CN112222384A

CN112222384A - Method for preparing nickel-based high-temperature alloy component by solidification under pressure

Info

Publication number: CN112222384A
Application number: CN202011156529.4A
Authority: CN
Inventors: 胡奎深; 邹鹑鸣; 王宏伟; 薛祥; 魏尊杰
Original assignee: Harbin Institute of Technology
Current assignee: Harbin Institute of Technology
Priority date: 2020-10-26
Filing date: 2020-10-26
Publication date: 2021-01-15

Abstract

A method for preparing a nickel-based superalloy component by solidification under pressure relates to a method for preparing a nickel-based superalloy component. The invention aims to solve the technical problem that the existing method for preparing the alloy by gas pressure solidification is not applicable to the nickel-based high-temperature alloy with high density and high melting point. In the invention, smelting is carried out in a vacuum environment, pouring is carried out under one atmospheric pressure, and solidification is carried out under two atmospheric pressures; two atmospheric pressures cannot be adopted during pouring, because the air entrainment and the filling resistance are feared during pouring, the pouring is further aerated and pressurized for solidification, so that the tissue is more compact; the silicate heat-insulating cotton is arranged outside the shell, so that the effect of compact tissue during solidification is achieved by matching with stress transfer in the pressurizing process.

Description

Method for preparing nickel-based high-temperature alloy component by solidification under pressure

Technical Field

The invention relates to a method for producing a nickel-base superalloy component.

Background

The nickel-based high-temperature alloy with high creep strength, thermal fatigue resistance and excellent oxidation resistance is widely applied to important fields of aerospace, ships, energy sources, automobiles and the like as an alloy used under severe conditions.

In general, the field of high-temperature alloy casting generally utilizes vacuum melting and pouring solidification technology to prepare the alloy, but the traditional technology can cause casting defects such as shrinkage cavity, slag inclusion, heat crack and the like frequently. At present, the technical development related to the solidification process control by utilizing gas pressure mainly focuses on the field of aluminum alloy, and for large thin-wall high-temperature alloy components with high quality and density and high smelting and pouring temperature, a convenient, convenient and effective gas pressure solidification method is not provided.

Through literature search, Chinese patent with application publication No. CN110026541A provides a vacuum melting and variable pressure solidification forming method for an ultrathin-wall high-air-tightness aluminum alloy piece. The smelting environment of the method is a low vacuum environment after nitrogen washing, and in the melt mold filling process, the solidification pressure of the casting is improved on the premise of ensuring the farthest end and good mold filling of the casting with different heights, so that the density of the solidified casting structure at different times is not influenced by the solidification gassing of the melt, and the internal quality of the casting at each solidification stage is ensured. However, this invention is only directed to low density and low melting point aluminum alloys, and for high density and high melting point nickel-based superalloys, this method is not applicable. The nitrogen reacts with molten metal under the high-temperature environment, so that the quality of the casting is seriously influenced, and the requirement on the strength of a mold shell is high during pouring and pressurizing due to the high density of the nitrogen; because the pressure adjustment is several times of the atmospheric pressure, the requirement on vacuum furnace equipment is high, and the production process is relatively dangerous, thus being not beneficial to popularization; the production efficiency is reduced by utilizing the nitrogen to wash in the furnace, and the nitrogen can also react with the alloy to a certain extent, so that the probability of generating impurities in the alloy is increased.

Disclosure of Invention

The invention aims to solve the problems that the existing method for preparing the alloy by gas pressure solidification is not applicable to the nickel-based high-temperature alloy with high density and high melting point, nitrogen can react with molten metal under the high-temperature environment to seriously affect the quality of a casting, and the requirement on the strength of a die shell is high during pouring and pressurizing due to the high density of the alloy; the nitrogen is utilized to reduce the production efficiency in the washing process in the furnace, and the nitrogen can also react with the alloy to a certain degree, thereby increasing the probability of generating impurities in the alloy.

The method for preparing the nickel-based superalloy component by solidification under pressure comprises the following steps:

firstly, preheating a shell to 1150-1200 ℃, then placing the shell into a metal box, placing the metal box into a vacuum induction melting furnace, then placing a master alloy ingot into a crucible, wherein the crucible is positioned in the vacuum induction melting furnace and above the shell; the upper part of the metal box is open, silicate heat-insulating cotton is arranged on the inner wall of the metal box, and the outer wall of the shell is tightly attached to the silicate heat-insulating cotton;

closing the furnace door, vacuumizing, starting the vacuum induction furnace to heat the crucible to 1470-1500 ℃ when the vacuum degree in the hearth reaches below 2.5Pa, and keeping the vacuum degree in the furnace to be 2.5-2 Pa in the heating process;

the whole process of the second step takes 45-50 min;

thirdly, when the temperature of the crucible is increased to 1470-1500 ℃, injecting inert gas into the hearth to enable the pressure inside and outside the furnace to be consistent, and keeping balance;

pouring the crucible, pouring the molten metal into the shell for pouring, continuously filling inert gas into the furnace after the pouring is finished until the pressure in the furnace is twice of the external atmospheric pressure, maintaining the pressure, naturally cooling for 25-30 min, and opening the furnace door to take out the casting.

In the invention, smelting is carried out in a vacuum environment, pouring is carried out under one atmospheric pressure, and solidification is carried out under two atmospheric pressures; two atmospheric pressures cannot be adopted during pouring, because the air entrainment and the filling resistance are feared during pouring, the pouring is further aerated and pressurized for solidification, so that the tissue is more compact, and the compactness is increased by 2-6% compared with the whole vacuum environment;

the silicate heat-insulating cotton is arranged outside the shell, so that the effect of compact tissue during solidification is achieved by matching with stress transfer in the pressurizing process.

The invention has the advantages that:

the invention adopts a vacuum induction smelting furnace, the smelting period is short, the smelting environment is a vacuum environment, and the pouring and solidifying environment is under high-purity inert gas pressure; the crucible using zirconia as a material is used as a smelting vessel, and the one-time feeding and all pouring are realized by adding a quantitative K418 master alloy ingot material, compared with the common vacuum pouring, the pressure of the casting during pouring and solidification is improved, so that the compact structure of the casting is not influenced by the solidification gassing or shrinkage cavity of the melt. The production efficiency is improved on the premise of improving the quality of the casting, the large-scale popularization and application in industrial production are easy, and the method has important significance for promoting the popularization and application of the aluminum alloy casting in the fields of aerospace and the like.

Drawings

FIG. 1 is an SEM image of a casting prepared in test one, the casting being a thin-walled sheet having a face dimension of 300mm by 400mm and a wall thickness of 3 mm;

FIG. 2 is an SEM image of a casting prepared in run two, the casting being a thin-walled sheet having a face dimension of 300mm by 400mm and a wall thickness of 3 mm;

FIG. 3 is an SEM image of a cast prepared in run one, the cast being a thin-walled sheet having face dimensions of 300mm by 400mm and a wall thickness of 5 mm;

FIG. 4 is an SEM image of a casting prepared in run two, the casting being a thin-walled sheet having face dimensions of 300mm by 400mm and a wall thickness of 5 mm;

FIG. 5 is an SEM of a casting prepared in run one, the casting being a thin-walled sheet with face dimensions of 300mm by 400mm and a wall thickness of 7 mm;

FIG. 6 is an SEM image of a casting prepared in run two, the casting being a thin-walled sheet having face dimensions of 300mm by 400mm and a wall thickness of 7 mm;

FIG. 7 is an SEM of a cast prepared according to run one, the cast being a thin-walled sheet having face dimensions of 300mm by 400mm and a wall thickness of 9 mm;

FIG. 8 is an SEM of a casting made in run two, which was a thin-walled sheet with face dimensions of 300mm by 400mm and a wall thickness of 9 mm;

FIG. 9 is a graph of density increase data for thin-walled sheet members of different thicknesses as compared to test one and test two;

FIG. 10 is a graph of microhardness increase data for thin-walled sheet members of different thicknesses as compared to test one and test two.

Detailed Description

The first embodiment is as follows: the embodiment is a method for preparing a nickel-based superalloy component by solidification under pressure, which comprises the following steps:

the whole process of the second step takes 45-50 min;

The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: the master alloy ingot in the step one is nickel-based superalloy. The rest is the same as the first embodiment.

The third concrete implementation mode: the second embodiment is different from the first embodiment in that: the grade of the nickel-based superalloy in the step one is K418. The rest is the same as the second embodiment.

The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: the vacuum induction smelting furnace in the step one is an intermittent vacuum induction smelting furnace with the model of ZG-0.05. The rest is the same as one of the first to third embodiments.

The fifth concrete implementation mode: the fourth difference between this embodiment and the specific embodiment is that: in step one, the shell is preheated to 1150 ℃. The rest is the same as the fourth embodiment.

The sixth specific implementation mode: the fifth embodiment is different from the fifth embodiment in that: and step two, starting the vacuum induction furnace to heat the crucible to 1470 ℃. The rest is the same as the fifth embodiment.

The seventh embodiment: the sixth embodiment is different from the sixth embodiment in that: and in the third step, when the temperature of the crucible is increased to 1470 ℃, starting to inject inert gas into the hearth so as to ensure that the air pressure inside and outside the furnace is consistent and the balance is kept. The rest is the same as the sixth embodiment.

The specific implementation mode is eight: the seventh embodiment is different from the seventh embodiment in that: the inert gas in the third step is argon. The rest is the same as the seventh embodiment.

The specific implementation method nine: the eighth embodiment is different from the eighth embodiment in that: the inert gas in the fourth step is argon. The rest is the same as the embodiment eight.

The detailed implementation mode is ten: the present embodiment differs from the ninth embodiment in that: the casting prepared in the fourth step is a thin-wall plate with the surface size of 300mm multiplied by 400mm and the wall thickness of 3mm, 5mm, 7mm or 9 mm. The rest is the same as in the ninth embodiment.

The invention was verified with the following tests:

test one: the test is a method for preparing a nickel-based high-temperature alloy component by solidification under pressure, and specifically comprises the following steps:

firstly, preheating a shell to 1150 ℃, then placing the shell into a metal box, placing the metal box into a vacuum induction melting furnace, then placing a master alloy ingot into a crucible, wherein the crucible is positioned in the vacuum induction melting furnace and above the shell; the upper part of the metal box is open, silicate heat-insulating cotton is arranged on the inner wall of the metal box, and the outer wall of the shell is tightly attached to the silicate heat-insulating cotton;

the master alloy ingot in the step one is nickel-based superalloy with the mark of K418;

the vacuum induction smelting furnace in the step one is an intermittent vacuum induction smelting furnace with the model ZG-0.05;

closing the furnace door, vacuumizing, starting the vacuum induction furnace to heat the crucible to 1470 ℃ when the vacuum degree in the hearth reaches below 2.5Pa, and keeping the vacuum degree in the furnace to be 2Pa in the heating process;

the whole process of the second step takes 45 min;

thirdly, when the temperature of the crucible is increased to 1470 ℃, starting to inject inert gas into the hearth to ensure that the air pressure inside and outside the furnace is consistent, and keeping balance; the inert gas in the third step is argon;

pouring the crucible, pouring the molten metal into the shell for pouring, continuously filling inert gas into the furnace after the pouring is finished until the pressure in the furnace is twice of the atmospheric pressure outside the furnace, maintaining the pressure, naturally cooling for 30min, and opening the furnace door to take out the casting;

the inert gas in the fourth step is argon.

And (3) repeating the process of the first test to prepare castings with different sizes, wherein the castings prepared in the fourth step are thin-wall plates, the surface sizes of the thin-wall plates are 300mm multiplied by 400mm, and the wall thicknesses of the thin-wall plates are 3mm, 5mm, 7mm and 9mm respectively.

And (2) test II: the test is a method for preparing a nickel-based high-temperature alloy component by vacuum solidification, and is specifically carried out according to the following steps:

firstly, preheating a shell to 1150 ℃, then placing the shell into a vacuum induction melting furnace, and then placing a master alloy ingot into a crucible which is positioned in the vacuum induction melting furnace and above the shell;

the whole process of the second step takes 45 min;

pouring the crucible, pouring the molten metal into the shell for pouring, maintaining the pressure, naturally cooling for 30min, and opening the furnace door to take out the casting; the vacuum degree in the furnace is maintained to be 2 Pa;

and (3) repeating the process of the second test to prepare castings with different sizes, wherein the castings prepared in the third step are thin-wall plates, the surface sizes of the thin-wall plates are 300mm multiplied by 400mm, and the wall thicknesses of the thin-wall plates are 3mm, 5mm, 7mm and 9 mm.

FIG. 1 is an SEM image of a cast prepared in run one, the cast being a thin-walled sheet having face dimensions of 300mm by 400mm and a wall thickness of 3 mm.

FIG. 2 is an SEM image of a cast prepared in run two, which was a thin-walled sheet with face dimensions of 300mm by 400mm and a wall thickness of 3 mm.

FIG. 3 is an SEM image of a cast prepared in run one, the cast being a thin-walled sheet with face dimensions of 300mm by 400mm and a wall thickness of 5 mm.

FIG. 4 is an SEM of a cast product prepared in run two, which was a thin-walled sheet having a face dimension of 300mm by 400mm and a wall thickness of 5 mm.

FIG. 5 is an SEM of a cast prepared according to test one, the cast being a thin-walled sheet having a face dimension of 300mm by 400mm and a wall thickness of 7 mm.

FIG. 6 is an SEM of a cast product prepared in run two, which was a thin-walled sheet having a face dimension of 300mm by 400mm and a wall thickness of 7 mm.

FIG. 7 is an SEM of a cast prepared according to test one, the cast being a thin-walled sheet having a face dimension of 300mm by 400mm and a wall thickness of 9 mm.

FIG. 8 is an SEM of a cast product prepared in run two, which was a thin-walled sheet having a face dimension of 300mm by 400mm and a wall thickness of 9 mm.

From fig. 1 to 8, it can be observed that the macroscopic structures of the thin-wall castings of 3mm to 9mm solidified under the gas pressure have densification phenomena of different degrees, particularly the structures of the thin-wall castings of 7mm are changed more obviously, the shrinkage cavities and the shrinkage porosity are reduced obviously, the dendritic crystals are finer, the sizes of eutectic structures among the dendrites are reduced, the quantity of the eutectic structures is increased, and the distribution is more uniform.

FIG. 10 is a plot of microhardness increase data for thin-walled sheet members of different thicknesses as compared to test one and test two;

for casting, the denser the hardness the better, and it can be seen from fig. 9 and 10 that the gas pressure effect of test one is significantly better than that of test two in a vacuum environment.

Table 1 shows the room temperature tensile strength and plasticity of the wall panels of different thicknesses at different pressures, and it can be seen that the tensile strength and elongation of the thin-walled castings of different sizes solidified at the air pressure of test one are significantly improved compared with the vacuum environment of test two.

TABLE 1

Table 2 shows that the tensile strength of the wall plates with different thicknesses at different pressures in the environment of 900 ℃, and it can be seen that the high-temperature tensile strength of the thin-wall castings with different sizes solidified under the air pressure of the first test and the vacuum environment of the second test are both obviously improved.

TABLE 2

Claims

1. The method for preparing the nickel-based superalloy component through solidification under pressure is characterized in that the method for preparing the nickel-based superalloy component through solidification under pressure is carried out according to the following steps:

2. The method for preparing a ni-based superalloy component by solidification under pressure according to claim 1, wherein the master alloy ingot in the first step is ni-based superalloy.

3. The method for preparing the nickel-base superalloy component by solidification under pressure as claimed in claim 2, wherein the nickel-base superalloy in step one is provided with a brand number of K418.

4. The method for preparing the nickel-base superalloy component by solidification under pressure according to claim 1, wherein the vacuum induction furnace in the first step is a batch vacuum induction furnace, model ZG-0.05.

5. A method of producing a nickel-base-superalloy component by solidification under pressure according to claim 1, wherein the shell is preheated to 1150 ℃ in step one.

6. The method for manufacturing a ni-based superalloy component by solidification under pressure as set forth in claim 1, wherein the vacuum induction furnace is started in the second step to raise the temperature of the crucible to 1470 ℃.

7. The method for preparing Ni-based superalloy component by solidification under pressure as claimed in claim 1, wherein in step three, when the crucible is heated to 1470 ℃, the inert gas is injected into the hearth to make the pressure inside and outside the furnace uniform and keep balance.

8. The method of claim 1, wherein the inert gas in step three is argon.

9. The method of claim 1, wherein the inert gas in step four is argon.

10. The method for preparing the nickel-base superalloy component by solidification under pressure according to claim 1, wherein the casting prepared in the fourth step is a thin-walled plate with a surface size of 300mm x 400mm and a wall thickness of 3mm, 5mm, 7mm or 9 mm.