Iridium-based alloy with high toughness and high oxidation resistance and preparation method thereof

Abstract

The invention discloses a high-toughness and high-oxidation-resistance iridium-based alloy and a preparation method thereof, and belongs to the technical field of alloy materials. The method comprises the following steps: (1) alloy smelting; (2) directional solidification; (3) homogenizing heat treatment; and (4) the iridium-based alloy containing Rh and Re is prepared through a hot forging machining method, the comprehensive performance of the alloy is remarkably improved on the basis that the number of alloy constituent elements is small, and therefore the alloy can adapt to more diversified application scenes and more strict application requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of alloy materials, and relates to an iridium-based alloy with high strength and toughness and high oxidation resistance and a preparation method thereof. Background Art

[0002] With the rapid development of modern industry, the demand for high-temperature structural materials is becoming increasingly urgent. For example, in the field of aerospace technology, aerospace engines have strict requirements on material performance. Therefore, improving the high-temperature comprehensive performance of materials can enable material performance to meet the development needs of more fields, which is of great significance.

[0003] The combustion temperature of the latest generation of green unit engines can reach about 1700℃. At present, special ceramics have attracted wide attention due to their advantages such as low density and high temperature resistance. However, the thermal expansion coefficients between ceramic materials and metal materials are quite different, and the connection between the two faces huge challenges, which limits the application of ceramic materials. The operating temperature of nickel-based high-temperature materials can reach above 2000℃, but their high-temperature oxidation resistance is poor, resulting in a short service life, which affects their practical application.

[0004] Therefore, it is necessary to provide a high-strength, high-toughness, high-oxidation-resistant iridium-based alloy and a preparation method thereof. By combining the alloy composition with the preparation method, a material with excellent comprehensive performance can be obtained to meet the use requirements in more extreme environments, laying a good foundation for the development of related technologies. Summary of the invention

[0005] In order to overcome the problems in the background technology, the present invention proposes a high-strength, high-toughness, and high-oxidation-resistance iridium-based alloy. Through a reasonable alloy component composition combined with a preparation method, an iridium-based alloy with toughness, plasticity, compressive strength, and high-temperature oxidation resistance maintained at a high level is obtained to meet the needs of related fields for high-temperature structural materials.

[0006] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0007] On one hand, the present invention provides a high-toughness, high-oxidation-resistant iridium-based alloy, wherein the alloy composition comprises 7% to 10% Rh, 0.5% to 5% Re, and the remainder is Ir by mass fraction.

[0008] Another aspect of the present invention provides a method for preparing the above-mentioned iridium-based alloy, the preparation method comprising the following steps:

[0009] (1) Alloy smelting: The alloy composition is prepared according to the design, and then the prepared alloy raw materials are arc-melted under vacuum and argon gas conditions to obtain pre-alloyed alloy ingots;

[0010] (2) directional solidification: performing directional solidification treatment on the alloy ingot pre-alloyed in step (1) under vacuum conditions, and obtaining an alloy sample after cooling;

[0011] (3) homogenization heat treatment: homogenization heat treatment is performed on the alloy sample in step (2) under vacuum conditions;

[0012] (4) Hot forging: The alloy sample after the homogenization heat treatment in step (3) is subjected to hot forging, with the deformation amount per pass not exceeding 5%. When the cumulative deformation amount reaches 30%, stress relief annealing is performed, and the iridium-based alloy is obtained after cooling.

[0013] Preferably, in the step (1), before the argon gas is filled, the ambient vacuum is not less than 0.01 Pa.

[0014] Preferably, in step (1), the smelting temperature is 1900-2400°C, the melting is turned over every 30-50 seconds, and the number of times of melting is turned over is 8-10 times.

[0015] Preferably, in the step (2), the directional solidification treatment temperature is 1900-2000°C. Under the condition of 1900-2000°C, the stretching rate of directional solidification is set to 5, 10, 20, 50, and 100 μm / s respectively. Under each stretching rate condition, the stretching is 600-2000s to perform directional solidification treatment on the pre-alloyed alloy ingot.

[0016] Preferably, in step (3), the heat treatment temperature is 1400-1700° C., and the heat treatment time is not less than 2 hours.

[0017] Preferably, in step (4), the annealing temperature is 1200-1400° C., and the annealing time is not less than 0.5 h.

[0018] Preferably, in steps (2) and (3), the vacuum degree is not less than 0.01 Pa.

[0019] Beneficial effects of the present invention:

[0020] 1. The Ir-Rh-Re alloy material prepared by the present invention has excellent toughness, plasticity, compressive strength, and high-temperature oxidation resistance, which reduces the mutual influence between properties during the process of improving the alloy performance, so that the alloy has better comprehensive performance and meets more stringent use requirements.

[0021] 2. The present invention effectively eliminates the influence between the interface of the matrix phase and the reinforcement phase through reasonable alloy composition design combined with the preparation method, which is beneficial to improving the comprehensive performance of the alloy.

[0022] 3. The alloy element composition of the present invention is simple. On the basis of simplifying the alloy element composition, excellent comprehensive performance is obtained, which is convenient for practical application and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The stress-strain curves of Examples 1, 2, 3 and Comparative Example 1 of the present invention are shown in FIG.

[0024] Figure 2 Element distribution diagrams of Example 1 and Comparative Example 1 of the present invention, wherein (a) is a backscattering composition image diagram of the alloy of Example 1, (a1) is an Ir element distribution diagram of the alloy of Example 1, (a2) is an Rh element distribution diagram of the alloy of Example 1, (b) is a backscattering composition image diagram of the alloy of Example 2, (b1) is a Re element distribution diagram of the alloy of Example 2, (b2) is an Rh element distribution diagram of the alloy of Example 2, (c) is a backscattering composition image diagram of the alloy of Example 3, (c1) is an Re element distribution diagram of the alloy of Example 3, and (c2) is an Rh element distribution diagram of the alloy of Example 3;

[0025] Figure 3 The SEM images of the alloys of Example 3 and Comparative Example 1 after oxidation, wherein (b) is a SEM image of the alloy of Comparative Example 1 oxidized at 1400°C for 2 h, (d) is a SEM image of the alloy of Example 3 oxidized at 1400°C for 2 h, (f) is a SEM image of the alloy of Comparative Example 1 oxidized at 1500°C for 4 h, and (h) is a SEM image of the alloy of Example 3 oxidized at 1500°C for 4 h;

[0026] Figure 4 XRD diagrams of the alloys of Examples 1, 2, 3 and Comparative Example 1 after oxidation;

[0027] Figure 5 The weight loss curves of the alloys of Examples 1, 2, and 3 of the present invention and Comparative Example 1 are as follows: DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with specific embodiments.

[0029] In the examples and comparative examples of the present invention, chemical reagents not otherwise specified were all commercially available analytically pure reagents for the experiments.

[0030] The alloy compositions of the comparative examples and embodiments of the present invention are shown in Table 1

[0031] Table 1

[0032]

[0033] Example 1

[0034] This example prepares the alloy according to the following method:

[0035] (1) The alloy composition is prepared according to Table 1, and the total weight of the ingredients is 20 g. Then, the prepared alloy raw material is placed in a crucible of a vacuum arc furnace, and the vacuum arc furnace is evacuated to a vacuum degree of not less than 0.01 Pa. Then, argon gas is filled into the vacuum arc furnace. Then, the alloy raw material is arc-melted. During the melting process, the alloy ingot is turned over and melted once every 30 seconds, and turned over 10 times in total to obtain a pre-alloyed alloy ingot. Before melting the alloy raw material, a titanium block is placed in another crucible, and the titanium block is melted to absorb oxygen, and then the alloy raw material is melted again.

[0036] (2) placing the pre-alloyed alloy ingot obtained after the above smelting into a directional solidification device, and evacuating the directional solidification device to a vacuum degree of not less than 0.01 Pa, while heating the alloy ingot to 1900° C., setting the stretching rates to 5, 10, 20, 50, and 100 μm / s, respectively, and stretching for 600 s under each stretching rate condition, and directional solidification is carried out during the process of stretching the alloy into a rod, and the directional solidification is completed, and the alloy sample is obtained after cooling;

[0037] (3) The alloy sample is placed in a vacuum furnace, and then the vacuum furnace is evacuated to a vacuum degree of not less than 0.01 Pa. The heating temperature in the vacuum furnace is adjusted to 1400°C, and the alloy sample is heated for 2 hours for homogenization heat treatment.

[0038] (4) The alloy sample after homogenization heat treatment was hot forged with a deformation of 3% per pass. After the cumulative deformation reached 30%, the alloy sample was stress relieved annealed at 1200°C for 0.5h. After cooling, an iridium-based alloy was obtained.

[0039] The chemical formula of the iridium-based alloy prepared in this example is recorded as Ir-7Rh-0.5Re.

[0040] Example 2

[0041] This embodiment adopts the same method as that of embodiment 1 to prepare the iridium-based alloy, except that, as shown in Table 1, the Re content in this embodiment is 1%.

[0042] The chemical formula of the iridium-based alloy prepared in this example is recorded as Ir-7Rh-1.0Re.

[0043] Example 3

[0044] This embodiment adopts the same method as that of embodiment 1 to prepare the iridium-based alloy, except that, as shown in Table 1, the Re content in this embodiment is 1.5%.

[0045] The chemical formula of the iridium-based alloy prepared in this example is recorded as Ir-7Rh-1.5Re.

[0046] Example 4

[0047] This example prepares the alloy according to the following method:

[0048] (1) The alloy composition is prepared according to Table 1, and the total weight of the ingredients is 20 g. Then, the prepared alloy raw material is placed in a crucible of a vacuum arc furnace, and the vacuum arc furnace is evacuated to a vacuum degree of not less than 0.01 Pa. Then, argon gas is filled into the vacuum arc furnace. Then, the alloy raw material is arc-melted. During the melting process, the alloy ingot is turned over and melted once every 40 seconds, and turned over 9 times in total to obtain a pre-alloyed alloy ingot. Before melting the alloy raw material, a titanium block is placed in another crucible, and the titanium block is melted to absorb oxygen, and then the alloy raw material is melted again.

[0049] (2) placing the pre-alloyed alloy ingot obtained after the above smelting into a directional solidification device, and evacuating the directional solidification device to a vacuum degree of not less than 0.01 Pa, while heating the alloy ingot to 2000° C., setting the stretching rates to 5, 10, 20, 50, and 100 μm / s, respectively, and stretching for 1000 s under each stretching rate condition, and directional solidification is carried out during the process of stretching the alloy into a rod. When the alloy is stretched to the required length, the directional solidification is completed, and the alloy sample is obtained after cooling;

[0050] (3) The alloy sample is placed in a vacuum furnace, and then the vacuum furnace is evacuated to a vacuum degree of not less than 0.01 Pa. The heating temperature in the vacuum furnace is adjusted to 1700°C, and the alloy sample is heated for 3 hours for homogenization heat treatment.

[0051] (4) The alloy samples after homogenization heat treatment were hot forged with a deformation of 4% per pass. After the cumulative deformation reached 30%, the alloy samples were stress relieved annealed at 1400°C for 1 h. After cooling, the iridium-based alloy was obtained.

[0052] The properties of the iridium-based alloy prepared in this example are similar to those in Example 1.

[0053] Example 5

[0054] This example prepares the alloy according to the following method:

[0055] (1) The alloy composition is prepared according to Table 1, and the total weight of the ingredients is 20 g. Then, the prepared alloy raw material is placed in a crucible of a vacuum arc furnace, and the vacuum arc furnace is evacuated to a vacuum degree of not less than 0.01 Pa. Then, argon gas is filled into the vacuum arc furnace. Then, the alloy raw material is arc-melted. During the melting process, the alloy ingot is turned over and melted once every 50 seconds, and turned over 8 times in total to obtain a pre-alloyed alloy ingot. Before melting the alloy raw material, a titanium block is placed in another crucible, and the titanium block is melted to absorb oxygen, and then the alloy raw material is melted again.

[0056] (2) placing the pre-alloyed alloy ingot obtained after the above smelting into a directional solidification device, and evacuating the directional solidification device to a vacuum degree of not less than 0.01 Pa, while heating the alloy ingot to 1950° C., setting the stretching rates to 5, 10, 20, 50, and 100 μm / s, respectively, and stretching for 2000 s under each stretching rate condition, and directional solidification is carried out during the process of stretching the alloy into a rod. When the alloy is stretched to the required length, the directional solidification is completed, and the alloy sample is obtained after cooling;

[0057] (3) The alloy sample is placed in a vacuum furnace, and then the vacuum furnace is evacuated to a vacuum degree of not less than 0.01 Pa. The heating temperature in the vacuum furnace is adjusted to 1500°C, and the alloy sample is heated for 4 hours for homogenization heat treatment.

[0058] (4) The alloy sample after homogenization heat treatment was hot forged with a deformation of 5% per pass. After the cumulative deformation reached 30%, the alloy sample was stress relieved annealed at 1300°C for 1.5 hours. After cooling, an iridium-based alloy was obtained.

[0059] The properties of the iridium-based alloy prepared in this example are similar to those in Example 1.

[0060] Comparative Example 1

[0061] The iridium-based alloy was prepared in the same manner as in Example 1, except that, as shown in Table 1, the alloy composition of the comparative example did not contain Re.

[0062] The alloys prepared in Examples 1, 2, 3 and Comparative Example 1 were subjected to stress-strain tests at room temperature, and the test results were as follows: Figure 1 shown.

[0063] The element distribution analysis of the alloys prepared in Example 1 and Comparative Example 1 was performed using an electron probe, and the results were as follows: Figure 2 shown.

[0064] The alloys prepared in Examples 1, 2, 3 and Comparative Example 1 were sampled by wire cutting, and then the samples were subjected to surface grinding and polishing treatment to remove impurities and defects on the surface of the samples. After that, the samples were divided into 4 groups, each group of samples consisted of 4 samples, which were the alloys prepared in Examples 1, 2, 3 and Comparative Example 1. The 4 groups of samples were subjected to oxidation experiments using a muffle furnace. The oxidation experiment conditions of the 4 groups of samples were oxidation at 1400°C for 2h, oxidation at 1400°C for 4h, oxidation at 1500°C for 2h, and oxidation at 1500°C for 4h. The oxidized samples were subjected to SEM experiments, XRD experiments, and unit area weight loss tests, and the results were as follows: Figure 3 , 4 , as shown in Figure 5.

[0065] pass Figure 1 It can be seen that when the alloy of comparative example 1 reaches the maximum compressive strength of 1212MPa, its strain is only 18%, while when the alloy of example 1 of the present invention reaches the maximum compressive strength of 1154MPa, the strain can be maintained at 36%. At the same time, when the strain of example 1 reaches 43%, the alloy still maintains a high compressive strength of 1142MPa. The maximum compressive strength of the alloy of example 1 decreases by about 4.7% relative to comparative example 1, while the strain is doubled. When the strain of the alloy of example 1 is increased to 43%, the compressive strength only decreases by about 5.7%, which fully demonstrates that the alloy prepared by the present invention can significantly improve the alloy performance while reducing the mutual influence of the performance, thereby improving the comprehensive performance of the experimental alloy. Only adding Rh is beneficial to improving the oxidation resistance and compressive strength of the alloy. However, due to the segregation of Rh at the grain boundaries (such as Figure 2 As shown in the figure), it will increase the brittleness of the alloy material and cause the overall performance of the alloy to be poor. After adding Re, Figure 2 As shown, Re is mainly distributed inside the crystal, and there is almost no Re at the grain boundary. Figure 2 It can be seen that Ir is uniformly distributed in the entire matrix. Ir has a face-centered cubic (FCC) lattice, which will also produce a significant hardening effect during deformation. Re has a hexagonal close-packed structure and can replace the Ir site in the Ir solid solution without occupying the tetrahedral and octahedral gaps. Therefore, the addition of Re reduces the dislocation slip ability on the octahedral plane, thereby significantly enhancing the plasticity of the alloy. At the same time, after adding Re, the grains in the alloy will be refined, thereby significantly reducing the degree of decrease in compressive strength, and ultimately achieving a significant improvement in the comprehensive performance of the alloy.

[0066] pass Figure 3 It can be seen that the alloys oxidized at 1500℃ will produce Rh2O3, which is relatively stable. Therefore, adding Rh can improve the oxidation resistance of the alloy. Figure 4It can be seen that after adding Re, ReO2 is generated, which can improve the density of the oxide film and reduce the volatilization of high-temperature oxides, thereby further enhancing the high-temperature oxidation resistance of the alloy.

[0067] pass Figure 5 It can be seen that the weight loss per unit area of ​​the alloy of Comparative Example 1 is 0.15 mg / mm 2 The unit weight loss area of ​​the alloy in Example 1 of the present invention is 0.06 mg / mm 2 The smaller the unit weight loss area is, the better the oxidation resistance of the alloy is. It can be seen that the alloy of the present invention has excellent oxidation resistance.

[0068] The hardness of the alloys prepared in Examples 1, 2, and 3 of the present invention was tested, and the hardness values ​​were 302 HV, 293 HV, and 287 HV, respectively. It can be seen that with the increase of the amount of Re added, the hardness of the alloy will decrease slightly. Figure 1 It can be seen that as the amount of Re added increases, the compressive strength of the alloy will also decrease slightly. Therefore, the amount of Re added must be controlled within a certain range.

[0069] The toughness and brittleness of the material can be characterized by the ratio of bulk modulus to shear modulus (B / G) according to Pugh's law. When the value of B / G is greater than 1.75, the material has good toughness, otherwise, the material exhibits brittleness. The alloy prepared by the present invention has a decreased shear modulus due to changes in the atomic distance and bonding strength between Rh, Re elements and Ir atoms, so that the B / G value is greater than 1.75, and the alloy exhibits excellent toughness.

[0070] Ir and Rh will form an infinite solid solution, Re will form a limited solid solution with Ir and Rh, no other intermetallic compounds will be produced, Ir, Rh, and Re are evenly distributed in the matrix, and the alloy is solid solution strengthened.

[0071] In summary, the present invention can reduce the mutual influence between alloy properties on the basis of simplifying the alloy element composition through reasonable alloy composition design combined with a suitable preparation method, and prepare an alloy material with excellent comprehensive performance.

[0072] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A high-toughness, high-oxidation-resistant iridium-based alloy, characterized in that: The alloy composition comprises 7% to 10% Rh, 0.5% to 5% Re, and the balance is Ir by mass fraction.

2. A method for preparing the iridium-based alloy according to claim 1, characterized in that: The preparation method comprises the following steps: (1) Alloy smelting: The alloy composition is prepared according to the design, and then the prepared alloy raw materials are arc-melted under vacuum and argon gas conditions to obtain pre-alloyed alloy ingots; (2) directional solidification: performing directional solidification treatment on the alloy ingot pre-alloyed in step (1) under vacuum conditions, and obtaining an alloy sample after cooling; (3) homogenization heat treatment: homogenization heat treatment is performed on the alloy sample in step (2) under vacuum conditions; (4) Hot forging: The alloy sample after the homogenization heat treatment in step (3) is subjected to hot forging, with the deformation amount per pass not exceeding 5%. When the cumulative deformation amount reaches 30%, stress relief annealing is performed, and the iridium-based alloy is obtained after cooling.

3. The preparation method according to claim 2, characterized in that: In the step (1), before the argon gas is filled, the vacuum degree of the environment is not less than 0.01 Pa.

4. The preparation method according to claim 2, characterized in that: In the step (1), the smelting temperature is 1900-2400° C., and the melting is turned over every 30 to 50 seconds, and the number of times of melting is turned over is 8 to 10 times.

5. The preparation method according to claim 2, characterized in that: In the step (2), the directional solidification treatment temperature is 1900-2000°C. Under the condition of 1900-2000°C, the stretching rate of directional solidification is set to 5, 10, 20, 50, and 100 μm / s respectively. Under each stretching rate condition, the stretching time is 600-2000s to perform directional solidification treatment on the pre-alloyed alloy ingot.

6. The preparation method according to claim 2, characterized in that: In the step (3), the heat treatment temperature is 1400-1700° C., and the heat treatment time is not less than 2 hours.

7. The preparation method according to claim 2, characterized in that: In the step (4), the annealing temperature is 1200-1400° C., and the annealing time is not less than 0.5 h.

8. The preparation method according to claim 2, characterized in that: In the steps (2) and (3), the vacuum degree is not less than 0.01 Pa.

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