Method for improving high-temperature endurance performance of deformed nickel-iron-chromium-based high-temperature alloy pipe

Abstract

The invention discloses a method for improving the high-temperature endurance performance of a deformed nickel-iron-chromium-based high-temperature alloy pipe, which belongs to the technical field of deformation and hot treatment processes of metal materials, and comprises the following steps: carrying out cold deformation on a solid-solution-state nickel-iron-chromium-based high-temperature alloy pipe at room temperature, and then keeping the temperature for 0.5-1 hour at 127-187 DEG C above the gamma'phase precipitation starting temperature; and finally, at the temperature 7-57 DEG C higher than the gamma'phase precipitation starting temperature, heat preservation is conducted for 1-2 h, and the precipitation-strengthened nickel-iron-based high-temperature alloy is obtained. According to the solid-solution-state ferro-nickel-chromium-based alloy pipe treated through the method, under the condition that the original structure grain size is not changed, the sigma CSL (sigma is smaller than or equal to 29) grain boundary proportion is reduced, precipitation of grain boundary and intracrystalline strengthening phases is promoted, precipitation of grain boundary harmful phases in the aging and high-temperature service process is restrained, good matching between the alloy grain boundary strength and the intracrystalline strength is achieved, and the service life of the alloy pipe is prolonged. And meanwhile, the endurance strength and plasticity of the alloy at high temperature are improved.

Description

Technical Field

[0001] The invention specifically relates to a method for improving the high temperature endurance performance of a deformed nickel-iron-chromium-based high temperature alloy tube, and belongs to the technical field of deformation and heat treatment of metal materials. Background Art

[0002] High temperature alloys are also called heat-resistant alloys, heat-resistant alloys or superalloys. High temperature alloys refer to a type of metal material based on iron, nickel and cobalt that can work for a long time at high temperatures above 600°C and under certain stresses. They have excellent high temperature strength, good oxidation resistance and thermal corrosion resistance, good fatigue performance, fracture toughness and other comprehensive properties. High temperature alloys have a high degree of alloying and are also called "superalloys". They are an important material widely used in aviation, aerospace, petroleum, chemical industry, and ships. According to the matrix elements, high temperature alloys are divided into iron-based, nickel-based, cobalt-based and other high temperature alloys. The use temperature of iron-based high temperature alloys can generally only reach 750-780°C. For heat-resistant parts used at higher temperatures, nickel-based and refractory metal-based alloys are used. Nickel-based high temperature alloys occupy a particularly important position in the entire field of high temperature alloys. They are widely used to manufacture the hottest parts of aviation jet engines and various industrial gas turbines. It can withstand certain complex stresses under oxidation and gas corrosion conditions above 600°C and can work reliably for a long time. According to the production process, it can be divided into deformed alloys, cast alloys and powder alloys. Among them, deformed high-temperature alloys are widely used in aerospace, electricity, oil and gas, vehicles and other fields due to their excellent oxidation and corrosion resistance and excellent high-temperature strength. According to their composition, high-temperature alloys can be divided into iron-based, nickel-based and cobalt-based alloys. Among them, iron-based alloys are mainly deformed and developed by adding alloying elements to the iron-nickel-chromium matrix. They have significant advantages over nickel-based and cobalt-based alloys in terms of cost economy. The performance of iron-nickel-chromium-based deformed alloys depends on the alloy composition, manufacturing process and heat treatment system. Among them, strength and the matching of strength and plasticity are one of the most important physical quality indicators of the alloy, which ultimately depends on the alloy composition and the microstructural state of the finished steel.

[0003] Deformed nickel-iron-chromium-based superalloy is a Ni3(Al,Ti)-γ′ phase strengthened polycrystalline nickel-iron-based superalloy. This alloy not only has excellent high-temperature mechanical properties, but also has good resistance to flue gas oxidation corrosion. It has a wide range of industrial applications in the final superheater tubes of high-parameter ultra-supercritical units. However, the medium-temperature plasticity of polycrystalline precipitation-strengthened superalloys is generally poor, which makes it difficult to weld alloy parts, thus affecting their application in engineering. It is well known that the medium-temperature brittleness of alloys is closely related to grain boundary precipitation phases, grain boundary sliding, slip plane cracking, dynamic strain aging, grain boundary segregation, etc. Studies have found that many failure behaviors of polycrystalline precipitation-strengthened superalloys, such as medium-temperature brittleness, intergranular corrosion cracking, stress corrosion cracking, and high-temperature long-lasting fracture, are all related to grain boundaries / twin boundaries and grain boundary precipitation phases. Therefore, optimizing the long-lasting strength and plasticity of alloys by regulating the microstructural characteristics of grain boundaries and twin boundaries and the precipitation phases in these regions has always been a research hotspot at home and abroad. A large number of studies have shown that coarsening grains and increasing the content of twins can improve the alloy's durability, but deteriorate the alloy's fatigue performance. At the same time, to a certain extent, coarsening the precipitation phase at the grain boundary and the precipitation strengthening phase within the grain can significantly improve the alloy's plasticity, but reduce the alloy's strength. Summary of the invention

[0004] In order to solve the problem of how to improve the high-temperature endurance strength and plasticity of high-temperature alloys, ensure that boiler tubes for superheaters / reheaters of high-parameter ultra-supercritical boilers do not crack prematurely during service, and improve the weldability of the alloy, the purpose of the present invention is to provide a method for improving the high-temperature endurance performance of deformed nickel-iron-chromium-based high-temperature alloy tubes. The method reduces the ∑CSL (∑≤29) grain boundary ratio without changing the original grain size of the alloy, promotes the precipitation of strengthening phases at grain boundaries and within grains, inhibits the precipitation of harmful phases at grain boundaries during aging and service, achieves a good match between grain boundary strength and intragranular strength, and simultaneously improves the endurance strength and plasticity of the alloy at high temperatures.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A method for improving the high temperature durability of a deformed nickel-iron-chromium-based high temperature alloy tube comprises the following steps:

[0007] 1) cold deformation of a solid solution nickel-iron-chromium based high temperature alloy tube;

[0008] 2) The alloy tube treated in step 1) is kept at 127-187°C above the precipitation temperature of the γ′ phase for 0.5-1h;

[0009] 3) The alloy tube treated in step 2) is kept at 7-57° C. above the precipitation temperature of the γ′ phase for 1-2 hours to obtain a precipitation-strengthened nickel-iron-based high-temperature alloy.

[0010] Furthermore, the chemical composition of the solid solution nickel-iron-chromium-based high-temperature alloy tube includes, by mass percentage, C: 0.03-0.08%, Si: ≤0.3%, Mn: ≤0.3%, P: ≤0.02%, S: ≤0.01%, Cr: 19-22%, Co: ≤3.0%, Mo: 0.3-0.7%, Fe: 25-30%, Ti: 2.0-2.5%, Al: 1.3-2.0%, B: 0.001-0.005%, N: ≤0.01%, W: ≤0.5%, Nb: ≤0.5%, and the balance is Ni and unavoidable impurities.

[0011] Furthermore, in step 1), the cold deformation is performed at 20-25°C.

[0012] Furthermore, the cold deformation amount is 9-35%.

[0013] Furthermore, in step 2), the mixture is kept warm and then air-cooled to room temperature.

[0014] Furthermore, in step 3), the mixture is kept warm and then air-cooled to room temperature.

[0015] Furthermore, the grain size of the precipitation strengthened nickel-iron based high temperature alloy is in the range of 2-4.

[0016] Furthermore, the γ′ phase in the precipitation-strengthened nickel-iron-based high-temperature alloy has a unimodal distribution and a particle size of 15-30 nm.

[0017] Furthermore, the precipitation-strengthened nickel-iron-based high-temperature alloy has a durability of 3756 h at 750 °C and 150 MPa.

[0018] Furthermore, the precipitation strengthened nickel-iron based high temperature alloy has an elongation of 13% at 750°C and 150MPa.

[0019] Compared with the prior art, the present invention has at least the following beneficial technical effects:

[0020] The present invention provides a method for improving the high-temperature endurance of a deformed nickel-iron-chromium-based high-temperature alloy tube. The method adopts room temperature cold deformation combined with recrystallization annealing and aging heat treatment processes. By regulating the temperature and time of recrystallization annealing, the ∑CSL (∑≤29) grain boundary ratio is reduced without changing the grain size of the original structure. By regulating the temperature and time of high-temperature aging heat treatment, the precipitation of strengthening phases at the grain boundaries and within the grains is promoted, a good match between the grain boundary strength and the intragranular strength of the alloy is achieved, the precipitation of harmful phases at the grain boundaries during aging and high-temperature service is suppressed, and the endurance strength and plasticity of the alloy at high temperatures are improved.

[0021] The grain size of the nickel-iron-chromium-based high-temperature alloy tube obtained by the present invention is 2-4, the ∑CSL (∑≤29) grain boundary ratio is 35-48%, the strengthening phase γ′ phase is unimodal distribution, and the particle size is 15-30nm. The precipitation-strengthened nickel-iron-based high-temperature alloy prepared by the present invention has a long-lasting life of 2724-3756h and an elongation after fracture of 12-13%.

[0022] Furthermore, the solid solution nickel-iron-chromium-based high temperature alloy tube is plastically deformed at room temperature with a deformation amount of 9-35% to ensure that sufficient deformation storage energy is formed in the alloy.

[0023] Furthermore, since the present invention does not require a quenching process and the starting temperature from air cooling is relatively low, the generation of internal stress can be effectively prevented, and the present invention is suitable for the performance recovery heat treatment of precipitation-strengthened nickel-iron-based high-temperature alloys for super / reheaters of high-parameter ultra-supercritical units after cold working. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The macrostructure of the nickel-iron-chromium-based high-temperature alloy obtained by using Example 1 of the present invention;

[0025] Figure 2 The intragranular γ / γ′ microstructure of the nickel-iron-chromium-based high-temperature alloy obtained by using Example 1 of the present invention;

[0026] Figure 3 The macrostructure of the nickel-iron-chromium-based high-temperature alloy obtained by using Example 2 of the present invention;

[0027] Figure 4 The macrostructure of the nickel-iron-chromium-based high-temperature alloy obtained by using Example 3 of the present invention;

[0028] Figure 5 The macrostructure of the nickel-iron-chromium-based high-temperature alloy obtained by comparative example 1 of the present invention;

[0029] Figure 6 The macrostructure of the nickel-iron-chromium-based high-temperature alloy obtained by comparative example 2 of the present invention;

[0030] Figure 7 This is the macrostructure of the nickel-iron-chromium based high temperature alloy obtained by comparative example 3 of the present invention. DETAILED DESCRIPTION

[0031] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly and comprehensively understood.

[0032] A method for improving the high temperature durability of a deformed nickel-iron-chromium-based high temperature alloy tube of the present invention comprises the following steps:

[0033] 1) A solid solution nickel-iron-chromium-based high-temperature alloy tube is obtained, which comprises, by mass fraction, C: 0.03-0.08%, Si: ≤0.3%, Mn: ≤0.3%, P: ≤0.02%, S: ≤0.01%, Cr: 19-22%, Co: ≤3.0%, Mo: 0.3-0.7%, Fe: 25-30%, Ti: 2.0-2.5%, Al: 1.3-2.0%, B: 0.001-0.005%, N: ≤0.01%, W: ≤0.5%, Nb: ≤0.5%, and the precipitation temperature of the γ′ phase is 963-983°C.

[0034] 2) Plastic deformation treatment: At 20-25° C., the solid solution nickel-iron-chromium-based high-temperature alloy tube is plastically deformed by 9-35% to ensure that sufficient deformation energy storage is formed in the alloy.

[0035] 3) Recrystallization annealing treatment: The alloy tube after plastic deformation treatment is kept at 127-187℃ above the precipitation temperature of γ′ phase for 0.5-1h, and then air-cooled to room temperature to ensure sufficient recrystallization in the alloy, reduce the ∑CSL (∑≤29) grain boundary ratio, promote the precipitation of grain boundary carbides, reduce the stress in the grain boundary, and inhibit the precipitation of harmful phases at the grain boundary during high temperature aging treatment.

[0036] Preferably, the alloy tube after plastic deformation treatment is kept at 147-167° C. above the precipitation temperature of the γ′ phase for 0.5-1 h.

[0037] 4) High temperature aging treatment: The alloy tube after plastic deformation and high temperature solution treatment is placed in a heat treatment furnace at 7-57°C above the precipitation temperature of the γ′ phase for 1-2 hours to promote the precipitation of carbides at the grain boundaries, and then air-cooled to room temperature to promote the precipitation of γ′ phase particles within the grain, thereby obtaining a nickel-iron-chromium-based high-temperature alloy with a matching strength between the intracrystalline strength and the grain boundary strength, further reducing the stress within the grain boundary, and inhibiting the precipitation of harmful phases at the grain boundary during service, thereby simultaneously improving the alloy's endurance strength and plasticity.

[0038] Preferably, the alloy tube after plastic deformation and high-temperature solution treatment is placed in a heat treatment furnace at 47° C. above the γ′ phase precipitation start temperature and kept warm for 1-2 hours.

[0039] The nickel-iron-chromium-based high-temperature alloy tube obtained by the invention has a grain size of 2-4, a ∑CSL (∑≤29) grain boundary ratio of 35-48%, a strengthening phase γ′ phase presents a single peak distribution, and a particle size of 15-30nm.

[0040] The following are specific embodiments of the present invention.

[0041] Example 1

[0042] Taking the nickel-iron-chromium-based high-temperature alloy within the above alloy composition range of the present invention, the precipitation temperature of the γ′ phase is 973°C.

[0043] The solid solution nickel-iron-chromium-based high-temperature alloy tube was subjected to 33% plastic deformation at 23°C, and then kept at 1130°C for 0.5h and air-cooled to room temperature to obtain an alloy structure with uniform grain size. Subsequently, after being kept at 1020°C for 1h and air-cooled to room temperature, the alloy structure was as follows: Figure 1 The average grain size of the alloy is 89μm, the ∑CSL (∑≤29) grain boundary ratio is 45.6%, and the particle size is 15-30nm. Figure 2 Table 1 shows the creep properties of the alloy treated by this method under the conditions of 750℃ / 150MPa.

[0044] Table 1 The creep properties of the alloy treated in Example 1 at 750℃ / 150MPa

[0045] Sample No. Durable life / h Elongation after break / % Example 1 3756 12

[0046] Example 2

[0047] Taking the nickel-iron-chromium-based high-temperature alloy within the above-mentioned gold component range in the present invention, the precipitation temperature of the γ′ phase is 963°C.

[0048] The solid solution nickel-iron-chromium-based high temperature alloy tube was subjected to 20% cold bending deformation at 23°C, and then kept at 1130°C for 0.5h and air cooled to room temperature to obtain an alloy structure with uniform grain size. Subsequently, after being kept at 1010°C for 1h and air cooled to room temperature, the alloy structure is as follows: Figure 3 The average grain size of the alloy is 109 μm, the ∑CSL (∑≤29) grain boundary ratio is 39.5%, and the particle size is 15-30 nm. Table 2 shows the creep performance of the alloy treated by this method at 750°C / 150 MPa.

[0049] Table 2: Creep properties of the alloy treated in Example 2 at 750°C / 150MPa

[0050] Sample No. Durable life / h Elongation after break / % Example 2 3946 12

[0051] Example 3

[0052] Taking the nickel-iron-chromium-based high-temperature alloy within the above-mentioned gold component range in the present invention, the precipitation temperature of the γ′ phase is 983°C.

[0053] The solid solution nickel-iron-chromium-based high-temperature alloy tube was subjected to 10% plastic deformation at 23°C, and then kept at 1130°C for 0.5h and air-cooled to room temperature to obtain an alloy structure with uniform grain size. Subsequently, after being kept at 1030°C for 1h and air-cooled to room temperature, the alloy structure was as follows: Figure 4 The average grain size of the alloy is 119 μm, the ∑CSL (∑≤29) grain boundary ratio is 47.5%, and the particle size is 15-30 nm. Table 3 shows the creep performance of the alloy treated by this method at 750°C / 150 MPa.

[0054] Table 3 Creep properties of the alloy treated in Example 3 at 750°C / 150MPa

[0055] Sample No. Durable life / h Elongation after break / % Example 3 2724 13

[0056] The precipitation-strengthened nickel-iron-based high-temperature alloy prepared by the invention has a lasting life of 2724-3756 hours and a post-fracture elongation of 12-13%.

[0057] Example 4

[0058] Taking the nickel-iron-chromium-based high-temperature alloy within the above alloy composition range of the present invention, the precipitation temperature of the γ′ phase is 973°C.

[0059] The solid solution nickel-iron-chromium-based high-temperature alloy tube was subjected to 9% plastic deformation at 20°C, and then kept at 1130°C for 0.5h and then air-cooled to room temperature to obtain an alloy structure with uniform grain size. Subsequently, it was kept at 1020°C for 1h and then air-cooled to room temperature.

[0060] Example 5

[0061] Taking the nickel-iron-chromium-based high-temperature alloy within the above alloy composition range of the present invention, the precipitation temperature of the γ′ phase is 973°C.

[0062] The solid solution nickel-iron-chromium-based high-temperature alloy tube was subjected to 35% plastic deformation at 25°C, and then kept at 1130°C for 0.5h and then air-cooled to room temperature to obtain an alloy structure with uniform grain size. Subsequently, it was kept at 1020°C for 1h and then air-cooled to room temperature.

[0063] Example 6

[0064] Taking the nickel-iron-chromium-based high-temperature alloy within the above alloy composition range of the present invention, the precipitation temperature of the γ′ phase is 973°C.

[0065] The solid solution nickel-iron-chromium-based high temperature alloy tube was subjected to cold bending deformation with a plastic deformation amount of 26% at 24°C, and then kept at 1130°C for 0.5h and then air-cooled to room temperature to obtain an alloy structure with uniform grain size. Subsequently, it was kept at 1020°C for 1h and then air-cooled to room temperature.

[0066] Example 7

[0067] Taking the nickel-iron-chromium-based high-temperature alloy within the above alloy composition range of the present invention, the precipitation temperature of the γ′ phase is 973°C.

[0068] The solid solution nickel-iron-chromium-based high-temperature alloy tube was subjected to 14% plastic deformation at 21°C, and then kept at 1130°C for 0.5h and then air-cooled to room temperature to obtain an alloy structure with uniform grain size. Subsequently, it was kept at 1020°C for 1h and then air-cooled to room temperature.

[0069] Example 8

[0070] Taking the nickel-iron-chromium-based high-temperature alloy within the above alloy composition range of the present invention, the precipitation temperature of the γ′ phase is 973°C.

[0071] The solid solution nickel-iron-chromium-based high-temperature alloy tube was subjected to 12% plastic deformation at 23°C, then kept at 1100°C for 1 hour and then air-cooled to room temperature to obtain an alloy structure with uniform grain size. Subsequently, the tube was kept at 980°C for 1 hour and then air-cooled to room temperature.

[0072] Example 9

[0073] Taking the nickel-iron-chromium-based high-temperature alloy within the above alloy composition range of the present invention, the precipitation temperature of the γ′ phase is 973°C.

[0074] The solid solution nickel-iron-chromium-based high temperature alloy tube was subjected to cold bending deformation with a plastic deformation amount of 25% at 25°C, and then kept at 1160°C for 0.7h and then air-cooled to room temperature to obtain an alloy structure with uniform grain size. Subsequently, it was kept at 1020°C for 2h and then air-cooled to room temperature.

[0075] Example 10

[0076] Taking the nickel-iron-chromium-based high-temperature alloy within the above alloy composition range of the present invention, the precipitation temperature of the γ′ phase is 973°C.

[0077] The solid solution nickel-iron-chromium-based high-temperature alloy tube was subjected to 33% plastic deformation at 20°C, and then kept at 1145°C for 0.6h and then air-cooled to room temperature to obtain an alloy structure with uniform grain size. Subsequently, it was kept at 993°C for 1.5h and then air-cooled to room temperature.

[0078] Embodiment 11

[0079] Taking the nickel-iron-chromium-based high-temperature alloy within the above alloy composition range of the present invention, the precipitation temperature of the γ′ phase is 973°C.

[0080] The solid solution nickel-iron-chromium-based high-temperature alloy tube was subjected to cold bending deformation at 25°C with a plastic deformation of 31%, and then kept at 1145°C for 0.6h and then air-cooled to room temperature to obtain an alloy structure with uniform grain size. Subsequently, it was kept at 1030°C for 1.8h and then air-cooled to room temperature.

[0081] Comparative Example 1

[0082] For the nickel-iron-chromium-based high-temperature alloy within the above-mentioned gold component range of the present invention, the precipitation temperature of the γ′ phase is 973°C.

[0083] The solid solution nickel-iron-chromium-based high temperature alloy tube is subjected to 10% stretching / cold bending deformation at 23°C, and the alloy structure is as follows Figure 5 The average grain size of the alloy is 125 μm, the ∑CSL (∑≤29) grain boundary ratio is 49.5%, and the particle size is 15-30 nm. Table 4 shows the creep performance of the alloy treated by this method at 750°C / 150 MPa.

[0084] Table 4 The creep properties of the alloys treated with Comparative 1 at 750℃ / 150MPa

[0085] Sample No. Durable life / h Elongation after break / % Comparative Example 1 1010 5.0

[0086] Comparative Example 2

[0087] For the nickel-iron-chromium-based high-temperature alloy within the above-mentioned gold component range of the present invention, the precipitation temperature of the γ′ phase is 973°C.

[0088] The alloy pipe is heat treated by the method in the patent application number: 202111335537.X. The alloy structure is as follows Figure 6 The average grain size of the alloy is 125 μm, the ∑CSL (∑≤29) grain boundary ratio is 49.5%, and the particle size is 15-30 nm. Table 5 shows the creep performance of the alloy after heat treatment in Comparative Example 2 at 750°C / 150 MPa.

[0089] Table 5: Creep properties of alloys treated with Comparative 1 at 750℃ / 150MPa

[0090] Sample No. Durable life / h Elongation after break / % Comparative Example 2 2492 4.2

[0091] Comparative Example 3

[0092] Take a nickel-iron-chromium-based high-temperature alloy within the above-mentioned gold component range of the present invention, the precipitation temperature of the γ′ phase is 973°C. The heat treatment process adopts the method in the patent application number: 202010295857.6. The alloy structure is as follows Figure 7 The average grain size of the alloy is 125 μm, the ∑CSL (∑≤29) grain boundary ratio is 49.5%, and the particle size is 15-30 nm. Table 6 shows the creep performance of the alloy after heat treatment in Comparative Example 3 at 750°C / 150 MPa.

[0093] Table 6 The creep properties of the alloys treated with comparison 3 at 750℃ / 150MPa

[0094] Sample No. Durable life / h Elongation after break / % Comparative Example 3 3253 7.4

[0095] By comparing the results of Example 1, Example 2, Example 3, Comparative Example 1, Comparative Example 2 and Comparative Example 3, it is shown that the nickel-iron-chromium-based alloy treated by the method in this embodiment not only has excellent endurance strength but also has good endurance plasticity. It has the characteristics of high strength and high plasticity at the service temperature, and because no quenching process is required and the starting temperature from air cooling is low, it can effectively prevent the generation of internal stress, and is suitable for the performance recovery heat treatment of precipitation-strengthened nickel-iron-based high-temperature alloy for super / reheater of high-parameter ultra-supercritical units after cold bending deformation.

[0096] In the present invention, cold bending deformation is carried out at room temperature, and combined with recrystallization annealing and aging heat treatment processes, by regulating the temperature and time of recrystallization annealing, the ∑CSL (∑≤29) grain boundary ratio is reduced without changing the grain size of the original structure, by regulating the temperature and time of high-temperature aging heat treatment, the precipitation of grain boundary and intragranular strengthening phases is promoted, a good match between the grain boundary strength and the intragranular strength of the alloy is achieved, the precipitation of harmful phases at the grain boundary during aging and high-temperature service is suppressed, and the long-lasting strength and plasticity of the alloy at high temperatures are improved.

[0097] The above description is only for the best embodiment of the present invention, but it should not be understood as limiting the claims. The present invention is not limited to the above embodiments, and its specific structure is allowed to be changed. However, all changes made within the protection scope of the independent claims of the present invention are within the protection scope of the present invention.

[0098] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

Claims

1. A method for improving the high temperature durability of a deformed nickel-iron-chromium-based high temperature alloy tube, characterized in that: The following steps are involved: 1) cold deformation of a solid solution nickel-iron-chromium based high temperature alloy tube; 2) The alloy tube treated in step 1) is kept at 127-187°C above the precipitation temperature of the γ′ phase for 0.5-1h; 3) The alloy tube treated in step 2) is kept at 7-57° C. above the precipitation temperature of the γ′ phase for 1-2 hours to obtain a precipitation-strengthened nickel-iron-based high-temperature alloy.

2. The method for improving the high temperature durability of a deformed nickel-iron-chromium-based high temperature alloy tube according to claim 1, characterized in that: The chemical composition of the solid solution nickel-iron-chromium-based high-temperature alloy tube includes, by mass percentage, C: 0.03-0.08%, Si: ≤0.3%, Mn: ≤0.3%, P: ≤0.02%, S: ≤0.01%, Cr: 19-22%, Co: ≤3.0%, Mo: 0.3-0.7%, Fe: 25-30%, Ti: 2.0-2.5%, Al: 1.3-2.0%, B: 0.001-0.005%, N: ≤0.01%, W: ≤0.5%, Nb: ≤0.5%, and the balance is Ni and unavoidable impurities.

3. The method for improving the high temperature durability of a deformed nickel-iron-chromium-based high temperature alloy tube according to claim 1, characterized in that: In step 1), cold deformation is carried out at 20-25°C.

4. The method for improving the high temperature durability of a deformed nickel-iron-chromium-based high temperature alloy tube according to claim 1 or 3, characterized in that: The cold deformation is 9-35%.

5. The method for improving the high temperature durability of a deformed nickel-iron-chromium-based high temperature alloy tube according to claim 1, characterized in that: In step 2), the mixture is kept warm and then air-cooled to room temperature.

6. The method for improving the high temperature durability of a deformed nickel-iron-chromium-based high temperature alloy tube according to claim 1, characterized in that: In step 3), the mixture is kept warm and then air-cooled to room temperature.

7. The method for improving the high temperature durability of a deformed nickel-iron-chromium-based high temperature alloy tube according to claim 1, characterized in that: The grain size of precipitation strengthened nickel-iron based high temperature alloy is in the range of 2-4.

8. The method for improving the high temperature durability of a deformed nickel-iron-chromium-based high temperature alloy tube according to claim 1, characterized in that: The γ′ phase in the precipitation-strengthened nickel-iron-based high-temperature alloy has a unimodal distribution and the particle size is 15-30nm.

9. The method for improving the high temperature durability of a deformed nickel-iron-chromium-based high temperature alloy tube according to claim 1, characterized in that: The precipitation-strengthened nickel-iron-based high-temperature alloy has a durability life of 3756 hours at 750℃ and 150MPa.

10. The method for improving the high temperature durability of a deformed nickel-iron-chromium-based high temperature alloy tube according to claim 1, characterized in that: The precipitation strengthened nickel-iron based high temperature alloy has an elongation of 13% at 750℃ and 150MPa.

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