CN115846403B - A cobalt-based alloy with a long rod-like phase structure with a large number of stacking faults and deformation nano-twins and its preparation method - Google Patents

Abstract

The invention discloses a cobalt-based alloy with a large number of faults and long rod-shaped phase structures of deformed nanometer twin crystals and a preparation method thereof, belonging to the technical field of MP159 cobalt-based superalloy forming processing and heat treatment. The cobalt-based alloy is an MP159 superalloy plate, and the preparation method comprises the following steps: heating and preserving heat of the MP159 high-temperature alloy plate, and then cooling to room temperature by water; soaking the heat-treated MP159 high-temperature alloy plate in liquid nitrogen, and performing cryogenic rolling; and (5) carrying out aging heat treatment on the MP159 high-temperature alloy plate after rolling, and then air-cooling to room temperature. The long rod-shaped gamma 'strengthening phase with a large amount of faults and deformation nanometer twin crystals is prepared in the MP159 high-temperature alloy through a preparation process of liquid nitrogen cryogenic rolling and aging heat treatment, and the long rod-shaped gamma' strengthening phase with a large amount of faults and deformation nanometer twin crystals can remarkably improve the hot corrosion resistance of the MP159 high-temperature alloy.

Description

A cobalt-based alloy with a long rod-like phase organization with a large number of stacking faults and deformation nanotwins Gold and its preparation method

technical field

The invention relates to a cobalt-based alloy with a long rod-like phase structure with a large number of stacking faults and deformation nano-twins and a preparation method thereof, belonging to the technical field of MP159 cobalt-based superalloy forming, processing and heat treatment.

Background technique

Due to its high strength, good ductility and excellent corrosion resistance, MP159 superalloy is widely used in the manufacture of ultra-high-strength bolt fasteners in aerospace and other fields. However, during space service, it will still be affected by the harsh and complex environment such as high temperature and high pressure generated by aero-engines and sodium, sulfur, and chlorides generated by fuel combustion. Therefore, further improving the corrosion resistance of MP159 cobalt-based superalloy is a key engineering problem to be solved in the aerospace field.

MP159 superalloy is a cobalt-based superalloy strengthened by cold deformation, and its strengthening method is mainly strengthened by precipitation of γ′ strengthening phase through cold deformation + aging heat treatment. At present, a lot of research work is only devoted to improving the mechanical properties of MP159 superalloy. For example, Cai Yeqing and others have studied that the cold drawing process can significantly improve the mechanical properties of the alloy, and its ultimate tensile strength has increased by 75% compared with the initial solid solution state. , Jia Yuhao and others strengthened the alloy plate through cold rolling + aging process, in which the tensile strength and elongation at room temperature could reach 1.8GPa and 12.5% respectively. With the rapid development of the aerospace field, the requirements for the hot corrosion resistance of MP159 superalloy are getting higher and higher. But there are few literature reports on how to improve the high temperature corrosion resistance of MP159 superalloy. In recent years, some literatures have reported that the γ′ phase with crystal defects can not only improve the mechanical properties of IN718 superalloy, but also improve the hot corrosion resistance of IN718 superalloy. However, there is no document reporting how to prepare the γ′-strengthened phase with crystal defects in the MP159 superalloy. Therefore, how to prepare a strengthening phase with a large number of crystal defects through a simple preparation process to improve the hot corrosion resistance of MP159 superalloy is particularly critical.

Contents of the invention

In view of the problems and deficiencies in the above-mentioned prior art, the present invention provides a cobalt-based alloy with a long rod-like phase structure with a large number of stacking faults and deformation nano-twins and its preparation method, that is, cryogenic rolling with liquid nitrogen + aging The preparation process of heat treatment produces a long rod-shaped γ′ strengthening phase with a large number of stacking faults and deformation nano-twins in the MP159 superalloy. This long rod-shaped γ′ strengthening phase with a large number of stacking faults and deformation nano-twins can significantly improve MP159 Hot corrosion resistance of superalloys.

To achieve the above object, the present invention provides the following scheme:

The present invention proposes a method for preparing a cobalt-based alloy with a long rod-like phase structure with a large number of stacking faults and deformation nano-twins. The cobalt-based alloy is an MP159 superalloy plate, and its chemical composition is: Co 35.7wt%, Ni25 .5wt%, Cr 19.0wt%, Fe 9.0wt%, Mo 7.0wt%, Ti 3.0wt%, Nb0.6wt% and Al balance; preparation method comprises the following steps:

(1) Solution treatment: heat and keep warm the MP159 superalloy plate, and then water-cool to room temperature;

(2) Cryogenic rolling: soak the MP159 superalloy plate processed in step (1) in liquid nitrogen, and carry out cryogenic rolling;

(3) Aging treatment: The MP159 superalloy plate rolled in step (2) is subjected to aging heat treatment, and then cooled to room temperature.

Further, in step (3), the temperature of the aging heat treatment is 800°C, and the holding time is 2-25h.

Further, in step (1), heat to 1050° C. and keep the temperature for 4 hours.

Further, in step (2), soak in liquid nitrogen for 15 minutes.

Further, in step (2), the cryogenic rolling is carried out in a multi-pass rolling manner, and after each pass of rolling is completed, it is quickly soaked in liquid nitrogen for 10 minutes, and then the next pass of rolling is performed.

Further, the reduction in each pass is 10% of the original thickness of the MP159 superalloy plate.

Further, in step (2), the deformation of the MP159 superalloy plate after cryogenic rolling is 48% of the original thickness.

The present invention also provides a cobalt-based alloy with a large number of stacking faults and a long rod-like phase structure of deformation nano-twins prepared by the above-mentioned preparation method.

The invention discloses the following technical effects:

(1) The present invention not only refines the crystal grains of the MP159 superalloy plate through cryogenic rolling, but also can greatly increase the dislocation density inside the alloy, as well as high-density stacking faults and deformation nano-twins. Compared with the ordinary room temperature rolling process, under the same conditions, the cryogenic rolling + aging heat treatment preparation process adopted in the present invention can prepare long rod-shaped γ′ strengthening phases with a large number of stacking faults and deformation nano-twins in the MP159 superalloy , during the hot corrosion process, the long rod-shaped γ′ phase with a large number of stacking faults and deformation nano-twins can be used as an effective channel for elements to diffuse outward from the matrix, forming a smoother and denser oxide film on the surface of the alloy, thereby significantly improving the high temperature of MP159. Hot corrosion resistance of alloy plates.

(2) The process of the present invention is simple, easy to operate, and is suitable for large-scale popularization and production.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required in the embodiments. Obviously, the accompanying drawings in the following description are only some of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without paying creative labor.

Fig. 1 is the TEM microstructure diagram of the MP159 superalloy plate treated in Example 1; where (a) is the bright-field image of the rod-shaped γ′ phase precipitated after aging for 2 h, and (b) is the enlargement of the area of (a) In the figure, the small picture in the upper left corner of (b) is the selected area electron diffraction spot in this area, and (c) is the high-resolution microstructure picture of the rod-shaped γ′ phase transmission;

Fig. 2 is the EDS elemental distribution figure of the MP159 superalloy sheet material after processing in Example 1;

Fig. 3 is the transmission electron microscope microstructural figure of the MP159 superalloy sheet material after processing in embodiment 2;

Fig. 4 is the EDS elemental distribution figure of the MP159 superalloy sheet material after processing in embodiment 2;

Fig. 5 is the transmission electron microscope microstructural figure of the MP159 superalloy plate after comparative example 1 processing;

Fig. 6 is the EDS elemental distribution diagram of the MP159 superalloy plate after the treatment of Comparative Example 1;

Figure 7 is a transmission electron microscope microstructure diagram of the MP159 superalloy plate treated in Comparative Example 2, where (a) is the precipitated phase after aging, (b) is the enlarged picture of the precipitated phase, and (c) is the selected area of the precipitated phase Electron diffraction pattern, the small picture in the upper right corner of (c) is the selected area electron diffraction spot in this area;

Fig. 8 is the MP159 superalloy plate mass loss in the embodiment 2 and comparative example 2 along with the change figure of hot corrosion time, (a) is the overall change figure, (b) is the second stage change figure;

Figure 9 is a cross-sectional transmission electron microscope microstructure diagram of the alloy sample of Example 2 of the present invention after the fifth cycle at 800°C;

Figure 10 is a cross-sectional EDS image of the alloy sample of Example 2 of the present invention after the fifth cycle at 800°C;

Fig. 11 is the cross-sectional transmission electron microscope microstructure diagram of the comparative example 2 alloy sample of the present invention after the 5th cycle at 800°C;

Fig. 12 is a cross-sectional EDS image of the alloy sample of Comparative Example 2 of the present invention after the fifth cycle at 800°C.

Detailed ways

Various exemplary embodiments of the present invention will now be described in detail. The detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features and embodiments of the present invention.

It should be understood that the terminology described in the present invention is only used to describe specific embodiments, and is not used to limit the present invention. In addition, regarding the numerical ranges in the present invention, it should be understood that each intermediate value between the upper limit and the lower limit of the range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated value or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded from the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only the preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and/or materials in connection with which the documents are described. In case of conflict with any incorporated document, the contents of this specification control.

It will be apparent to those skilled in the art that various modifications and changes can be made in the specific embodiments of the present invention described herein without departing from the scope or spirit of the present invention. Other embodiments will be apparent to the skilled person from the description of the present invention. The description and examples of the invention are illustrative only.

As used herein, "comprising", "comprising", "having", "comprising" and so on are all open terms, meaning including but not limited to.

The embodiment of the present invention proposes a method for preparing a cobalt-based alloy with a long rod-like phase structure with a large number of stacking faults and deformation nano-twins. The cobalt-based alloy is an MP159 superalloy plate, and its chemical composition is: Co 35.7wt% , Ni25.5wt%, Cr 19.0wt%, Fe9.0wt%, Mo 7.0wt%, Ti 3.0wt%, Nb0.6wt% and Al balance; The preparation method comprises the following steps:

(1) Solution treatment: heat and keep warm the MP159 superalloy plate, and then water-cool to room temperature;

(2) Cryogenic rolling: soak the MP159 superalloy plate processed in step (1) in liquid nitrogen, and carry out cryogenic rolling;

(3) Aging treatment: The MP159 superalloy plate rolled in step (2) is subjected to aging heat treatment, and then cooled to room temperature.

In the embodiment of the present invention, in step (3), the temperature of the aging heat treatment is 800°C, and the holding time is 2-25h.

In the embodiment of the present invention, in step (1), heat to 1050° C. and keep the temperature for 4 hours.

In the embodiment of the present invention, in step (2), soak in liquid nitrogen for 15 minutes.

In the embodiment of the present invention, in step (2), the deep-cold rolling adopts multi-pass rolling method for rolling, and after each pass of rolling, quickly put it into liquid nitrogen and soak for 10 minutes, and then proceed to the next pass of rolling.

In the embodiment of the present invention, the reduction in each pass is 10% of the original thickness of the MP159 superalloy plate.

In the embodiment of the present invention, in step (2), the deformation of the MP159 superalloy plate after cryogenic rolling is 48% of the original thickness.

The embodiment of the present invention also provides a cobalt-based alloy with a long rod-like phase structure with a large number of stacking faults and deformation nano-twins prepared by the above preparation method.

The MP159 superalloy plate in the embodiment of the present invention was purchased from Guizhou Aerospace Precision Manufacturing Co., Ltd.

The technical solution of the present invention will be further described below through examples.

Example 1

(1) Solution treatment: Put the MP159 superalloy plate into a muffle furnace and heat it from room temperature to 1050 °C at a heating rate of 10 °C/min with the furnace, keep it for 4 hours, and then water cool to room temperature.

(2) Cryogenic rolling: Pour liquid nitrogen into the iron tank. After the vaporization of liquid nitrogen is stable, MP159 superalloy plates with a length, width and thickness of 100mm, 50mm and 6mm respectively processed in step (1) Soak in liquid nitrogen for 15 minutes;

Apply lubricating oil on the surface of the rolls of the rolling mill, turn on the rolling mill, set the roll speed to 0.5m/min, and after the rolls rotate evenly, take the MP159 superalloy plate out of the liquid nitrogen, and roll it in 5 passes. The amount of deformation in each pass is 10% of the original plate thickness. After each pass of rolling, quickly put the rolled sample into liquid nitrogen for immersion. The soaking time is 10 minutes. After the immersion, proceed to the next pass of rolling Deformation; until the total deformation reaches 48% of the original plate thickness of MP159 superalloy.

(3) Aging treatment: put the MP159 superalloy plate rolled in step (2) into a muffle furnace at 800°C, keep it warm for 2 hours, and then air-cool to room temperature.

The transmission electron microscope microstructure diagram of the MP159 superalloy plate treated in Example 1 of the present invention is shown in Figure 1, wherein (a) is the bright field image of the rod-shaped γ′ phase precipitated after aging for 2h, and (b) is (a) The enlarged view of the area, (b) the small image in the upper left corner is the selected area electron diffraction spot of this area, (c) is the high-resolution microstructure image of the rod-shaped γ′ phase transmission; the EDS element distribution map is shown in Figure 2. It can be seen from Figure 1 and Figure 2 that long rod-shaped precipitates have begun to form inside the MP159 superalloy plate. The rod-like phase was determined to be the γ' phase with L12 superlattice by the selected area electron diffraction technique. The distribution of alloying elements in the long rod-shaped γ′ phase was analyzed by TEM-EDS technology, mainly including Ti, Ni, Co and Cr elements. Through high-resolution transmission structure analysis, it can be seen that a large number of stacking faults and deformation nano-twins are generated inside this kind of precipitated phase.

Example 2

(1) Solution treatment: Put the MP159 superalloy plate into a muffle furnace and heat it from room temperature to 1050 °C at a heating rate of 10 °C/min with the furnace, keep it for 4 hours, and then water cool to room temperature.

(2) Cryogenic rolling: Pour liquid nitrogen into the iron tank. After the vaporization of liquid nitrogen is stable, MP159 superalloy plates with a length, width and thickness of 100mm, 50mm and 6mm respectively processed in step (1) Soak in liquid nitrogen for 15 minutes;

Apply lubricating oil on the surface of the rolls of the rolling mill, turn on the rolling mill, set the roll speed to 0.5m/min, and after the rolls rotate evenly, take the MP159 superalloy plate out of the liquid nitrogen, and roll it in 5 passes. The amount of deformation in each pass is 10% of the original plate thickness. After each pass of rolling, quickly put the rolled sample into liquid nitrogen for immersion. The soaking time is 10 minutes. After the immersion, proceed to the next pass of rolling Deformation; until the total deformation reaches 48% of the original plate thickness of MP159 superalloy.

(3) Aging treatment: put the MP159 superalloy plate rolled in step (2) into a muffle furnace at 800°C, keep it warm for 25 hours, and then air-cool to room temperature.

The transmission electron microscope microstructure diagram of the MP159 superalloy plate treated in Example 2 of the present invention is shown in FIG. 3 , and the EDS element distribution diagram is shown in FIG. 4 . It can be seen from Figure 3 and Figure 4 that with the increase of aging time, the number of long rod-like γ′ phases inside the cryogenically rolled 48% MP159 superalloy plate is increasing, and the shape gradually becomes long rod-like. -EDS structure analysis shows that there are a large number of stacking faults and deformation nano-twins inside the long rod-shaped γ′-strengthened phase obtained by long-time aging.

Comparative example 1

(1) Solution treatment: Put the MP159 superalloy plate into a muffle furnace and heat it from room temperature to 1050 °C at a heating rate of 10 °C/min with the furnace, keep it for 4 hours, and then water cool to room temperature.

(2) Cryogenic rolling: Pour liquid nitrogen into the iron tank. After the vaporization of liquid nitrogen is stable, MP159 superalloy plates with a length, width and thickness of 100mm, 50mm and 6mm respectively processed in step (1) Soak in liquid nitrogen for 15 minutes;

Apply lubricating oil on the surface of the rolls of the rolling mill, turn on the rolling mill, set the roll speed to 0.5m/min, and after the rolls rotate evenly, take the MP159 superalloy plate out of the liquid nitrogen, and roll it in 5 passes. The amount of deformation in each pass is 10%-15% of the original plate thickness. After each pass of rolling, quickly put the rolled sample into liquid nitrogen for immersion. The soaking time is 10-15min. After the immersion, proceed to the next One rolling deformation; until the total deformation reaches 48% of the original plate thickness of the MP159 superalloy.

(3) Aging treatment: put the MP159 superalloy plate rolled in step (2) into a muffle furnace at 800°C, keep it warm for 0.5h, and then air-cool to room temperature.

The transmission electron microscope microstructure diagram of the MP159 superalloy plate treated in Comparative Example 1 of the present invention is shown in FIG. 5 , and the EDS element distribution diagram is shown in FIG. 6 . It can be seen from Figure 5 and Figure 6 that there is no precipitated phase in the alloy, and all elements are evenly distributed.

Comparative example 2

Ordinary room temperature rolling process for MP159 superalloy plate:

(1) Solution treatment: Put the MP159 superalloy plate into a muffle furnace and heat it from room temperature to 1050 °C at a heating rate of 10 °C/min with the furnace, keep it for 4 hours, and then water cool to room temperature.

(2) Rolling at room temperature: the surface of the roll of the rolling mill is coated with lubricating oil, the rolling mill is turned on, and the roll speed is set to 0.5m/min; 50mm and 6mm MP159 superalloy plates were rolled and deformed. The total rolling deformation is 48% of the original plate thickness of MP159 superalloy, rolling is divided into 5 passes, and the deformation amount of each pass is 10% of the original plate thickness, until the total deformation reaches 48% of the original plate thickness of MP159 superalloy %, to obtain an MP159 superalloy plate with a rolling deformation of 48% at room temperature.

(3) Aging treatment: put the MP159 superalloy plate rolled in step (2) into a muffle furnace at 800°C, keep it warm for 25 hours, and then air-cool to room temperature.

The transmission electron microscope microstructure diagram of the MP159 superalloy plate treated in Comparative Example 2 of the present invention is shown in Figure 7, wherein (a) is the precipitated phase after aging, (b) is the enlarged picture of the precipitated phase, and (c) is the precipitated phase The selected area electron diffraction pattern of the phase, the small picture in the upper left corner of (c) is the selected area electron diffraction pattern of this area, in order to prove the composition of the phase in this area. It can be seen from Figure 7 that the precipitated phase in the alloy is in the shape of short rods, and the selected area electron diffraction spots prove that its structure is still the L12 superlattice γ′ phase, but there are no diffraction spots of nano twins and stacking faults.

Performance Testing

In order to test its corrosion resistance, the long rod-shaped γ′ strengthening phase with a large number of stacking faults and deformation nano-twins precipitated after aging for 25 hours was compared with the short rod-shaped γ′ without nano-twins precipitated after aging for 25 h. The MP159 superalloy plate after the treatment of example 2 is subjected to the hot corrosion resistance test, and the salt solution (75wt% _Na2SO4 +25wt%NaCl) is evenly sprayed on the alloy sample ( _embodiment 2 and comparative example 2) by the salt solution spraying method After treatment, the surface of the MP159 high-temperature alloy plate) is weighed until the deposition rate reaches 6-6.5 mg/cm ² . Put the sample with attached salt into a muffle furnace at 800°C for heat preservation. Take 5h as a cycle, and after each cycle, the sample is taken out of the furnace and air-cooled to room temperature. The cooling rate was 2.5°C/min. In order to obtain the net weight change of the MP159 superalloy plate, the sample was ultrasonically cleaned in acetone for 15 minutes, and the alloy sample after ultrasonic cleaning was weighed with a precision balance. In the next hot corrosion cycle, the salt layer was deposited on the surface of the alloy sample again until 50h, that is, 10 cycles, and then air-cooled to room temperature.

(a) in Fig. 8 is the overall change diagram of mass loss of MP159 superalloy plate in Example 2 and Comparative Example 2 with hot corrosion time, (b) is the MP159 high temperature in Example 2 and Comparative Example 2 in the second stage Alloy plate mass loss with hot corrosion time change diagram (the meaning of RTR48 in the figure is room temperature rolled 48% of MP159 is comparative example 2, CR48 is cryogenically rolled 48% of MP159 is the embodiment 2). It can be seen from Figure 8 that the hot corrosion curve can be divided into three stages according to the weight loss of hot corrosion samples. In the first stage (1st to 2nd cycle), since the 48% MP159 superalloy plate cryogenically rolled at 0.5h has not yet precipitated rod-shaped γ′ strengthening phase, and the alloy sample has just begun to precipitate long rod-shaped γ′ at 2h 'strengthening phase, so it can be observed that the change trend of weight loss between the alloy samples of Comparative Example 2 and Example 2 is the same, and the difference is very small. With the prolongation of the aging time, the size of the long rod-like γ′-strengthened phase becomes thicker and the number gradually increases at 25h, and there are more stacking faults and deformation nano-twins inside it. Therefore, it can be seen that the weight loss of the alloy sample of Example 2 in the second stage (the 2nd to the 6th cycle) is always less than that of Comparative Example 2, which shows that the alloy sample of Example 2 of the present invention and the alloy of Comparative Example 2 The specimens have higher hot corrosion resistance than the samples. Especially in the 4th hot corrosion cycle, the difference in weight loss between the alloy samples of Comparative Example 2 and Example 2 is the largest, reaching 19.65 mg cm ^-2 .

In order to further confirm that the hot corrosion resistance of the alloy is related to the long rod-shaped γ′ strengthening phase precipitated after aging, Fig. 9 and Fig. 10 are the cross-sections of the alloy sample of Example 2 after the fifth cycle at 800°C and aging for 25 hours TEM microstructure and EDS images, Figure 11 and Figure 12 are the cross-sectional TEM microstructure and EDS images of the alloy sample of Comparative Example 2 after the fifth cycle at 800°C and instant aging for 25 hours. It can be seen that, compared with the room temperature rolled 48% sample (comparative example 2), the alloy sample of Example 2 of the present invention has formed a more uniform and denser oxide layer after hot corrosion. This is because the long rod-shaped γ′ strengthening phase with a large number of stacking faults and deformation nano-twins precipitated after 25 hours of cryogenic rolling. As an effective channel for alloying elements to diffuse outward from the matrix, it forms a dense oxide film on the surface of the alloy, thereby improving the hot corrosion resistance of the alloy.

The above-mentioned embodiments are only to describe the preferred mode of the present invention, and are not intended to limit the scope of the present invention. Variations and improvements should fall within the scope of protection defined by the claims of the present invention.

Claims (6)

1. The preparation method of the cobalt-based alloy with a large number of stacking faults and deformation nanometer twin crystal long rod-shaped phase structures is characterized by comprising the following steps of:

(1) Heating and preserving heat of the MP159 high-temperature alloy plate, and then cooling to room temperature by water;

(2) Immersing the MP159 high-temperature alloy plate processed in the step (1) in liquid nitrogen, and performing cryogenic rolling;

(3) Carrying out aging heat treatment on the MP159 high-temperature alloy plate rolled in the step (2), and then cooling to room temperature;

in the step (3), the temperature of the aging heat treatment is 800 ℃, and the heat preservation time is 2-25h;

in the step (2), the deformation of the MP159 superalloy sheet material after cryogenic rolling is 48% of the original thickness.

2. The method according to claim 1, wherein in the step (1), the temperature is raised to 1050℃and the temperature is kept for 4 hours.

3. The method according to claim 1, wherein in the step (2), the mixture is immersed in liquid nitrogen for 15 minutes.

4. The method according to claim 1, wherein in the step (2), the deep cold rolling is performed by multi-pass rolling, and after each pass of rolling is completed, the deep cold rolling is rapidly immersed in liquid nitrogen for 10 minutes, and then the next pass of rolling is performed.

5. The method of claim 4, wherein the reduction per pass is 10% of the original thickness of the MP159 superalloy sheet.

6. A cobalt-based alloy having a long rod-like phase structure of a plurality of layer errors and deformed nano twin crystals prepared by the preparation method of any one of claims 1 to 5.