CN117488220A

CN117488220A - Preparation method for improving powder nickel-based superalloy and product holding crack propagation resistance thereof

Info

Publication number: CN117488220A
Application number: CN202311315029.4A
Authority: CN
Inventors: 于苏洋; 王晓峰; 王旭青; 刘光旭; 杨杰
Original assignee: AECC Beijing Institute of Aeronautical Materials
Current assignee: AECC Beijing Institute of Aeronautical Materials
Priority date: 2023-10-11
Filing date: 2023-10-11
Publication date: 2024-02-02

Abstract

The invention belongs to the field of superalloy, and relates to a preparation method for improving the load-holding crack propagation resistance of a powder nickel-based superalloy and a workpiece thereof. According to the method, two component alloys with gamma 'phase solid solution temperature difference of more than 25 ℃ are selected and prepared according to final components of the alloy, powder of the two component alloys is uniformly mixed and then is prepared into an alloy and a part blank by using thermomechanical processing modes such as hot isostatic pressing and the like, and a heat treatment system is selected according to the solid solution temperature of the gamma' phase in the two component alloys. The powder nickel-based superalloy and the manufactured part thereof prepared by the method can coordinate and improve the load-holding crack propagation resistance of the material by regulating and controlling the components and the proportion of the two component alloys, and improve the service performance and the service life of the prepared aeroengine turbine disk.

Description

Preparation method for improving powder nickel-based superalloy and product holding crack propagation resistance thereof

Technical Field

The invention belongs to the technical field of powder superalloy, and relates to a preparation method for improving the load-holding crack propagation resistance of a powder nickel-based superalloy and a workpiece thereof, which is particularly suitable for preparing high-temperature rotating parts in aeroengines or gas turbines.

Background

The high-temperature rotating parts, particularly the high-pressure compressor disk and the high-pressure turbine disk, are key parts in the aeroengine, and the service performance of the high-temperature rotating parts greatly determines the performance, efficiency and safety of the aeroengine, so that the high-temperature structural materials used are required to have higher working temperature and excellent comprehensive service performance, including high-temperature strength, oxidation resistance, creep performance, and protection crack extension resistance.

Nickel-based superalloy is a critical material for manufacturing high-pressure compressors and high-pressure turbine rotors in aircraft engines, and is prepared into blanks mainly by a "cast-forge" deformation process or a powder metallurgy process, and then into final parts by machining. Because the materials and parts prepared by the powder metallurgy process have uniform and fine tissues, the materials and parts prepared by the casting-forging deformation process have better service performance. In addition, the powder metallurgy process can overcome macro element segregation, and is more suitable for preparing high-temperature-bearing high-temperature alloy materials and parts with high alloying.

The rotating piece prepared by the existing powder superalloy is prepared by carrying out hot isostatic pressing, extrusion, forging and other thermo-mechanical treatment and heat treatment on alloy powder prepared by an alloy ingot with single component through argon atomization or a rotating electrode method, and has good component and tissue uniformity. As shown in FIG. 1, for the powder superalloy and its article produced by this prior art route, when the final part blank is heat treated, solution heat treatment may be selected to be performed above or below the gamma prime strengthening phase solution temperature to obtain an oversolved coarse or sub-solutionized fine grain structure of uniform structure. For the uniform structure materials prepared by the existing process route, the performance regulation and control of the alloy and the parts mainly adjusts the microstructure (including crystal grains, gamma' strengthening and the like) in the final product through the alloy design, extrusion, forging and heat treatment processes in the preparation process so as to obtain the performance meeting the requirements.

In order to improve the temperature bearing capacity of the powder nickel-based superalloy, the high-temperature strength, creep resistance, fatigue resistance and the like of materials and parts are improved, more alloy elements are added into the materials, and the volume fraction of gamma' strengthening phases in the materials is improved. The volume fraction of gamma' strengthening phase at room temperature in most of the prior powder nickel-based superalloy with higher temperature bearing capacity is more than or equal to 45 percent, and the method can lead the brittleness resistance of the material to the fracture along the crystal caused by oxidation at high temperature to be reduced, and the material is represented as poor load-holding crack propagation resistance, thus greatly influencing the damage tolerance performance of the disc. In order to improve the load-holding crack growth resistance of the powder nickel-based superalloy with higher gamma prime strengthening phase content, one idea is to reduce the cooling rate of the material and the part blank after solution heat treatment, however, the method can sacrifice the tensile strength and creep resistance of the material and has limited effect on improving the load-holding crack growth resistance. Another approach is to form necklace-like tissue in the material by thermo-mechanical deformation, however, this approach has great difficulty in controlling in practical engineering and it is difficult to obtain a controlled, evenly distributed beneficial tissue.

In a word, the existing high-temperature-bearing-capacity powder nickel-based superalloy is difficult to coordinate and improve the key performances required by service such as the load-holding crack growth resistance, the high-temperature strength, the creep resistance and the like of the material.

Disclosure of Invention

The purpose of the invention is that: aiming at high-temperature rotating parts in an aeroengine or a gas turbine, such as a high-pressure compressor disk and a high-pressure turbine disk in the aeroengine, in particular to a powder nickel-based superalloy material with the gamma' -strengthening phase volume fraction of more than or equal to 45% at room temperature and a part thereof, a preparation method capable of coordinately improving key performances required by service such as the crack growth resistance under load retention, high-temperature strength, creep resistance and the like is designed.

In order to solve the technical problem, the technical scheme of the invention is as follows:

the preparation method designs two alloys with different components as component alloys according to the chemical components of the target alloy, wherein the components of the two component alloys after being mixed according to the mass ratio are the same as the components of the target alloy; the gamma' -phase solid solution temperature difference of the two component alloys is more than or equal to 25 ℃;

uniformly mixing the two component alloys according to the mass ratio, and preparing a part blank by a thermo-mechanical processing mode; carrying out heat treatment on the part blank to regulate and control microstructure of the part blank;

the solution heat treatment temperature in the heat treatment process is selected according to the gamma' -phase solution temperature in the two-component alloy as follows:

the solution heat treatment temperature is between the solid solution temperature of gamma' phase in the alloy with two components, so as to obtain a double-distribution grain structure of sub-solid solution and over-solid solution;

the solution heat treatment temperature is higher than the solid solution temperature of gamma 'phase in the alloy with two components at the same time, so as to obtain the double-distribution grain structure of over-solid solution and over-solid solution, and the solution heat treatment temperature is 0-30 ℃ higher than the solid solution temperature of gamma' phase with higher temperature in the alloy with two components.

The preparation method comprises the following steps:

step 1, designing two component alloys A and B with different components according to the chemical components of a target alloy;

step 2, respectively preparing materials for the nickel-based superalloy A and the nickel-based superalloy B, and respectively preparing master alloys by vacuum induction melting;

step 3, preparing master alloys of the two components into alloy powder respectively, and sieving the alloy powder to the selected granularity respectively;

step 4, evenly mixing the screened alloy powder with two components according to a certain proportion;

step 5, filling the mixed alloy powder into a hot isostatic pressing sheath, and degassing and sealing welding;

step 6, placing the hot isostatic pressing package into hot isostatic pressing equipment for densification treatment to obtain a hot isostatic pressing ingot blank or a part blank; if the ingot blank is obtained, performing shaping thermal mechanical treatment such as extrusion, forging and the like on the ingot blank to obtain a part blank;

step 7, performing heat treatment on the part blank obtained in the step 6; wherein the solution heat treatment temperature in the heat treatment process is selected according to the gamma' -phase solution temperature in the two component alloys A and B;

and 8, machining the part blank into a part.

The thermo-mechanical processing process may be one or a combination of methods of hot isostatic pressing, hot sintering, extrusion, forging, additive manufacturing, and the like.

The space of the target components of the nickel-based powder superalloy is as follows: 5.0 to 20.0 percent of Cr, 5.0 to 25.0 percent of Co, 0.0 to 15.0 percent of W, 0.0 to 5.0 percent of Mo, 0.0 to 6.0 percent of Al, 0.0 to 6.0 percent of Ti, 0.0 to 8.0 percent of Nb, 0.0 to 6.0 percent of Ta, 0.0 to 1.0 percent of Hf, 0.0 to 0.2 percent of Zr, 0.01 to 0.3 percent of C, 0.01 to 0.3 percent of B, and the balance of Ni, other trace elements beneficial to high-temperature alloys and unavoidable trace or impurity elements.

Preferably, the space of the target component of the nickel-based powder superalloy is: 7.0 to 18.0 percent of Cr, 7.0 to 23.0 percent of Co, 1.0 to 12.0 percent of W, 1.0 to 3.5 percent of Mo, 2.0 to 5.0 percent of Al, 0.5 to 5.0 percent of Ti, 0.5 to 8.0 percent of Nb, 0.0 to 6.0 percent of Ta, 0.0 to 0.5 percent of Hf, 0.0 to 0.2 percent of Zr, 0.01 to 0.2 percent of C, 0.01 to 0.2 percent of B, and the balance of Ni, other trace elements beneficial to high-temperature alloys and unavoidable trace or impurity elements.

Further, 8.0 to 16.0 percent of Cr, 8.0 to 19.0 percent of Co, 2.0 to 11.0 percent of W, 1.4 to 3.2 percent of Mo, 2.1 to 5.0 percent of Al, 0.5 to 4.3 percent of Ti, 0.5 to 7.9 percent of Nb, 0.0 to 5.0 percent of Ta, 0.0 to 0.4 percent of Hf, 0.0 to 0.1 percent of Zr, 0.02 to 0.15 percent of C and 0.015 to 0.025 percent of B.

The preparation method is used for preparing the high-temperature rotating member in the aeroengine or the gas turbine, is suitable for preparing the nickel-based powder superalloy, and is particularly suitable for the volume fraction of the gamma' strengthening phase in the final alloy material at room temperature to be more than or equal to 45%.

The beneficial effects of the invention are as follows:

according to the preparation method, two materials with different gamma' -phase solid solution temperatures are prepared through design or selection, and different grain sizes of the two component materials can be changed in subsequent solid solution heat treatment. If the solution heat treatment temperature is between the solution temperature of the gamma' -phase of the two-component alloy, a material structure in which small-size sub-solution grains and large-size over-solution grains are uniformly mixed and distributed can be obtained. If the solid solution temperature is higher than the solid solution temperature of the gamma' -phase of the alloy with two components, although the two components have oversolid solution crystal grain growth, the crystal grain growth rate is different due to different initial chemical components, so that the double-distribution oversolid solution crystal grain structure can be obtained. In addition, regardless of the heat treatment mode, the gamma' phase distribution in the crystal is different while the crystal grain structure is subjected to different growth processes.

Thus, the present invention actually achieves a material with a non-uniform distribution of properties on the meso-microscopic scale due to the difference in grain size and intra-crystalline gamma prime phase distribution. The material structure thus obtained will produce a local non-uniform deformation and stress distribution under load, which may reduce the stress strain level at certain grain boundaries, thereby reducing the driving force for propagation of the load along the grain boundaries and thus the propagation rate of the load in the material. Furthermore, this tissue type is even beneficial to the tensile strength and plasticity of the material due to mechanisms such as co-reinforcement and co-deformation; the method of the present invention is also beneficial for maintaining tensile strength and creep resistance of materials and articles because it is not necessary to increase the material's crack growth resistance on hold by reducing the cooling rate after solution heat treatment.

Drawings

FIG. 1 is a schematic diagram of a process flow according to the present invention in comparison with a prior art process flow;

FIG. 2 is a schematic view of the microstructure of an alloy prepared by the process of the present invention and the prior art in examples 1, 2, 3, and 4, wherein FIG. 2 (a) is a sub-solution heat treated microstructure of a single component A alloy obtained by the heat treatment temperature of each example, wherein hexagons represent grain structures, black spots at the junctions of hexagons represent primary gamma prime phases in the sub-solution heat treated material, FIG. 2 (B) is an over-solution heat treated microstructure of a single component B alloy obtained by the heat treatment temperature of each example, wherein hexagons represent grain structures (the junctions have no primary gamma prime phase), FIG. 2 (C) is an alloy C prepared by the heat treatment temperature of each example by the solution heat treatment process of the present invention at a temperature lower than the gamma prime phase solution temperature of the component A alloy and higher than the gamma prime phase solution temperature of the component B alloy, large representative of the over-solution large size grains changed by the component B alloy, small hexagons represent sub-small size grains changed by the sub-solution A alloy (the black spots at the junctions remain primary gamma prime phases), and FIG. 2 (d) is a comparative heat treated microstructure obtained by the heat treated microstructure of each example; as can be seen in the figure: the alloy prepared by the process has a double-distribution grain structure, and is obviously different from the uniform material structure prepared by the prior process;

FIG. 3 is a schematic view of the microstructure of the alloy prepared by the process of the present invention and the prior art process in example 5, wherein FIG. 3 (a) is the single component A alloy's over-solution heat treated microstructure obtained by the heat treatment temperature of each example, wherein hexagons represent grain structures, FIG. 2 (B) is the single component B alloy's over-solution heat treated microstructure obtained by the heat treatment temperature of each example, FIG. 2 (C) is alloy C prepared by the heat treatment temperature of each example by solution heat treatment at a temperature simultaneously higher than the gamma ' -phase solution temperatures of the component A alloy and the component B alloy, large hexagons represent larger sized over-solution grains into which the component B alloy is grown, small hexagons represent smaller sized over-solution grains into which the component A alloy is grown, and FIG. 2 (d) is the corresponding comparative over-solution heat treated microstructure obtained by the prior art process by the single component C and the heat treatment temperature of each example; as can be seen in the figure: the alloy prepared by the process has double-distribution oversolved grain structures, and is obviously different from the uniform oversolved material structures prepared by the prior process;

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It will be apparent that the described embodiments are some, but not all, embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without making any inventive effort are intended to fall within the scope of the present invention.

Features of various aspects of embodiments of the invention are described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details. The following description of the embodiments is merely for a better understanding of the invention by showing examples of the invention. The present invention is not limited to any particular arrangement and method provided below, but covers any modifications, substitutions, etc. of all product constructions, methods, and the like covered without departing from the spirit of the invention.

Well-known structures and techniques have not been shown in detail in the various drawings and the following description in order not to unnecessarily obscure the present invention.

Example 1:

this example consisted of comparative example 1 and examples 1-1 to 1-4 (the material composition is shown in Table 1). Examples 1-1 to 1-4 were prepared by mixing component A and component B in the proportions shown in the tables using the process of the present invention. The proportion of the component A and the component B comprises 95 percent (5 percent), 90 percent (10 percent), 80 percent (20 percent) and 50 percent (50 percent) (all are mass fractions).

The ingredients of the comparative examples were identical to the equivalent ingredients of the examples after mixing of component a and component B in the proportions shown in the table and were prepared using prior art techniques (i.e., without the powder mixing step, resulting in a uniform grain structure).

The final solution heat treatment temperatures in this series of examples (including the comparative examples) were 1140 c, which is between the gamma prime phase solution temperatures of component a and component B in examples 1-1 to 1-4 and below the gamma prime phase solution temperature of the materials in the comparative examples. Thus, comparative example 1 gave a uniform sub-solid solution grain structure, while examples 1-1 to 1-4 gave sub-solid solution grain structures in which coarser over-solid solution grain structures were distributed.

Described by taking example 1-1 as an example:

a powder nickel-based superalloy prepared from a two-component alloy powder has the target composition shown in Table 1, example 1-1. The alloy composition was equivalent to 95% of the component A alloy plus 5% of the component B alloy in example 1-1 of Table 1, and was the same as comparative example 1 (i.e., component C).

First, the elemental materials were prepared into master alloy ingots of component a and component B corresponding to example 1-1 in table 1, respectively, using vacuum induction melting, and then the alloy ingots were prepared into alloy powders of component a and component B, respectively, using an argon atomization method, and were sieved to-270 mesh. The solid solution temperature of the gamma prime strengthened phase in the component A alloy is approximately 1160 ℃ and the solid solution temperature of the gamma prime strengthened phase in the component B alloy is approximately 1120 ℃.

Uniformly mixing 95% of component A alloy powder and 5% of component B alloy powder, then filling into a steel sheath, and degassing, sealing and hot isostatic pressing. Subjecting the hot isostatically pressed compact blank to solution heat treatment at 1140 ℃ which is between the solution temperatures of the two component alloys, so that the B component undergoes solution heat treatment to change into a coarse crystal structure; the A component is subjected to sub-solution heat treatment, and a fine crystal structure is reserved. As schematically shown in fig. 1, the alloy obtained by this method has two grain size distributions, a small number of large-size grains having a size of about 20 to 40 μm are uniformly distributed in fine grains having a size of about 10 μm, and a primary γ' strengthening phase having a size of about 1 μm is also dispersed at grain boundaries of the small grains.

Comparative example 1, prepared using the existing process, i.e., using only the target alloy component C, was prepared as a master alloy and alloy powder, followed by the same hot isostatic pressing process and heat treatment process. Since the gamma prime strengthening phase of the alloy of comparative example 1 has a solid solution temperature of 1156 ℃ which is higher than the solution heat treatment temperature of 1140 ℃, the microstructure of the prepared alloy is a uniform sub-solid solution grain structure, and the difference from the alloy structure in this case is that there are no large-size grains dispersed uniformly. Compared with the target alloy prepared by the prior art, the load-retaining crack growth rate of the bi-grain size distribution alloy prepared by the route of the bi-component alloy mixed preparation in the invention is obviously reduced. For example, at 650 ℃, under maximum stress for 2 minutes, the crack growth rate is reduced to about 60% at Δk=30 MPa; meanwhile, the room temperature tensile property, the tensile property at 650 ℃ and the creep property at 650 ℃ of the material are unchanged.

Examples 1-2 to 1-4 were prepared by the same procedure as in example 1-1, except that the ratio between component A and component B was changed. Examples 1-2 to 1-4 also have better resistance to propagation of the holding crack than comparative example 1.

Examples 1-2 to 1-4 may also be prepared by means of hot isostatic pressing + extrusion + forging. After the hot isostatic pressing process, the mixed powder is wrapped, hot extrusion and isothermal forging are carried out at the blank temperature which is lower than the solid solution temperature of the two alloys at the same time, a part blank with a specific shape is obtained, then solid solution heat treatment is carried out at 1140 ℃, and an alloy material with double-grain size distribution is still obtained, wherein the heat preservation crack extension resistance is equivalent to that of the material obtained by direct hot isostatic pressing, and is superior to that of the alloy of comparative example 1 prepared by adopting the same process.

TABLE 1

Example 2:

this example contains comparative example 2 and examples 2-1 to 2-3 (the material composition is shown in Table 2). This example is similar to example 1, but the chemical composition of the comparative example and the example is different from example 1. The proportion of the component A and the component B in the embodiment comprises 90 percent (10 percent), 80 percent (20 percent) and 60 percent (40 percent) (all are mass percent).

In this example 2, the heat treatment temperature of the comparative example and the example was 1173 ℃, which is lower than the comparative example, which is likewise between the solid solution temperatures of the gamma 'phases of component a and component B, which is lower than the solid solution temperature of the gamma' phase of the material in the comparative example. The above examples intersect the comparative examples and the crack growth rate was reduced to about 10-60% at Δk=30 MPa when held at the highest stress of 650-700 ℃ for 2 minutes.

TABLE 2

Example 3:

this example contains comparative example 3 and examples 3-1 and 3-2 (the material composition is detailed in Table 3). This example is similar to examples 1 and 2, but the chemical composition of the comparative examples and examples is different from examples 1 and 2. The proportions of component A and component B in this example include 95% to 5% and 90% to 10% (both mass fractions).

The heat treatment temperature of the comparative example and the example in this example 3 was 1165 c, which is lower than the gamma prime solid solution temperature of the comparative example, which is also between the gamma prime solid solution temperatures of the component a and the component B, which is lower than the gamma prime solid solution temperature of the material in the comparative example.

TABLE 3 Table 3

Example 4:

this example contains 4 sets of comparisons of chemical composition (see Table 4 for details of the material composition). The proportions of component A and component B in the examples are in each case 90% to 10% by mass. The heat treatment temperatures of the comparative examples and examples in examples 4-1 to 4-4 are each between the gamma prime phase solid solution temperatures of component A and component B and lower than the gamma prime phase solid solution temperature of the materials in the comparative examples.

TABLE 4 Table 4

Example 5:

this example contains a comparison of 4 different chemical compositions, each of which is identical to that of example 4, with the material compositions detailed in Table 5. The proportion of component A and component B in this example is 90% to 10% by mass. The heat treatment temperatures of the comparative examples and examples in examples 5-1 to 5-4 are both higher than the solid solution temperature of the gamma 'phase between the solid solution temperatures of the component A and the component B and the gamma' phase of the material in the comparative examples. The above examples reduced the crack growth rate to about 5-50% at Δk=30 MPa when held at the highest stress of 650-750 ℃ for 2 minutes compared to the comparative examples.

TABLE 5

In the examples obtained by this process, both component a and component B evolved into an over-solid solution coarse crystal in the over-solid solution heat treatment, but the grain size after the heat treatment was different and the intra-crystalline strength was different due to the difference in the initial chemical composition.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily think about various equivalent modifications or substitutions within the technical scope of the present invention, and these modifications or substitutions should be covered in the scope of the present invention.

Claims

1. A preparation method for improving the resistance of a powder nickel-based superalloy and a finished product thereof to propagation of a load-maintaining crack is characterized by comprising the following steps:

according to the preparation method, according to the chemical components of the target alloy, two alloys with different components are designed to be component alloys, and the components of the two component alloys after being mixed according to the mass ratio are identical with the components of the target alloy; the gamma' -phase solid solution temperature difference of the two component alloys is more than or equal to 25 ℃;

2. The method of manufacturing according to claim 1, characterized in that: the preparation method comprises the following steps:

and 8, machining the part blank into a part.

3. The method of manufacturing according to claim 1, characterized in that: the thermo-mechanical processing process may be one or a combination of methods of hot isostatic pressing, hot sintering, extrusion, forging, additive manufacturing, and the like.

4. The preparation method according to claim 2, characterized in that: the space of the target components of the nickel-based powder superalloy is as follows: 5.0 to 20.0 percent of Cr, 5.0 to 25.0 percent of Co, 0.0 to 15.0 percent of W, 0.0 to 5.0 percent of Mo, 0.0 to 6.0 percent of Al, 0.0 to 6.0 percent of Ti, 0.0 to 8.0 percent of Nb, 0.0 to 6.0 percent of Ta, 0.0 to 1.0 percent of Hf, 0.0 to 0.2 percent of Zr, 0.01 to 0.3 percent of C, 0.01 to 0.3 percent of B, and the balance of Ni, other trace elements beneficial to high-temperature alloys and unavoidable trace or impurity elements.

5. The method of manufacturing according to claim 4, wherein: the space of the target components of the nickel-based powder superalloy is as follows: 7.0 to 18.0 percent of Cr, 7.0 to 23.0 percent of Co, 1.0 to 12.0 percent of W, 1.0 to 3.5 percent of Mo, 2.0 to 5.0 percent of Al, 0.5 to 5.0 percent of Ti, 0.5 to 8.0 percent of Nb, 0.0 to 6.0 percent of Ta, 0.0 to 0.5 percent of Hf, 0.0 to 0.2 percent of Zr, 0.01 to 0.2 percent of C, 0.01 to 0.2 percent of B, and the balance of Ni, other trace elements beneficial to high-temperature alloys and unavoidable trace or impurity elements.

6. The method of manufacturing according to claim 5, wherein: 8.0 to 16.0 percent of Cr, 8.0 to 19.0 percent of Co, 2.0 to 11.0 percent of W, 1.4 to 3.2 percent of Mo, 2.1 to 5.0 percent of Al, 0.5 to 4.3 percent of Ti, 0.5 to 7.9 percent of Nb, 0.0 to 5.0 percent of Ta, 0.0 to 0.4 percent of Hf, 0.0 to 0.1 percent of Zr, 0.02 to 0.15 percent of C and 0.015 to 0.025 percent of B.

7. The method of manufacturing according to claim 1, characterized in that: the preparation method is suitable for preparing nickel-based powder superalloy, and particularly the volume fraction of gamma' strengthening phase in the final alloy material at room temperature is more than or equal to 45%.

8. The method of manufacturing according to claim 1, characterized in that: the preparation method is used for preparing the high-temperature rotating part in the aero-engine or the gas turbine.