Method for inhibiting anisotropy of high-temperature alloy formed by melting metal powder bed through powder pretreatment

Abstract

The invention relates to a method for inhibiting anisotropy of a metal powder bed melt-formed superalloy through powder pretreatment, which comprises the following specific steps: taking a proper amount of nickel-based superalloy powder, and carrying out vacuum sheathing treatment; s2, after the nickel-based high-temperature alloy powder in the step S1 is subjected to vacuum sheathing treatment, the nickel-based high-temperature alloy powder is subjected to heat treatment for a proper time at a proper temperature, and furnace cooling is carried out, so that a proper amount of endogenous nanoparticles are separated out; in this way, powder element distribution and dendritic crystal distribution of atomized powder are improved, and nano-particles are endogenously separated out. After heat treatment of the nickel-based superalloy powder in the step S2 is completed, proper printing parameters are selected, the powder is printed and formed through a metal powder bed fusion forming technology, and the nickel-based superalloy material with weakened anisotropy and excellent mechanical performance is obtained; and the nickel-based high-temperature alloy part obtained in the S3 is subjected to solution treatment, the anisotropy is further eliminated, and the performance is improved. Compared with an existing nickel-based composite material, the mechanical property of the prepared nickel-based high-temperature alloy material is obviously improved.

Description

Technical Field

[0001] The invention relates to the technical field of high-temperature alloy powder material preparation technology, in particular to a method for powder pretreatment to suppress anisotropy of high-temperature alloys formed by metal powder bed fusion. Background Art

[0002] Nickel-based high-temperature alloys can withstand large and complex stresses at temperatures of 600°C and above, have good high-temperature stability, corrosion resistance, and oxidation resistance, and are widely used. However, their high melting point, difficulty in deformation, easy cracking, and difficulty in cutting will cause traditional processing to have problems such as long process flow, low yield rate, high energy consumption, and rapid mold / tool ​​loss.

[0003] Additive manufacturing integrates material and structural design into manufacturing, and can flexibly produce metal parts with excellent mechanical properties and complex structures. The use of additive manufacturing technology, especially the metal powder bed fusion forming of nickel-based high-temperature alloys, is expected to break through the production difficulties of high-performance and complex engine hot end parts, thereby promoting the development of key fields such as aerospace.

[0004] Metal powder bed fusion forming, including laser powder bed fusion and electron beam powder bed fusion, uses this technology to form nickel-based high-temperature alloys. Due to the extremely large longitudinal thermal gradient during cooling during the metal powder bed fusion forming process, the sample has a clear longitudinal growth direction and the shape is close to columnar crystals. This will cause the nickel-based high-temperature alloy products to have poor transverse tensile properties at room temperature and low high-temperature plasticity, which seriously restricts the application of the alloy. Therefore, solving the anisotropy problem of nickel-based high-temperature alloys will help further improve the performance of the alloy and promote its application and development.

[0005] To solve the serious anisotropy problem of nickel-based high-temperature alloy metal powder bed fusion forming, the current idea is mainly to use heat treatment. Through high-temperature heat treatment, the organization undergoes solid solution recrystallization and improves the alloy organization and performance. However, for some nickel-based high-temperature alloys formed by metal powder bed fusion, the conventional heat treatment system cannot make the alloy organization completely equiaxed. Although excessively high heat treatment temperature can further promote the equiaxed organization, it is easy to cause coarse grains, affect mechanical properties, and put higher requirements on the heat treatment furnace. There is also a risk of product damage, which limits the industrial application of some high-temperature alloys. In addition, the addition of nanoparticles can also suppress anisotropy through grain refinement, but it is difficult to prepare large quantities of powders for industrial-grade applications with the addition of nanoparticles, and the samples formed by metal powder bed fusion have the problem of unqualified high-temperature performance.

[0006] Based on this, the present invention combines heat treatment and added nanoparticles to improve the anisotropy mechanism of high-temperature alloys in metal powder bed melt forming. By heat treating the powder, the powder element distribution, the dendrite distribution of the atomized powder, and the endogenous precipitation of nanoparticles are improved, and ultimately the anisotropy problem of nickel-based high-temperature alloy materials in additive manufacturing is suppressed. Summary of the invention

[0007] 1. Technical issues to be resolved

[0008] In view of the shortcomings of the prior art, the present invention provides a method for suppressing the anisotropy of a high-temperature alloy formed by metal powder bed fusion by powder pretreatment. The purpose is to suppress the anisotropy problem of nickel-based high-temperature alloy formed by metal powder bed fusion, improve the longitudinal columnar crystal orientation, and enhance the transverse room-temperature tensile properties and transverse high-temperature plasticity of the high-temperature alloy formed by metal powder bed fusion.

[0009] (II) Technical solution

[0010] To achieve the above object, the present invention provides the following technical solution: a method for suppressing anisotropy of a high-temperature alloy formed by metal powder bed fusion by powder pretreatment, comprising the following specific steps:

[0011] S1: Take an appropriate amount of nickel-based high-temperature alloy powder and perform vacuum encapsulation treatment;

[0012] S2: After the nickel-based high-temperature alloy powder in S1 is vacuum-encapsulated, the nickel-based high-temperature alloy powder is heat-treated at 600°C-1300°C for 1-4 hours, and cooled with the furnace to precipitate an appropriate amount of endogenous nanoparticles; thereby improving the powder element distribution, the dendrite distribution of the atomized powder, and the endogenous precipitation of nanoparticles;

[0013] S3: After the nickel-based high-temperature alloy powder in S2 is heat-treated, select appropriate printing parameters, laser power 100W-400W, scanning speed 500mm / s-1200mm / s, powder layer thickness 20-80μm. Use metal powder bed fusion forming technology to print the powder to obtain a nickel-based high-temperature alloy material with reduced anisotropy and excellent mechanical properties;

[0014] S4: performing solid solution treatment on the nickel-based high-temperature alloy parts obtained in S3 to further eliminate their anisotropy and improve their performance.

[0015] Preferably, the nickel-based high-temperature alloy powder in S1 is a powder of 15-53 μm level. Nickel powders of different particle sizes can achieve the purpose of adjusting the plasticity of the material within a certain range.

[0016] The powder is heat treated to improve the element distribution of the powder, the dendrite distribution of the atomized powder, and the endogenous precipitation of nanoparticles.

[0017] Preferably, the improvement of the element distribution of the powder in S2 and the dendrite distribution of the atomized powder can change the element diffusion behavior during the printing process and affect the deposited tissue state, thereby suppressing anisotropy and improving material properties.

[0018] Preferably, the endogenous nanoparticles in S2 can be used as heterogeneous agents for nickel-based high-temperature alloy materials, wherein the endogenous nanoparticles are carbide, nitride, oxide or boride nanoparticles. The nanoparticles act as heterogeneous agents to promote nucleation, reduce anisotropy and improve material properties.

[0019] Preferably, the heat treatment process in S2 is to select different temperatures and times according to the alloy powder composition. For example, for GH4099 powder, 800-1100°C is selected for treatment for 1-4 hours to improve the powder element distribution, the dendrite distribution of the atomized powder, and precipitate endogenous nanoparticles with suitable size, morphology, and distribution, thereby reducing anisotropy and improving material properties.

[0020] Preferably, the printing parameters in S3 can select appropriate layer thickness, power and printing speed to ensure appropriate energy density, so as to print nickel-based high-temperature alloy prints with excellent mechanical properties and weak anisotropy.

[0021] Preferably, the solution temperature and time in S4 are determined according to the alloy material composition. For example, GH4099 is heat treated at 1080-1200° C. for 1 hour.

[0022] (III) Beneficial effects

[0023] Compared with the prior art, the present invention provides a method for powder pretreatment to suppress anisotropy of high-temperature alloys formed by metal powder bed fusion, which has the following beneficial effects:

[0024] In the process of laser melting, when a new layer of powder is melted by the laser, it will heat the previous layer. This repeated heating causes columnar crystals to grow upward along the thermal gradient direction of the Z axis. The printed sample is easily affected by the thermal gradient in the longitudinal direction, generating obvious columnar crystals. The material has obvious anisotropy and texture orientation, which affects the performance of the material to a certain extent. One of the purposes of subsequent solution treatment of the sample is to obtain a more stable organization and eliminate anisotropy.

[0025] The present invention adopts a powder pretreatment method. First, the powder is vacuum-encapsulated and pretreated under the condition of preventing the powder from oxidation, thereby improving the distribution of powder elements, the dendrite distribution of atomized powder, and the endogenous precipitation of nanoparticles. Then, appropriate printing parameters are selected, and the powder is printed and formed using SLM technology to obtain a material with reduced anisotropy and excellent mechanical properties.

[0026] The present invention pre-treats the powder without changing the powder composition or adding nanoparticles, improves the powder element distribution, the dendrite distribution of the atomized powder, and the endogenous precipitation of nanoparticles, and uses the powder for 3D printing to prepare a nickel-based high-temperature alloy material with weak anisotropy. The process is simple, energy-saving, and time-consuming, and it breaks through the problem that the anisotropy of the nickel-based high-temperature alloy in additive manufacturing seriously affects the room-temperature tensile properties and high-temperature plasticity of the material. The nickel-based high-temperature alloy material prepared in the present invention has significantly improved mechanical properties compared to existing nickel-based composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a metallographic micrograph of the GH4099 nickel-based high-temperature alloy after heat treatment in Example 1 of the present invention;

[0028] Figure 2 This is a metallographic micrograph of the GH4099 nickel-based high-temperature alloy after heat treatment in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Embodiment 1:

[0031] S1: Powder pretreatment

[0032] Take an appropriate amount of GH4099 powder and perform vacuum encapsulation treatment; after the powder vacuum encapsulation treatment, heat treat the GH4099 powder at a suitable temperature and cool it with the furnace to improve the powder element distribution, the dendrite distribution of the atomized powder, and the endogenous precipitation of nanoparticles;

[0033] S2: Selective Laser Melting Additive Manufacturing

[0034] The pretreated powder described in step S1 is additively manufactured using laser selective melting technology. First, the pretreated powder is evenly spread on the substrate to form a powder layer. Then, the laser beam scanning strategy is controlled according to the slicing information to selectively melt the powder layer. The above process is repeated until multiple powder layers are melted and accumulated, and finally a GH4099 nickel-based high-temperature alloy entity with weak anisotropy is obtained.

[0035] S3: Solution aging treatment

[0036] The printed GH4099 nickel-based high-temperature alloy entity was subjected to solution aging treatment to further weaken and eliminate its anisotropy, and obtain an additively manufactured GH4099 nickel-based high-temperature alloy product with qualified industrial application performance.

[0037] The nickel-based high-temperature alloy powder described in S1 is a powder of 15-53μm grade, and the chemical composition of the nickel-based high-temperature alloy powder is: C0-0.08%, Cr17-20%, Co5-8%, W5-7%, Mo3.5-4.5%, Al1.7-2.4%, Ti1-1.5%, Fe0-2%, B0-0.005%, Ce0-0.02%, Mg0-0.01%, Mn0-0.4%, Si0-0.5%, P0-0.015%, S0-0.15%, and the balance is nickel and unavoidable impurities.

[0038] The powder heat treatment process in S1 has a reference temperature of 700-1200° C. and a treatment time of 1-4 hours.

[0039] The parameters of laser selective melting in S2 are: laser power 140W-220W, scanning speed 800mm / s-1000mm / s, powder layer thickness 30μm. Argon is used as protective gas during the forming process.

[0040] The solution aging treatment system in S3 is as follows: the solution temperature is 1080℃-1200℃, the time is 1h; the aging temperature is 800℃-900℃, the time is 5-8h.

[0041] The metallographic micrograph of the first pre-treated powder printed sample after solution aging treatment in this example is as follows Figure 1 shown.

[0042] Comparative Example 1:

[0043] The GH4099 nickel-based superalloy powder was additively manufactured using laser selective melting technology. First, the GH4099 nickel-based superalloy powder was evenly spread on the substrate to form a powder layer. Then, the laser beam scanning strategy was controlled according to the slice information to selectively melt the powder layer. The above process was repeated until multiple powder layers were melted and accumulated, and finally the GH4099 nickel-based superalloy entity was obtained. The sample was then subjected to the same solution aging treatment as in Example 1.

[0044] The nickel-based high-temperature alloy powder is a powder of 15-53μm grade, and the chemical composition of the nickel-based high-temperature alloy powder is: C0-0.08%, Cr17-20%, Co5-8%, W5-7%, Mo3.5-4.5%, Al1.7-2.4%, Ti1-1.5%, Fe0-2%, B0-0.005%, Ce0-0.02%, Mg0-0.01%, Mn0-0.4%, Si0-0.5%, P0-0.015%, S0-0.15%, and the balance is nickel and unavoidable impurities.

[0045] The powder heat treatment process has a reference temperature of 700-1200° C. and a treatment time of 1-4 hours.

[0046] The parameters of laser selective melting are: laser power 140W-220W, scanning speed 800mm / s-1000mm / s, powder layer thickness 30μm. Argon is used as protective gas during the forming process.

[0047] Solution aging treatment system: solution temperature 1080℃-1200℃, time 1h; aging temperature 800℃-900℃, time 5-8h.

[0048] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for suppressing anisotropy of a high-temperature alloy formed by metal powder bed fusion by powder pretreatment, characterized in that: The specific steps include: S1: Take an appropriate amount of nickel-based high-temperature alloy powder and perform vacuum encapsulation treatment; S2: After the nickel-based high-temperature alloy powder in S1 is vacuum-encapsulated, the nickel-based high-temperature alloy powder is heat-treated at a suitable temperature for a suitable time, and cooled with the furnace, so as to precipitate a suitable amount of endogenous nanoparticles; thereby improving the powder element distribution, the dendrite distribution of the atomized powder, and the endogenous precipitation of nanoparticles; S3: After the nickel-based high-temperature alloy powder in S2 is heat-treated, appropriate printing parameters are selected, and the powder is printed and formed using a metal powder bed fusion forming technology to obtain a nickel-based high-temperature alloy material with reduced anisotropy and excellent mechanical properties; S4: performing solid solution treatment on the nickel-based high-temperature alloy parts obtained in S3 to further eliminate their anisotropy and improve their performance.

2. The method for suppressing anisotropy of high-temperature alloys by powder pretreatment in metal powder bed fusion forming according to claim 1, characterized in that: The nickel-based high-temperature alloy powder in S1 is a powder of 15-53 μm. Nickel powders of different particle sizes can achieve the purpose of adjusting the plasticity of the material within a certain range. The powder is heat treated to improve the element distribution of the powder, the dendrite distribution of the atomized powder, and the endogenous precipitation of nanoparticles.

3. The method for suppressing anisotropy of high-temperature alloy by powder pretreatment in metal powder bed fusion forming according to claim 1, characterized in that: The improvement of the powder element distribution in S2 and the dendrite distribution of the atomized powder can change the element diffusion behavior during the printing process and affect the deposited tissue state, thereby suppressing anisotropy and improving material properties.

4. The method for suppressing anisotropy of high-temperature alloy by powder pretreatment in metal powder bed fusion forming according to claim 1, characterized in that: The endogenous nanoparticles in S2 can be used as heterogeneous agents for nickel-based high-temperature alloy materials, wherein the endogenous nanoparticles are carbide, nitride, oxide or boride nanoparticles. The nanoparticles act as heterogeneous agents to promote nucleation, reduce anisotropy and improve material properties.

5. The method for suppressing anisotropy of high-temperature alloy by powder pretreatment in metal powder bed fusion forming according to claim 1, characterized in that: The heat treatment process in S2 is to select different temperatures and times according to the alloy powder composition, improve the powder element distribution, the dendrite distribution of the atomized powder, and precipitate endogenous nanoparticles with suitable size, morphology and distribution, so as to reduce anisotropy and improve material properties.

6. The method for suppressing anisotropy of high-temperature alloy by powder pretreatment in metal powder bed fusion forming according to claim 1, characterized in that: The printing parameters in S3 can select appropriate layer thickness, power and printing speed to ensure appropriate energy density, so as to print nickel-based high-temperature alloy prints with excellent mechanical properties and weak anisotropy.

7. The method for suppressing anisotropy of high temperature alloy by powder pretreatment in metal powder bed fusion forming according to claim 1, characterized in that: The solution temperature and time in S4 are determined according to the composition of the alloy material.

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