A method for reducing powder adhesion on the surface of parts manufactured by selective laser melting additive manufacturing

Abstract

This invention proposes a method for reducing powder adhesion on the surface of additively manufactured parts using selective laser melting. By performing two edge-cutting operations on the part edge during the additive manufacturing process, the first edge-cutting scan amplifies the powder ablation effect by adjusting parameters such as laser power and scanning speed, forming powder-free zones / grooves on both sides of the melt path, ensuring that no new powder adhesion occurs subsequently. The second edge-cutting scan simply remelts the adhered powder to achieve zero or minimal powder adhesion on the sidewalls. This invention proposes a method for reducing powder adhesion on the surface of additively manufactured parts using selective laser melting. The method is applicable to most powder materials suitable for additive manufacturing using selective laser melting, including metals, composite materials, and ceramics.

Description

Technical Field

[0001] The present invention belongs to the field of additive manufacturing technology, and relates to a process method for reducing powder adhesion on the surface of a laser selective melting formed part, and in particular to a method for reducing powder adhesion on the surface of a laser selective melting additively manufactured part by using powder ablation. Background Art

[0002] Selective laser melting (SLM) additive manufacturing (AM) uses a high-energy laser beam to selectively melt thin layers of pre-placed metal powder, allowing them to solidify and form. Layer by layer, this process creates high-density, high-precision three-dimensional metal parts. However, SLM AM parts often experience surface defects caused by a large amount of incompletely melted powder adhering to their surfaces. This powder adhesion defect is one of the main factors affecting the mechanical properties, particularly fatigue performance, of SLM AM parts.

[0003] Currently, methods for removing powder adhered to the surfaces of selective laser melting additively manufactured parts include polishing methods such as sandblasting, chemical solvent etching, electrochemical etching, and abrasive flow scouring. While these methods are effective for exposed areas, they are difficult to achieve precise and uniform surface removal for parts with complex internal flow channels, complex internal cavities, or lattice structures. Therefore, methods to reduce powder adherence to the surfaces of selective laser melting additively manufactured parts are urgently needed. Summary of the Invention

[0004] (1) Technical issues

[0005] To address the technical problem of incompletely melted powder adhering to the surface of additively manufactured parts manufactured by laser selective melting, especially those with complex internal flow channels, complex internal cavities, or lattice structures, forming adhesion defects and seriously affecting the mechanical properties, especially fatigue performance, of the parts, the present invention proposes a method for reducing powder adhesion on the surface of additively manufactured parts manufactured by laser selective melting. The method performs two edge contouring operations on the edge of the part during the additive manufacturing process. During the first edge contouring scan, the powder erosion effect is amplified by adjusting parameters such as laser power and scanning speed to form powder-free areas / grooves on both sides of the melt path, ensuring that no new powder will adhere subsequently. The second edge contouring scan only requires remelting the already adhered powder to achieve the goal of no or low powder adhesion on the sidewalls. The present invention proposes a method for reducing powder adhesion on the surface of additively manufactured parts manufactured by laser selective melting. The method is applicable to most powder materials that can be used for additively manufactured by laser selective melting, such as metals, composite materials, and ceramics.

[0006] (2) Technical solution

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0008] A method for reducing powder adhesion on the surface of a part manufactured by selective laser melting additive manufacturing, characterized in that the method comprises at least the following steps:

[0009] SS1. During the selective laser melting additive manufacturing process, the internal area is laser scanned using conventional parameters applicable to the material.

[0010] SS2. When contouring the edge of a part, the powder erosion effect is amplified by adjusting parameters, creating an erosion zone without powder or grooves around the melt path.

[0011] SS3. Based on step SS2, perform a second edge contouring operation on the part edge. By adjusting the parameters, the heat-affected zone can be precisely controlled to reduce or avoid overmelting, which can cause the molten pool to extend or flow downward and adhere to new powder.

[0012] Preferably, in step SS2, the parameters are adjusted by increasing the laser power, reducing the laser scanning speed, and / or reducing the pressure in the molding chamber.

[0013] Preferably, the two edge-cutting scans in steps SS2 and SS3 reduce the warping deformation caused by the accumulation of thermal stress by changing the starting and ending positions or pausing for a certain time.

[0014] Preferably, in step SS3, precise control of the heat-affected zone is achieved by adjusting the laser spot radius, laser power, and / or scanning speed parameters.

[0015] In the method of reducing powder adhesion on the surface of a part manufactured by laser selective melting additive manufacturing of the present invention, an erosion zone is formed at the edge of the melt path during the first edge scanning. No new powder adhesion occurs during the second edge scanning. The goal of no or low powder adhesion on the sidewalls can be achieved by simply melting the already adhered powder.

[0016] (3) Technical effects

[0017] Compared with the existing technology, the method of reducing powder adhesion on the surface of parts manufactured by laser selective melting additive manufacturing created by the present invention has the following significant technical effects and advantages:

[0018] (1) The method for reducing powder adhesion on the surface of a part manufactured by selective laser melting additive manufacturing created by the present invention can significantly reduce the powder adhesion phenomenon on the surface of a part manufactured by selective laser melting additive manufacturing, reduce surface defects, improve surface finish, reduce tiny stress concentration points and possible crack sources, thereby improving the mechanical properties of the part, especially the fatigue performance.

[0019] (2) The method for reducing powder adhesion on the surface of parts manufactured by laser selective melting additive manufacturing created by the present invention can realize high-precision and high-surface finish forming and manufacturing of parts with complex internal flow channels, complex internal cavities or lattice structures, eliminating the process of removing powder adhered to the surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of internal printing to reduce erosion effects.

[0021] Figure 2 Schematic diagram of the erosion zone formed by the first outlining.

[0022] Figure 3 This is a schematic diagram of the start of the secondary edge scanning.

[0023] Figure 4 Schematic diagram of secondary outlining and melting of adhered powder.

[0024] Figure 5 Schematic diagrams of the morphology and roughness of specimens 1 to 4. In the figure, (A) is the morphology and roughness of specimen 1, (B) is the morphology and roughness of specimen 2, (C) is the morphology and roughness of specimen 3, and (D) is the morphology and roughness of specimen 4. DETAILED DESCRIPTION

[0025] In order to better understand the present invention, the content of the present invention will be further illustrated below in conjunction with the embodiments so that the advantages and features of the present invention can be more easily understood by those skilled in the art. It should be noted that the following are only preferred embodiments of the present invention, but the content of the present invention is not limited to the following embodiments. In fact, various modifications and variations can be made in the present invention without departing from the scope or spirit of the present invention, which will be apparent to those skilled in the art. For example, the features shown or described as part of one embodiment can be used together with another embodiment to produce another embodiment. Therefore, it is intended that the present invention include such modifications and variations within the scope of the appended claims and their equivalents.

[0026] In order to solve the technical problem that incompletely melted powder adheres to the surface of laser selective melting additively manufactured parts, especially those with complex internal flow channels, complex internal cavities or lattice structures, forming adhesion defects and seriously affecting the mechanical properties of parts, especially fatigue performance, in the laser selective melting additive manufacturing process, when the laser power is large and the laser scanning speed is low, the high-speed injection of metal vapor may push away the powder on both sides of the melt channel, and the high-speed steam injection may also drive the gas around the melt channel to move, thereby entraining particles to fly out, resulting in powder-free areas on both sides of the melt channel (this phenomenon is called powder erosion phenomenon, and the powder-free area is called powder erosion area). The present invention proposes a method for reducing powder adhesion on the surface of parts manufactured by selective laser melting additive manufacturing. The method performs two edge contouring operations on the edge of the part during the additive manufacturing process. During the first edge contouring scan, the powder erosion effect is amplified by adjusting parameters such as laser power and scanning speed, forming powder-free areas / grooves on both sides of the melt path to ensure that no new powder will adhere subsequently. The second edge contouring scan only requires remelting the already adhered powder to achieve the goal of no or low powder adhesion on the sidewalls.

[0027] Specifically, if Figures 1 to 4 As shown, the method proposed by the present invention for reducing powder adhesion on the surface of a part manufactured by selective laser melting additive manufacturing is implemented according to the following steps:

[0028] During the additive manufacturing process of selective laser melting, the internal area is laser scanned according to the conventional parameters applicable to the corresponding material, such as Figure 1 As shown;

[0029] When performing the edge contouring operation on the edge of the part, the powder erosion effect can be amplified by adjusting the parameters (such as increasing the laser power, reducing the scanning speed, reducing the molding chamber pressure, etc.), forming a powder-free / grooved erosion zone around the melt channel. This process only occurs at the edge and has little effect on the internal forming quality of the entire micro-truss. Figure 2 As shown;

[0030] Then, the second edge drawing is performed. It is necessary to precisely control the heat-affected zone by adjusting the parameters such as spot radius, power, and scanning speed to reduce / avoid over-melting, which may cause the molten pool to extend or flow downward to adhere to new powder. Figure 3 The two edge scans can reduce warping and deformation caused by thermal stress accumulation by changing the starting and ending positions or pausing for a certain period of time.

[0031] In this way, the first edge scan has formed an erosion zone at the edge of the melt channel. No new powder will adhere during the second edge scan. The goal of no or little powder adhesion on the side wall can be achieved by simply melting the already adhered powder. Figure 4 shown.

[0032] As a more specific example, in the experiment of reducing powder adhesion on the surface of GH3536 material formed by SLM, the first edge scan of the specimen edge was performed with a larger laser power and a lower scanning speed to form an erosion zone outside the melt channel. Then, the second edge scan was performed, and the powder adhesion on the surface was significantly reduced (the specimen morphology is shown in FIG. Figure 5 The process parameters are shown in Table 1). Thus, the feasibility of the method of reducing powder adhesion by using powder erosion phenomenon was proved by experimental method.

[0033] Table 1 Powder erosion and anti-adhesion test parameters

[0034]

[0035] The above embodiments fully and effectively achieve the purpose of the present invention. Any equivalent or simple changes made based on the structure, features, and principles described in the patent concept of the present invention are included in the scope of protection of the patent of the present invention. Those skilled in the art of the present invention can make various modifications or supplements to the specific embodiments described, or replace them with similar methods. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they should fall within the scope of protection of the present invention.

Claims

1. A method for reducing powder adhesion on the surface of a part manufactured by selective laser melting additive manufacturing, characterized in that: The method comprises at least the following steps: SS1. During the selective laser melting additive manufacturing process, the internal area is laser scanned using conventional parameters applicable to the material. SS2. During the initial outlining operation on the part edge, the powder erosion effect is amplified by adjusting parameters, forming a powder-free or grooved erosion zone around the melt path. Parameter adjustments are made by increasing laser power, reducing laser scanning speed, and lowering the build chamber pressure to ensure that no new powder adheres. SS3. Based on step SS2, a second edge contouring operation is performed on the edge of the part to remelt the powder that has been adhered for the first time, and the heat-affected zone is precisely controlled by adjusting the parameters to reduce or avoid over-melting that causes the molten pool to extend or flow downward and adhere to new powder. The heat-affected zone is precisely controlled by adjusting the laser spot radius, laser power, and scanning speed parameters. The two edge contouring scans are performed by changing the starting and ending positions or pausing for a certain period of time to reduce warping caused by thermal stress accumulation.

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