阅读说明：本技术 一种减少沉淀强化镍基高温合金热裂的激光粉床熔融成形方法 (Laser powder bed fusion forming method for reducing heat cracks of precipitation strengthening nickel-based high-temperature alloy ) 是由 郭川 朱强 徐振 李干 周阳 于 2020-12-30 设计创作，主要内容包括：本发明提供一种减少沉淀强化镍基高温合金热裂的激光粉床熔融成形方法,所述激光粉床熔融成形方法包括：沉淀强化镍基高温合金粉末在频率为5～10kHz、占空比为50～90％的脉冲激光下激光粉床熔融成形,成形件经冷却后,得到沉淀强化镍基高温合金零件,利用脉冲激光高冷却速率的特点,大大细化了晶粒尺寸,而且减少了易发生开裂的大角度晶界,控制了元素的在晶界处的偏析,从而解决了激光粉床熔融成形沉淀强化镍基高温合金的热裂问题,并提高了成形零件的力学性能。(The invention provides a laser powder bed fusion forming method for reducing heat cracks of precipitation strengthening nickel-based high-temperature alloy, which comprises the following steps: the precipitation-strengthened nickel-based superalloy powder is subjected to laser powder bed melting forming under the pulse laser with the frequency of 5-10 kHz and the duty ratio of 50-90%, and a formed part is cooled to obtain the precipitation-strengthened nickel-based superalloy part.)

1. The laser powder bed fusion forming method for reducing the heat cracking of the precipitation strengthening nickel-based superalloy is characterized by comprising the following steps of: and melting and forming the precipitation-strengthened nickel-based superalloy powder by a laser powder bed under pulse laser with the frequency of 5-10 kHz and the duty ratio of 50-90%, and cooling a formed part to obtain the precipitation-strengthened nickel-based superalloy part.

2. The method of claim 1, wherein the precipitation-strengthened nickel-base superalloy is IN738 LC;

preferably, the particle size D50 of the precipitation strengthening nickel-based superalloy powder is 20-35 μm.

3. The method according to claim 1 or 2, wherein the device for laser powder bed fusion forming is a laser powder bed fusion device;

preferably, the precipitation-strengthened nickel-based superalloy powder is placed in a forming cavity of laser powder bed melting equipment to form a powder layer, and then the laser powder bed melting forming is carried out;

preferably, the thickness of the powder layer is 30-50 μm.

4. The method of claim 3, wherein prior to forming the powder layer, evacuating a forming chamber of the laser powder bed fusion apparatus;

preferably, the vacuum degree after vacuumizing is 3-10 Pa.

5. The method according to any of claims 3 or 4, wherein the powder layer is preheated before the laser powder bed is melt-formed;

preferably, the temperature of the preheating is more than or equal to 100 ℃.

6. The method according to any one of claims 1 to 5, wherein the laser powder bed fusion forming is performed in a protective atmosphere;

preferably, the protective atmosphere comprises argon and/or helium.

7. The method according to any one of claims 1 to 6, wherein the pulsed laser has a beam diameter of 50 to 100 μm;

preferably, the power of the pulse laser is 100-300W;

preferably, the scanning speed of the pulse laser is 500-1500 mm/s;

preferably, the scanning interval of the pulse laser is 50-100 μm.

8. The method according to any one of claims 1 to 7, wherein the frequency of the pulsed laser is 6 to 8 kHz;

preferably, the duty ratio of the pulse laser is 40-80%.

9. The method of any one of claims 1 to 8, wherein the cooling comprises natural cooling.

10. A method according to any one of claims 1 to 9, characterized in that the method comprises the steps of:

(1) vacuumizing a forming cavity of laser powder bed melting equipment to 3-10 Pa, and filling protective atmosphere;

(2) placing precipitation strengthening high-temperature alloy powder with the particle size D50 of 20-35 mu m in a forming cavity of the laser powder bed melting equipment under a protective atmosphere to form a powder layer with the particle size of 30-50 mu m, and preheating the powder layer to the temperature of more than or equal to 100 ℃;

(3) and melting and forming the powder layer by a laser powder bed under pulse laser with the frequency of 5-10 kHz, the duty ratio of 50-90%, the beam diameter of 50-100 mu m, the power of 100-300W, the scanning speed of 500-1500 mm/s and the scanning distance of 50-100 mu m, and naturally cooling the formed part to obtain the precipitation-strengthened nickel-based superalloy part.

Technical Field

The invention relates to the technical field of machine manufacturing, in particular to a laser powder bed fusion forming method for reducing heat cracks of precipitation strengthening nickel-based high-temperature alloy.

Background

The laser powder bed fusion forming method is the most common and rapidly developed technology in the field of metal 3D printing in recent years, and has received wide attention from the industry and academia. In the forming process, a computer system controls laser high-energy beam to selectively melt metal powder, rapid forming of complex parts is realized by a layer-by-layer accumulation method, the method has the advantages of material saving, high size precision and the like, and the forming requirements of partial metal structural materials (such as nickel-based high-temperature alloy, aluminum alloy, titanium alloy, stainless steel and the like) are met at present.

However, the precipitation strengthening nickel-based superalloy component which is widely applied to the fields of aerospace, automobiles, energy industry and the like and has higher working temperature has great technical difficulty. In order to improve the high-temperature mechanical property and long-time stability, the precipitated nickel-based superalloy mainly adopts gamma' phase precipitation strengthening, and the aluminum and titanium elements in the chemical components are required to be higher, so that the heat cracking sensitivity of the alloy is high, and the alloy is difficult to apply to welding and other laser additive manufacturing processes. The high temperature (more than 3000 ℃) and the faster cooling rate (107K/s magnitude) generated in the process of laser powder bed melting forming generate great residual stress, and under the adverse effect of grain boundary segregation, the precipitation strengthening nickel-based high-temperature alloy generates slight in the process and seriously affects the compactness and the mechanical property of the alloy.

At present, the cracking problem of titanium alloy (see "Additive manufacturing of ultra-fine-grained high-strength titanium alloys", Duyao Zhang et al, Nature, volume 576, page 91-95) and high-strength aluminum alloy (see "3D printing of high-strength aluminum alloys", John h.martin et al, Nature, volume 549, page 365-369) during the laser powder bed melt forming process is solved by a method of Additive grain refinement. The method greatly converts columnar crystals in the printing tissue into isometric crystals, and greatly improves the feeding of liquid phase, thereby solving the problem of cracks. However, most of the common refiners cannot refine the structure of the precipitation-strengthened nickel-based superalloy serving at high temperature for a long time and keeping the structure stable, so that the precipitation-strengthened nickel-based superalloy is not suitable for solving the problem of heat cracking generated during laser powder bed melt forming.

Although some research work for improving the hot cracking of the cast Ni-based superalloy by laser powder bed fusion forming method through optimized process has been carried out at home and abroad and certain results have been obtained (see "Selective laser sintering of the hard-to-well IN738LC super alloy: efficiency to yield defects and the residual microstructure and mechanical properties", H.Wang et al, Journal of Alloys and Compounds, volume 807), suitable process parameters need to be searched again for the same alloy powder of different powder suppliers or different batches of alloy powder raw materials of the same supplier and different 3D printing equipment combinations, and the time cost is high. In addition, for precipitation strengthening nickel-base high-temperature alloy with high aluminum and titanium contents, the process window of laser powder bed fusion forming is very small, and the process stability cannot be ensured.

Therefore, it is necessary to develop a laser powder bed fusion forming method for the precipitation-strengthened nickel-based superalloy, so as to solve the problem of thermal cracking of the precipitation-strengthened nickel-based superalloy.

Disclosure of Invention

In view of the problems in the prior art, the invention provides a laser powder bed fusion forming method for reducing heat cracking of a precipitation-strengthened nickel-based superalloy, wherein pulse laser with the frequency of 5-10 kHz and the duty ratio of 50-90% is used for acting on the precipitation-strengthened nickel-based superalloy in the laser powder bed fusion forming method, the heat cracking problem of the precipitation-strengthened nickel-based superalloy formed by the laser powder bed fusion forming is solved, and the crystal grains of a formed piece are obviously refined, so that the mechanical property of the material is improved.

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

in a first aspect, the present invention provides a laser powder bed fusion forming method for reducing heat checking of precipitation-strengthened nickel-base superalloy, comprising: and melting and forming the precipitation-strengthened nickel-based superalloy powder by a laser powder bed under pulse laser with the frequency of 5-10 kHz and the duty ratio of 50-90%, and cooling a formed part to obtain the precipitation-strengthened nickel-based superalloy part.

According to the laser powder bed fusion forming method for reducing heat cracks of the precipitation strengthening nickel-based high-temperature alloy, the pulse laser with the frequency of 5-10 kHz and the duty ratio of 50-90% has a better grain refining effect compared with continuous laser, large-angle grain boundaries which are easy to crack can be reduced, and the segregation of elements at the grain boundaries is controlled, so that the heat cracks of formed parts can be eliminated, and the mechanical properties of the formed parts are improved.

The invention controls the pulse laser frequency and the duty ratio in a specific range, thereby being more beneficial to grain refinement and reducing thermal cracks.

The precipitation strengthening nickel-based superalloy of the invention is an alloy which takes nickel as a main matrix element and generates strengthening effect by a solute atom segregation area in a supersaturated solid solution and/or particles desolventized from a saturated solid solution which are dispersed and distributed in the matrix.

The frequency of the pulsed laser light of the present invention is 5 to 10kHz, and may be, for example, 5kHz, 5.5kHz, 6kHz, 6.5kHz, 7kHz, 8kHz, or 10kHz, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.

Preferably, the duty ratio of the pulsed laser is 50 to 90%, for example, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or 90%, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.

Preferably, the precipitation strengthened nickel-base superalloy is IN738LC precipitation strengthened nickel-base superalloy.

For the precipitation strengthening nickel-based superalloy which is in service at high temperature for a long time and keeps stable structure, the structure of the precipitation strengthening nickel-based superalloy cannot be refined by a conventional refiner adding method, the grain size of the precipitation strengthening nickel-based superalloy is greatly refined by adopting a pulse laser mode, the mechanical property is improved, and the service life is prolonged.

Preferably, the particle size D50 of the precipitation-strengthened nickel-base superalloy powder is 20 to 35 μm, and may be, for example, 20 μm, 22 μm, 24 μm, 25 μm, 26 μm, 28 μm, 30 μm, 32 μm, or 35 μm, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.

According to the invention, the precipitation strengthening nickel-based high-temperature alloy powder with the granularity D50 of 20-35 μm is preferably selected, so that a formed part with finer crystal grains and better mechanical property can be obtained.

Preferably, the IN738LC precipitation-strengthened nickel-base superalloy comprises the following composition C IN mass fraction: 0.10-0.20%, Cr: 15.7-16.3%, Co: 8.0-9.0%, W: 2.4-2.8%, Mo: 1.5-2.0%, Al: 3.2-3.7%, Ti: 3.0-3.5%, Fe: less than or equal to 0.5 percent, Nb: 0.6 to 1.1%, Ta: 1.5-2.0%, B: 0.005-0.015%, Zr: 0.05-0.15%, impurity elements: less than or equal to 0.55 percent, and the balance being nickel.

The IN738LC precipitation-strengthened nickel-base superalloy of the present invention may have a C content of 0.10 to 0.20%, for example, 0.10%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.20%, but is not limited to the above-mentioned values, and other values not shown IN this range are also applicable.

The Cr content is 15.7 to 16.3%, and may be, for example, 15.7%, 15.8%, 15.9%, 16%, 16.1%, 16.2%, 16.3%, or the like, but is not limited to the values listed, and other values not listed in the range are also applicable.

The Co content is 8.0 to 9.0%, and may be, for example, 8.0%, 8.2%, 8.3%, 8.4%, 8.5%, 8.6%, 8.7%, 8.8%, 8.9%, or 9.0%, but is not limited to the above-mentioned values, and other values not listed in this range are also applicable.

The W content is 2.4 to 2.8%, and may be, for example, 2.4%, 2.45%, 2.49%, 2.54%, 2.58%, 2.63%, 2.67%, 2.72%, 2.76%, or 2.8%, but is not limited to the above-mentioned values, and other values not listed in the above range are also applicable.

The Mo content is 1.5 to 2.0%, and may be, for example, 1.5%, 1.56%, 1.62%, 1.67%, 1.73%, 1.78%, 1.84%, 1.89%, 1.95%, or 2.0%, but is not limited to the above-mentioned values, and other values not listed in this range are also applicable.

The Al content is 3.2 to 3.7%, and may be, for example, 3.2%, 3.26%, 3.32%, 3.37%, 3.43%, 3.48%, 3.54%, 3.59%, 3.65%, or 3.7%, but is not limited to the above-mentioned values, and other values not listed in the above range are also applicable.

The Ti content is 3.0 to 3.5%, and may be, for example, 3.0%, 3.06%, 3.12%, 3.17%, 3.23%, 3.28%, 3.34%, 3.39%, 3.45%, or 3.5%, but is not limited to the above-mentioned values, and other values not listed in the above range are also applicable.

The Fe content is 0.5% or less, and may be, for example, 0.1%, 0.15%, 0.19%, 0.24%, 0.28%, 0.33%, 0.37%, 0.42%, 0.46%, or 0.5%, but is not limited to the values listed, and other values not listed in the range are also applicable.

The Nb content is 0.6 to 1.1%, and may be, for example, 0.6%, 0.66%, 0.72%, 0.77%, 0.83%, 0.88%, 0.94%, 0.99%, 1.05%, or 1.1%, but is not limited to the above-mentioned values, and other values not listed in this range are also applicable.

The Ta content is 1.5 to 2.0%, and may be, for example, 1.5%, 1.56%, 1.62%, 1.67%, 1.73%, 1.78%, 1.84%, 1.89%, 1.95%, or 2.0%, but is not limited to the above-mentioned values, and other values not listed in the above range are also applicable.

The B content is 0.005 to 0.015%, and for example, 0.005%, 0.007%, 0.008%, 0.009%, 0.01%, 0.011%, 0.012%, 0.013%, 0.014%, or 0.015% may be used, but not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.

The Zr content is 0.05 to 0.15%, and may be, for example, 0.05%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, or 0.15%, but is not limited to the above-mentioned values, and other values not listed in the above range are also applicable.

The content of the impurity element is not more than 0.55%, and may be, for example, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, or 0.55%, etc., but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.

Preferably, the device for laser powder bed fusion forming is a laser powder bed fusion device.

Preferably, the precipitation strengthening nickel-based superalloy powder is placed in a forming cavity of laser powder bed melting equipment to form a powder layer, and then the laser powder bed melting forming is carried out.

Preferably, the powder layer has a thickness of 30 to 50 μm, and may be, for example, 30 μm, 32 μm, 35 μm, 40 μm, 42 μm, 45 μm, or 50 μm.

Preferably, the forming chamber of the laser powder bed fusing apparatus is evacuated prior to forming the powder layer.

Preferably, the degree of vacuum after evacuation is 3 to 10Pa, and may be, for example, 3Pa, 4Pa, 5Pa, 6Pa, 7Pa, 8Pa, 9Pa, or 10 Pa.

Preferably, the powder layer is preheated before the laser powder bed is melt-formed.

Preferably, the temperature of the preheating is not less than 100 ℃, for example, 100 ℃, 120 ℃, 150 ℃, 180 ℃, 200 ℃, 220 ℃ or 230 ℃, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

The invention preferably preheats the alloy and then carries out the fusion forming of the laser powder bed, which is more beneficial to preventing the heat cracking of the precipitation strengthening nickel-based high-temperature alloy.

Preferably, the laser powder bed fusion forming is performed in a protective atmosphere.

Preferably, the protective atmosphere comprises argon and/or helium.

Preferably, the beam diameter of the pulsed laser is 50 to 100 μm, and may be, for example, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, or 80 μm, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.

Preferably, the power of the pulsed laser is 100 to 300W, for example, 150W, 180W, 200W, 220W, 250W, or 300W, but is not limited to the values listed above, and other values not listed above within the range of values are also applicable.

Preferably, the scanning speed of the pulsed laser is 500 to 1500mm/s, and may be, for example, 500mm/s, 600mm/s, 700mm/s, 800mm/s, 900mm/s, 1200mm/s, etc., but is not limited to the values listed, and other values not listed in the range of the values are also applicable.

Preferably, the scanning pitch of the pulsed laser is 50 to 100 μm, and may be, for example, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, or 100 μm, but is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned range are also applicable.

Preferably, the frequency of the pulsed laser is 6 to 8kHz, for example, 6kHz, 6.5kHz, 7kHz or 8kHz, but not limited to the recited values, and other values not recited in the recited value range are also applicable.

Preferably, the duty ratio of the pulsed laser is 40 to 80%, and may be, for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 80%, but is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable.

Preferably, the cooling comprises natural cooling.

As a preferred technical scheme of the invention, the method comprises the following steps:

(1) vacuumizing a forming cavity of laser powder bed melting equipment to 3-10 Pa, and filling protective atmosphere;

(2) placing precipitation strengthening high-temperature alloy powder with the particle size D50 of 20-35 mu m in a forming cavity of the laser powder bed melting equipment under a protective atmosphere to form a powder layer with the particle size of 30-50 mu m, and preheating the powder layer to the temperature of more than or equal to 100 ℃;

(3) and melting and forming the powder layer by a laser powder bed under pulse laser with the frequency of 5-10 kHz, the duty ratio of 50-90%, the beam diameter of 50-100 mu m, the power of 100-300W, the scanning speed of 500-1500 mm/s and the scanning distance of 50-100 mu m, and naturally cooling the formed part to obtain the precipitation-strengthened nickel-based superalloy part.

The shape of the precipitation strengthening nickel-based high-temperature alloy part is not particularly limited, and the precipitation strengthening nickel-based high-temperature alloy parts with different shapes can be obtained according to the actual process requirements.

Compared with the prior art, the invention has at least the following beneficial effects:

(1) the laser powder bed fusion forming method for reducing the heat cracking of the precipitation strengthening nickel-base high-temperature alloy reduces the high-angle crystal boundary which is easy to crack by utilizing the characteristic of high cooling rate of the pulse laser, and controls the segregation of elements at the crystal boundary, thereby solving the heat cracking problem of the precipitation strengthening nickel-base high-temperature alloy formed by the laser powder bed fusion forming;

(2) the laser powder bed fusion forming method for reducing heat cracks of the precipitation strengthening nickel-based high-temperature alloy improves the mechanical property of formed parts, the tensile strength is improved by more than 30 percent, and the tensile strength is more than or equal to 900 MPa;

(3) the laser powder bed fusion forming method for reducing the heat cracks of the precipitation strengthening nickel-based superalloy greatly refines the grain size, and the grain size of a formed part is less than or equal to 60 mu m.

Drawings

FIG. 1 is a schematic view of a precipitation-strengthened nickel-base superalloy component produced by a laser powder bed fusion forming method for reducing thermal cracking in a precipitation-strengthened nickel-base superalloy, according to example 1 of the present disclosure.

FIG. 2 is an optical microscope photograph of the precipitation strengthened nickel-base superalloy parts of example 1 of the present invention and comparative example 1.

FIG. 3 is an electron back-scattered diffraction pattern of the precipitation-strengthened nickel-base superalloy components of example 1 of the present invention and comparative example 1.

FIG. 4 is a drawing graph of precipitation strengthened nickel-base superalloy parts made according to example 1 of the present invention and comparative example 1.

Detailed Description

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.

The present invention is described in further detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.

First, an embodiment

Example 1

The embodiment provides a laser powder bed fusion forming method for reducing heat cracks of a precipitation strengthening nickel-based superalloy, which comprises the following steps:

(1) vacuumizing a forming cavity of laser powder bed melting equipment to 5Pa, and filling argon with the purity of 99.99 percent as protective atmosphere;

(2) placing IN738LC precipitation strengthening high-temperature alloy powder with the particle size range of 15-53 mu m and the particle size D50 of 30.1 mu m IN a forming cavity of laser powder bed melting equipment under a protective atmosphere to form a 30 mu m powder layer, and preheating the powder layer to the temperature of 150 ℃;

(3) and melting and forming the powder layer by a laser powder bed under pulse laser with the frequency of 7kHz, the duty ratio of 70%, the beam diameter of 100 mu m, the power of 250W, the scanning speed of 800mm/s and the scanning interval of 50 mu m, and naturally cooling a formed part to obtain the precipitation-strengthened nickel-based superalloy part shown in the figure 1.

The precipitation strengthening high-temperature alloy powder with the material IN738LC comprises the following components IN percentage by mass: 0.12%, Cr: 15.82%, Co: 8.32%, W: 2.58%, Mo: 1.82%, Al: 3.50%, Ti: 3.48%, Nb: 0.88%, Ta: 1.78%, B: 0.01%, Zr: 0.06%, impurity elements: less than or equal to 0.55 percent, and the balance being nickel.

Example 2

The embodiment provides a laser powder bed fusion forming method for reducing heat cracks of a precipitation strengthening nickel-based superalloy, which comprises the following steps:

(1) vacuumizing a forming cavity of laser powder bed melting equipment to 6Pa, and filling helium with the purity of 99.99% as protective atmosphere;

(2) placing IN738LC precipitation strengthening high-temperature alloy powder with the particle size range of 16-45 mu m and the particle size D50 of 25.3 mu m IN a forming cavity of laser powder bed melting equipment under a protective atmosphere to form a 50 mu m powder layer, and preheating the powder layer to 100 ℃;

(3) and melting and forming the powder layer by a laser powder bed under pulse laser with the frequency of 10kHz, the duty ratio of 50%, the beam diameter of 80 mu m, the power of 100W, the scanning speed of 500mm/s and the scanning interval of 100 mu m, and naturally cooling the formed part to obtain the precipitation-strengthened nickel-based superalloy part.

The precipitation strengthening high-temperature alloy powder with the material IN738LC comprises the following components IN percentage by mass: 0.12%, Cr: 15.82%, Co: 8.32%, W: 2.58%, Mo: 1.82%, Al: 3.50%, Ti: 3.48%, Nb: 0.88%, Ta: 1.78%, B: 0.01%, Zr: 0.06%, impurity elements: less than or equal to 0.55 percent, and the balance being nickel.

Example 3

The embodiment provides a laser powder bed fusion forming method for reducing heat cracks of a precipitation strengthening nickel-based superalloy, which comprises the following steps:

(1) vacuumizing a forming cavity of laser powder bed melting equipment to 4Pa, and filling argon with the purity of 99.99% as protective atmosphere;

(2) placing IN738LC precipitation strengthening high-temperature alloy powder with the particle size range of 10-33 mu m and the particle size D50 of 21.2 mu m IN a forming cavity of laser powder bed melting equipment under a protective atmosphere to form a 40 mu m powder layer, and preheating the powder layer to 160 ℃;

(3) and melting and forming the powder layer by a laser powder bed under pulse laser with the frequency of 1kHz, the duty ratio of 80%, the beam diameter of 85 mu m, the power of 300W, the scanning speed of 1500mm/s and the scanning interval of 70 mu m, and naturally cooling the formed part to obtain the precipitation-strengthened nickel-based superalloy part.

The precipitation strengthening high-temperature alloy powder with the material IN738LC comprises the following components IN percentage by mass: 0.12%, Cr: 15.82%, Co: 8.32%, W: 2.58%, Mo: 1.82%, Al: 3.50%, Ti: 3.48%, Nb: 0.88%, Ta: 1.78%, B: 0.01%, Zr: 0.06%, impurity elements: less than or equal to 0.55 percent, and the balance being nickel.

Example 4

This example provides a laser powder bed fusion forming method for reducing thermal cracking of precipitation strengthened nickel-base superalloy, which is the same as example 1 except that "frequency 7 kHz" in step (3) is replaced with "frequency 5 kHz".

Example 5

This example provides a laser powder bed fusion forming method for reducing thermal cracking of precipitation strengthened nickel-base superalloy, which is the same as example 1 except that "frequency 7 kHz" in step (3) is replaced with "frequency 10 kHz".

Example 6

The present example provides a laser powder bed fusion forming method for reducing thermal cracking of precipitation-strengthened nickel-base superalloy, which is the same as example 1 except that "duty ratio of 70%" in step (3) is replaced with "duty ratio of 50%".

Example 7

The present example provides a laser powder bed fusion forming method for reducing thermal cracking of precipitation-strengthened nickel-base superalloy, which is the same as example 1 except that "duty cycle of 70%" in step (3) is replaced with "duty cycle of 90%".

Example 8

This example provides a laser powder bed fusion forming method for reducing thermal cracking of precipitation-strengthened nickel-base superalloy, which is the same as example 1 except that no preheating is performed in step (2).

Second, comparative example

Comparative example 1

The present comparative example provides a laser powder bed fusion forming method of precipitation strengthening nickel-base superalloy thermal cracking, which is the same as example 1 except that "pulsed laser with frequency of 7kHz, duty cycle of 70%, beam diameter of 100 μm, power of 250W, scanning speed of 800mm/s and scanning pitch of 50 μm" in step (3) is replaced with "continuous laser with beam diameter of 100 μm, power of 250W, scanning speed of 800mm/s and scanning pitch of 50 μm".

Comparative example 2

This comparative example provides a laser powder bed fusion forming process for heat cracking of a precipitation strengthened nickel-base superalloy, which is the same as example 1 except that "frequency 7 kHz" in step (3) is replaced with "frequency 2 kHz".

Comparative example 3

This comparative example provides a laser powder bed fusion forming process for heat cracking of a precipitation strengthened nickel-base superalloy, which is the same as example 1 except that "frequency 7 kHz" in step (3) is replaced with "frequency 15 kHz".

Comparative example 4

The comparative example provides a laser powder bed fusion forming method for heat cracking of a precipitation-strengthened nickel-base superalloy, which is the same as that in example 1 except that the duty ratio of 70% in the step (3) is replaced by 30%.

Third, test and results

Taking example 1 and comparative example 1 as examples, the prepared precipitation-strengthened nickel-based superalloy part is mechanically polished, then placed on a Buehler VibroMet vibration polishing machine for vibration polishing for 2 hours, and the surface of the part is tested by using an optical microscope, and the result is shown in FIG. 2; while fig. 2 (a) shows the precipitation strengthened nickel-base superalloy part obtained in comparative example 1 and fig. 2 (b) shows the precipitation strengthened nickel-base superalloy part obtained in example 1, it can be seen from fig. 2 that there are no thermal cracks on the surface of the precipitation strengthened nickel-base superalloy part in example 1 and there are significant thermal cracks on the surface of the precipitation strengthened nickel-base superalloy part obtained in comparative example 1.

Using example 1 and comparative example 1 as examples, a mapping test was performed using an EDASDigiview4 electron backscatter probe equipped with a ZEISSMerlin scanning electron microscope at a voltage of 20kV and a current of 5nA, and the results are shown in FIG. 3. FIG. 3 (a) shows the precipitation strengthened nickel-base superalloy component produced in comparative example 1, FIG. 3 (b) shows the precipitation strengthened nickel-base superalloy component produced in example 1, and it can be seen from FIG. 3 and calculations that the grain size of the precipitation strengthened nickel-base superalloy component produced by the method of example 1 is reduced from 86.3 μm using comparative example 1 to 57.5 μm.

The precipitation-strengthened nickel-base superalloy parts prepared in example 1 and comparative example 1 were subjected to a high temperature tensile test at 850 ℃, room temperature (25 ℃), a strain rate of 0.01mm/mm/min, a ZJSYRDL100 tester, and the precipitation-strengthened nickel-base superalloy parts prepared in example 1 and comparative example 1 were subjected to a tensile test, and the results are shown in fig. 4. As can be seen from FIG. 4 and the calculations, the strength of the precipitation strengthened nickel-base superalloy part prepared by the method of example 1 is increased from 802.4MPa to 1167.3MPa in comparative example 1.

The test results of the two are compared and calculated, and the formed part prepared by the method has no crack defects compared with a continuous laser formed part.

The test results of the above examples and comparative examples are shown in table 1.

TABLE 1

From table 1, the following points can be seen:

(1) it can be seen from the comprehensive examples 1 to 8 that the laser powder bed fusion forming method for reducing the thermal cracking of the precipitation-strengthened nickel-base superalloy, provided by the invention, adopts pulsed laser to process, so that the grain size is refined, the size is less than or equal to 84 μm, and the tensile strength is greater than or equal to 880MPa, thereby solving the thermal cracking problem of the precipitation-strengthened nickel-base superalloy formed by the laser powder bed fusion forming, and improving the mechanical properties of formed parts;

(2) by combining example 1 with comparative example 1, it can be seen that the tensile strength of example 1 is 1167.3MPa and the grain size is 57.5 μm compared to the continuous laser used in example 1, the tensile strength of comparative example 1 is only 802.4MPa and the grain size is as high as 86.3 μm, thus showing that the grain is refined and the tensile strength of the precipitation-strengthened nickel-base superalloy is improved by using the pulsed laser;

(3) by combining examples 1, 4 to 5 and comparative examples 2 to 3, it can be seen that the frequencies of examples 1 and 4 to 5 were 7kHz, 5kHz and 10kHz, respectively, and the tensile strength of example 1 was 1167.3MPa and the grain size was 57.5 μm, compared to the frequencies of 2kHz and 15kHz, respectively, in comparative examples 2 to 3, in examples 4 to 5, the tensile strengths were 886.9MPa and 986.7MPa, respectively, and the crystal grain sizes were 83.4 μm and 77.6. mu.m, respectively, comparative examples 2 to 3 had tensile strengths of only 832.7MPa and 756.3MPa, the grain size was 85.6 μm in comparative example 2, the grain size could not be measured due to excessive porosity in comparative example 3, it is thus shown that the present invention improves tensile strength and reduces grain size by controlling the frequency of the pulse laser within a specific range, and further obtains the precipitation strengthening nickel-based high-temperature alloy with better mechanical property through a further optimized range;

(4) it can be seen from the combination of examples 1, 6 to 7 and comparative example 4 that the duty ratios of examples 1 and 6 to 7 are 70%, 50% and 90%, respectively, and the tensile strength of example 1 is 1167.3MPa and the grain size is 57.5 μm, while the tensile strengths of examples 6 to 7 are 1032.7MPa and 936.4MPa, respectively, and the grain sizes of examples are 74.5 μm and 79.3 μm, respectively, as compared to the duty ratio of 30% of comparative example 4, and the tensile strength of comparative example 4 is only 732.1MPa, and the grain size cannot be measured due to excessive porosity, thereby showing that the present invention improves the tensile strength and reduces the grain size by controlling the duty ratio of the pulse laser within a specific range, and further obtains a precipitation-strengthened nickel-based superalloy with better mechanical properties through a further preferable range.

In conclusion, the laser powder bed fusion forming method for reducing heat cracks of the precipitation strengthening nickel-based superalloy, provided by the invention, has the advantages that the characteristic of high cooling rate of pulse laser is utilized, the grain size is greatly refined and is less than or equal to 84 mu m, the large-angle grain boundary which is easy to crack is reduced, the mechanical property of a formed part is improved, the tensile strength is greater than or equal to 880MPa, and the application prospect is wide.

The applicant declares that the present invention illustrates the detailed structural features of the present invention through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must be implemented depending on the above detailed structural features. It should be understood by those skilled in the art that any modifications of the present invention, equivalent substitutions of selected components of the present invention, additions of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.