Laser powder bed fusion preparation method suitable for local structure regulation and control of complex parts and application of laser powder bed fusion preparation method

Abstract

The invention discloses a laser powder bed fusion preparation method suitable for local structure regulation and control of complex parts and application. The invention belongs to the technical field of metal additive manufacturing. The method aims at solving the technical problems that an in-situ heat treatment process after powder single-time fusion forming at present is not suitable for regulating, controlling and improving local structures of complex parts, and shrinkage cracks appear after solidification. The method comprises the following steps: repeatedly building 1-4 three-dimensional models by adopting software, superposing the models, and endowing each model with a group of scanning parameters; and repeatedly scanning layer by layer according to the established model by adopting a laser powder bed fusion technology. According to the invention, transformation of columnar crystal orientation isometric crystals is realized. And meanwhile, cracks formed by solidification and shrinkage can be fed, and a crack-free and compact printing component is prepared. And the forming process is simpler and more convenient, and the method is widely applied to the field of forming complex alloy parts and suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal additive manufacturing, and specifically relates to a laser powder bed fusion preparation method suitable for local structure regulation of complex parts and its application. Background Art

[0002] Additive manufacturing, as a technology that subverts traditional manufacturing, has unique advantages in molding complex structures and thin-walled components, while also being able to minimize the loss of raw materials. In terms of molding accuracy and size, laser selective melting technology stands out among many additive manufacturing technologies. It uses a computer-aided design (CAD) part model, divides the model into several thin layers, and deposits them layer by layer, ultimately achieving the manufacture of parts with various structures and complex geometric shapes.

[0003] Laser selective melting technology usually uses the best molding process to batch mold parts. The best process generally refers to the process used when the prepared parts have the lowest porosity. After the powder is fused into a single shape, the internal structure and overall performance of the entire part can only be further controlled by heat treatment. However, the in-situ heat treatment process is not suitable for the local organization control and improvement of complex parts, and shrinkage cracks appear after solidification. Therefore, it is of great significance to develop a laser powder bed fusion method suitable for the local organization control and improvement of complex parts. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problems that the current in-situ heat treatment process after single fusion molding of powder is not suitable for local microstructure control and improvement of complex parts, and shrinkage cracks appear after solidification, and to provide a laser powder bed fusion preparation method and application suitable for local microstructure control of complex parts.

[0005] The technical solution of the present invention is as follows:

[0006] One of the purposes of the present invention is to provide a laser powder bed fusion preparation method suitable for local structure control of complex parts, the method is carried out according to the following steps:

[0007] S1: Use Materialise Magics software to build a 3D model. First, build a 3D model according to the component structure and name it the basic model. Repeat the construction of 1-4 3D models and name each one as the remelting model n. Superimpose the models and assign a set of scanning parameters to each model.

[0008] S2: Laser powder bed fusion technology is used to repeatedly scan layer by layer according to the established model. The specific process parameters of the model are: powder layer thickness is 0.03-0.12mm, laser layer rotation angle is 30-90°, and body energy density is 50-250J / mm 3, the laser power is 50-250W, the scanning speed is 100-2500mm / s, and the scanning spacing is 0.05-0.15mm. The powder layer thickness of each model is the same.

[0009] It is further defined that two three-dimensional models are repeatedly constructed in S1.

[0010] It is further defined that in S2, the substrate is preheated to a temperature of 170-190°C.

[0011] It is further defined that the oxygen content inside the S2 compartment is less than 50 ppm.

[0012] It is further defined that the thickness of the powder layer in S2 is 0.03 mm.

[0013] It is further defined that the interlayer laser rotation angle in S2 is 67°.

[0014] A second object of the present invention is to provide an alloy material prepared by the above method.

[0015] A third object of the present invention is to provide an application of the above method in laser powder bed fusion molding of complex alloy parts.

[0016] It is further defined that the alloy comprises a NiTi alloy.

[0017] It is further defined that when laser powder bed fusion is used to form complex alloy NiTi parts, spherical NiTi alloy powder and pure nickel powder are used as raw materials, and the pure nickel powder is 2-4wt% of the NiTi alloy powder.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] (1) The present invention is directed to laser selective melting equipment that cannot perform remelting. By designing a three-dimensional model of a component and assigning a corresponding process, the present invention solves the technical problem that each model can only have the same process parameter and cannot perform remelting.

[0020] (2) The method of the present invention solves the technical problem that the in-situ heat treatment process after the current single fusion molding of powder is not suitable for the local organization control and improvement of complex parts, and shrinkage cracks appear after solidification. The present invention adopts interlayer remelting technology and realizes the transformation of columnar crystals to equiaxed crystals and the homogenization of components by regulating the remelting process. At the same time, the cracks formed by solidification shrinkage are also compensated to prepare crack-free and dense printed components.

[0021] (3) The method of the present invention eliminates the in-situ heat treatment process after single fusion molding, and the molding process is simpler. It has a wide range of applications in the field of molding complex alloy parts and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic diagram of a three-dimensional model constructed in the present invention;

[0023] Figure 2 The metallographic diagrams of the NiTi alloys obtained in Comparative Example 1 and Examples 1-2; wherein a) represents Comparative Example 1, b) represents Example 2, and c) represents Example 1;

[0024] Figure 3 These are backscattered images of the NiTi alloy obtained in Comparative Example 1 and Examples 1-2; wherein a) represents Comparative Example 1, b) represents Example 2, and c) represents Example 1. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0026] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0027] The terms "comprising," "including," "having," "containing," or any other variations thereof, as used in the following examples, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus comprising the listed elements is not necessarily limited to only those elements, but may include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus.

[0028] When equivalent, concentration or other value or parameter is represented by the range limited by range, preferred range or a series of upper preferred value and lower preferred value, this should be understood as specifically disclosing all ranges formed by any pairing of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether the scope is disclosed separately. For example, when disclosing range "1 to 5", described range should be interpreted as including range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5" etc. When numerical range is described in this article, unless otherwise stated, the scope is intended to include its end value and all integers and fractions within the scope. In the present application specification and claims, range limitation can be combined and / or interchanged, if these ranges are not otherwise stated, include all sub-ranges contained therein.

[0029] The indefinite articles "a" and "an" before the elements or components of the present invention have no limitation on the quantity requirements (i.e. the number of occurrences) of the elements or components. Therefore, "a" or "an" should be interpreted as including one or at least one, and the elements or components in the singular form also include the plural form, unless the quantity obviously refers to the singular form only.

[0030] The "one embodiment" or "embodiment" of the present invention refers to a specific feature, structure or characteristic that can be included in at least one implementation of the present invention. The "in one embodiment" that appears in different places in this specification does not refer to the same embodiment, nor is it a separate or selective embodiment that is mutually exclusive with other embodiments.

[0031] The endpoints and any values ​​of the ranges disclosed in the invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in this article.

[0032] Embodiment 1: The laser powder bed fusion preparation method suitable for local structure control of complex parts of this embodiment is carried out according to the following steps:

[0033] (1) Combination Figure 1 , Materialise Magics software was used to build a 10mm*10mm*10mm basic block 3D model, named basic model, and a 10mm*10mm*10mm basic block 3D model was repeatedly built, named remelting model 1, and a 10mm*10mm*3mm block 3D model was repeatedly built, named remelting model 2, and the three models were superimposed, and each model was assigned a set of scanning parameters (see Table 1 for details);

[0034] (2) Laser powder bed fusion technology was used, spherical pre-alloyed NiTi powder (Ni: 50.8at.%, particle size 18-53μm) and pure nickel powder (particle size 18-53μm) were used as raw materials, and the pre-alloyed NiTi powder and pure nickel powder accounting for 3.1wt% of the pre-alloyed NiTi powder were mechanically mixed for 12h to obtain mixed NiTi metal powder (Ni: 51.8at.%). The mixed metal powder was placed in a powder bin, and an equiatomic NiTi alloy was used as a substrate. The substrate preheating temperature was 180°C, the powder layer thickness was 0.03mm, and each layer was laser scanned 3 times. The first (basic model) laser scanning parameters were: body energy density was 222.22J / mm 3, laser power is 250W, scanning speed is 750mm / s, scanning spacing is 0.05mm; secondary (remelting model 1) laser scanning parameters: body energy density is 211.64J / mm 3 , laser power is 200W, scanning speed is 450mm / s, scanning spacing is 0.07mm; three times (remelting model 2) laser scanning parameters: body energy density is 154.32J / mm 3 The laser power is 250W, the scanning speed is 600mm / s, the scanning spacing is 0.09mm, and the laser layer rotation angle is 67°. The specific printing process parameters are shown in Table 1.

[0035] Embodiment 2: The laser powder bed fusion preparation method suitable for local structure control of complex parts in this embodiment is carried out according to the following steps:

[0036] (1) Combination Figure 1 , Materialise Magics software was used to build a 10mm*10mm*10mm basic block 3D model, named basic model, and a 10mm*10mm*10mm basic block 3D model was repeatedly built, named remelting model 1, the two models were superimposed, and each model was given a set of scanning parameters (see Table 1 for details);

[0037] (2) Laser powder bed fusion technology was used, spherical pre-alloyed NiTi powder (Ni: 50.8at.%, particle size 18-53μm) and pure nickel powder (particle size 18-53μm) were used as raw materials, and the pre-alloyed NiTi powder and pure nickel powder accounting for 3.1wt% of the pre-alloyed NiTi powder were mechanically mixed for 12h to obtain a mixed metal powder (Ni: 51.8at.%). The mixed metal powder was placed in a powder bin, and an equiatomic NiTi alloy was used as a substrate. The substrate preheating temperature was 180°C, the powder layer thickness was 0.03mm, and each layer was laser scanned twice. The first (basic model) laser scanning parameters were: body energy density was 222.22J / mm 3 , laser power is 250W, scanning speed is 750mm / s, scanning spacing is 0.05mm; secondary (remelting model 1) laser scanning parameters: body energy density is 198.41J / mm 3 The laser power is 250W, the scanning speed is 600mm / s, the scanning spacing is 0.07mm, and the laser layer rotation angle is 67°. The specific printing process parameters are shown in Table 1.

[0038] Comparative Example 1: The laser powder bed fusion preparation method of this comparative example is carried out according to the following steps:

[0039] Laser powder bed fusion technology was used, spherical pre-alloyed NiTi powder (Ni: 50.8at.%, particle size 18-53μm) and pure nickel powder (particle size 18-53μm) were used as raw materials, and the pre-alloyed NiTi powder and pure nickel powder accounting for 3.1wt% of the pre-alloyed NiTi powder were mechanically mixed for 12 hours to obtain mixed metal powder (Ni: 51.8at.%). The mixed metal powder was placed in a powder bin, and an equiatomic NiTi alloy was used as a substrate. The substrate preheating temperature was 180°C, the powder layer thickness was 0.03mm, and each layer was laser scanned once. The laser scanning parameters were: the volume energy density was 222.22J / mm 3 The laser power is 250W, the scanning speed is 750mm / s, the scanning spacing is 0.05mm, and the laser layer rotation angle is 67°. The specific printing process parameters are shown in Table 1.

[0040] Table 1: Molding process parameters

[0041]

[0042] Figure 2 a is a high nickel NiTi alloy sample printed in Example 1, which has obvious cracks inside. This crack is mainly caused by the presence of unmelted Ni powder in the alloy. The unmelted Ni powder will form a local stress concentration area, which will directly tear the softer NiTi alloy matrix, resulting in the formation of cracks.

[0043] Figure 3 a shows the backscattering image of the high nickel NiTi alloy powder sample without remelting printing in comparative example 1, in which the white area is the Ni powder that is not fully melted, and the gray area is the matrix NiTi alloy. It can be clearly seen from the figure that there is a large amount of Ni powder that is not fully melted.

[0044] Figure 2 b is a metallographic image of the high nickel NiTi alloy printed in Example 2. The model reconstruction strategy proposed in the present invention can realize accurate remelting of the sample, and the cracks inside the alloy are significantly improved.

[0045] Figure 3 b is the backscattering image of the high nickel NiTi alloy after one remelting in Example 2. Compared with the unremelted sample ( Figure 3 a), its internal composition has been significantly improved, and only a small amount of Ni powder that is not fully melted exists.

[0046] Figure 2 c is a metallographic image of the high-nickel NiTi alloy printed in Example 1. After two remeltings, no cracks appeared inside the high-nickel NiTi alloy, indicating that the remelting strategy proposed in the present invention can effectively suppress cracks in the mixed powder printed NiTi alloy.

[0047] Figure 3 c is a backscattered image of the high-nickel NiTi alloy printed after two remeltings in Example 1. It can be seen from the figure that the internal pure nickel powder has been almost completely melted. The stress concentration area caused by the unmelted Ni powder also disappears, thus balancing the distribution of internal stress in the high-nickel NiTi alloy and inhibiting the cracking of the high-nickel NiTi alloy.

[0048] In summary, based on the model reconstruction method proposed in the present invention, crack-free preparation of mixed powder high-nickel NiTi alloy is successfully achieved, and internal composition homogenization is achieved.

[0049] The above are only preferred specific embodiments of the present invention, which are all different implementations based on the overall concept of the present invention, and the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A laser powder bed fusion preparation method suitable for local structure control of complex parts, characterized in that: The method: S1: Use Materialise Magics software to build a 3D model. First, build a 3D model according to the component structure and name it the basic model. Repeat the construction of 1-4 3D models and name each one as the remelting model n. Superimpose the models and assign a set of scanning parameters to each model. S2: Laser powder bed fusion technology is used to repeatedly scan layer by layer according to the established model. The specific process parameters of the model are: powder layer thickness is 0.03-0.12mm, laser layer rotation angle is 30-90°, and body energy density is 50-250J / mm 3 , the laser power is 50-250W, the scanning speed is 100-2500mm / s, and the scanning spacing is 0.05-0.15mm. The powder layer thickness of each model is the same.

2. The method according to claim 1, characterized in that Repeat S1 to build two three-dimensional models.

3. The method according to claim 1, characterized in that In S2, the substrate is preheated to a temperature of 170-190°C.

4. The method according to claim 1, characterized in that: The oxygen content inside the S2 compartment is less than 50ppm.

5. The method according to claim 1, characterized in that The thickness of the powder layer in S2 is 0.03 mm.

6. The method according to claim 1, characterized in that The interlayer laser rotation angle in S2 was 67°.

7. The alloy material obtained by the method according to any one of claims 1 to 6.

8. Use of the method according to any one of claims 1 to 6 in laser powder bed fusion molding of complex alloy parts.

9. The use according to claim 8, characterized in that: The alloys include NiTi alloys.

10. The use according to claim 9, characterized in that: When laser powder bed fusion is used to form complex alloy NiTi parts, spherical NiTi alloy powder and pure nickel powder are used as raw materials, and the pure nickel powder accounts for 2-4wt% of the NiTi alloy powder.

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