Ni-Cr-Al series high-temperature alloy for fingertip sealing as well as preparation method and application of Ni-Cr-Al series high-temperature alloy

Abstract

The embodiment of the invention discloses Ni-Cr-Al series high-temperature alloy for fingertip sealing and a preparation method and application of the Ni-Cr-Al series high-temperature alloy. The invention relates to a Ni-Cr-Al series high-temperature alloy for fingertip sealing, which comprises the following components in percentage by weight: 17 to 21 percent of Cr, 3 to 3.9 percent of Al, 2.9 to 4 percent of Fe, 1.1 to 4 percent of Mo, 0.1 to 1 percent of Mn, 0.01 to 0.1 percent of C, 0.005 to 0.03 percent of Y and the balance of nickel and inevitable impurities. The alloy provided by the invention is relatively low in tensile strength and yield strength at room temperature, is beneficial to production and processing molding of the alloy, can keep higher strength at high temperature, is beneficial to improving the use effect of a sealing structure at high temperature, also has relatively good high-temperature oxidation resistance and heat-conducting property, and is suitable for popularization and application. And the design and use requirements of advanced aero-engines and gas turbines can be met.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of metallurgical technology, and specifically to a Ni-Cr-Al series high temperature alloy for fingertip sealing, and a preparation method and application thereof. Background Art

[0002] In order to meet the requirements of long-term, high stability and safety during the service of engines and gas turbines, the main materials used for the hot end parts are high-temperature alloys. High-temperature alloys refer to alloys that can work at temperatures above 600°C and can withstand large stresses, while having good high-temperature properties such as corrosion resistance and oxidation resistance. Today, nickel-based high-temperature alloys are most widely used in the aerospace field, and about 45% of high-temperature alloys are nickel-based high-temperature alloys. The main components of nickel-based high-temperature alloys are Ni, Co, Cr, W, Mo, Re, Al, Ta, Ti and other elements. Ni is the matrix, and the general content is above 55%. The main working temperature range is 650-1100°C. When the serviceable temperature is not exceeded, it has excellent high-temperature strength, good oxidation resistance and thermal corrosion resistance.

[0003] The fingertip seal in the mechanical seal is a new type of high-efficiency damping seal. Its leakage is 1 / 5 to 1 / 10 of that of the comb labyrinth seal. When the transient non-concentricity between dynamic and static switching is not maintained, the sealing capacity can be maintained unchanged. The rotor linear speed that the new seal can withstand has exceeded 305m / s, and the operating temperature has reached 690℃. It is one of the key technologies for the development of modern advanced turbine machinery. The new seal is currently used in multiple models of engines by foreign airlines such as GE and RR. In recent years, the engines of many key aircraft models in China have also been tested and verified and model finalized. At the same time, nuclear power, wind power, thermal power and other power generation fields have gradually begun to use new sealing structures to improve thermal efficiency, and have achieved remarkable results. Therefore, under the background of national carbon peak and carbon neutrality, the development of materials with better comprehensive performance for the manufacture of new seals with higher technical indicators is an urgent need for power and power generation equipment and has practical economic significance for energy conservation and emission reduction. Summary of the invention

[0004] The present invention is based on the inventor's discovery and understanding of the following facts and problems:

[0005] Nickel-based superalloys are key materials for important parts such as turbine disks, blades and other hot end parts on aircraft engines. With the continuous development and improvement of the thrust level of aircraft engines and the flight speed of missiles, as well as the increasingly high requirements for indicators such as thrust-to-weight ratio, the currently used nickel-based superalloys are gradually unable to meet the design requirements, and are prone to defects such as oxidation and cracks, which affect the service life and service performance of aircraft engines. Therefore, it is necessary to study and develop a nickel-based superalloy with better comprehensive performance to meet the higher use needs of aircraft engines.

[0006] In order to achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0007] According to a first aspect of an embodiment of the present invention, the present invention provides a Ni-Cr-Al high-temperature alloy for fingertip sealing, wherein the high-temperature alloy includes, by weight percentage, Cr: 17-21%, Al: 3-3.9%, Fe: 2.9-4%, Mo: 1.1-4%, Mn: 0.1-1%, C: 0.01-0.1%, Y: 0.005-0.03%, and the remainder is nickel and unavoidable impurities.

[0008] Advantages and technical effects of the Ni-Cr-Al high temperature alloy for fingertip seals according to the present invention:

[0009] 1. In the embodiment of the present invention, compared with the existing nickel-based high-temperature alloy, the amount of Cr element is increased. A part of the Cr element enters the γ' phase to play a strengthening role and forms a small amount of carbide to play a strengthening role. The rest of the majority is dissolved in the γ matrix to play a solid solution strengthening role. In addition, the Cr element forms a Cr2O3 type oxide film, which further improves the oxidation resistance and corrosion resistance of the alloy. Excessive Cr content in the high-temperature alloy will lead to the formation of harmful phases such as μ phase and θ phase. On the one hand, the consumption of strengthening elements leads to a weakening of the alloy strengthening effect. On the other hand, the presence of harmful phases deteriorates the hot working performance and increases the risk of failure of the alloy during service. In the embodiment of the present invention, the Cr content is controlled within the range of 17-21wt%.

[0010] 2. In the embodiment of the present invention, Al is a forming element of the strengthening phase γ′ in the age-strengthening nickel-based alloy. As the Al content increases, the amount of γ′ phase increases, achieving the improvement of high-temperature creep and rupture performance and room temperature strength, but too much γ′ phase will deteriorate welding performance and damage hot working performance. In the embodiment of the present invention, the content of Al element is controlled within the range of 3 to 3.9wt%.

[0011] 3. In the embodiment of the present invention, after Fe is added, on the one hand, because its lattice constant is about 3% different from that of Ni, the lattice expands to generate a long-range stress field, providing resistance to dislocation movement; on the other hand, it can reduce the stacking fault energy of nickel-based austenite, which is conducive to improving the yield strength; in addition, the price of Fe raw materials is low, and appropriate addition can take into account the need to reduce costs. In the embodiment of the present invention, the content of Fe is controlled in the range of 2.9 to 4wt%.

[0012] 4. In the embodiment of the present invention, most of the Mo atoms are dissolved in the γ matrix, accounting for about 1 / 4 in the γ' phase. Mo significantly increases the lattice constant of the Ni solid solution and significantly improves the room temperature and high temperature yield strength. The addition of Mo will also form a large amount of M 23C6 carbides, which are fine and dispersed, can also play a strengthening role. Mo can also refine austenite grains. However, Mo will also promote the formation of μ phase, which is not good for long-term structural stability. In the embodiment of the present invention, the added content of Mo is controlled not to exceed 4wt%, and at the same time, it is not less than 1.1wt% to ensure sufficient strengthening effect.

[0013] 5. In the embodiment of the present invention, Mn is added as a refining agent in the smelting process, reacting with harmful element S to form MnS, which can reduce the harmful effect of S. In the embodiment of the present invention, the content of Mn element is controlled in the range of 0.1-1wt%.

[0014] 6. In the embodiment of the present invention, the role of the C element is, on the one hand, to act as a refining agent, used for deoxidation during vacuum induction melting to reduce the oxygen content of the alloy; on the other hand, appropriate C elements can form carbides, precipitate granular discontinuous carbides at the grain boundaries, hinder grain boundary movement and crack propagation to improve mechanical strength, but too high C will lead to more large primary carbides, forming fatigue crack sources and crack propagation channels to degrade performance. In the embodiment of the present invention, the content of C element is controlled within the range of 0.01-0.1wt%.

[0015] 7. In the embodiment of the present invention, the addition of Y can react with free oxygen in the melt, which is beneficial to improving the purity of the alloy. Excessive addition of Y element will significantly deteriorate the hot working performance of the alloy and cause cracking and scrapping. In the embodiment of the present invention, the content of Y element is controlled in the range of 0.005-0.03wt%.

[0016] Furthermore, the weight percentages of Cr, Al and Y satisfy the relationship 2.0≤(0.7Cr+20Y) / (1.3Al)≤3.8. The present invention has found that under the above conditions, the obtained Ni-Cr-Al high temperature alloy has excellent processing performance, high temperature use effect, oxidation resistance and thermal conductivity.

[0017] Furthermore, the weight percentages of Cr, Al and Y satisfy the relationship 2.5≤(0.7Cr+20Y) / (1.3Al)≤3.2.

[0018] Furthermore, in terms of weight percentage, the high-temperature alloy includes Cr: 17-19%, Al: 3.1-3.9%, Fe: 2.9-3.75%, Mo: 2.2-3.75%, Mn: 0.5-0.8%, C: 0.05-0.07%, Y: 0.01-0.03%, and the balance is nickel and unavoidable impurities.

[0019] According to a second aspect of an embodiment of the present invention, the present invention provides a method for preparing a Ni-Cr-Al high temperature alloy for fingertip sealing as described in any one of the above items, the method comprising:

[0020] (1) Cr, Fe, Mo, and Ni raw materials that are not easy to burn are placed in a vacuum induction furnace, heated to melt, cooled, and Al, Mn, C, and Y raw materials that are easy to burn are added, and then the temperature is raised, stirred evenly, and then cooled again, and cast in a vacuum environment to obtain an electrode rod;

[0021] (2) performing atmosphere-protected electroslag remelting on the electrode rod to obtain a remelted alloy ingot;

[0022] (3) performing pre-forging heat treatment and forging on the remelted alloy ingot to obtain a strip slab;

[0023] (4) performing pre-rolling heat treatment and hot treatment on the strip slab to obtain a strip intermediate slab;

[0024] (5) Cold rolling the strip intermediate billet to obtain the high-temperature alloy.

[0025] Furthermore, in step (1), the vacuum degree of the vacuum induction furnace is 0.1-0.5 Pa, the heating temperature is 1530-1600°C, the cooling temperature is 1400-1450°C, the heating temperature is 1530-1600°C, and the cooling temperature is 1400-1480°C; the size of the electrode rod is Φ140-Φ320 mm.

[0026] Furthermore, in step (2), the conditions for atmosphere-protected electroslag remelting are: argon protection is adopted, the flow rate is controlled to be 15-40 L / min, the power of the arc-starting melting stage is set to 80-200 KW, the power of the normal melting stage is set to 100-160 KW, and the power of the ending stage is set to 80-140 KW; the size of the remelted alloy ingot is Φ180-Φ380 mm.

[0027] Furthermore, in step (3), the conditions of the heat treatment before forging are: the heating temperature is 1180-1260°C, the holding time is 60-100min; the forging conditions are: the forging is completed in one time, the time from the furnace to the start of forging does not exceed 1min, the pressing amount each time is 20-35%, the number of pressing times is 10-16 times, and air cooling is performed after forging; the thickness of the strip slab is 60-80mm;

[0028] In step (4), the conditions for the heat treatment before rolling are: the heating temperature is 1170-1250°C, and the holding time is 40-70 minutes; the conditions for hot rolling are: the time from the furnace to the start of rolling does not exceed 1 minute, the rolling passes are 5-7 passes, the reduction amount of each pass is 15-40%, and air cooling is performed after rolling; the thickness of the intermediate blank of the strip is 4-6 mm.

[0029] Furthermore, in step (5), the cold rolling conditions are as follows: the deformation between each rolling process is 40% to 75%, and the intermediate billet is heat treated to eliminate work hardening, and the heat treatment temperature is 950 to 1030°C.

[0030] According to a third aspect of an embodiment of the present invention, the present invention provides use of the Ni—Cr—Al series high temperature alloy for fingertip sealing as described in any one of the above items in an aircraft engine or a gas turbine.

[0031] The embodiments of the present invention have the following advantages:

[0032] The Ni-Cr-Al high-temperature alloy provided by the present invention has low tensile strength and yield strength at room temperature, which is beneficial to the production and processing of the alloy, can maintain higher strength at high temperatures, and is beneficial to improving the use effect of the sealing structure at high temperatures. At the same time, it also has good high-temperature oxidation resistance and thermal conductivity, and can meet the requirements of the design and use of advanced aircraft engines and gas turbines. DETAILED DESCRIPTION

[0033] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] Example 1

[0035] This embodiment provides a Ni-Cr-Al high temperature alloy for fingertip sealing, and the preparation method thereof includes:

[0036] (1) Cr, Fe, Mo, and Ni raw materials that are not easy to burn are placed in a vacuum induction furnace (maintaining a vacuum degree of 0.1 to 0.5 Pa), melted at 1550°C for 60 minutes, then cooled to 1450°C, Al, Mn, C, and Y raw materials that are easy to burn are added to the melt, heated to 1530°C, stirred evenly, and then the temperature is adjusted. After the temperature drops to 1450°C, they are directly cast into electrode rods of Φ140 to Φ320 mm in a vacuum environment;

[0037] (2) The electrode rod is subjected to atmosphere protection electroslag remelting under the following conditions: argon protection, flow control of 25L / min, power of 150KW in the arc melting stage, power of 120KW in the normal melting stage, and power of 90KW in the end stage, to obtain a Φ180-Φ380mm remelted alloy ingot;

[0038] (3) The remelted alloy ingot is subjected to pre-forging heat treatment and forging. The pre-forging heat treatment is as follows: the heating temperature is 1200° C. and the holding time is 90 min. The forging conditions are as follows: the forging is completed in one step, the time from the furnace out to the start of forging is no more than 1 min, the pressing amount is 30% each time, the number of pressings is 12 times, and the forging is air-cooled to obtain a strip slab with a thickness of 60 to 80 mm.

[0039] (4) subjecting the strip slab to pre-rolling heat treatment and hot rolling, wherein the pre-rolling heat treatment process is as follows: heating temperature is 1200° C., holding time is 60 min; hot rolling conditions are as follows: the time from leaving the furnace to the start of rolling is no more than 1 min, the number of rolling passes is 6, the reduction amount of each pass is 25%, and air cooling is performed after rolling to obtain a strip with a thickness of 4 to 6 mm;

[0040] (5) The strip is cold rolled under the following conditions: the deformation amount between each rolling process is 65%, and the intermediate billet is heat treated to eliminate work hardening at a heat treatment temperature of 1000°C to obtain a product of target specifications.

[0041] The alloy composition obtained in Example 1 is shown in Table 1.

[0042] Embodiment 2-6

[0043] The preparation methods of Examples 2-6 are the same as those of Example 1, except that the alloy compositions are different. The alloy compositions prepared in Examples 2-6 are shown in Table 1 below.

[0044] Comparative Examples 1-5

[0045] The preparation methods of Comparative Examples 1-5 are the same as those of Example 1, except that the alloy compositions are different. The alloy compositions prepared in Comparative Examples 1-5 are shown in Table 2 below.

[0046] Table 1 Alloy composition of Examples 1-6

[0047]

[0048] Table 2 Alloy composition of comparative examples 1-5

[0049]

[0050] Test Case

[0051] The high temperature alloys provided in Examples 1-6 and Comparative Examples 1-5 were tested for mechanical properties, oxidation resistance and thermal conductivity.

[0052] (1) Mechanical properties

[0053] The test was carried out according to the requirements of GB / T 228.1. The test results are shown in Table 3 below.

[0054] Table 3 Mechanical properties of alloys

[0055]

[0056]

[0057] The results show that the tensile strength and yield strength of the alloys of Examples 1-6 are low at room temperature, which is beneficial to the production and processing of the alloys. They can maintain higher strength at high temperatures, which is beneficial to improving the use effect of the sealing structure at high temperatures. At the same time, when the room temperature strength is too high, it will lead to a large loss of processing molds, and it is difficult to achieve the ideal molding size at one time. Therefore, the finished product needs to have more suitable performance. The yield strength at room temperature is below 750MPa to meet the part processing requirements.

[0058] (2) Antioxidant properties

[0059] Oxidation rate detection method: Prepare a Φ15mm*30mm sample on the alloy intermediate billet, grind the surface roughness to 1μm, clean the sample surface with alcohol and dry it in a drying oven for 1h, and measure the original weight. Then, carry out an oxidation test at 900℃ in a box furnace. After a certain period of time, take out the sample and measure the weight. The data obtained is calculated according to the formula of HB5258. The oxidation weight gain per unit area (G + ):

[0060]

[0061] Wherein, m2 is the total weight of the sample and container before the test, g;

[0062] m1—the total weight of the sample and container before the test, g;

[0063] S—original surface area of ​​the sample, m 2 .

[0064] Take 3 samples for each test duration and calculate G according to the above formula. + Then take the average value

[0065] The average oxidation rate was then calculated according to the following formula:

[0066]

[0067] in, —Average weight gain per unit area due to oxidation, g / m 2 ;

[0068] t—test time, h.

[0069] The test results of the average oxidation rate of the alloys of Examples 1-6 and Comparative Examples 1-5 at different oxidation times are shown in Table 4 below.

[0070] Table 4 Alloy oxidation rate test results

[0071]

[0072] The results show that the oxidation rate of the alloys of Examples 1-6 of the present invention is kept at a relatively low level during the high temperature oxidation process of 96 to 528 hours, which is lower than that of the alloys of Comparative Examples 1-5, indicating that the alloys of the present invention have good high temperature oxidation resistance at 900°C and can extend the service life. Among them, the high temperature oxidation resistance of Examples 1-3 is better.

[0073] (3) Thermal conductivity

[0074] Thermal conductivity detection method: Prepare a Φ12mm sample from the alloy intermediate billet, clean the sample surface, and cut a sample of a specified thickness for testing at different temperatures according to the requirements of GB / T 22588. The thermal conductivity coefficients of the alloys of Examples 1-6 and Comparative Examples 1-5 at different temperatures are shown in Table 5 below.

[0075] Table 5 Alloy thermal conductivity test results

[0076]

[0077]

[0078] The results show that at a relatively low temperature of 200-500°C, the thermal conductivity of the alloys of Examples 1-6 and Comparative Examples 1-5 is substantially similar, and at a high temperature of 600-1100°C, the thermal conductivity of the alloys of Examples 1-6 is higher than that of Comparative Examples 1-5. The above content shows that as the service temperature increases, the alloys of the embodiments of the present invention have better thermal conductivity and have the potential to be used in higher temperature environments. Among them, the thermal conductivity of Example 1-3 is better.

[0079] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A Ni-Cr-Al high temperature alloy for fingertip sealing, characterized in that: Calculated in weight percentage, the high-temperature alloy includes Cr: 17-21%, Al: 3-3.9%, Fe: 2.9-4%, Mo: 1.1-4%, Mn: 0.1-1%, C: 0.01-0.1%, Y: 0.005-0.03%, and the balance is nickel and inevitable impurities.

2. The Ni-Cr-Al high temperature alloy for fingertip sealing according to claim 1, characterized in that: The weight percentages of Cr, Al and Y satisfy the relationship 2.0≤(0.7Cr+20Y) / (1.3Al)≤3.

8.

3. The Ni-Cr-Al high temperature alloy for fingertip sealing according to claim 1, characterized in that: The weight percentages of Cr, Al and Y satisfy the relationship 2.5≤(0.7Cr+20Y) / (1.3Al)≤3.

2.

4. The Ni-Cr-Al high temperature alloy for fingertip sealing according to claim 1, characterized in that: Calculated in weight percentage, the high-temperature alloy includes Cr: 17-19%, Al: 3.1-3.9%, Fe: 2.9-3.75%, Mo: 2.2-3.75%, Mn: 0.5-0.8%, C: 0.05-0.07%, Y: 0.01-0.03%, and the balance is nickel and inevitable impurities.

5. The method for preparing the Ni-Cr-Al high temperature alloy for fingertip sealing according to any one of claims 1 to 4, characterized in that: The method comprises: (1) Cr, Fe, Mo, and Ni raw materials that are not easy to burn are placed in a vacuum induction furnace, heated to melt, cooled, and Al, Mn, C, and Y raw materials that are easy to burn are added, and then the temperature is raised, stirred evenly, and then cooled again, and cast in a vacuum environment to obtain an electrode rod; (2) performing atmosphere-protected electroslag remelting on the electrode rod to obtain a remelted alloy ingot; (3) performing pre-forging heat treatment and forging on the remelted alloy ingot to obtain a strip slab; (4) performing pre-rolling heat treatment and hot rolling on the strip slab to obtain a strip intermediate slab; (5) Cold rolling the strip intermediate billet to obtain the high-temperature alloy.

6. The method for preparing the Ni-Cr-Al high temperature alloy for fingertip sealing according to claim 5, characterized in that: In step (1), the vacuum degree of the vacuum induction furnace is 0.1-0.5 Pa, the heating temperature is 1530-1600° C., the cooling temperature is 1400-1450° C., the heating temperature is 1530-1600° C., and the cooling temperature is 1400-1480° C.; the size of the electrode rod is Φ140-Φ320 mm.

7. The method for preparing the Ni-Cr-Al high temperature alloy for fingertip sealing according to claim 5, characterized in that: In step (2), the conditions for atmosphere-protected electroslag remelting are: argon protection is adopted, the flow rate is controlled to be 15-40 L / min, the power of the arc-starting melting stage is set to 80-200 KW, the power of the normal melting stage is set to 100-160 KW, and the power of the ending stage is set to 80-140 KW; the size of the remelted alloy ingot is Φ180-Φ380 mm.

8. The method for preparing the Ni-Cr-Al high temperature alloy for fingertip sealing according to claim 5, characterized in that: In step (3), the conditions of the heat treatment before forging are: the heating temperature is 1180-1260°C, the holding time is 60-100min; the forging conditions are: the forging is completed in one time, the time from the furnace out to the start of forging does not exceed 1min, the pressing amount each time is 20-35%, the number of pressing times is 10-16 times, and air cooling is performed after forging; the thickness of the strip slab is 60-80mm; In step (4), the conditions for the pre-rolling heat treatment are: the heating temperature is 1170-1250°C, and the holding time is 40-70min; the conditions for the hot rolling are: the time from the furnace to the start of rolling does not exceed 1min, the rolling passes are 5-7 passes, the reduction amount for each pass is 15-40%, and air cooling is performed after rolling; the thickness of the intermediate blank of the strip is 4-6mm.

9. The method for preparing Ni-Cr-Al high temperature alloy for fingertip sealing according to claim 5, characterized in that: In step (5), the cold rolling conditions are: the deformation between each rolling process is 40% to 75%, and the intermediate billet is heat treated to eliminate work hardening, and the heat treatment temperature is 950 to 1030°C.

10. Use of the Ni-Cr-Al high temperature alloy for fingertip seal according to any one of claims 1 to 4 in aircraft engines or gas turbines.

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