TWI663263B - High creep-resistant equiaxed grain nickel-based superalloy - Google Patents

Abstract

The invention aims to provide a high creep-resistant equiaxed nickel-based superalloy, which is characterized in that its chemical composition contains, by weight: Cr is 8.0 to 9.5% by weight, W is 9.5 to 10.5% by weight, and Co is 9.5 to 10.5. wt%, Al is 5.0 ~ 6.0wt%, Ti is 0.5 ~ 1.5wt%, Mo is 0.5 ~ 1.0wt%, Ta is 2.5 ~ 4.0wt%, Hf is 1.0 ~ 2.0wt%, Ir is 2.0 ~ 4.0wt% , C is 0.1 ~ 0.2wt%, B is 0.01 ~ 0.1wt%, Zr is 0.01 ~ 0.10wt%, and the rest is composed of Ni and unavoidable impurities.

Description

   High creep resistance equiaxed nickel-based superalloy   

The invention relates to a nickel-based alloy, in particular to a high creep-resistant equiaxed nickel-based superalloy.

Nickel has high strength, corrosion resistance and oxidation resistance at high temperatures, so it is one of the most widely used materials in today's advanced turbine engine high temperature resistant components. Traditionally, nickel-based superalloys are mainly formed by casting and forging. And powder metallurgy process methods, among which casting technology has the advantage of producing complex shapes of workpieces, so in practice, if the shape of the workpiece is complex, the casting method is used to make the workpiece; and currently, the temperature of nickel-based superalloys is increased. There are two main methods. The first method is to improve the alloy composition. For example, in conventional casting (CC), the use of Mar-M247 superalloy (grain structure is equiaxed) can have a relatively high temperature. However, to further improve the temperature resistance of superalloys, in addition to the improvement of the alloy composition design, it can be improved from traditional casting methods. For example, based on the Bridgeman growth principle, during the solidification stage of the alloy, the temperature gradient of the environment is controlled in a single direction. So-called directional solidification crystal (DC) or single crystal (SC) structure Lift temperature alloys.

Although equiaxed crystal alloys have lower temperature resistance than unidirectional crystals or single crystal alloys, unidirectional crystals or single crystal castings can only make simple shapes of castings (such as turbine blades), so they are like turbine rotors for turbine engines. And other complex parts, using isometric crystal alloys to make complex shaped and integrally formed castings using traditional isometric crystal casting, and the production rate and manufacturing cost of traditional isometric crystal casting are also better than unidirectional or single crystal casting. Therefore, traditional equiaxed crystal casting is still one of the main methods for producing high-performance nickel-based superalloy castings.

The phenomenon that the latent material slowly changes in plastic under the action of high temperature and stress is one of the main reasons for the damage of the material at high temperature. Among them, the turbine engine used in the aerospace industry needs to maintain good performance in high temperature environments. Creep performance. In the creep performance, two types of material performance data, creep life and creep resistance, are used to measure the pros and cons of the creep performance of the material. The creep life refers to the material breaking at a specific temperature and stress. The anti-mutation ability refers to the ability of a material to resist deformation under a specific temperature and stress, which is usually expressed as the time to reach a specific amount of deformation. For example, in the application of aerospace turbine engine turbine blades, the deformation of the parts is usually limited to 2%, and some severe loading conditions require the deformation to be within 1%. If the parts exceed the limit of deformation, the Due to the interference and collision between the workpiece and the workpiece, the entire component is damaged. Therefore, the material has a deformation time of 1% and 2% (hereinafter expressed as t1% and t2%). It is often used to measure whether the material can be used for turbine blades. One of the important indicators. Therefore, the industry currently needs to develop a nickel-based superalloy with excellent high-temperature creep resistance. In this way, it can have both cost and mechanical characteristics to prepare a nickel-based superalloy with high temperature creep resistance.

In view of the shortcomings of the above-mentioned conventional technologies, the main object of the present invention is to provide a high creep-resistant equiaxed nickel-based superalloy, which integrates a vacuum melting, a vacuum casting, and the addition of appropriate elements to prepare a high creep-resistant equiaxed nickel Base superalloy.

In order to achieve the above object, according to a solution proposed by the present invention, a high creep-resistant equiaxed nickel-based superalloy is provided, which has the following composition in terms of weight percentage: Cr is 8.0 to 9.5% by weight, and W is 9.5 to 10.5% by weight. Co, 9.5 ~ 10.5wt%, Al 5.0 ~ 6.0wt%, Ti 0.5 ~ 1.5wt%, Mo 0.5 ~ 1.0wt%, Ta 2.5 ~ 4.0wt%, Hf 1.0 ~ 2.0wt%, Ir It is 2.0 to 4.0 wt%, C is 0.1 to 0.2 wt%, B is 0.01 to 0.1 wt%, Zr is 0.01 to 0.10 wt%, and the rest is composed of Ni and unavoidable impurities.

The above-mentioned high creep resistance isometric crystal nickel-based superalloy is smelted in a vacuum induction furnace, and then vacuum precision casting is performed in a vacuum environment. The molten alloy liquid is poured into a ceramic mold, and then cooled to complete the nickel-based superalloy. Of ingot work.

The ingot of the above nickel-based superalloy has an equiaxed crystal structure, and further heat treatment procedures are required. The nickel-based superalloy is subjected to two-stage heat treatment in the present invention. The first-stage heat treatment is performed on the nickel-based alloy at 1100-1300 ° C. The superalloy ingot is heat treated for at least one hour, and then the nickel-based superalloy is cooled and quenched with an inert gas (such as argon); the second-stage heat treatment is performed on the nickel-based superalloy at 800-1000 ° C. The ingot was heat-treated for at least ten hours, and then the high creep-resistant equiaxed nickel-based superalloy was cooled by natural cooling to prepare a high creep-resistant equiaxed nickel-based superalloy.

The above summary and the following detailed descriptions are to further explain the methods, means, and effects adopted by this creation to achieve the intended purpose. The other purposes and advantages of this creation will be explained in the subsequent description and drawings.

The following is a specific example to illustrate the implementation of this creation. Those who are familiar with this technique can easily understand the advantages and effects of this creation from the content disclosed in this manual.

The alloy design of the present invention starts from a nickel-based superalloy with an equiaxed crystal structure, adds aluminum and titanium elements thereto, and uses the γ 'precipitation strengthening phase of Ni3 (Al, Ti) formed by Al, Ti, and Ni to strengthen the alloy. High temperature mechanical strength, but if the number of γ 'phase is too much, it will increase the brittleness of the alloy, which will easily cause the phenomenon of alloy brittleness during casting or use. Therefore, the optimal content of Al in the nickel-based superalloy in the present invention should be The content of Ti should be between 5.0 and 6.0 wt%, and the content of Ti should be between 0.5 and 1.5 wt%. When nickel-based superalloys are used at high temperature for a long time, the γ 'phase will coarsen and the volume fraction gradually increase with time. It will reduce the strength of nickel-based superalloys. In order to improve this phenomenon, the Ta element in the alloy of the present invention is beneficial to improve the stability of the γ 'phase at high temperature. However, if too much Ta element is added, it is easy to produce coarse TaC type. Carbides, this type of carbides easily become the origin of cracks and cracks, reducing the strength of the alloy. Therefore, the content of Ta in the nickel-based superalloy in the present invention is controlled to 2.5 ~ 4.0wt.%; Co in the present invention mainly plays an role of increasing γ The solidus temperature of the 'phase reduces Al and Ti in γ The function of ground solubility increases the number of γ 'precipitated phases, which increases the high-temperature strength of the alloy, but after adding a certain amount of Co, the effect of increasing the number of γ' phases becomes insignificant. In addition, Co can provide solid Solution strengthening effect, but the atomic size of Co and Ni are similar, and it does not provide a solid solution strengthening effect. Therefore, the Co content of the nickel-based superalloy in the present invention is controlled between 9.5 and 10.5 wt%; the carbon (C) is in the range of In the nickel-based superalloy of the invention, carbides with high atomic bonding strength can be formed with other alloying elements. The carbides mainly play the role of grain boundary strengthening, which helps to suppress the slippage of the grain boundary at high temperature, thereby improving the creep life. However, if the carbon content is too high, it is easy to form large granular MC-type (M represents metal atoms, C represents carbon atoms) bulk or long carbides, making the carbides easily become the origin of cracks, and the carbon content When the temperature is too high, the temperature of the alloy's initial melting phase will be reduced. In order to avoid the generation of the initial melting phase, heat treatment conditions with a lower solution temperature must be adopted. This will make the alloy strengthen the effect of the alloy after heat treatment after casting. Discount because The carbon content of the nickel-based superalloy in the present invention should be between 0.1 and 0.2 wt%; the main role of Cr in this experiment is to improve the oxidation resistance and heat corrosion resistance of the alloy, but in the alloy of the present invention, Cr has In addition to the above advantages, it is still the main component for forming M23C6 carbides. After a series of experiments, it was found that the Cr content of the nickel-based superalloy in the present invention should be limited to 8.0 to 9.5% by weight; the main effect of Hf in the present invention is to form a large amount Γ-γ 'rose-like eutectic structure, this kind of eutectic structure has good toughness, precipitates on the grain boundaries, increases the intrinsic toughness of the grain boundaries, prevents the high-speed propagation of cracks, and thus toughens the grain boundaries, but Hf element is added Too much, it is easy to produce coarse HfC type carbides, which easily become the origin of cracks and cracks, reducing the strength of the alloy. Therefore, the Hf content range of the nickel-based superalloy in the present invention should be controlled between 1.0 and 2.0 wt%; In the present invention, Mo and W can increase the stability temperature of the γ 'phase, that is, increase the dissolution temperature of the γ' phase. However, if Mo and W are added in excess, the composition distribution will be uneven, and in severe cases, TCP (Topologically) will form in the alloy. -close-packed) The TCP phase is a very brittle and hard phase, and it is easy to cause stress concentration due to differential discharge accumulation to make it the origin of cracks, thereby reducing the material strength. In addition, when the TCP phase is formed, a large amount of solid solution strengthening elements in the γ base are consumed. Reduce the strength of the gamma base. In the present invention, the addition of an appropriate content of Ir can increase the uniformity of the composition distribution and prevent the formation of the TCP phase. In addition, the addition of Ir can also increase the effect of solid solution strengthening of the alloy and increase the high-temperature stability of the γ 'phase. The content of Mo, W, and Ir in the nickel-based superalloy of the invention should be limited to 0.5 to 1.0 wt%, 9.5 to 10.5 wt%, and 2 to 4 wt%, respectively; B and Zr mainly have grain boundary strengthening effects, and a small amount of B, Zr has the effect of purifying and strengthening the grain boundaries, but excessive addition will weaken the grain boundaries or harmful structures with various harmful strengths and reduce the strength. Therefore, the range of the B and Zr content of the nickel-based superalloy in the present invention should be controlled to 0.01 ~ 0.1wt%.

According to the foregoing experimental results, the present invention develops a highly creep-resistant equiaxed nickel-based superalloy whose chemical composition is (in weight percent): Cr is 8.0 to 9.5 wt%, W is 9.5 to 10.5 wt%, and Co is 9.5 ~ 10.5wt%, Al is 5.0 ~ 6.0wt%, Ti is 0.5 ~ 1.5wt%, Mo is 0.5 ~ 1.0wt%, Ta is 2.5 ~ 4.0wt%, Hf is 1.0 ~ 2.0wt%, Ir is 2.0 ~ 4.0 wt%, C is 0.1 ~ 0.2wt%, B is 0.01 ~ 0.1wt%, Zr is 0.01 ~ 0.10wt%, and the rest is composed of Ni and unavoidable impurities.

Example one

The nickel-based superalloy of the present invention is smelted in a vacuum induction furnace according to its chemical composition ratio (as shown in Table 1), and then vacuum precision casting is performed, and the molten alloy liquid is poured into a ceramic mold;      After casting, this nickel-based superalloy must undergo heat treatment to optimize the microstructure inside the alloy. The heat treatment procedure is as follows: (1) Vacuum solid solution treatment at 1100-1300 ℃ for at least one hour, and then quenched with argon to At room temperature, (2) followed by vacuum aging treatment at 800-1000 ℃ for at least ten hours, then the furnace was cooled to room temperature, and the test rod was subjected to 982 ℃ / 200MPa creep test after heat treatment. The test results are shown in Table 2:     

Example two

The nickel-based superalloy of the present invention is smelted in a vacuum induction furnace according to its chemical composition ratio (as shown in Table 3), and then vacuum precision casting is performed, and the molten alloy liquid is poured into a ceramic mold;      After casting, this nickel-based superalloy must undergo heat treatment to optimize the microstructure inside the alloy. The heat treatment procedure is as follows: (1) Vacuum solid solution treatment at 1100-1300 ℃ for at least one hour, and then quenched with argon to At room temperature, (2) followed by vacuum aging treatment at 800-1000 ℃ for at least ten hours, then the furnace was cooled to room temperature, and the test rod was subjected to 982 ℃ / 200MPa creep test after heat treatment. The test results are shown in Table 4:     

The most commonly used equiaxed nickel-based superalloys currently in commercial use are mainly Mar-M247, In713LC, and In718 alloys. Among them, Mar-M247 alloy has the best high temperature creep performance. Therefore, Mar-M247 alloy is used in the present invention. For comparison and reference to the EMS 55447 aeronautical material specification of Mar-M247 alloy, the creep test condition of 982 ℃ / 200MPa is selected as the comparison benchmark; since the EMS 55447 specification does not stipulate the t1% and t2% standards, the same implementation The process conditions of the example are to cast an alloy that complies with the Mar-M247 alloy composition specification, and after the creep test, supplement the creep-related data in Table 5, where t1% refers to the creep time of the material to reach the elongation deformation of 1%. , T2% refers to the creep time of the material up to 2% of the amount of elongation deformation; after comparing the creep properties of the alloy of the present invention and the Mar-M247 alloy, it shows in terms of creep life and creep resistance (t1%, t2%) The alloy of the present invention performs best, and is similar to Mar-M247 in terms of elongation, but still meets the EMS 55447 specification. It can be seen that the alloy of the present invention has improved creep properties.

The above-mentioned embodiments are only for illustrative purposes to explain the features and effects of this creation, and are not intended to limit the scope of the substantial technical content of this creation. Anyone familiar with the art can modify and change the above embodiments without departing from the spirit and scope of the creation. Therefore, the scope of protection of the rights of this creation shall be as listed in the scope of patent application mentioned later.

Claims (8)

A highly creep-resistant equiaxed nickel-based superalloy, having the following composition in terms of weight percentage: Cr is 8.0 to 9.5% by weight, W is 9.5 to 10.5% by weight, Co is 9.5 to 10.5% by weight, and Al is 5.0 to 6.0%. %, Ti is 0.5 ~ 1.5wt%, Mo is 0.5 ~ 1.0wt%, Ta is 2.5 ~ 4.0wt%, Hf is 1.0 ~ 2.0wt%, Ir is 2.0 ~ 4.0wt%, C is 0.1 ~ 0.2wt%, B is 0.01 to 0.1 wt%, Zr is 0.01 to 0.10 wt%, and the rest is composed of Ni and unavoidable impurities. The high creep-resistant equiaxed nickel-based superalloy as described in item 1 of the scope of patent application, wherein the high creep-resistant equiaxed nickel-based superalloy is smelted in a vacuum induction furnace. The high creep-resistant equiaxed nickel-based superalloy as described in item 1 of the scope of the patent application, wherein the high creep-resistant equiaxed nickel-based superalloy is cast in a vacuum environment. The high creep-resistant equiaxed nickel-based superalloy as described in item 3 of the patent application scope, wherein the high creep-resistant equiaxed nickel-based superalloy is heat-treated in one or two stages after casting. The high creep-resistant equiaxed nickel-based superalloy according to item 4 of the scope of the patent application, wherein the first-stage heat treatment is performed at a temperature of 1100 ° C or higher. The high creep-resistant equiaxed nickel-based superalloy as described in item 5 of the scope of the patent application, wherein the first-stage heat treatment is to cool the high creep-resistant equiaxed nickel-based superalloy with an inert gas. The high creep-resistant equiaxed nickel-based superalloy according to item 6 of the scope of the patent application, wherein the second-stage heat treatment is performed at 800 ° C or higher. The equiaxed nickel-based superalloy with high creep resistance as described in item 7 of the scope of patent application, wherein the second-stage heat treatment is performed by natural cooling.