CN114871425B

CN114871425B - Application of refractory high-entropy alloy powder material in additive manufacturing

Info

Publication number: CN114871425B
Application number: CN202210462970.8A
Authority: CN
Inventors: 冯凯; 徐金涛; 李铸国; 段然; 张显程
Original assignee: Shanghai Jiaotong University
Current assignee: Shanghai Jiaotong University
Priority date: 2022-04-28
Filing date: 2022-04-28
Publication date: 2023-05-23
Anticipated expiration: 2042-04-28
Also published as: CN114871425A

Abstract

The invention discloses a refractory high-entropy alloy powder material, which relates to the fields of additive manufacturing and high-entropy alloy and is characterized in that a main material component of the refractory high-entropy alloy powder material comprises Nb, mo, ta, W powder material, the atomic percentage of each metal is respectively 10% -40%, the additive powder comprises one or two of NbC, moC, taC, WC, zrC, tiC and C, the atomic percentage content is 0< x and less than or equal to 5%, and the atomic percentage sum is 100%. The preparation method comprises the steps of removing oxide layers and impurities of the powder material, weighing, proportioning, performing ball milling, uniformly mixing the powder, and finally drying the composite powder material by adopting vacuum heating equipment for later use. The invention also discloses an application method of the refractory high-entropy alloy powder material in additive manufacturing. The refractory high-entropy alloy powder material provided by the invention overcomes the problems of easy cracking and defects in additive manufacturing, and has a wide application prospect in the fields of high temperature and ultrahigh temperature.

Description

Application of refractory high-entropy alloy powder material in additive manufacturing

Technical Field

The invention relates to the technical field of additive manufacturing and high-entropy alloy, in particular to a refractory high-entropy alloy powder material, a preparation method and application thereof in additive manufacturing.

Background

Refractory superalloy has gained widespread attention throughout the world due to its excellent high temperature resistance, and is believed to lead to a revolutionary transformation in the superalloy field. The NbMoTaW refractory high-entropy alloy is reported by Senkov team in air force laboratory in the United states for the first time in 2010, and can keep stable phase structure and structure at 1400 ℃, still has outstanding comprehensive mechanical properties at high temperature of 1600 ℃, and has far super-nickel-based superalloy with yield strength, specific yield strength and other high-temperature mechanical properties at above 1000 ℃.

However, most refractory high entropy alloys have not been reasonably coordinated between strength and formability. The NbMoTaW refractory high-entropy alloy has poor room-temperature plasticity and severe brittleness (the room-temperature compressive strain is only 2.1 percent), and the fracture is quasi-cleavage fracture, so that the machinability is extremely poor. Therefore, the existing preparation modes of arc melting, powder metallurgy and the like of refractory high-entropy alloy have great limitations: the defects of insufficient size, simple shape, poor processability and the like of the prepared refractory high-entropy alloy severely limit the further popularization and application of the refractory high-entropy alloy.

The additive manufacturing has the advantages of near net forming, short production flow, controllable local shape and the like, and has unique advantages in part weight reduction design, rapid iteration design and high-performance manufacturing. Due to the characteristic of near net shape formation of the technology, the bottleneck of complex structure preparation of refractory high-entropy alloy can be well solved. However, the refractory high-entropy alloy has great room temperature brittleness and great solid state cooling temperature interval (high melting point) resulting in difficult stress control, so that the additive manufacturing of the refractory high-entropy alloy has extremely high difficulty. If the NbMoTaW refractory high-entropy alloy powder material suitable for additive manufacturing can be designed and prepared, the preparation of large-size components of the NbMoTaW refractory high-entropy alloy can be realized, the method can be effectively promoted to be popularized and applied in the field of high-temperature structural materials, and a solid new-generation material support is provided for the innovation and development of new-generation equipment in important fields such as aerospace vehicles, power devices, nuclear reactors, power generation equipment and the like.

The pursuit of good toughness matching of NbMoTaW refractory high-entropy alloys, in particular improvement of room temperature brittleness, is an important pursuit goal. The refractory high-entropy alloy is high in strength and fragile at room temperature, and is difficult to promote strengthening by mechanical processing induced deformation, and the currently adopted method is still mainly optimized in composition. At present, the material design for NbMoTaW refractory high-entropy alloy mainly aims at an arc melting process, a solid-phase sintering process and the like, and lacks a material and powder material design method special for the characteristic of rapid unbalanced solidification of additive manufacturing. In order to solve the cracking and forming problems caused by brittleness of refractory high-entropy alloy in the process of rapid unbalanced cooling in laser additive manufacturing, the key parameters such as the components and the grain size range of the powder material need to be specially designed.

Accordingly, those skilled in the art have focused their efforts on developing a refractory high-entropy alloy powder material suitable for additive manufacturing and methods of application that are very important to drive its application.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, the technical problem to be solved by the present invention is that the refractory high-entropy alloy has poor workability due to room temperature brittleness, and is extremely prone to generate defects such as cracks and poor forming quality in additive manufacturing, and meanwhile, the refractory high-entropy alloy has the defects of insufficient size, simple shape and the like in the conventional preparation methods such as arc melting, powder metallurgy and the like.

In order to achieve the above object, the present invention provides a refractory high-entropy alloy powder material, which comprises a main component and an additive powder, wherein the main component comprises Nb, mo, ta, W powder material, the additive powder comprises one or two of NbC, moC, taC, WC, zrC, tiC and C, and one or two of the above substances are added mainly to solve the problem of room temperature brittleness of the refractory high-entropy alloy and improve the room temperature strength and toughness of the refractory high-entropy alloy. By adding these powder materials, nanophase can be precipitated in the bulk material structure of additive manufacturing. .

Further, the atomic percentages of the Nb, mo, ta, W powder materials are respectively 10% -40%, the atomic percentage content of the additive powder is 0< x < 5%, and the total atomic percentage is 100%.

Further, the particle size of the Nb, mo, ta, W powder material is 5 to 250 μm, and the particle size of the additive powder is 10 to 50 μm.

The invention provides a preparation method of the refractory high-entropy alloy powder material, which comprises the following steps:

step a, removing oxide layers and impurities of the powder material by adopting the Nb, mo, ta, W powder material with the purity of more than 99.9 percent and one or two of the additive powder NbC, moC, taC, WC, zrC, tiC and the additive powder C;

step b, calculating the mass of each element and compound required by each powder material according to the atomic percentage of the designed components, and then weighing and proportioning;

c, performing ball milling and uniform powder mixing treatment on the composite powder material with the weighed proportion by adopting a ball mill until all components in the composite powder material are uniformly mixed;

and d, drying the composite powder material subjected to uniform powder mixing by adopting vacuum heating and drying equipment, and sufficiently removing water vapor, various gases and impurities attached to the surface of the powder to obtain the refractory high-entropy alloy powder material.

The invention also provides an application of the refractory high-entropy alloy powder material obtained by the preparation method in additive manufacturing, which comprises the following steps:

step 1: selecting a metal substrate with proper size, and cleaning the metal substrate until the metal substrate is clean, free of oil dirt, dust and rust;

step 2: adopting a powder feeding type additive manufacturing system, carrying a heat source by adopting an industrial robot, and connecting a feeding system in parallel, sieving the refractory high-entropy alloy powder material and filling the sieved refractory high-entropy alloy powder material into the feeding system;

step 3: establishing a 3D model of a workpiece to be printed in software, converting the model into a robot scanning path file, and inputting the robot scanning path file into a computer controlled by the industrial robot;

step 4: scanning in a given path while feeding new refractory high-entropy alloy powder material through the feed system;

step 5: after all scanning is completed and cooling is performed, separating the workpiece from the metal substrate by using linear cutting;

step 6: and cleaning, grinding and polishing the workpiece to obtain a refractory high-entropy alloy block sample.

Further, step 2 may be a powder bed powder additive manufacturing system, in which a doctor blade is disposed for laying the refractory high-entropy alloy powder material of the first layer on the metal substrate of step 1.

Further, the phase structure of the refractory high-entropy alloy block sample at room temperature is a composite structure of a body-centered cubic crystal structure and a nano precipitation strengthening phase.

The invention combines the requirements of the additive manufacturing field with the characteristics of refractory high-entropy alloy, provides a refractory high-entropy alloy powder material suitable for the rapid unbalanced cooling characteristic of additive manufacturing and a modified design method, effectively solves the defect problems of cracks and the like of the refractory high-entropy alloy additive manufacturing, and improves the cracking resistance of the refractory high-entropy alloy;

the precipitation of the nano reinforced phase in the body-centered cubic solid solution matrix is promoted under the extra-normal metallurgical condition of additive manufacturing by utilizing a small amount of added carbide, the grain size of the additive manufacturing is thinned, and the room temperature strength, the plasticity and the high temperature strength of the refractory high-entropy alloy of the additive manufacturing are further improved at the same time;

the material utilization rate can be greatly improved, the material cost can be reduced by utilizing the advantages of the additive manufacturing technology, such as near net forming, short production flow, controllable local shape and the like, and the method has obvious advantages in the aspects of weight reduction design, rapid iteration design, high-performance manufacturing and the like of parts;

the powder material has the advantages of fewer elements, simple preparation, easy realization of industrial production, low cost, environmental friendliness and the like.

The conception, specific structure, and technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, features, and effects of the present invention.

Drawings

FIG. 1 is a typical SEM morphology of a NbMoTaW refractory high-entropy alloy powder material after uniform mixing and drying;

FIG. 2 is a photograph of a bulk sample (a) prepared by selective laser melting of a refractory high-entropy alloy of NbMoTaW system according to the third embodiment of the invention and a SEM photograph of a bulk sample (b) prepared by selective laser melting of a refractory high-entropy alloy of NbMoTaW system according to the invention;

FIG. 3 is an XRD pattern of a sample prepared from NbMoTaW-based refractory high-entropy alloy additive manufacturing according to example III of the present invention;

FIG. 4 is a TEM bright field image of a sample of NbMoTaW-based refractory high-entropy alloy additive manufacturing preparation according to example III of the present invention;

fig. 5 is a room temperature compression curve and fracture morphology of a sample prepared by NbMoTaW-based refractory high-entropy alloy additive manufacturing according to example three of the present invention.

Detailed Description

The following description of the preferred embodiments of the present invention refers to the accompanying drawings, which make the technical contents thereof more clear and easy to understand. The present invention may be embodied in many different forms of embodiments and the scope of the present invention is not limited to only the embodiments described herein.

Example 1

Adopting Nb, mo, ta, W powder material with the particle size of 50-150 mu m, wherein the atomic percentages are 25%, 24.5%, 25% and 25%, adding ZrC powder with the particle size of 50-200 nm, the atomic percentage is 0.5%, the purity of the used powder material is more than or equal to 99.9%, and carrying out additive manufacturing after ball milling, uniform mixing and vacuum drying, the steps are as follows:

step 1), selecting a tungsten substrate with the thickness of 100mm multiplied by 20mm, and cleaning the tungsten substrate to be clean, free of oil dirt, dust, rust and the like;

step 2) carrying a laser by an industrial robot, connecting a powder feeding type laser additive manufacturing system in parallel, sieving powder, and filling the powder into the powder feeding system;

step 3), establishing a 3D model of a cube array with the side length of 20mm to be printed in software, converting the model into a robot scanning path file, and inputting the robot scanning path file into a robot control computer;

step 4) scanning at a given path at a scanning speed of 8mm/s, a power of 4000W, a layer thickness of 0.6 mm; every time a layer is scanned, the computer controls the robot to rise by a distance of one layer of thickness, and meanwhile, a new layer of alloy powder is fed through the powder feeding mechanism;

step 5) separating the workpiece from the substrate by using linear cutting after all scanning is completed and cooling is carried out;

and 6) cleaning, grinding and polishing the workpiece until the requirement is met.

Example 2

Adopting Nb, mo, ta, W powder material with the particle size of 15-60 mu m, wherein the atomic percentages are 24%, and adding TiC powder with the particle size of 10-100 nm, the atomic percentage is 4%, the purity of the used powder material is more than or equal to 99.95%, and the additive manufacturing is carried out after ball milling, uniform mixing and vacuum drying, and the steps are as follows:

step 1), selecting a Nb substrate with the thickness of 100mm multiplied by 10mm, and cleaning the Nb substrate to be clean, free of oil dirt, dust, rust and the like;

step 2) adopting a powder bed powder type additive manufacturing system, sieving the powder, filling the powder into a powder laying system, and simultaneously laying a first layer of powder on a substrate by a scraper in the powder laying system;

step 3), establishing a 3D model of a cylindrical array with the radius of 5mm and the height of 10mm to be printed in software, converting the model into a robot scanning path file, and inputting the robot scanning path file into a robot control computer;

step 4) scanning at a given path according to a scanning speed of 1000mm/s, a scanning interval of 0.04mm, a power of 180W, a laser spot diameter of 0.03mm and a layer thickness of 0.03 mm; every time a layer is scanned, the computer controls the distance that the substrate descends by one layer of thickness, and meanwhile, a new layer of alloy powder is paved through a powder paving mechanism;

Example 3

Nb, mo, ta, W powder material with the particle size of 5-80 mu m is adopted, the atomic percentages are respectively 20%, 30% and 28%, WC powder with the particle size of 100 nm-50 mu m is added, the atomic percentage is 2%, the purity of the used powder material is more than or equal to 99.9%, and the additive manufacturing is carried out after ball milling, uniform mixing and vacuum drying, and the steps are as follows:

step 1), selecting a Mo substrate with the thickness of 200mm multiplied by 10mm, and cleaning the Mo substrate to be clean, free from oil dirt, dust, rust and the like;

step 4) scanning at a given path according to a scanning speed of 700mm/s, a scanning interval of 0.04mm, a power of 280W, a laser spot diameter of 0.03mm and a layer thickness of 0.03mm, wherein a computer controls a substrate to descend by a distance of one layer thickness every scanning, and simultaneously, a new layer of alloy powder is paved in through a powder paving mechanism;

and 6) grinding and polishing until the requirements are met.

Example 4

Adopting Nb, mo, ta, W powder material with the particle size of 50-250 mu m, wherein the atomic percentages are 25%, 25.9%, C powder with the particle size of 10-200 nm is added, the atomic percentage is 0.1%, the purity of the used powder material is more than or equal to 99.9%, and the additive manufacturing is carried out after ball milling, uniform mixing and vacuum drying, and the steps are as follows:

step 1), selecting a Ta substrate with the thickness of 200mm multiplied by 150mm multiplied by 20mm, and cleaning the Ta substrate to be clean, free of oil dirt, dust, rust and the like;

step 3), establishing a 3D model of a cylindrical array with the radius of 50mm and the height of 50mm to be printed in software, converting the model into a robot scanning path file, and inputting the robot scanning path file into a robot control computer;

step 4) scanning at a given path at a scanning speed of 5mm/s, a power of 4000W, a layer thickness of 1.0 mm; every time a layer is scanned, the computer controls the robot to rise by a distance of one layer of thickness, and meanwhile, a new layer of alloy powder is fed through the powder feeding mechanism;

Example 5

Adopting Nb, mo, ta, W powder material with particle size of 15-53 μm, wherein the atomic percentages are 24%, 25% and 25%, adding TiC powder and ZrC powder with particle size of 10-50 nm, the atomic percentages are 1% and 1%, the purity of the used powder material is more than or equal to 99.95%, ball milling, uniform mixing, vacuum drying and additive manufacturing, the steps are as follows:

step 1), selecting a W substrate with the thickness of 100mm multiplied by 10mm, and cleaning the W substrate to be clean, free of oil dirt, dust, rust and the like;

step 3), a cuboid 3D model with the size of 80mm being 50mm being 10mm to be printed is established in software, and is converted into a robot scanning path file and is input into a robot control computer;

step 4) scanning at a scanning speed of 500mm/s, a scanning interval of 0.04mm, a power of 280W, a laser spot diameter of 0.03mm and a layer thickness of 0.03mm in a given path; every time a layer is scanned, the computer controls the distance that the substrate descends by one layer of thickness, and meanwhile, a new layer of alloy powder is paved through a powder paving mechanism;

The typical SEM morphology of the powder material of the typical NbMoTaW refractory high-entropy alloy prepared in the above embodiment 3 after being uniformly mixed and dried is shown in fig. 1.

The NbMoTaW refractory high-entropy alloy block sample prepared by the typical additive manufacturing process is shown in figure 2, and the structure of the additive manufacturing process is compact and has no cracks and good formability.

Figures 3 and 4 show the XRD pattern and TEM bright field phase, respectively, of an additive manufactured refractory high entropy alloy block sample, indicating that the additive structure consists of MC carbides, which are solid solution phase-precipitated from body-centered cubic BCC, and that the MC carbides are nano-scale.

FIG. 5 shows the room temperature compression curve and fracture morphology of a sample of an additively manufactured refractory high-entropy alloy block, and the results show that the room temperature compressive strength and the compression rate of NbMoTaW refractory high-entropy alloy without carbide are 1341MPa and 5.6%, respectively, and the room temperature compressive strength and the compression rate are respectively improved to 1853MPa and 7.9% and respectively improved by 38.2% and 41.1% after a small amount of carbide is added. Meanwhile, the compression fracture is converted into a carbon-containing cleavage-ductile pit mixed fracture morphology from a quasi-cleavage brittle fracture, which also shows that the room-temperature brittleness of the NbMoTaW refractory high-entropy alloy is well reduced after carbide is added, and the strength and plasticity can be effectively improved by introducing optimized components into the carbide in-situ precipitation phase precipitation strengthening and pinning grain boundary refinement grains.

The invention combines the requirements of the field of additive manufacturing with the characteristics of refractory high-entropy alloy, and provides a NbMoTaW refractory high-entropy alloy powder material suitable for additive manufacturing and an application method. The method for reasonably optimizing the addition of nano reinforced strong induced precipitation elements and the different particle size ratios of powder materials effectively inhibits cracks and defects in the manufacturing process of the NbMoTaW refractory high-entropy alloy additive, and simultaneously improves the room-temperature strength, the room-temperature plasticity and the high-temperature strength of the additive manufacturing material. Meanwhile, the whole performance and the material utilization rate of the component are greatly improved by adopting the additive manufacturing technology. And because the related elements are fewer, the preparation is simple, and the industrial production is easy to realize; meanwhile, the method has the advantages of low cost, environmental friendliness and the like.

The foregoing describes in detail preferred embodiments of the present invention. It should be understood that numerous modifications and variations can be made in accordance with the concepts of the invention without requiring creative effort by one of ordinary skill in the art. Therefore, all technical solutions which can be obtained by logic analysis, reasoning or limited experiments based on the prior art by the person skilled in the art according to the inventive concept shall be within the scope of protection defined by the claims.

Claims

1. Use of a refractory high-entropy alloy powder material in additive manufacturing, comprising the steps of:

step 6: cleaning, grinding and polishing the workpiece to obtain a refractory high-entropy alloy block sample;

the preparation method of the refractory high-entropy alloy powder material comprises the following steps:

step a, adopting Nb, mo, ta, W powder material with purity of more than 99.9 percent, adding one or two of powder NbC, moC, taC, WC, zrC, tiC and powder C, and removing oxide layers and impurities of the powder material;

step d, drying the composite powder material subjected to uniform powder mixing by adopting vacuum heating and drying equipment, and sufficiently removing water vapor, various gases and impurities attached to the surface of the powder to obtain the refractory high-entropy alloy powder material;

the atomic percentages of the Nb, mo, ta, W powder materials are respectively 10% -40%, the atomic percentage content of the added powder is 0< x and less than or equal to 5%, and the total atomic percentage is 100%;

the particle size of the Nb, mo, ta, W powder material is 5-250 mu m, and the particle size of the additive powder is 10-50 mu m.

2. Use of a refractory high-entropy alloy powder material according to claim 1 in additive manufacturing, wherein step 2 is further performed using a powder bed powder additive manufacturing system in which a doctor blade is provided for tiling a first layer of the refractory high-entropy alloy powder material on the metal substrate of step 1.

3. Use of a refractory high-entropy alloy powder material according to claim 1 in additive manufacturing, wherein the phase structure of the refractory high-entropy alloy bulk sample at room temperature is a composite structure of a body-centered cubic crystal structure + a nano precipitation-strengthened phase.