Gamma apos is ultrahigh; cobalt-based high-temperature alloy with phase volume fraction and preparation method thereof

Abstract

The invention discloses a cobalt-based superalloy with ultrahigh gamma'phase volume fraction, the cobalt-based superalloy is composed of Co, Ni, Al, Mo and Nb, the general formula of the cobalt-based superalloy is CoaNibAlcModNbe, a, b, c, d and e respectively represent atomic percentages of corresponding elements, 53% < = a < = 83%, 0% < = b < = 30%, 5% < = c < = 15%, 1% < = d < = 10%, 1% < = e < = 5%, and a + b + c + d + e = 100%. The cobalt-based superalloy is a superalloy which does not contain Ta, W and other heavy metal elements with large density, the cobalt-based superalloy is composed of a gamma phase and a gamma'phase, nickel serves as a gamma 'phase stable element, the gamma / gamma' two-phase interval is enlarged, the volume fraction of the gamma 'phase in the cobalt-based superalloy is 50-82%, the dissolution temperature of the gamma' phase is 860-1000 DEG C, and the particle size of the cobalt-based superalloy is 1-5 micrometers. Meanwhile, the density is low, and the mechanical property is excellent.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature alloys, and in particular to a cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction and a preparation method thereof. Background Art

[0002] High-temperature alloys refer to high-end metal structural materials based on metals such as iron, nickel, and cobalt, which can work for a long time at high temperatures above 600°C and under certain stresses. High-temperature alloy materials belong to high-end metal structural materials in the field of new materials. They have superior comprehensive performance, excellent high-temperature strength and plasticity, good oxidation resistance and thermal corrosion resistance, excellent creep resistance, fracture resistance and good organizational stability. They have become key special materials for the development of many important industrial fields such as aerospace, electricity, and petrochemicals. For example, the technological progress of aircraft engines is closely related to the development of high-temperature alloys. High-temperature alloys are the most critical structural materials for promoting the development of aircraft engines. Military aircraft engines can usually use their thrust-to-weight ratio (thrust / weight) to comprehensively evaluate the level of the engine. The most direct and effective technical measure to improve the thrust-to-weight ratio is to increase the gas temperature before the turbine. Therefore, the performance and selection of high-temperature alloy materials are key factors in determining the performance of aircraft engines. With the continuous upgrading of aviation equipment, the requirements for the thrust-to-weight ratio of aircraft engines are constantly increasing, and the engine is increasingly dependent on high-performance high-temperature alloy materials.

[0003] In recent years, with the increasing demand for higher operating temperatures for hot end components such as aircraft engine turbine blades and gas turbines, there is also a need to further improve the performance of high-temperature alloys. For the γ' phase-enhanced nickel-based superalloy system that has been developed earlier, the solid solution temperature of the γ' phase is close to the melting point of the nickel-based superalloy, while the γ' phase-enhanced cobalt-based alloy has a higher temperature upper limit, and its melting point is 50 to 150 ° C higher than that of the nickel-based superalloy. This makes the cobalt-based superalloy theoretically have the potential for better high-temperature performance than the nickel-based superalloy. Therefore, the γ' phase-enhanced cobalt-based superalloy has greater development space and application prospects. In addition, γ' phase precipitation strengthening is the main strengthening mechanism of superalloys, and the volume fraction of γ' phase largely determines the mechanical strength and high-temperature deformation resistance of superalloys. Therefore, developing a superalloy containing a high volume fraction of γ' phase has important scientific research significance and practical application value. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction and a preparation method thereof. The cobalt-based high-temperature alloy is a high-temperature alloy that does not contain heavy metal elements with high density such as Ta and W. It is composed of γ and γ' phases. Nickel is used as a γ' phase stabilizing element to expand the γ / γ' two-phase interval. The volume fraction of the γ' phase in the cobalt-based high-temperature alloy is 50-82%, and the dissolution temperature of the γ' phase is 860-1000°C. At the same time, it has a relatively low density (8.35-8.38 g / cm 3 ) and excellent mechanical properties.

[0005] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0006] A cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction, the cobalt-based high-temperature alloy is composed of Co, Ni, Al, Mo and Nb, and its general formula is Co a Ni b Al c Mo d Nb e , where a, b, c, d, and e represent the atomic percentage of the corresponding elements, respectively, 53%≤a≤83%, 0%≤b≤30%, 5%≤c≤15%, 1%≤d≤10%, 1%≤e≤5%, and a+b+c+d+e=100%.

[0007] Furthermore, the cobalt-based high-temperature alloy has a γ / / γ' two-phase structure, wherein the volume fraction of the γ' phase is 50-82%.

[0008] The present invention further provides a method for preparing a cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction. The cobalt-based high-temperature alloy is prepared by a smelting method.

[0009] Furthermore, the preparation method of the cobalt-based high-temperature alloy with ultra-high γ' phase volume fraction is specifically as follows: the high-purity metal raw material of the cobalt-based high-temperature alloy is ultrasonically cleaned and then smelted, and then the alloy ingot obtained after smelting is successively subjected to solution treatment and aging treatment to obtain the cobalt-based high-temperature alloy with ultra-high γ' phase volume fraction.

[0010] Furthermore, in the preparation method, the melting method adopts vacuum arc melting.

[0011] Furthermore, the preparation method of the cobalt-based high-temperature alloy with ultra-high γ' phase volume fraction specifically comprises the following steps:

[0012] (1) Ultrasonic cleaning: The high-purity metal raw materials of Co, Ni, Al, Mo and Nb are mechanically polished to remove the oxide layer on the surface of the metal raw materials, and then placed in different containers and ultrasonically cleaned with alcohol, and the metal raw materials are taken out and dried;

[0013] (2) Ingredients: The Co, Ni, Al, Mo and Nb metal raw materials processed in step (1) are accurately weighed and mixed according to the atomic percentage of the cobalt-based high-temperature alloy:

[0014] (3) Master alloy smelting: Place the mixed metal raw materials into the crucible of a vacuum non-consumable arc furnace, close the furnace door, and evacuate to 1×10 -3 Pa, and then high-purity argon is filled to 0.06-0.08MPa; after arcing, the pure titanium ingot is first melted to absorb the residual oxygen in the furnace, and then the raw materials in the crucible are melted, and electromagnetic stirring is turned on to allow the melt to rotate and flow for uniform melting; after the raw materials are melted and thoroughly cooled, they are turned over and melted repeatedly four times to ensure the uniformity of the alloy ingot composition, and the alloy ingot is obtained after the melting is completed;

[0015] (4) In a high-purity Ar protective atmosphere, the prepared cobalt-based high-temperature alloy ingot is subjected to a solid solution treatment and an aging treatment in sequence to obtain a cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction.

[0016] Furthermore, the solution treatment is carried out at a solution temperature of 1250-1300° C. for 12-24 hours, and the aging treatment is carried out at a temperature of 600-850° C. for 15-30 hours.

[0017] Furthermore, the purity of each metal raw material Co, Ni, Al, Mo and Nb is ≥99.9%.

[0018] The beneficial effects of the present invention are:

[0019] (1) The present invention provides a cobalt-based high-temperature alloy that does not contain heavy metal elements with high density such as Ta and W, wherein the introduction of low-density Al metal elements significantly reduces the density of the cobalt-based high-temperature alloy, and the theoretical density is about 8.35-8.38 g / cm 3 ; The cobalt-based high-temperature alloy in the present invention does not contain metal elements such as Ta and W, because metal elements such as Ta and W will promote the formation of harmful phases, such as TCP phase; TCP phase not only destroys the stability of the alloy structure, but also has an irregular morphology, which easily causes stress concentration during service, causing the alloy to fail prematurely, thereby reducing the service performance of the alloy; The cobalt-based high-temperature alloy provided by the present invention does not contain TCP harmful phase;

[0020] (2) The cobalt-based high-temperature alloy provided by the present invention has a typical coarse columnar crystal structure in the cast state. After solution treatment and aging treatment, recrystallization occurs to form equiaxed crystals, and the γ' phase precipitates from the γ matrix, and the volume fraction of the γ' phase is 50-82%;

[0021] (3) After solution treatment and aging treatment, the cobalt-based high-temperature alloy provided by the present invention has very excellent tensile properties at room temperature, with a tensile yield strength of 700 to 850 MPa, a tensile strength of up to 900 to 1500 MPa, and a uniform elongation of up to 20% to 30%. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a SEM image of the cobalt-based high-temperature alloy prepared in Example 1 after solid solution and aging treatment. DETAILED DESCRIPTION

[0023] The technical solutions in the present invention will be described clearly and completely below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. 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.

[0024] The present invention provides a cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction. The cobalt-based high-temperature alloy is composed of Co, Ni, Al, Mo and Nb, and has a general formula of Co a Ni b Al c Mo d Nb e , wherein a, b, c, d, and e represent the atomic percentages of the corresponding elements, 53%≤a≤83%, 0%≤b≤30%, 5%≤c≤15%, 1%≤d≤10%, 1%≤e≤5%, and a+b+c+d+e=100%. The cobalt-based high-temperature alloy has a γ / / γ' two-phase structure, wherein the volume fraction of the γ' phase is 50-82%.

[0025] The cobalt-based superalloy with ultra-high γ' phase volume fraction is prepared by a smelting method. Specifically, the high-purity metal raw material of the cobalt-based superalloy is smelted after ultrasonic cleaning, and then the alloy ingot obtained after smelting is successively subjected to solid solution treatment and aging treatment to obtain a cobalt-based superalloy with ultra-high γ' phase volume fraction.

[0026] Furthermore, the preparation method of the cobalt-based high-temperature alloy with ultra-high γ' phase volume fraction specifically comprises the following steps:

[0027] (1) Ultrasonic cleaning: The high-purity metal raw materials of Co, Ni, Al, Mo and Nb are mechanically polished to remove the oxide layer on the surface of the metal raw materials, and then placed in different containers and ultrasonically cleaned with alcohol, and the metal raw materials are taken out and dried;

[0028] (2) Ingredients: The Co, Ni, Al, Mo and Nb metal raw materials processed in step (1) are accurately weighed and mixed according to the atomic percentage of the cobalt-based high-temperature alloy:

[0029] (3) Master alloy smelting: Place the mixed metal raw materials into the crucible of a vacuum non-consumable arc furnace, close the furnace door, and evacuate to 1×10 -3 Pa, and then high-purity argon is filled to 0.06-0.08MPa; after arcing, the pure titanium ingot is first melted to absorb the residual oxygen in the furnace, and then the raw materials in the crucible are melted, and electromagnetic stirring is turned on to allow the melt to rotate and flow for uniform melting; after the raw materials are melted and thoroughly cooled, they are turned over and melted repeatedly four times to ensure the uniformity of the alloy ingot composition, and the alloy ingot is obtained after the melting is completed;

[0030] (4) In a high-purity Ar protective atmosphere, the prepared cobalt-based high-temperature alloy ingot is kept at a solution temperature of 1250-1300° C. for 12-24 hours, taken out and water quenched; then, it is kept at an aging temperature in the range of 600-850° C. for 15-30 hours for aging treatment, and water quenched to obtain a cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction.

[0031] The present invention is further described in detail below through specific examples.

[0032] Example 1

[0033] A cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction has the following chemical compositions in atomic percentage: Co: 53%, Ni: 30%, Al: 10%, Mo: 5%, and Nb: 2%.

[0034] The method for preparing the cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction of the embodiment 1 comprises the following steps:

[0035] (1) Ultrasonic cleaning: The high-purity metal raw materials of Co, Ni, Al, Mo and Nb are mechanically polished to remove the oxide layer on the surface of the metal raw materials, and then placed in different containers and ultrasonically cleaned with alcohol, and the metal raw materials are taken out and dried;

[0036] (2) Ingredients: The Co, Ni, Al, Mo and Nb metal raw materials processed in step (1) are accurately weighed and mixed according to the atomic percentage of the cobalt-based high-temperature alloy:

[0037] (3) Master alloy smelting: Place the mixed metal raw materials into the crucible of a vacuum non-consumable arc furnace, close the furnace door, and evacuate to 1×10 -3 Pa, and then high-purity argon is filled to 0.06-0.08MPa; after arcing, the pure titanium ingot is first melted to absorb the residual oxygen in the furnace, and then the raw materials in the crucible are melted, and electromagnetic stirring is turned on to allow the melt to rotate and flow for uniform melting; after the raw materials are melted and thoroughly cooled, they are turned over and melted repeatedly four times to ensure the uniformity of the alloy ingot composition, and the alloy ingot is obtained after the melting is completed;

[0038] (4) In a high-purity Ar protective atmosphere, the prepared cobalt-based high-temperature alloy ingot is kept at a solution temperature of 1300° C. for 20 hours, taken out and water quenched; then, it is kept at an aging temperature range of 750° C. for 25 hours for aging treatment, and water quenched to obtain a cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction.

[0039] The cobalt-based high-temperature alloy prepared in Example 1 was subjected to a scanning electron microscope (SEM) characterization test to determine the microstructure morphology of the cobalt-based high-temperature alloy. Figure 1 This is a SEM image of the cobalt-based high-temperature alloy prepared in Example 1 after solution and aging treatment. The purpose of high-temperature solution treatment is mainly to eliminate element segregation and eliminate the low-melting point γ-γ' eutectic structure. Figure 1 (a) Equiaxed crystals can be observed. During the aging stage, the γ' phase precipitates in the supersaturated solid solution. Figure 1 (b) Figure 1 In the area within a grain in (a), a large amount of γ' phase can be observed to precipitate in the grain. The γ' phase is evenly distributed in the grain, with a size of about 80nm and a rectangular shape. No other impurity phases are observed in the grain.

[0040] Example 2

[0041] A cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction has the following chemical compositions by atomic percentage: Co: 58%, Ni: 25%, Al: 10%, Mo: 5%, and Nb: 2%.

[0042] Example 3

[0043] A cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction has the following chemical compositions by atomic percentage: Co: 63%, Ni: 20%, Al: 10%, Mo: 5%, and Nb: 2%.

[0044] Example 4

[0045] A cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction has the following chemical compositions in atomic percentage: Co: 68%, Ni: 15%, Al: 10%, Mo: 5%, and Nb: 2%.

[0046] Example 5

[0047] A cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction has the following chemical compositions in atomic percentage: Co: 73%, Ni: 10%, Al: 10%, Mo: 5%, and Nb: 2%.

[0048] Example 6

[0049] A cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction has the following chemical compositions by atomic percentage: Co: 78%, Ni: 5%, Al: 10%, Mo: 5%, and Nb: 2%.

[0050] Example 7

[0051] A cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction has the following chemical compositions in atomic percentage: Co: 83%, Ni: 0%, Al: 10%, Mo: 5%, and Nb: 2%.

[0052] The microstructures of the cobalt-based superalloys in Examples 1-7 were observed using a scanning electron microscope (SEM), and the SEM images were analyzed using Image J software to determine the volume fraction of the γ' phase. In order to ensure the rigor and accuracy of the analysis data, more than 50 SEM images were taken for the cobalt-based superalloy samples in Examples 1-7 for the determination of the volume fraction of the γ' phase.

[0053] The samples of Examples 1 to 7 were subjected to tensile stress-strain tests at room temperature. According to the national mechanical property test standard, the samples of Examples 1 to 7 were prepared into tensile test samples that met the national standard, and room temperature tensile property experiments were performed.

[0054] The volume fraction of the γ' phase in the cobalt-based high-temperature alloys of Examples 1-7 and the actual measured values ​​of various properties are shown in Table 1. In Table 1, σ 0.2 , σ u , δ and Ф are the yield strength, tensile strength, elongation after fracture and the volume fraction of γ' phase, respectively.

[0055] Table 1 Actual measured values ​​of various properties and volume fraction of γ' phase

[0056]

[0057] The cobalt-based high-temperature alloys of Examples 1-7 of the present invention have very excellent tensile properties, wherein the tensile yield strength reaches 700-850 MPa, the tensile strength is as high as 900-1500 MPa, the elongation after fracture is as high as 20%-30%, and the volume fraction of the γ' phase is 50-82%.

[0058] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

[0059] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction, characterized in that: The cobalt-based high-temperature alloy is composed of Co, Ni, Al, Mo and Nb, and its general formula is Co a Ni b Al c Mo d Nb e , where a, b, c, d, and e represent the atomic percentage of the corresponding elements, respectively, 53%≤a≤83%, 0%≤b≤30%, 5%≤c≤15%, 1%≤d≤10%, 1%≤e≤5%, and a+b+c+d+e=100%.

2. The cobalt-based high-temperature alloy with ultra-high γ' phase volume fraction according to claim 1, characterized in that: The cobalt-based high-temperature alloy has a γ / / γ' two-phase structure, wherein the volume fraction of the γ' phase is 50-82%.

3. A method for preparing the cobalt-based high-temperature alloy with ultra-high γ' phase volume fraction according to claim 1 or 2, characterized in that: The cobalt-based high-temperature alloy is prepared by a smelting method.

4. The method for preparing the cobalt-based high-temperature alloy with ultra-high γ' phase volume fraction according to claim 3, characterized in that: The high-purity metal raw material of the cobalt-based high-temperature alloy is ultrasonically cleaned and then smelted, and then the alloy ingot obtained after smelting is successively subjected to solid solution treatment and aging treatment to obtain a cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction.

5. The method for preparing the cobalt-based high-temperature alloy with ultra-high γ' phase volume fraction according to claim 4, characterized in that: The melting method adopts vacuum arc melting.

6. The method for preparing the cobalt-based high-temperature alloy with ultra-high γ' phase volume fraction according to claim 5, characterized in that: The steps include: (1) Ultrasonic cleaning: The high-purity metal raw materials of Co, Ni, Al, Mo and Nb are mechanically polished to remove the oxide layer on the surface of the metal raw materials, and then placed in different containers and ultrasonically cleaned with alcohol, and the metal raw materials are taken out and dried; (2) Ingredients: The Co, Ni, Al, Mo and Nb metal raw materials processed in step (1) are accurately weighed and mixed according to the atomic percentage of the cobalt-based high-temperature alloy: (3) Master alloy smelting: Place the mixed metal raw materials into the crucible of a vacuum non-consumable arc furnace, close the furnace door, and evacuate to 1×10 -3 Pa, and then high-purity argon is filled to 0.06-0.08MPa; after arcing, the pure titanium ingot is first melted to absorb the residual oxygen in the furnace, and then the raw materials in the crucible are melted, and electromagnetic stirring is turned on to allow the melt to rotate and flow for uniform melting; after the raw materials are melted and thoroughly cooled, they are turned over and melted repeatedly four times to ensure the uniformity of the alloy ingot composition, and the alloy ingot is obtained after the melting is completed; (4) In a high-purity Ar protective atmosphere, the prepared cobalt-based high-temperature alloy ingot is subjected to a solid solution treatment and an aging treatment in sequence to obtain a cobalt-based high-temperature alloy with an ultra-high γ' phase volume fraction.

7. The method for preparing the cobalt-based high-temperature alloy with ultra-high γ' phase volume fraction according to claim 6, characterized in that: The solution treatment is carried out at a solution temperature of 1250-1300° C. for 12-24 hours, and the aging treatment is carried out at a temperature of 600-850° C. for 15-30 hours.

8. The method for preparing the cobalt-based high-temperature alloy with ultra-high γ' phase volume fraction according to claim 6, characterized in that: The purity of each metal raw material Co, Ni, Al, Mo and Nb is ≥99.9%.

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