steel meets the internal control target requirements, the steel is tapped and the vacuum induction electrode is cast. The casting temperature of the vacuum induction electrode is controlled at 1400~1500℃.

[0068] 2. Vacuum consumable remelting process:

[0069] The surface of the induction electrode should be ground clean to its original metallic color, free from oxide scale and other contaminants. The melting rate should be set between 2.5-4.5 kg / min, with a current of 3000-9000 A and a voltage of 18-28 V. After remelting, the consumable ingot should be demolded and air-cooled 60 minutes later.

[0070] 3. Homogenization process:

[0071] After demolding, the consumable ingots are homogenized at a temperature of 1180–1280℃ for a time of ≥60h.

[0072] 4. Forging process

[0073] The consumable ingot is ground to remove the surface oxide scale, and then forged at a heating temperature of 1080-1180℃. The consumable ingot is upset twice on a forging machine. The multiple upsetting and drawing process breaks down the as-cast structure and improves the hot plasticity of the alloy. Finally, the ingot is drawn and forged into forging bars of different diameters at multiple forging processes, with a final forging temperature ≥900℃.

[0074] In summary, the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A low-expansion high-temperature alloy with good high-temperature performance, characterized in that, Alloy chemical composition (wt%): C: ≤0.030, Cr: 6.00~10.00, Ni: 35.00~40.00, Al: 6.00~7.00, Ti: 2.50~3.50, Fe: 15.00~20.00, Nb: 0.50~1.00, B: 0.005~0.015, Si: ≤0.30, Mn: ≤0.30, W: 0.80~1.

50. Mo: 1.80~2.50, Cu: ≤0.30, Zr: 0.01~0.04, Y: 0.005~0.015, S: ≤0.002, P: ≤0.015, with the remainder consisting of Co and unavoidable impurities.

2. The low-expansion high-temperature alloy with good high-temperature performance according to claim 1, characterized in that, The alloying elements (wt%) are: C: 0.010–0.020, Cr: 7.00–9.00, Ni: 37.00–39.00, Al: 6.30–6.80, Ti: 2.80–3.30, Fe: 17.00–19.00, Zr: 0.02–0.03, Y: 0.007–0.

012.

3. A method for preparing a low-expansion high-temperature alloy with good high-temperature performance as described in any one of claims 1-2, characterized in that, The process involves vacuum induction smelting → vacuum consumable remelting → homogenization treatment → forging into finished products.

4. The method for preparing a low-expansion high-temperature alloy with good high-temperature performance according to claim 3, characterized in that, The preparation method specifically includes the following steps: (1) Vacuum induction smelting: The ingredients are prepared according to the chemical composition described in any one of claims 1-2; the vacuum degree during the smelting process is controlled at ≤3.0 Pa; (2) Vacuum consumable remelting: The surface of the induction electrode is ground clean to its original metal color. The melting rate is set at 2.5-4.5 kg / min, and the current is controlled at 3000-9000 A and the voltage at 18-28 V. The consumable ingot is demolded and air-cooled 60 minutes after the remelting is completed. (3) Homogenization treatment: After demolding, the consumable ingot is homogenized at a temperature of 1180–1280℃ for a time of ≥60h. (4) Forged materials The consumable ingot is ground to remove the surface oxide scale, and the forging heating temperature is 1080~1180℃, with a final forging temperature ≥900℃.

5. The method for preparing a low-expansion high-temperature alloy with good high-temperature performance according to claim 4, characterized in that, The specific process of step (1) vacuum induction smelting is as follows: First, Ni, Co, Fe, W and Mo main materials are added during the melting period, and high vacuum and high power smelting is carried out. After the melt is cleared, it is refined. Al, Ti, Nb and Cr alloy are added in batches, melted and refined. Zr and Y are added at the end of the refining period. The refining power is controlled at 300-1200KW and the total refining time is ≥60min. Finally, the finished product sample is taken for composition analysis. After the chemical composition of the molten steel meets the internal control target requirements, the steel is tapped and the vacuum induction electrode is cast.

6. The method for preparing a low-expansion high-temperature alloy with good high-temperature performance according to claim 5, characterized in that, The casting temperature of the vacuum induction electrode is controlled at 1400-1500℃.

7. The method for preparing a low-expansion high-temperature alloy with good high-temperature performance according to claim 4, characterized in that, In step (4), the consumable ingot is upset twice on the forging machine. The multiple upsetting and drawing process breaks down the as-cast structure, improves the hot plasticity of the alloy, and finally, it is drawn and forged into forging bars of different diameters.

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