Heat-resistant and corrosion-resistant nickel-iron-based high-temperature alloy and preparation method thereof

Abstract

The invention discloses a heat-resistant and corrosion-resistant nickel-iron-based high-temperature alloy and a preparation method thereof. The nickel-iron-based high-temperature alloy comprises the following components in percentage by weight: 25 to 30 percent of Fe, 18 to 22 percent of Cr, 0.5 to 1 percent of Mo, 0.1 to 0.8 percent of W, 1.5 to 1.8 percent of Ti, 1.2 to 2.0 percent of Al, 0.3 to 1 percent of Nb, less than or equal to 0.1 percent of Si, 0.03 to 0.10 percent of C, 0.001 to 0.005 percent of B and the balance of Ni. The ferronickel-based high-temperature alloy disclosed by the invention is high in endurance strength, high in impact toughness and good in corrosion resistance; ni3Al uniformly dispersed in the crystal is a main strengthening phase; compared with the prior art, the alloy has the advantages of equivalent processing performance, lower material cost, more excellent structure stability, higher high-temperature strength, higher impact toughness and higher corrosion resistance, and can be used for manufacturing high-temperature components such as high-temperature superheaters and reheaters of ultra-supercritical thermal power generating units at the temperature of 650 DEG C or above, main steam pipelines, headers, blades, fasteners and the like.

Description

Technical Field

[0001] The invention belongs to the field of heat-resistant metal material preparation, and specifically relates to a nickel-based high-temperature alloy and a preparation method thereof. Background Art

[0002] With the increasing demand for electricity, energy shortage and environmental pollution problems are becoming increasingly prominent, and the need to develop efficient, energy-saving and environmentally friendly power generation methods is becoming more urgent. As the most important power generation technology in my country for a long time, thermal power generation is considered to be the most effective way to solve the above problems by improving the steam parameters of the unit. A large number of previous practices have shown that the service performance of key component materials is the main reason restricting the improvement of steam parameters of boiler units. As one of the key components with the most stringent service conditions in the boiler of thermal power units, the reheater tube has put forward extremely high requirements on the service performance of materials. The main function of the reheater is to reheat the exhaust steam of the high-pressure cylinder of the steam turbine to the required temperature to enter the medium-pressure cylinder to continue to work. During its service, it will be affected by multiple factors such as high-temperature creep, thermal fatigue, oxidation and high-temperature flue gas corrosion. With the substantial increase in the main steam parameters of thermal power units, the development of high-temperature alloy materials that can meet the performance requirements of the reheater tubes of 700℃ units has become a topic that needs to be urgently solved in the thermal power industry.

[0003] At present, the reheaters of thermal power units below 600℃ at home and abroad mainly use ferritic heat-resistant steel (Cr: 9wt.%-12wt.%) and austenitic heat-resistant steel. Commonly used ferritic heat-resistant steels are T / P91, NF616, E911, HCM12A, etc. These materials have excellent durability and corrosion resistance, and are therefore widely used in reheaters of units below 600℃. Among them, T / P91 has been fully domestically produced and widely used in subcritical and supercritical thermal power units in my country, and has accumulated rich performance data. These results all show that ferritic heat-resistant steel is difficult to meet the performance requirements of reheater tube materials at higher temperature parameters.

[0004] For ultra-supercritical units with steam temperature parameters above 600℃, the reheater materials mainly use coarse-grained (TP304H, TP347H, etc.), fine-grained (Super304H, TP347HFG, etc.) and high-chromium (HR3C, NF709, SAVE25, etc.) austenitic heat-resistant steels. Compared with ferritic heat-resistant steels, austenitic steels have better endurance strength, oxidation resistance and corrosion resistance. However, in the process of application, it also exposes many problems such as low heat transfer efficiency, high thermal expansion coefficient and high cost. Especially when the reheat steam temperature reaches above 700℃, the strength of austenitic heat-resistant steels cannot meet the service performance requirements of the reheater tubes for materials.

[0005] In response to the demand for material performance of key components of 700℃ ultra-supercritical boilers, a series of nickel-based deformed high-temperature alloy materials have been developed abroad, such as Inconel740H developed by Special Metals Corporation of the United States, Haynes 282 developed by Hastelloy Corporation of the United States, CCA 617 developed by ThyssenKrupp of Germany, Nimonic 263 developed by Rolls-Royce of the United Kingdom, and USC41 developed by Hitachi of Japan. These materials have excellent high-temperature endurance strength and corrosion resistance, but they are expensive and have high technical requirements such as smelting and hot processing, which limits their rapid promotion and application. In addition, Sumitomo Corporation of Japan has also developed iron-nickel-based high-temperature alloys such as HR6W and HR35; Sandvik of Sweden has developed Sanicro 25 iron-nickel-based alloy; Shenyang Institute of Metals of the Chinese Academy of Sciences and General Iron and Steel Research Institute have also developed iron-nickel-based deformed high-temperature alloys such as GH2984 and GH110. However, these materials are mainly developed for superheaters of 700℃ ultra-supercritical boilers, and the alloy strength is mainly used as a key performance evaluation indicator in the design process. Since the service pressure of the reheater pipe is relatively low, it is generally believed that the reheater pipe can be used by thinning the superheater pipe wall. However, compared with the service conditions of the superheater, although the internal pressure of the reheater pipe is lower, the service temperature is often higher. Therefore, factors such as material oxidation corrosion and its structural stability will also have a significant impact on the service life of the alloy. Summary of the invention

[0006] The purpose of the present invention is to solve the problems in the prior art and to provide a nickel-iron-based high-temperature alloy having good high-temperature mechanical properties, excellent structural stability and anti-oxidation / corrosion properties and a preparation method thereof. To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A heat-resistant and corrosion-resistant nickel-iron-based high-temperature alloy comprises the following components by mass percentage: Fe: 25-30%, Cr: 18-22%, Mo: 0.5-1%, W: 0.1-0.8%, Ti: 1.5-1.8%, Al: 1.2-2.0%, Nb: 0.3-1%, Si≤0.1%, C: 0.03-0.10%, B: 0.001-0.005%, and the balance is Ni.

[0008] A method for preparing a heat-resistant and corrosion-resistant nickel-iron-based high-temperature alloy, characterized in that it comprises the following steps:

[0009] Step 1, using Fe, Ni, Cr, Al, Ti, Si and Nb metal blocks and Fe-C, Fe-Mo, Fe-W, Fe-B alloy blocks as raw materials, heating them to 1600° C. to 1650° C. in a vacuum induction melting furnace and keeping them warm for 20 to 25 minutes, then pouring them into a steel mold for cooling to obtain an alloy ingot;

[0010] Step 2: placing the alloy ingot in a heating furnace for homogenization treatment; then cold working the homogenized alloy; finally placing the cold worked alloy in a heating furnace for solution treatment and aging treatment to obtain a heat-resistant and corrosion-resistant nickel-iron-based high-temperature alloy.

[0011] Furthermore, in step 1, the purity of the Fe, Co, Ni, Cr, Al, Ti and Nb metal blocks is not less than 99.9%.

[0012] Furthermore, in step 2, the method for homogenization treatment is: placing the alloy ingot in a heating furnace at 1200° C. to 1250° C. for homogenization treatment, keeping the temperature for 12 to 24 hours, then taking it out of the furnace and placing it in water for cooling.

[0013] Furthermore, in step 2, the cold working method is: cold rolling the homogenized alloy, and the total rolling deformation is 30 to 90%.

[0014] Furthermore, in step 2, the solution treatment method is: placing the cold-worked alloy in a heating furnace at 800°C to 1000°C for 2 hours, then taking it out of the furnace and cooling it in water to control its grain size to 10 to 100 μm.

[0015] Furthermore, in step 2, the aging treatment method is: placing the alloy after solid solution in a heating furnace at 700°C to 800°C for 1 to 8 hours, and then taking it out of the furnace for air cooling.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1. The alloy obtained by the present invention has the characteristics of heat resistance, corrosion resistance, high strength and high toughness, and contains a relatively high Fe content, has a low material cost, and has a high engineering application value.

[0018] 2. The alloy obtained by the present invention has a simple microstructure, and a large amount of nano-sized Ni3Al-type intermetallic compound strengthening phase coherent with the matrix is ​​precipitated on the FCC matrix, which significantly improves the strength of the alloy while maintaining the high plasticity of the alloy.

[0019] 3. The alloy obtained by the present invention can change the grain size and the size of the precipitated phase by controlling parameters such as the temperature and time of the solution treatment and the aging treatment, thereby achieving regulation of the mechanical properties of the alloy. High-entropy alloys with different organizational structures and properties can be obtained through heat treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the grain boundary discontinuous carbide phase formed in the heat-resistant and corrosion-resistant high-temperature alloy in Example 1.

[0021] Figure 2 It is the grain boundary discontinuous carbide phase formed in the heat-resistant and corrosion-resistant high-temperature alloy in Example 3.

[0022] Figure 3 It is a large amount of dispersed nano-sized N3Al strengthening phase formed in the crystal after the aging process in Example 3. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with embodiments.

[0024] The element symbols in the formulas of the present invention represent the mass percentage of the element content.

[0025] Example 1

[0026] In this embodiment, a precipitation-strengthened high-entropy alloy is prepared by vacuum induction melting and heat treatment technology, and the preparation process is as follows:

[0027] 1) Raw material preparation: The components, by mass percentage, include: C: 0.06%, Cr: 21%, Nb: 0.5%, Si: 0.1%, Fe: 25%, Mo: 1.5%, W: 0.5%, Ti: 1.5%, Al: 1.5%, B: 0.004%, and the balance is Ni.

[0028] 2) Melting: The metal raw material is heated to 1650°C in a vacuum induction melting furnace and kept warm for 10 minutes, and then the molten steel is poured into a steel mold for cooling to obtain an alloy ingot.

[0029] 3) After the surface of the alloy ingot is mechanically polished, it is placed in a heating furnace at 1200° C. for homogenization treatment, kept warm for 12 hours, then taken out of the furnace and quickly placed in water for cooling.

[0030] 4) The homogenized alloy is subjected to room temperature rolling deformation, using multiple rolling passes, each with a reduction of 5% and a total deformation of 60%, to obtain a rolled alloy.

[0031] 5) The rolled alloy is placed in a heating furnace at 1000° C. for solution treatment and kept warm for 2 hours. The rolled alloy is then taken out of the furnace and quickly placed in water for cooling to obtain a solid solution nickel-iron based high temperature alloy.

[0032] 6) The solid solution alloy is placed in a heating furnace at 750° C. for aging treatment, kept warm for 8 hours, and then taken out of the furnace for air cooling to obtain a heat-resistant and corrosion-resistant nickel-iron-based high-temperature alloy.

[0033] 7) After testing, the grain size, precipitate phase size, yield strength, tensile strength and elongation of the nickel-iron based alloy obtained in this embodiment are 50 μm, 10 nm, 610 MPa, 1050 MPa and 54%, respectively.

[0034] Example 2

[0035] In this embodiment, a precipitation-strengthened high-entropy alloy is prepared by vacuum induction melting and heat treatment technology, and the preparation process is as follows:

[0036] 1) Raw material preparation: The ingredients are calculated by mass percentage, including: C: 0.07%, Cr: 22%, Nb: 0.6%, Si: 0.1%, Fe: 25%, Mo: 1%, W: 0.5%, Ti: 1.8%, Al: 1.2%, B:

[0037] 0.004%, the balance being Ni.

[0038] 2) Melting: The metal raw material is heated to 1650°C in a vacuum induction melting furnace and kept warm for 10 minutes, and then the molten steel is poured into a steel mold for cooling to obtain an alloy ingot.

[0039] 3) After the surface of the alloy ingot is mechanically polished, it is placed in a heating furnace at 1200° C. for homogenization treatment, kept warm for 12 hours, then taken out of the furnace and quickly placed in water for cooling.

[0040] 4) The homogenized alloy is subjected to room temperature rolling deformation, using multiple rolling passes, each with a reduction of 5% and a total deformation of 60%, to obtain a rolled alloy.

[0041] 5) The rolled alloy was placed in a heating furnace at 1050° C. for solution treatment and kept warm for 2 hours. The rolled alloy was then taken out of the furnace and quickly placed in water for cooling to obtain a solid solution nickel-iron based high temperature alloy.

[0042] 6) The solid solution alloy is placed in a heating furnace at 750° C. for aging treatment, kept warm for 8 hours, and then taken out of the furnace for air cooling to obtain a heat-resistant and corrosion-resistant nickel-iron-based high-temperature alloy.

[0043] After testing, the grain size, precipitated phase size, yield strength, tensile strength and elongation of the nickel-iron based alloy obtained in this embodiment are 60 μm, 18 nm, 650 MPa, 1140 MPa and 48%, respectively.

[0044] Example 3

[0045] In this embodiment, a precipitation-strengthened high-entropy alloy is prepared by vacuum induction melting and heat treatment technology, and the preparation process is as follows:

[0046] 1) Raw material preparation: The ingredients are calculated by mass percentage, including: C: 0.07%, Cr: 22%, Nb:

[0047] 0.6%, Si: 0.1%, Fe: 25%, Mo: 1%, W: 0.5%, Ti: 1.8%, Al:

[0048] 1.2%, B: 0.004%, and the balance is Ni.

[0049] 2) Melting: The metal raw material is heated to 1650°C in a vacuum induction melting furnace and kept warm for 10 minutes, and then the molten steel is poured into a steel mold for cooling to obtain an alloy ingot.

[0050] 3) After the surface of the alloy ingot is mechanically polished, it is placed in a heating furnace at 1200° C. for homogenization treatment, kept warm for 12 hours, then taken out of the furnace and quickly placed in water for cooling.

[0051] 4) The homogenized alloy is subjected to room temperature rolling deformation, using multiple rolling passes, each with a reduction of 5% and a total deformation of 60%, to obtain a rolled alloy.

[0052] 5) The rolled alloy was placed in a heating furnace at 1050° C. for solution treatment and kept warm for 2 hours. The rolled alloy was then taken out of the furnace and quickly placed in water for cooling to obtain a solid solution nickel-iron based high temperature alloy.

[0053] 6) The solid solution alloy is placed in a heating furnace at 800° C. for aging treatment, kept warm for 8 hours, and then taken out of the furnace for air cooling to obtain a heat-resistant and corrosion-resistant nickel-iron-based high-temperature alloy.

[0054] After testing, the grain size, precipitated phase size, yield strength, tensile strength and elongation of the nickel-iron based alloy obtained in this embodiment are 60 μm, 25 nm, 750 MPa, 1250 MPa and 52%, respectively.

[0055] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A heat-resistant and corrosion-resistant nickel-iron-based high-temperature alloy, characterized in that: The components of the nickel-iron-based high-temperature alloy include, by weight percentage, Fe: 25-30%, Cr: 18-22%, Mo: 0.5-1%, W: 0.1-0.8%, Ti: 1.5-1.8%, Al: 1.2-2.0%, Nb: 0.3-1%, Si≤0.1%, C: 0.03-0.10%, B: 0.001-0.005%, and the balance is Ni.

2. A method for preparing a heat-resistant and corrosion-resistant nickel-iron-based high-temperature alloy, characterized in that: The following steps are involved: 1) Raw material preparation: Alloy composition by mass percentage includes Fe: 25-30%, Cr: 18-22%, Mo: 0.5-1%, W: 0.1-0.8%, Ti: 1.5-1.8%, Al: 1.2-2.0%, Nb: 0.3-1%, Si≤0.1%, C:0.03-0.10%, B:0.001-0.005%, the balance is Ni; 2) Melting: The prepared alloy is melted into an alloy mother liquid in a medium frequency vacuum induction arc furnace. Finally, when the temperature of the alloy mother liquid reaches 1600-1650°C, it is taken out of the furnace and cast into alloy ingots; 3) In step 1, Fe, Ni, Cr, Al, Ti, Si, and Nb metal blocks and Fe-C, Fe-Mo, Fe-W, and Fe-B alloy blocks are used as raw materials, heated to 1600° C. to 1650° C. in a vacuum induction melting furnace and kept at this temperature for 20 to 25 minutes, and then poured into a steel mold and cooled to obtain an alloy ingot; 4) Step 2: placing the alloy ingot in a heating furnace for homogenization treatment; then cold working the homogenized alloy; finally, placing the cold-worked high-entropy alloy in a heating furnace for solution treatment and aging treatment to obtain a heat-resistant and corrosion-resistant nickel-iron-based high-temperature alloy.

3. The preparation process according to claim 2, characterized in that: In step 1, the purity of the Fe, Ni, Cr, Al, Ti and Nb metal blocks is not less than 99.9%.

4. The preparation process according to claim 2, wherein: In step 2, the homogenization treatment method is: placing the alloy ingot in a heating furnace at 1200° C. to 1250° C. for homogenization treatment, keeping the temperature for 12 to 24 hours, then taking it out of the furnace and placing it in water for cooling.

5. The preparation process according to claim 2, characterized in that: In step 2, the cold working method is: cold rolling the homogenized alloy, with the total rolling deformation being 30 to 90%.

6. The preparation process according to claim 2, characterized in that: In step 2, the solution treatment method is: placing the cold-worked alloy in a heating furnace at 800°C to 1000°C for 2 hours, then taking it out of the furnace and cooling it in water to control its grain size to 10 to 100 μm.

7. The preparation process according to claim 2, characterized in that: In step 2, the aging treatment method is: placing the alloy after solid solution in a heating furnace at 700° C. to 800° C. and keeping the temperature for 1 to 8 hours, and then taking it out of the furnace and air cooling it.

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