阅读说明：本技术 一种镍钴基高温合金涡轮盘及其制备方法 (Nickel-cobalt-based high-temperature alloy turbine disc and preparation method thereof ) 是由 张瑞 崔传勇 周亦胄 孙晓峰 于 2020-05-25 设计创作，主要内容包括：本发明是关于一种镍钴基高温合金涡轮盘及其制备方法,主要采用的技术方案为：所述镍钴基高温合金涡轮盘的表层具有微孪晶,且所述表层处于压应力状态。所述镍钴基高温合金涡轮盘的制备方法包括对锻造成型的涡轮盘坯进行表面处理,得到镍钴基高温合金涡轮盘；其中,表面处理包括：对锻造成型的涡轮盘坯进行固溶处理、对固溶处理后的涡轮盘坯进行切削粗加工、对切削粗加工处理后的涡轮盘坯进行时效处理、对时效处理后的涡轮盘坯进行热喷丸处理、对热喷丸处理后的涡轮盘坯进行热机械表面处理,得到镍钴基高温合金涡轮盘。本发明主要用于在涡轮盘的表层中引入微孪晶,以增强涡轮盘表层的抗蠕变、抗疲劳性能,以延长涡轮盘的服役寿命。(The invention relates to a nickel-cobalt-based high-temperature alloy turbine disc and a preparation method thereof, and the technical scheme mainly adopted is as follows: the surface layer of the nickel-cobalt-based superalloy turbine disk is provided with micro twin crystals, and the surface layer is in a compressive stress state. The preparation method of the nickel-cobalt-based high-temperature alloy turbine disc comprises the steps of carrying out surface treatment on a forged and formed turbine disc blank to obtain the nickel-cobalt-based high-temperature alloy turbine disc; wherein the surface treatment comprises: the method comprises the steps of carrying out solution treatment on a forged turbine disc blank, carrying out cutting rough machining on the turbine disc blank after the solution treatment, carrying out aging treatment on the turbine disc blank after the cutting rough machining, carrying out thermal shot blasting treatment on the turbine disc blank after the aging treatment, and carrying out thermal mechanical surface treatment on the turbine disc blank after the thermal shot blasting treatment to obtain the nickel-cobalt-based high-temperature alloy turbine disc. The method is mainly used for introducing the micro twin crystal into the surface layer of the turbine disk so as to enhance the creep resistance and fatigue resistance of the surface layer of the turbine disk and prolong the service life of the turbine disk.)

1. The nickel-cobalt-based high-temperature alloy turbine disk is characterized in that a surface layer of the nickel-cobalt-based high-temperature alloy turbine disk is provided with micro twin crystals and is in a compressive stress state;

preferably, an enriched micro-twin crystal layer is formed on the surface layer of the nickel-cobalt-based high-temperature alloy turbine disc;

preferably, the thickness of the surface layer is more than or equal to 0.5 mm.

2. The nickel cobalt based superalloy turbine disk of claim 1, wherein the nickel cobalt based superalloy turbine disk comprises the following composition in weight percent: 20-35% of Co, 0-5% of Ta, 10-25% of Cr, 3-7% of Ti, 0.2-5% of Al, 0.1-5% of W, 0.1-5% of Mo, 0.1-5% of Nb, 0.1-1% of Mn, 0.1-1% of V, 0.005-0.2% of C, 0.01-0.1% of ZrC, 0.001-0.1% of B, and the balance of Ni and inevitable impurities.

3. The nickel cobalt superalloy turbine disk of claim 1 or 2,

the surface roughness Ra of the nickel-cobalt-based high-temperature alloy turbine disc is less than or equal to 0.2 mu m; and/or

The surface micro-hardness of the nickel-cobalt-based high-temperature alloy turbine disc is more than or equal to 700 HV; and/or

The dimensional accuracy of the nickel-cobalt-based superalloy turbine disk at least reaches IT 5.

4. A method of making a nickel cobalt superalloy turbine disk as claimed in any of claims 1 to 3, comprising: carrying out surface treatment on the forged and formed turbine disc blank to obtain a nickel-cobalt-based high-temperature alloy turbine disc; preferably, the forged turbine disk blank is a hot-die forged turbine disk blank or an isothermal forged turbine disk blank;

wherein the surface treatment comprises:

solution treatment: carrying out solution treatment on the forged and formed turbine disc blank;

cutting rough machining treatment: carrying out cutting rough machining on the turbine disc blank subjected to the solution treatment;

aging treatment: carrying out aging treatment on the turbine disc blank subjected to the cutting rough machining treatment;

thermal shot blasting treatment: spraying the shot to the surface of the aged turbine disc blank to hammer a depression on the surface of the aged turbine disc blank;

thermal mechanical surface treatment: and carrying out surface machining treatment on the turbine disc blank subjected to the thermal shot spraying treatment to obtain the nickel-cobalt-based high-temperature alloy turbine disc.

5. The method of manufacturing a nickel cobalt superalloy turbine disk of claim 4,

the step of solution treatment comprises: carrying out solution treatment on the forged and formed turbine disc blank at the temperature of 0.75-0.95Tm for 2-10h, and cooling to obtain a solution-treated turbine disc blank; wherein Tm is the melting point of the nickel-cobalt-based high-temperature alloy for the turbine disc; and/or

In the step of the cutting roughing treatment: the target size of the cutting rough machining is 4-10mm more than the final size of the turbine disc; and/or

The surface roughness Ra of the turbine disk blank after the cutting rough machining treatment is 25-50 mu m.

6. The method of manufacturing a nickel cobalt superalloy turbine disk of claim 4, wherein the aging step comprises:

the first step of aging treatment: preserving the heat of the turbine disc blank subjected to the cutting rough machining for a first set time at a first temperature, and cooling to obtain the turbine disc blank subjected to the first-step aging treatment; preferably, the first temperature is lower than the precipitation phase solid solution temperature of the nickel-cobalt-based high-temperature alloy for the turbine disc by 450-550 ℃; preferably, the first set time is 15-30 h;

the second step of aging treatment: preserving the heat of the turbine disc blank subjected to the first-step aging treatment at a second temperature for a second set time to obtain an aged turbine disc blank; preferably, the second temperature is lower than the precipitation phase solid solution temperature of the nickel-cobalt-based high-temperature alloy for the turbine disc by 350-450 ℃; preferably, the second set time is 10-30 h.

7. The method for manufacturing a nickel cobalt-based superalloy turbine disk according to claim 4 or 6, wherein the step of thermally shot-spraying is performed in an incubator; preferably, the uncooled turbine disc blank after the aging treatment is transferred into an incubator to be subjected to thermal shot spraying treatment; and/or

In the thermal shot-blasting step: the depth of the recess is 2-5 mm; and/or

In the thermal shot-blasting step: the diameter of the projectile is 1.2-2.5 mm; and/or

The temperature of the thermal spraying pill treatment is 10-50 ℃ higher than the service temperature of the nickel-cobalt-based high-temperature alloy turbine disc.

8. The method of making a nickel cobalt superalloy turbine disk of claim 4, wherein the step of thermomechanical surface treating comprises:

after the turbine disc blank subjected to thermal shot spraying treatment is returned to the furnace for heat preservation, transferring the turbine disc blank into a heat preservation box, performing surface machining treatment on the turbine disc blank subjected to thermal shot spraying treatment by using a cutter, and cooling to obtain a nickel-cobalt-based high-temperature alloy turbine disc;

preferably, the temperature of the thermal mechanical surface treatment is 10-50 ℃ higher than the service temperature of the nickel-cobalt-based superalloy turbine disk.

9. The method of making a nickel cobalt superalloy turbine disk of claim 4, wherein the step of preparing the forged turbine disk blank is as follows:

1) carrying out vacuum induction melting, electroslag remelting and vacuum induction consumable melting on the raw materials to obtain an ingot;

2) homogenizing the cast ingot;

3) cogging and forging the cast ingot after the homogenization treatment to obtain a two-phase fine-grain bar;

4) forging and forming the two-phase fine-grain bar to obtain a forged and formed turbine disc blank;

preferably, the raw materials comprise the following components in percentage by weight: 20-35% of Co, 0-5% of Ta, 10-25% of Cr, 3-7% of Ti, 0.2-5% of Al, 0.1-5% of W, 0.1-5% of Mo, 0.1-5% of Nb, 0.1-1% of Mn, 0.1-1% of V, 0.005-0.2% of C, 0.01-0.1% of Zr, 0.001-0.1% of B and the balance of Ni.

10. The method of manufacturing a nickel cobalt superalloy turbine disk of claim 9,

in the step 2): firstly, carrying out first-step homogenization treatment at the temperature of 1000-1150 ℃, and then carrying out second-step homogenization treatment at the temperature of 1100-1250 ℃; and/or

In the step 3): cogging and forging the cast ingot on a quick forging machine by adopting a soft packing process; preferably, the temperature of cogging forging is 850-1150 ℃; and/or

In the step 4): performing hot die forging on the two-phase fine-grain bar by using forging equipment to obtain a hot die forging molded turbine disc blank, wherein the temperature of the hot die forging is 900-1150 ℃; or performing isothermal forging on the dual-phase fine-grain bar by using forging equipment to obtain a turbine disc blank formed by isothermal forging, wherein the temperature of the isothermal forging is 900-1150 ℃.

Technical Field

The invention relates to the technical field of turbine disks, in particular to a nickel-cobalt-based high-temperature alloy turbine disk and a preparation method thereof.

Background

The turbine disc is an important hot-end component of a modern aeroengine and mainly used for fixing turbine blades and transmitting power; turbine disks operate in extreme environments subject to complex temperature, centrifugal and aerodynamic loads. With the gradual development of the aero-engine towards high performance, high reliability, long service life and large scale, the requirements on the temperature bearing capacity and the mechanical property of key parts such as an aero turbine disc are continuously improved, and the turbine disc is often broken or deformed too much to fail under the action of repeated load because of the increase of internal stress and unqualified surface quality.

In order to meet the development requirements of advanced aeroengines, a large amount of alloy elements are added into the high-temperature alloy for the turbine disc during design so as to realize solid solution strengthening and precipitation strengthening, thereby improving the service temperature of the turbine disc. However, high alloying also increases the difficulty of hot working the turbine disk.

The nickel-cobalt-based high-temperature alloy has the same strength and poor thermal conductivity as other advanced alloys for turbine disks, and belongs to the alloy difficult to machine. After the alloy is machined, the surface finish is poor, and residual lathe tool marks can easily form crack sources under the action of high-temperature cyclic stress in the service process, so that the service life of a disc piece is seriously influenced. Meanwhile, the high cooling speed in the hot working or heat treatment process generates a large temperature gradient in the disc, so that thermal stress is formed, residual stress caused by the large thermal stress can cause deformation of the disc, and the disc is finally scrapped when the size of the disc is not in accordance with the requirement.

In the preparation of the turbine disk, the surface treatment technology of a turbine disk blank is very important, and the surface performance and the service life of the turbine disk are directly influenced. The surface treatment technology in the prior art specifically comprises the following steps: and carrying out solution treatment, aging treatment and cutting processing on the hot-die-forged turbine disc blank in sequence to obtain the turbine disc with the final size. However, the inventors of the present invention found that: the turbine disk treated by the surface treatment technology is easy to form fatigue cracks or creep failure during service, and has short service life.

Disclosure of Invention

In view of the above, the present invention provides a nickel-cobalt-based superalloy turbine disk and a method for manufacturing the same, and mainly aims to introduce micro twin crystals into a surface layer of the turbine disk to enhance creep resistance and fatigue resistance of the surface layer of the turbine disk, so as to prolong a service life of the turbine disk.

In order to achieve the purpose, the invention mainly provides the following technical scheme:

in one aspect, an embodiment of the present invention provides a nickel-cobalt-based superalloy turbine disk, wherein a surface layer of the nickel-cobalt-based superalloy turbine disk has microtwinkles, and the surface layer is in a compressive stress state; preferably, the surface layer of the nickel-cobalt-based high-temperature alloy turbine disc is an enriched micro-twin crystal layer. Preferably, the thickness of the surface layer is more than or equal to 0.5 mm.

Preferably, the nickel-cobalt-based superalloy turbine disk comprises the following components in percentage by weight: 20-35% of Co, 0-5% of Ta, 10-25% of Cr, 3-7% of Ti, 0.2-5% of Al, 0.1-5% of W, 0.1-5% of Mo, 0.1-5% of Nb, 0.1-1% of Mn, 0.1-1% of V, 0.005-0.2% of C, 0.01-0.1% of Zr, 0.001-0.1% of B, and the balance of Ni and inevitable impurities.

Preferably, the surface roughness Ra of the nickel-cobalt-based high-temperature alloy turbine disc is less than or equal to 0.2 mu m;

preferably, the surface micro-hardness of the nickel-cobalt-based high-temperature alloy turbine disc is more than or equal to 700 HV; the dimensional accuracy of the nickel-cobalt-based superalloy turbine disk at least reaches IT5(IT5 or higher order dimensional accuracy).

On the other hand, the embodiment of the invention also provides a preparation method of the nickel-cobalt-based superalloy turbine disk, wherein the preparation method comprises the following steps: carrying out surface treatment on the forged and formed turbine disc blank to obtain a nickel-cobalt-based high-temperature alloy turbine disc; preferably, the forged turbine disk blank is a hot-die forged turbine disk blank or an isothermal forged turbine disk blank;

wherein the surface treatment comprises:

solution treatment: carrying out solution treatment on the forged and formed turbine disc blank;

cutting rough machining treatment: carrying out cutting rough machining on the turbine disc blank subjected to the solution treatment;

aging treatment: carrying out aging treatment on the turbine disc blank subjected to the cutting rough machining treatment;

thermal shot blasting treatment: spraying the shot to the surface of the aged turbine disc blank to hammer a depression on the surface of the aged turbine disc blank;

thermal mechanical surface treatment: and carrying out surface machining treatment on the turbine disc blank subjected to the thermal shot spraying treatment to obtain the nickel-cobalt-based high-temperature alloy turbine disc.

Preferably, the solution treatment step includes: carrying out solution treatment on the forged and formed turbine disc blank at the temperature of 0.75-0.95Tm for 2-10h, and cooling to obtain a solution-treated turbine disc blank; wherein Tm is a melting point of the nickel-cobalt-based high-temperature alloy for the turbine disk.

Preferably, in the step of cutting rough machining: the target size of the cutting rough machining is 4-10mm more than the final size of the turbine disc.

Preferably, the surface roughness Ra of the turbine disk blank after the cutting rough machining treatment is 25-50 μm.

Preferably, the aging treatment step includes:

the first step of aging treatment: preserving the heat of the turbine disc blank subjected to the cutting rough machining for a first set time at a first temperature, and cooling to obtain the turbine disc blank subjected to the first-step aging treatment; preferably, the first temperature is lower than the precipitation phase solid solution temperature of the nickel-cobalt-based high-temperature alloy for the turbine disc by 450-550 ℃; preferably, the first set time is 15-30 h;

the second step of aging treatment: preserving the heat of the turbine disc blank subjected to the first-step aging treatment at a second temperature for a second set time to obtain an aged turbine disc blank; preferably, the second temperature is lower than the precipitation phase solid solution temperature of the nickel-cobalt-based high-temperature alloy for the turbine disc by 350-450 ℃; preferably, the second set time is 10-30 h.

Preferably, the step of thermal spray-pill treatment is performed in an incubator; preferably, the uncooled turbine disc blank after the aging treatment is transferred into an incubator to be subjected to thermal shot spraying treatment; and/or

In the thermal shot-blasting step: the depth of the recess is 2-5 mm; and/or

In the thermal shot-blasting step: the diameter of the projectile is 1.2-2.5 mm; and/or

The temperature of the thermal spraying pill treatment is 10-50 ℃ higher than the service temperature of the nickel-cobalt-based high-temperature alloy turbine disc.

Preferably, the step of thermomechanical surface treatment comprises:

after the turbine disc blank subjected to thermal shot spraying treatment is returned to the furnace for heat preservation, transferring the turbine disc blank into a heat preservation box, performing surface machining treatment on the turbine disc blank subjected to thermal shot spraying treatment by using a cutter, and cooling to obtain a nickel-cobalt-based high-temperature alloy turbine disc;

preferably, the temperature of the thermal mechanical surface treatment is 10-50 ℃ higher than the service temperature of the nickel-cobalt-based superalloy turbine disk.

Preferably, the preparation steps of the forged turbine disk blank are as follows:

1) carrying out vacuum induction melting, electroslag remelting and vacuum induction consumable melting on the raw materials to obtain an ingot;

2) homogenizing the cast ingot;

3) cogging and forging the cast ingot after the homogenization treatment to obtain a two-phase fine-grain bar;

4) and forging and forming the two-phase fine-grain bar to obtain a turbine disc blank formed by forging.

Preferably, the raw materials comprise the following components in percentage by weight: 20-35% of Co, 0-5% of Ta, 10-25% of Cr, 3-7% of Ti, 0.2-5% of Al, 0.1-5% of W, 0.1-5% of Mo, 0.1-5% of Nb, 0.1-1% of Mn, 0.1-1% of V, 0.005-0.2% of C, 0.01-0.1% of Zr, 0.001-0.1% of B and the balance of Ni.

Preferably, in the step 2): first homogenizing treatment at the temperature of 1000-1150 deg.c and then second homogenizing treatment at the temperature of 1100-1250 deg.c.

Preferably, in the step 3): cogging and forging the cast ingot on a quick forging machine by adopting a soft packing process; preferably, the temperature for the cogging forging is 850-.

Preferably, in the step 4): performing hot die forging on the two-phase fine-grain bar by using forging equipment to obtain a hot die forging molded turbine disc blank, wherein the temperature of the hot die forging is 900-1150 ℃; or performing isothermal forging on the dual-phase fine-grain bar by using forging equipment to obtain a turbine disc blank formed by isothermal forging, wherein the temperature of the isothermal forging is 900-1150 ℃.

Compared with the prior art, the nickel-cobalt-based high-temperature alloy turbine disc and the preparation method thereof have the following beneficial effects:

on one hand, the surface layer of the nickel-cobalt-based high-temperature alloy turbine disc provided by the embodiment of the invention has micro twin crystals and is in a compressive stress state, so that the surface layer of the turbine disc forms a high-hardness surface layer, the fatigue resistance and the creep resistance of the turbine disc can be synergistically improved, and the crack initiation can be inhibited. Furthermore, the nickel-cobalt-based high-temperature alloy turbine disc provided by the embodiment of the invention has high precision and surface finish, and the difficulty of fatigue crack initiation in the service process of the turbine disc is increased. Therefore, the nickel-cobalt-based high-temperature alloy turbine disk provided by the embodiment of the invention has long service life.

On the other hand, in the preparation method of the nickel-cobalt-based high-temperature alloy turbine disc provided by the embodiment of the invention, in the surface treatment step, the turbine disc blank is subjected to solid solution treatment, rough cutting, aging treatment, thermal shot blasting treatment and thermal mechanical surface treatment in sequence, so that the surface layer of the turbine disc is plastically deformed to generate a large number of micro-twin crystals (faults), and the strengthening layer is in a compressive stress state, so that the fatigue resistance and creep resistance of the turbine disc are synergistically improved, and the crack initiation can be inhibited; and the surface treatment step ensures that the size precision and the surface finish of the turbine disk are high, and the difficulty of fatigue crack initiation of the turbine disk in the service process can be increased.

Further, according to the preparation method of the nickel-cobalt-based high-temperature alloy turbine disc provided by the embodiment of the invention, through the solution treatment in the surface treatment step, the blank of the turbine disc is completely recrystallized and homogenized, the residual internal stress generated in the alloy due to hot die forging or isothermal forging is eliminated, a large amount of gamma' phase in the matrix is dissolved, the alloy hardness is reduced, and the difficulty of the next step of cutting rough machining is reduced.

Further, according to the preparation method of the nickel-cobalt-based superalloy turbine disk provided by the embodiment of the invention, the size and shape of a turbine disk blank are close to the size and shape of a target disk piece through cutting rough machining in the surface treatment step, so that the cutting difficulty of the turbine disk piece can be reduced, and the subsequent finish machining treatment (namely, thermal surface mechanical treatment) is facilitated.

Further, according to the preparation method of the nickel-cobalt-based superalloy turbine disc provided by the embodiment of the invention, the gamma 'phase is fully precipitated from the matrix through the aging treatment in the surface treatment step, and the gamma' phase is distributed in a multi-scale manner, so that the precipitation strengthening effect is fully exerted.

Further, according to the method for manufacturing a nickel-cobalt-based superalloy turbine disk provided by the embodiment of the present invention, a micro-twin (stacking fault) layer with a certain thickness is induced on the surface of the turbine disk through thermal spray processing in the surface processing step, and a compressive stress state is formed in the micro-twin (stacking fault) layer, so that a high hardness surface layer with a large number of micro-twin (stacking fault) layers is provided, and the fatigue and creep properties can be synergistically improved, and crack initiation can be inhibited.

Further, according to the method for manufacturing the nickel-cobalt-based superalloy turbine disk provided by the embodiment of the invention, the thermomechanical surface treatment in the surface treatment step is adopted to improve the dimensional accuracy of the turbine disk, reduce the roughness, and further generate more volume fractions of micro-twin crystals (stacking faults) on the surface layer. The hot-spraying shot treatment can enable the turbine disk to generate a surface strengthening layer with large thickness, the thermomechanical surface treatment can increase the content of micro twin crystals (faults) in the strengthening layer, and the two processes are cooperatively combined to enable the turbine disk to obtain excellent service performance and prolong the service life of the turbine disk.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.

Drawings

FIG. 1 is a surface microstructure of a nickel-cobalt-based superalloy turbine disk prepared in comparative example 1;

FIG. 2 is a surface microstructure of a nickel-cobalt-based superalloy turbine disk prepared in example 1;

FIG. 3 is a surface microstructure of a nickel-cobalt-based superalloy turbine disk prepared in example 2;

FIG. 4 is a surface microstructure of a nickel-cobalt-based superalloy turbine disk prepared in example 3;

FIG. 5 is a surface microstructure of a nickel-cobalt-based superalloy turbine disk prepared in example 4;

fig. 6 is a surface microstructure of a nickel-cobalt-based superalloy turbine disk prepared in example 5.

Detailed Description

To further explain the technical means and effects of the present invention adopted to achieve the predetermined object, the following detailed description of the embodiments, structures, features and effects according to the present invention will be made with reference to the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "an embodiment" refers to not necessarily the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

The invention mainly introduces a micro-twin crystal structure on the surface layer of the nickel-cobalt-based high-temperature alloy turbine disc (namely, the surface layer of the turbine disc is induced into a strengthening layer enriched with micro-twin crystals), and the strengthening layer enriched with micro-twin crystals is in a pressure stress state, so that the surface quality of the turbine disc is improved, the creep resistance and fatigue resistance of the surface layer of the turbine disc are synergistically enhanced, fatigue cracks are prevented from being initiated, the service life of the turbine disc is prolonged, performance guarantee is provided for core components of advanced aeroengines, and the thrust-weight ratio of the aeroengines is improved.

Here, the term "microtwintwins" in the present invention means: twin crystals on a nanometer scale (thickness of several to several tens of atomic layers). The micro-twin crystal is an important deformation mechanism of the nickel-based or nickel-cobalt-based high-temperature alloy, and mainly occurs under medium-high temperature conditions, and the micro-twin crystal can block dislocation movement, so that the effect of strengthening the high-temperature alloy is achieved.

In addition, the term "microtwintwinning layer" with respect to the present invention: because the content of the microtwinnes in the surface layer of the turbine disc cannot be quantified; the "enriched microtwinned layer" refers to a surface layer structure having a large number of lamellar structures as seen from surface layer micrographs of a TEM as shown in fig. 2 to 6 (the lamellar structures are microtwins as shown in fig. 2 to 6).

On one hand, the invention provides a preparation method of a nickel-cobalt-based high-temperature alloy turbine disc, which comprises the following steps:

solution treatment: the hot-die-forged turbine disk blank is subjected to solution treatment at a temperature of 0.75-0.95Tm (Tm is the melting point temperature of the nickel-cobalt-based superalloy) for 2-10 hours, and then oil-cooled to room temperature (here, the hot-die-forged turbine disk blank may be replaced with an isothermal-forged turbine disk blank).

Cutting rough machining treatment: and (3) carrying out cutting rough machining on the turbine disc blank subjected to the solution treatment, wherein the target size of the cutting rough machining is 4-10mm more than the final size of the turbine disc. According to a profile diagram of the turbine disc, the position of a center hole of the turbine disc needs to be aligned, the surface of a turbine disc blank subjected to solution treatment is subjected to rough cutting, and the surface roughness Ra is 25-50 mu m.

Aging treatment: and (3) keeping the temperature of the turbine disc blank subjected to the cutting rough machining for 15-30h at the temperature which is 450-550 ℃ lower than the precipitation phase solid solution temperature of the nickel-cobalt-based high-temperature alloy for the turbine disc, and cooling the turbine disc blank to room temperature in air (namely, the first-step aging treatment). And then, preserving the heat of the turbine disc subjected to the first-step aging treatment for 10-30h at the temperature which is 350-450 ℃ lower than the precipitation phase solid solution temperature of the nickel-cobalt-based high-temperature alloy for the turbine disc so as to perform the second-step aging treatment.

Thermal shot blasting treatment: and transferring the uncooled turbine disc blank subjected to the second-step aging treatment into a heat preservation box, and performing shot blasting treatment on the turbine disc blank in the heat preservation box. And (3) spraying the shot with the diameter of 1.2-2.5mm onto the surface of the disc piece by using high pressure, so that the surface of the disc piece is hammered with a pit with the depth of about 2-5 mm. The temperature of the thermal spraying pill treatment is 10-50 ℃ higher than the service temperature of the turbine disk.

Thermal mechanical surface treatment: and (3) carrying out furnace returning and heat preservation on the turbine disc blank subjected to the thermal shot spraying, then transferring the turbine disc blank into a heat preservation box, carrying out surface processing treatment on the disc by using a high-hardness cutter to obtain the final size of the disc, and finally air-cooling the disc to room temperature to obtain the nickel-cobalt-based high-temperature alloy turbine disc. The surface treatment tool is made of hard alloy, and the tool must be cooled by circulating water. The thermomechanical surface treatment can be a thermomechanical rolling and rolling method, the dimensional accuracy of the disk after the thermomechanical surface treatment at least reaches IT5, the surface roughness Ra is less than or equal to 0.2 mu m, and the surface microhardness is more than or equal to 700 HV. The temperature of the thermal mechanical surface treatment is 10-50 ℃ higher than the service temperature of the turbine disk.

In addition, the preparation method of the hot-die-forged turbine disk blank (or the isothermal-forged turbine disk blank) comprises the following steps: respectively carrying out vacuum induction melting, electroslag remelting and vacuum induction consumable melting on the raw materials according to the proportion to obtain a triple smelting ingot; then carrying out two-step homogenization treatment at two temperature ranges of 1000-1150 ℃ and 1100-1250 ℃, then carrying out soft covering on the cast ingot, and carrying out cogging forging at the temperature range of 850-1150 ℃ by using a quick forging machine to obtain a two-phase fine-grained bar material with uniform structure; blanking by using a sawing machine, and further performing hot die forging (or isothermal forging) by using forging equipment at the temperature range of 900-1150 ℃, thereby finally obtaining a hot die forging molded turbine disk blank (or isothermal forging molded turbine disk blank).

Preferably, the raw materials are as follows: the raw materials comprise, by weight, 20-35% of Co, 0-5% of Ta, 78-25% of Cr10, 3-7% of Ti, 0.2-5% of Al, 0.1-5% of W, 0.1-5% of Mo, 0.1-5% of Nb, 0.1-1% of Mn, 0.1-1% of V, 0.005-0.2% of C, 0.01-0.1% of Zr, 0.001-0.1% of B and the balance of Ni.

In the formula, the alloy fault energy is reduced through the content of Co and Ta, so that the alloy generates a deformation mechanism of a fault (micro-twin crystal) in a service temperature range, and a great amount of micro-twin crystals or faults, the interaction between the faults (micro-twin crystals) and the action of the faults (micro-twin crystals) and a precipitated phase realize the strengthening of the micro-twin crystals; and the alloy is still a recrystallization deformation mechanism in a high-temperature deformation interval, so that the alloy has relatively excellent plastic processing performance.

In addition, it should be noted that: although shot peening and surface mechanical treatment are common surface treatment methods for metal materials, conventional shot peening and mechanical rolling (rolling) treatment methods are performed at room temperature. When the turbine disc processed at room temperature is in service at high temperature, the micro structure on the surface of the disc may generate the recovery and growth of nano-crystalline grains or deformed crystalline grains, so that the surface strengthening effect is not obvious in the service temperature interval of the disc, and the improvement on the service life is not obvious. The invention uses the synergistic combination of shot blasting and surface mechanical treatment methods in the surface treatment process of the turbine disk blank for the first time, and adopts thermal shot blasting and thermal surface mechanical treatment for the first time.

In the preparation method, the thickness and the surface roughness of a micro-twin crystal (stacking fault) layer on the surface of the turbine disc can be effectively regulated and controlled through hot shot spraying treatment, so that the aims of improving the high-temperature strength, the hardness, the creep resistance and the fatigue crack initiation resistance of the turbine disc are fulfilled.

In the preparation method, the purpose of the solution treatment is to completely recrystallize and homogenize the turbine disc blank, eliminate residual internal stress generated by hot die forging (or isothermal forging) in the alloy, enable a large amount of gamma' phase in a matrix to be redissolved, reduce the alloy hardness and reduce the difficulty of the next step of cutting and processing. The selection of the solid solution temperature and the heat preservation time is based on eliminating residual stress, redissolving a gamma ' phase and controlling the size of crystal grains, so the solid solution treatment is carried out for 2 to 10 hours at the temperature of 0.75 to 0.95Tm, and the oil quenching is carried out on the turbine disc blank, on one hand, sufficient time is provided to ensure that the recrystallization is sufficient, the residual internal stress is completely recovered, and the gamma ' phase is greatly redissolved, on the other hand, the growth of alloy crystal grains is inhibited, the abnormal growth of the crystal grains is prevented, and simultaneously, the large precipitation of the gamma ' phase is inhibited in the cooling process.

In the above production method, the purpose of the cutting rough machining is to make the size and shape of the turbine disk blank close to the size and shape of the target disk piece. In contrast to the machining of conventional turbine disks, the present invention is only rough machined at this step. The high-temperature alloy for the turbine disc is high in alloying degree, contains a large amount of precipitated phases, is high in hardness, deformation resistance and poor in thermal conductivity, belongs to a material difficult to machine, and is difficult to ensure the surface roughness and the dimensional accuracy of a disc part when the high-temperature alloy is directly processed into a target disc part in a fine machining mode, and the poor surface quality can cause fatigue cracks to occur in the service process of the turbine disc, so that the disc part fails. The cutting processing in the step is rough processing, so that the surface roughness Ra of the disc piece is 25-50 mu m, and the size of the disc piece is 4-10mm more than that of a target disc piece, thereby obviously reducing the cutting difficulty of the disc piece.

In the above preparation method, the purpose of the aging treatment is mainly to fully precipitate a γ 'phase in the matrix, to make the γ' phase in a multi-scale distribution, and to fully exert the precipitation strengthening effect, so that the dual aging treatment is performed, specifically: keeping the temperature for 15-30h in an environment which is 550-450 ℃ lower than the solid solution temperature of the precipitated phase of the nickel-cobalt-based high-temperature alloy to ensure that the gamma 'phase in the crystal grains is fully precipitated, and then keeping the temperature for 10-30h in an environment which is 450-350 ℃ lower than the solid solution temperature of the precipitated phase of the nickel-cobalt-based high-temperature alloy to ensure that the gamma' phase precipitated by the first-step aging heat treatment is partially grown.

In the preparation method, the purpose of the hot-spraying pill treatment is mainly to induce a micro-twin crystal (stacking fault) layer with a certain thickness on the surface of the turbine disk part, form a compressive stress state on the micro-twin crystal (stacking fault) layer, have a high-hardness surface layer with a large number of micro-twin crystals (stacking faults), and can synergistically improve the fatigue and creep properties and inhibit crack initiation. The nickel-cobalt-based high-temperature alloy can generate micro-twin crystals (faults) only when deformed in a service temperature interval, and ensures that the micro-twin crystal (fault) layer is stable when the turbine disk is in service, so that shot blasting treatment must be carried out in an environment which is 10-50 ℃ higher than the rated temperature of the turbine disk. The hot shot spraying treatment adopts the waste heat of the second step of aging treatment, does not need reheating, saves energy and reduces processing cost.

In the above production method, the purpose of the thermo-mechanical surface treatment is to improve the dimensional accuracy of the turbine disk, reduce the roughness, and further generate more volume fractions of micro-twins (stacking faults) in the surface layer. In the invention, the cutting processing and the thermal spraying processing are rough processing, the dimensional accuracy and the surface roughness of the disc part do not meet the use requirements, so the final finish processing is needed, and the mechanical rolling or rolling is a method for workpiece surface nanocrystallization. The hot spraying pill generates a surface strengthening layer with large thickness, the content of micro twin crystal (stacking fault) in the strengthening layer is increased by hot mechanical rolling or rolling, and the two processes are combined for use, so that the disc part can obtain excellent service performance, and the service life of the disc part is prolonged.

In summary, the present invention utilizes thermal spray shots and thermal mechanical surface treatments to achieve improved surface strengthening of nickel-cobalt-based superalloy turbine disks. Compared with the turning and milling processing of the traditional turbine disk, the invention leads the disk part to generate a large amount of micro-twin crystals (faults) through surface layer plastic deformation, and the strengthening layer is in a compressive stress state, and the microstructure and the mechanical state of the surface layer of the disk part are superior to those of the traditional mechanical processing; meanwhile, for the nickel-cobalt-based high-temperature alloy which is a difficult-to-machine material, the alloy is gradually removed from the disc blank through a multi-step process of turning rough machining, shot blasting and rolling (or rolling), so that the alloy removal difficulty is reduced, the size precision and the surface smoothness of the final disc piece are high, and the fatigue crack initiation difficulty in the service process is increased. Compared with surface treatment methods such as coating, the method does not generate obvious interface on the surface of the disc, and even does not cause shedding phenomenon due to poor combination of the coating and the matrix, and the method is a physical method and has the advantage of environmental friendliness; in addition, the process of the invention is a synergistic combination of the traditional processing means, the steps of the whole process are less, the operation is simple, the optimization of the performance of the disc piece is realized under the condition of not changing the alloy components of the turbine disc, and the purpose of prolonging the service life of the turbine disc is achieved.

The following are further detailed by specific experimental examples as follows:

in examples 1 to 5 and comparative example 1 below: the nickel-cobalt-based superalloy turbine disk comprises the following components (in weight percent): 25% of Co, 2% of Ta, 15% of Cr, 5% of Ti, 2.5% of Al, 2% of W, 2% of Mo, 1% of Nb, 0.5% of Mn, 0.1% of V, 0.005% of C, 0.01% of Zr, 0.01% of B and the balance of Ni. The Tm of the nickel-cobalt-based superalloy with the above composition is 1400 ℃, and the precipitated phase solid solution temperature is 1160 ℃.

In addition, the nickel-cobalt-based superalloy turbine disks prepared in examples 1 to 5 and comparative example 1 were characterized as follows: observing the surface microstructure of the nickel-cobalt-based high-temperature alloy turbine disc by using a Transmission Electron Microscope (TEM); testing the surface micro-hardness of the nickel-cobalt-based superalloy turbine disk (GB/T4340.1-2009 Vickers hardness test part 1: test method); the surface roughness and the dimensional accuracy of the nickel-cobalt-based superalloy turbine disk are tested (GB/T10610-2009 product geometric technical Specification (GPS) surface structure contour method is used for evaluating the rules and the method of the surface structure).