CN116752014A

CN116752014A - Large-size ETA phase reinforced high-temperature alloy and preparation method thereof

Info

Publication number: CN116752014A
Application number: CN202310688164.7A
Authority: CN
Inventors: 谭黎明; 刘锋; 黄岚; 刘咏
Original assignee: Central South University
Current assignee: Central South University
Priority date: 2023-06-12
Filing date: 2023-06-12
Publication date: 2023-09-15
Anticipated expiration: 2043-06-12
Also published as: CN116752014B

Abstract

The invention discloses a large-size ETA phase-strengthened high-temperature alloy and a preparation method thereof, aiming to improve the high-temperature resistance of the alloy. To this end, embodiments of the present invention provide a large-sized ETA phase-strengthened high-temperature alloy on the one hand. In terms of phase composition, the high-temperature alloy includes a matrix, a γ' phase and an eta phase; wherein the grain size of the matrix is 10 to 30 μm, the γ′ phase is dispersedly distributed in the matrix, the eta phase is evenly distributed in the matrix, the distribution form of the eta phase is divided into needle-like and flaky, and the average length of the eta phase The size of the γ′ phase is 30 to 50 μm, and the size of the γ′ phase is 30 to 200 nm.

Description

Large-size ETA phase reinforced high-temperature alloy and preparation method thereof

Technical Field

The application belongs to the technical field of high-temperature alloy preparation, and particularly relates to a large-size ETA phase reinforced high-temperature alloy and a preparation method thereof.

Background

The nickel-based superalloy has excellent tensile strength, creep resistance, fatigue resistance and oxidation resistance in the temperature range of 540-1000 ℃, and is a necessary material for key high-temperature components in core components of aeroengines, gas turbines and the like. From the composition point of view, the high temperature strength of nickel-base superalloys is mainly enhanced by solid solution strengthening and precipitation phase precipitation, wherein the effect of precipitation strengthening is most remarkable.

However, in order to improve the efficiency of aeroengines and gas turbines, increasing the gas temperature before the turbine is the most effective means, and more stringent requirements are placed on the high Wen Fuyi performance of superalloy materials. For example, as an important rotating part on an engine, the working temperature of a wheel rim is increased from 750 ℃ to more than 800 ℃, however, the long-term use temperature of the existing nickel-based turbine disc is limited to 600-750 ℃, so that development of a superalloy material with high yield strength and excellent high-temperature durability is needed.

Disclosure of Invention

The application mainly aims to provide a large-size ETA phase reinforced high-temperature alloy and a preparation method thereof, aiming at improving the high-temperature resistance of the alloy.

To this end, in one aspect, the present application provides a large-size ETA phase strengthened superalloy comprising, in terms of phase composition, a matrix, a gamma prime phase, and an ETA phase; wherein,,

the grain size of the matrix is 10-30 mu m, the gamma 'phase is dispersed in the matrix, the eta phase is uniformly distributed in the matrix, the average length of the eta phase is 30-50 mu m, the size of the gamma' phase is 30-200 nm, and the distribution form of the eta phase is divided into needle-shaped and sheet-shaped.

Specifically, the volume fraction of the gamma' -phase is 40% -50%, and the volume fraction of the eta phase is 8-12%.

Specifically, in terms of component composition, the high-temperature alloy comprises the following elements in percentage by weight:

2.5% -4% of Al, 3.8% -5% of Ti, 10% -14% of Cr, 13% -18% of Co, 0% -3.3% of Nb, 2.8% -3.3% of Mo, 2.8% -7.5% of Ta, 2.5% -3.2% of W, 0.01% -0.05% of C, 0% -0.01% of B, 0% -0.1% of rare earth element and the balance of Ni.

Specifically, the ratio of the mass fraction of Ti to Al is in the range of 1.4-2.0;

the mass fraction of Al+Ti+Nb+Ta is in the range of 11.8-16%;

the ratio of the mass fraction of (Ti+Nb+Ta)/Al is in the range of 2.5 to 4.5;

the mass fraction of Mo+W is in the range of 5.5-6.3%.

Specifically, the rare earth element is one or a combination of a plurality of Zr, hf, sc, la or Y.

Specifically, the method comprises the steps of filling prealloyed powder into a hot extrusion sheath, heating in a vacuum sealing manner, placing the hot extrusion sheath in an extrusion die for hot extrusion, and air-cooling to room temperature to obtain a hot extrusion bar; removing the sheath from the hot extrusion bar and performing heat treatment to obtain a high-temperature alloy product; wherein,,

the heat treatment process comprises the following steps: the hot extrusion bar is air cooled to 720 ℃ to 760 ℃ after heat preservation for 1.5 to 2.5 hours at 1180 ℃ to 1200 ℃, and then is cooled along with a furnace after heat preservation for 22 to 24 hours at 720 ℃ to 760 ℃.

Specifically, the extrusion temperature of the hot extrusion bar is 1120-1140 ℃, and the extrusion ratio is 15:1-17:1.

Specifically, the prealloyed powder is filled into a stainless steel sheath with the diameter of 96mm and the height of 230mm, and the stainless steel sheath is subjected to air suction sealing welding at 400 ℃.

Specifically, the diameter of the hot extrusion bar is about 24mm.

Specifically, the prealloyed powder adopts gas atomization powder with the granularity of 15-53 microns.

Principle and advantages

The length dimension of eta phase of the high-temperature alloy provided by the application is obviously larger than the dimension of gamma 'phase, and the large-dimension coupling strengthening from nano-scale to micron-scale is realized, so that although the fine gamma' phase can be dissolved back into a matrix at high temperature, the precipitation strengthening effect is lost, but the large-dimension eta phase is difficult to dissolve back and can continuously block the movement of grain boundary and dislocation, thereby playing the role of precipitation strengthening.

In addition, the distribution form of eta phase is divided into a flaky form and a needle-shaped form, part of needle-shaped eta phase (the length is larger than the grain size of the matrix phase and the width is far smaller than the grain size of the matrix phase) can penetrate and string two or more grains across the grains, the pinning effect on the grain boundary is obvious, the grain boundary is difficult to slide and deform under the action of external stress, and the effects of strengthening and pinning the grain boundary are realized, so that the alloy has excellent high temperature resistance.

According to the preparation method provided by the application, the inventor reasonably regulates and controls the contents of elements such as Ti, ta and the like, and is matched with a proper heat treatment system, so that a sigma phase, a mu phase and other harmful TCP phases are not separated out while a eta phase is separated out, and the eta phase and the gamma' phase realize nano-to-micron-scale large-size coupling reinforcement in scale.

Specifically, in terms of component design: considering the influence of alloy composition on the structure and properties, promoting eta phase (Ni by increasing Ti/Al ratio ₃ Ti), controlling the total amount of ti+al+nb+ta to ensure the content of gamma 'phase to be more than 40%, maintaining the precipitation strengthening level, reasonably adjusting the content of solid solution strengthening elements such as W, mo, strengthening the matrix phase, simultaneously not precipitating brittle harmful phase, controlling the content of antioxidant element Cr to be an effective level, realizing the effects of grain boundary strengthening and grain boundary purifying by adding trace elements such as C, B, zr, and developing a high-temperature alloy material capable of working at higher temperature and stress level by utilizing the mode of eta phase and gamma' phase coupling strengthening.

On the heat treatment system: the hot extrusion bar is air cooled to 720-760 ℃ after heat preservation for 1.5-2.5 hours at 1180-1200 ℃, precipitation of large-size eta phase is guaranteed, re-dissolution of initial large-size gamma ' -phase and re-precipitation of small-size gamma ' -phase are promoted, and then the bar is cooled along with a furnace after heat preservation for 22-24 hours at 720-760 ℃ so as to fully precipitate fine tertiary gamma ' -phase.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for the description of the embodiments will be briefly described below, and it is apparent that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a microstructure of a superalloy prepared in example 1;

FIG. 2 is a microstructure of a superalloy prepared in example 1;

FIG. 3 is a microstructure of the superalloy prepared in comparative example 1;

FIG. 4 is a microstructure of a superalloy prepared in comparative example 2;

wherein: the picture size of FIG. 1 is 100 μm by 100. Mu.m, and the picture size of FIG. 2 is 10 μm by 10. Mu.m.

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.

From the composition point of view, the high temperature strength of nickel-base superalloys is mainly enhanced by solid solution strengthening and precipitation phase precipitation, wherein the effect of precipitation strengthening is most remarkable. At present, the strengthening phases of the nickel-based superalloy mainly have equal gamma ', gamma' and are usually in a form of fine square or sphere, but the flaky eta phase with a hexagonal structure is larger in size and is often accompanied by the occurrence of some topological close-packed phases, and more crack sources are provided for the failure of the superalloy while the strengthening elements such as Al, ti, ta and the like are consumed, so the eta phase is often considered to be unfavorable for the structural stability of materials, and the precipitation of the eta phase is avoided as much as possible in the prior component design process.

However, the inventor researches and discovers that if the harmful TCP phases such as sigma phase and mu phase are not precipitated when eta phase is precipitated, and eta phase and gamma 'phase are coupled in large size from nano scale to micro scale, the length size of eta phase is designed to be obviously larger than that of matrix phase, the introduced eta phase not only does not reduce the performance of alloy, but also can improve the high temperature resistance of alloy, because the tiny gamma' phase can be dissolved back into the matrix at high temperature, and then the precipitation strengthening effect is lost, but the large-size eta phase is difficult to dissolve back and can continuously prevent the movement of grain boundary and dislocation, thereby playing the role of precipitation strengthening.

In addition, the eta phase is divided into a flaky form and a needle-shaped form, two or more grains can be strung across the grains by the slender needle-shaped eta phase, the pinning effect on the grain boundary is obvious, the grain boundary is difficult to slide and deform under the action of external stress, and the effects of strengthening particles and pinning the grain boundary are realized, so that the alloy has excellent high temperature resistance.

A large-size ETA phase strengthened superalloy comprising, in phase composition, a matrix, a gamma prime phase and an ETA phase; wherein, the grain size of the matrix is 10-30 mu m, the gamma 'phase is dispersed in the matrix, the eta phase is uniformly distributed in the matrix in a sheet shape or a needle shape, the length of the eta phase is 30-50 mu m, and the size of the gamma' phase is 30-200 nm.

According to the high-temperature alloy provided by the application, on the phase composition, the eta phase and the gamma' phase realize nano-to-micron-scale large-size coupling on the scale, and when the length size of the needle-shaped eta phase is larger than that of the matrix phase and the width size is obviously smaller than that of the matrix phase, the eta phase penetrates through the matrix and two or more matrix grains are connected in series, and the analysis proves that the high-temperature alloy provided by the application has excellent high-temperature resistance.

Specifically, the volume fraction of the gamma' -phase is 40-50%, the volume fraction of the eta phase is 8-12%,

in order to obtain the high-temperature alloy with the phase composition, the high-temperature alloy comprises the following elements in percentage by weight: 2.5% -4% of Al, 3.8% -5% of Ti, 10% -14% of Cr, 13% -18% of Co, 0% -3.3% of Nb, 2.8% -3.3% of Mo, 2.8% -7.5% of Ta, 2.5% -3.2% of W, 0.01% -0.05% of C, 0% -0.01% of B, 0% -0.1% of rare earth element and the balance of Ni; furthermore, the processing unit is configured to,

the ratio of the mass fraction of Ti to Al is in the range of 1.4-2.0, the mass fraction of Al+Ti+Nb+Ta is in the range of 11.8-16%, the ratio of the mass fraction of (Ti+Nb+Ta)/Al is in the range of 2.5-4.5, and the mass fraction of Mo+W is in the range of 5.5-6.3%.

In the application, the ratio of the mass fraction of (Ti+Nb+Ta)/Al is in the range of 2.5-4.5 by improving the ratio of Ti/Al to 1.4-2.0, thereby promoting eta phase (Ni) ₃ Ti), controlling the total amount of Ti+Al+Nb+Ta to ensure the gamma' -phase content to be more than 40%, maintaining the precipitation strengthening level, reasonably adjusting the content of solid solution strengthening elements such as W, mo, and strengthening the matrixThe brittle harmful phase is not separated out at the same time, the content of the oxidation resistant element Cr is controlled at an effective level, and the effects of strengthening the grain boundary and purifying the grain boundary are realized through the addition of trace elements such as C, B, zr and the like.

The preparation method of the large-size ETA phase reinforced superalloy adopts the superalloy prealloy powder with the proportion, and the preparation process is as follows: the prealloyed powder is put into a hot extrusion sheath for vacuum sealing and heating, and then is put into an extrusion die for hot extrusion, and then air-cooled to room temperature to obtain a hot extrusion bar; and removing the sheath from the hot extrusion bar and performing heat treatment to obtain the high-temperature alloy product.

Wherein, in order to obtain ideal alloy structure, the heat treatment process is as follows: the hot extrusion bar is air cooled to 720 ℃ to 760 ℃ after heat preservation for 1.5 to 2.5 hours at 1180 ℃ to 1200 ℃, and then is cooled along with a furnace after heat preservation for 22 to 24 hours at 720 ℃ to 760 ℃.

In this embodiment, the solution treatment temperature is controlled between 1180 ℃ and 1200 ℃, and appropriate heat preservation time is added to ensure precipitation of large-size eta phase, so as to promote re-dissolution of the initial large-size gamma ' phase and re-precipitation of the small-size gamma ' phase, and when the temperature exceeds the temperature, the crystal grains grow abnormally, and are lower than the temperature, thereby being unfavorable for precipitation of the large-size eta phase, and the gamma ' phase is difficult to re-dissolve and re-precipitate the fine-size secondary gamma ' phase and the subsequent tertiary gamma ' phase. The aging treatment temperature is controlled between 720 ℃ and 760 ℃, and proper heat preservation time is added, so that the fine tertiary gamma' phase can be fully separated out. While temperatures above this may lead to growth of the gamma prime phase and precipitation of other deleterious phases, temperatures below this may lead to tertiary fine gamma prime phases that are difficult to sufficiently precipitate.

The present application will be described in detail with reference to specific examples

Example 1

A preparation method of large-size ETA phase strengthening superalloy comprises the steps of loading prealloy powder with granularity of 15-53 micrometers into a hot extrusion sheath with diameter of 96mm and height of about 230mm, performing vacuum air suction seal welding, placing the prealloy powder into an extrusion die with extrusion temperature of 1120-1140 ℃ and extrusion ratio of 15:1-17 for hot extrusion, performing air cooling to room temperature to obtain a hot extrusion bar with diameter of about 24mm, removing the sheath of the hot extrusion bar, performing air cooling to 750 ℃ after heat preservation at 1180 ℃ for 2 hours, performing furnace cooling after heat preservation at 750 ℃ for 24 hours, and obtaining the superalloy; wherein, the weight percentage of each element in the prealloyed powder is as follows:

al2.7%, ti4.1%, cr12.5%, co13.3%, nb3.3%, mo3.0%, ta3.1%, W3.2%, C0.05%, B0.01%, sc 0.01%, and Ni in balance.

The obtained material structure is shown in figures 1 and 2, the grain size of the matrix phase is 14 μm, the white color is eta phase in the figure, the average size of the length direction of the size is 45 μm, the volume fraction of the whole eta phase is 12%, the average size of the gamma' phase is 185nm, and the volume fraction is 45%.

In addition, as can be seen from fig. 1, the η phase is divided into two forms of a plate form and a needle form, and the needle-like η phase with a part of larger size (the length is greater than the grain size of the matrix phase, and the width is far smaller than the grain size of the matrix phase, such as the needle-like η phase with the length of 35 μm and the width of 1 μm) can penetrate and string two or more grains across the grains, so that the pinning effect on the grain boundary is obvious, the grain boundary is difficult to slip and slide and deform under the action of external stress, and the effects of strengthening and pinning the grain boundary are realized, so that the alloy has excellent high temperature resistance.

Example 2

Unlike example 1, the prealloyed powder in this example has the following composition: al3.3%, ti4.8%, cr10.6%, co18.0%, nb3.0%, mo2.9%, ta4.6%, W3.0%, C0.04%, B0.01%, sc 0.01%, and the balance Ni.

In the obtained material structure, the grain size of the matrix phase is 15 mu m, the eta phase is equally divided into two forms of a sheet shape and a needle shape, the average size of the whole eta phase in the length direction is about 40 mu m, the volume fraction is about 10%, the size of the gamma' phase is 185nm, and the volume fraction is 43%.

Example 3

Unlike example 1, the prealloyed powder in this example has the following composition: al2.6%, ti5%, cr11.8%, co13.1%, nb3.2%, mo2.8%, ta3.3%, W2.9%, C0.03%, B0.01%, hf 0.01%, and the balance Ni.

In the obtained material structure, the grain size of the matrix phase is 16 mu m, the eta phase is divided into two forms of a sheet form and a needle form, the average size of the eta phase in the length direction is 40 mu m, the volume fraction is about 13%, the size of the gamma' phase is 152nm, and the volume fraction is 41%.

Example 4

Unlike example 1, the hot extruded bar was de-jacketed, air cooled to 730 ℃ after maintaining the temperature at 1200 ℃ for 2.5 hours, and then furnace cooled after maintaining the temperature at 730 ℃ for 22 hours.

In the obtained material structure, the grain size of the matrix phase is 25 mu m, the eta phase is divided into two forms of a sheet form and a needle form, the average size of the eta phase in the length direction is 48 mu m, the volume fraction is about 12%, the size of the gamma' phase is 180nm, and the volume fraction is 45%.

Comparative example 1

Unlike example 1, the composition of the prealloyed powder in this comparative example was: al2.5%, ti6%, cr16%, co15%, nb0%, mo3.0%, ta0%, W1.3%, C0.05%, B0.01%, sc 0.01%, and Ni in balance.

As in the material structure obtained in FIG. 3, the grain size of the matrix phase is 27 μm, and since (Ti+Nb+Ta)/Al is less than 2.5, no eta phase is precipitated in the structure, and gamma' phase is the only strengthening phase, the average size is 220nm, and the volume fraction is 50%.

Comparative example 2

Unlike example 1, the composition of the prealloyed powder in this comparative example was: al3.5%, ti2.5%, cr13%, co8%, nb3.5%, mo3.5%, ta0%, W3.5%, C0.06%, B0.01%, sc 0.01%, and the balance Ni. The material structure obtained in fig. 4 shows a harmful white TCP phase such as sigma phase and mu phase, because the content of refractory elements such as W, mo is too high, when the mass fraction of mo+w is more than 6.3wt%, the harmful compatibility is easy to separate out, and the tissue stability is reduced.

Comparative example 3

Unlike example 1, the comparative example removed the sheath from the hot extruded bar, and then air cooled to 650 c after 2 hours of incubation at 1150 c, and then cooled with the oven after 22 hours of incubation at 650 c. In the obtained material structure, the grain size of the matrix phase is 20 mu m, the length direction size of the platy or acicular phase is eta phase only about 4 mu m, because the processing temperature is lower, eta phase cannot be separated out and grow up, the volume fraction is about 7%, the size of the gamma' phase is 130nm, and the volume fraction is 40%.

The mechanical properties of the alloy of the examples were analyzed to be better than those of the alloy of the comparative examples in terms of tensile properties at room temperature and high temperature, as shown in tables 1 and 2. This is because the conventional superalloy is reinforced only by the γ' phase, and it is difficult to achieve the effect of cross-scale coupling reinforcement. And the gamma '-phase is less than micron in size, fine gamma' -phase can be redissolved in the matrix at high temperature, then the precipitation strengthening effect is lost, and the large-size eta phase difficult to redissolve can continuously block the movement of grain boundaries and dislocation, so that the effects of strengthening and pinning the grain boundaries by the particles are realized, and therefore, the performance advantage of the alloy of the embodiment at high temperature can be more obvious.

Table 1 room temperature tensile properties of example alloys and comparative alloys prepared by powder metallurgy process

Table 2 tensile properties at 650 ℃ of example alloys and comparative alloys prepared by powder metallurgy process

The above examples are only illustrative of the application and are not intended to be limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. Nor is it necessary or impossible to exhaust all embodiments herein. And obvious variations or modifications thereof are contemplated as falling within the scope of the present application.

Claims

1. A large-size ETA phase strengthening superalloy is characterized in that: in phase composition, the superalloy comprises a matrix, a gamma prime phase, and an eta phase; wherein,,

the grain size of the matrix is 10-30 mu m, the gamma 'phase is dispersed in the matrix, and the size of the gamma' phase is 30-200 nm; the eta phase is uniformly distributed in the matrix, the average length of the eta phase is 30-50 mu m, and the distribution form of the eta phase is divided into needle-shaped and sheet-shaped.

2. The large-size ETA phase strengthened superalloy of claim 1, wherein: the volume fraction of the gamma' -phase is 40% -50%, and the volume fraction of the eta-phase is 8% -12%.

3. The large-size ETA phase strengthened superalloy of claim 1 or 2, wherein: in terms of component composition, the high-temperature alloy comprises the following elements in percentage by weight:

4. A large-size ETA phase strengthened superalloy as claimed in claim 3, wherein:

the ratio of the mass fraction of Ti to Al is in the range of 1.4-2.0;

the mass fraction of Al+Ti+Nb+Ta is in the range of 11.8-16%;

the ratio of the mass fraction of (Ti+Nb+Ta)/Al is in the range of 2.5 to 4.5;

the mass fraction of Mo+W is in the range of 5.5-6.3%.

5. The large-size ETA phase strengthened superalloy of claim 1, wherein: the rare earth element is one or a combination of Zr, hf, sc, la or Y.

6. The method for preparing the large-size ETA-phase reinforced superalloy according to any of claims 1 to 5, comprising the steps of placing prealloyed powder into a hot extrusion sheath, heating the prealloyed powder in a vacuum sealing manner, placing the prealloyed powder into an extrusion die for hot extrusion, and air-cooling the prealloyed powder to room temperature to obtain a hot extrusion bar; removing the sheath from the hot extrusion bar and performing heat treatment to obtain a high-temperature alloy product; wherein,,

7. The method of manufacturing according to claim 6, wherein: the extrusion temperature of the hot extrusion bar is 1120-1140 ℃, and the extrusion ratio is 15:1-17:1.

8. The method of manufacturing according to claim 7, wherein: the prealloyed powder is put into a stainless steel sheath with the diameter of 96mm and the height of 230mm, and the stainless steel sheath is subjected to air suction sealing welding at 400 ℃.

9. The method of manufacturing according to claim 8, wherein: the diameter of the hot extruded rod is about 24mm.

10. The method of manufacturing according to claim 6, wherein: the prealloyed powder adopts gas atomization powder with the granularity of 15-53 microns.