Method for preparing alloy through large-layer-thickness high-pressure selective laser melting

Abstract

The invention discloses a method for preparing an alloy through large-layer-thickness high-pressure selective laser melting, which specifically comprises the following steps of: (1) putting alloy powder into a powder bin, scraping the powder and leveling; (2) closing the powder bin, vacuumizing, and filling inert gas; (3) printing is started through a laser beam according to preset forming process parameters, the alloy powder is laid on the current layer and scraped and leveled every time the laser scans one layer, then scanning is conducted on the second layer, stacking and selective printing are conducted layer by layer in this way, and finally a three-dimensional solid alloy part is formed; and (4) the laser is closed, the inert gas is exhausted, the three-dimensional solid alloy part is taken out, and residual alloy powder is collected for recycling. According to the method, high-pressure in-situ densification melting solidification is adopted, and the problem of large-layer thickness porosity is solved; the powder spreading layer is thick and large, the powder spreading frequency is low, the production period is shortened, and the production efficiency is improved; the prepared alloy product has few cracks and high density; the method is applicable to preparation of various laser high-temperature molten and solidified alloys.

Description

Technical Field

[0001] The invention relates to the field of metallurgical technology, and more particularly to a method for preparing alloy by high-pressure laser selective melting with large layer thickness. Background Art

[0002] Large layer thickness printing technology has always been an important research topic in the field of 3D printing. The traditional laser powder bed fusion (LPBF) process usually uses a low layer thickness (such as 30μm) when manufacturing metal materials, which leads to problems such as low preparation efficiency and high cost. Especially in the field of aerospace, the demand for high-strength aluminum alloys has promoted the development of large layer thickness printing technology. However, problems such as difficult molding and poor molding quality are prone to occur during large layer thickness printing, which limits its application.

[0003] As an advanced additive manufacturing technology, selective laser melting (SLM) technology has received extensive attention and research at home and abroad in recent years. SLM technology melts metal powder through a high-energy-density laser beam to achieve layer-by-layer stacking. Although SLM technology excels in precision and detail, it still faces many challenges in large-layer printing, such as thermal cracks, porosity, and decreased mechanical properties.

[0004] Researchers at home and abroad have conducted a lot of exploration on the problem of large layer thickness printing. Academician Wu Xinhua's team has cooperated with many universities and research institutions to successfully achieve a breakthrough in large layer thickness and high efficiency 3D printing of Sc-containing high-strength aluminum alloy. Studies have shown that by using low-cost coarse powder and optimizing process parameters, a relative density of more than 99.2% can be achieved at a layer thickness of 120μm, and it has good mechanical properties. In addition, the BLT-A320M equipment developed by Polylite uses a 140μm large layer thickness process, which significantly improves the printing efficiency. Compared with the traditional process under the same layer thickness, the efficiency is increased by about 10%, and the efficiency is increased by about 160% while ensuring density.

[0005] However, traditional SLM technology still has some problems when preparing large-layer alloys, such as difficult molding. As the layer thickness increases, the size and shape of the molten pool change, making the molding process more complicated; poor molding quality. Increased layer thickness can easily lead to increased porosity, poor fusion and other problems, affecting the mechanical properties and appearance quality of the molded parts; thermal cracks. High energy input and rapid cooling process can easily produce thermal stress in the material, leading to the generation of thermal cracks.

[0006] Therefore, how to develop a new type of SLM technology to prepare thick alloy layers is an urgent problem that technicians in this field need to solve. Summary of the invention

[0007] In view of this, the object of the present invention is to provide a method for preparing alloys by high-pressure laser selective melting with large layer thickness, so as to solve the deficiencies in the prior art.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A method for preparing alloy by high-pressure laser selective melting with large layer thickness, specifically comprising the following steps:

[0010] (1) Put the alloy powder into the powder bin and scrape the powder to level it;

[0011] (2) Close the powder bin, evacuate the chamber, and fill it with inert gas;

[0012] (3) The laser beam starts printing according to the preset forming process parameters. Each time the laser scans a layer, the alloy powder is spread on the current layer and scraped and leveled, and then the second layer is scanned. In this way, layer by layer is accumulated and selected areas are printed layer by layer, and finally a three-dimensional solid alloy part is formed;

[0013] (4) Turn off the laser, exhaust the inert gas, take out the three-dimensional solid alloy part, and collect the residual alloy powder for recycling.

[0014] Furthermore, in the above step (1), the alloy powder is a spherical powder with a particle size of 5 to 100 μm. Furthermore, the above alloy powder is graded, wherein the mass proportion of 15 to 53 μm powder is ≥ 60%, and the mass ratio of 5 to 15 μm powder to 53 to 100 μm powder is 1:2 or 3:5. Furthermore, the above alloy powder is 316L stainless steel powder or Co-Cr-Fe-Ni-Mn powder.

[0015] Furthermore, in the above step (2), the inert gas is argon or nitrogen, and the powder bin environment is replaced with a desired atmosphere according to the properties of the alloy powder. Furthermore, the gas pressure of the above inert gas filled into the powder bin is 1.0-20.0 MPa, so that the powder bin becomes a high pressure environment.

[0016] Furthermore, in the above step (3), the forming process parameters include laser power, scanning speed and powder thickness. Furthermore, the above laser power is 250-350W. Furthermore, the above scanning speed is 800-1000mm / s. Furthermore, the above powder thickness is 0.01-0.50mm, preferably 0.30-0.50mm.

[0017] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] The present invention adopts high-pressure in-situ densification melting and solidification to overcome the porosity problem of large layer thickness; the powder layer thickness is large, the number of powder spreading times is small, the production cycle is shortened, and the production efficiency is improved; the alloy products thus obtained have fewer cracks and high density; this method is applicable to the preparation of various types of laser high-temperature melting and solidification alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a physical picture of the three-dimensional solid alloy part obtained in Example 1;

[0020] Figure 2 This is a physical picture of the three-dimensional solid alloy part produced in Example 2. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention are described clearly and completely below. 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.

[0022] Example 1

[0023] The method for preparing alloy by high-pressure laser selective melting with large layer thickness specifically comprises the following steps:

[0024] (1) Place 316L stainless steel powder into the powder bin, install the base plate, and scrape the powder to level it;

[0025] Among them, 316L stainless steel powder is a spherical powder with a particle size of 5 to 100 μm, and is graded and matched, with a mass ratio of 5 to 15 μm powder, 15 to 53 μm powder and 53 to 100 μm powder being 10:70:20;

[0026] (2) Close the powder bin, evacuate the powder bin, and fill it with argon until the gas pressure in the powder bin reaches 10.0 MPa;

[0027] (3) The laser power of the laser beam is adjusted to 350W, the scanning speed is 1000mm / s, the powder thickness is 0.50mm, and continuous printing begins. Each time the laser scans a layer, the scraper automatically spreads the 316L stainless steel powder on the current layer and scrapes it flat and level it, and then scans the second layer. In this way, layer by layer is accumulated and selected and printed, and finally a three-dimensional solid alloy part with a certain structure is formed;

[0028] (4) Turn off the laser, exhaust the inert gas, take out the three-dimensional solid alloy part, and collect the residual alloy powder for recycling.

[0029] Example 2

[0030] The method for preparing alloy by high-pressure laser selective melting with large layer thickness specifically comprises the following steps:

[0031] (1) Place Co-Cr-Fe-Ni-Mn powder into the powder bin, install the substrate, and scrape the powder to level it;

[0032] Among them, the Co-Cr-Fe-Ni-Mn powder is a spherical powder with a particle size of 5 to 100 μm, and is graded and matched, with the mass ratio of 5 to 15 μm powder, 15 to 53 μm powder and 53 to 100 μm powder being 15:60:25;

[0033] (2) Close the powder bin, evacuate the powder bin, and fill it with nitrogen until the gas pressure in the powder bin reaches 12.0 MPa;

[0034] (3) The laser power of the laser beam is adjusted to 250W, the scanning speed is 800mm / s, the powder thickness is 0.35mm, and continuous printing is started. Each time the laser scans a layer, the scraper automatically spreads the Co-Cr-Fe-Ni-Mn powder on the current layer and scrapes it flat, and then scans the second layer. In this way, layer by layer is accumulated and selected and printed, and finally a three-dimensional solid alloy part with a certain structure (such as Figure 2 shown);

[0035] (4) Turn off the laser, exhaust the inert gas, take out the three-dimensional solid alloy part, and collect the residual alloy powder for recycling.

[0036] Performance Testing

[0037] 1. The actual picture of the three-dimensional solid alloy part obtained in Example 1 is as follows: Figure 1 As shown. Figure 1 It can be seen that the sample has good density, high surface smoothness, and no defects such as cracks and pores.

[0038] According to the test, the density of the three-dimensional solid alloy part prepared in Example 1 is 98.8%, which exceeds the density level (about 98%) of the conventional layer thickness normal pressure printing part.

[0039] 2. The actual picture of the three-dimensional solid alloy part obtained in Example 2 is as follows: Figure 2 As shown. Figure 2 It can be seen that the sample has good density, high surface smoothness, and no defects such as cracks and pores.

[0040] After testing, the nitrogen content of the three-dimensional solid alloy part prepared in Example 2 is 2%, and the density is 98.5%. The nitrogen content is increased and exceeds the density level of conventional layer thickness normal pressure prints (below 98%).

[0041] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing alloys by high-pressure laser selective melting with large layer thickness, characterized in that: The specific steps include: (1) Put the alloy powder into the powder bin and scrape the powder to level it; (2) Close the powder bin, evacuate the chamber, and fill it with inert gas; (3) The laser beam starts printing according to the preset forming process parameters. Each time the laser scans a layer, the alloy powder is spread on the current layer and scraped and leveled, and then the second layer is scanned. In this way, layer by layer is accumulated and selected areas are printed layer by layer, and finally a three-dimensional solid alloy part is formed; (4) Turn off the laser, exhaust the inert gas, take out the three-dimensional solid alloy part, and collect the residual alloy powder for recycling.

2. The method for preparing alloy by high pressure laser selective melting with large layer thickness according to claim 1, characterized in that: In step (1), the alloy powder is a spherical powder with a particle size of 5 to 100 μm.

3. The method for preparing alloy by high pressure laser selective melting with large thickness according to claim 2, characterized in that: The alloy powders are graded, wherein the mass proportion of 15-53 μm powders is ≥ 60%, and the mass ratio of 5-15 μm powders to 53-100 μm powders is 1:2 or 3:

5.

4. The method for preparing alloy by high pressure laser selective melting with large thickness according to claim 2, characterized in that: The alloy powder is 316L stainless steel powder or Co-Cr-Fe-Ni-Mn powder.

5. The method for preparing alloy by high pressure laser selective melting with large thickness according to claim 1, characterized in that: In step (2), the inert gas is argon or nitrogen.

6. The method for preparing alloy by high pressure laser selective melting with large thickness according to claim 5, characterized in that: The gas pressure of the inert gas filled into the powder bin is 1.0-20.0 MPa.

7. The method for preparing alloy by high pressure laser selective melting with large thickness according to claim 1, characterized in that: In step (3), the forming process parameters include laser power, scanning speed and powder thickness.

8. The method for preparing alloy by high pressure laser selective melting with large thickness according to claim 7, characterized in that: The laser power is 250-350W.

9. The method for preparing alloy by high pressure laser selective melting with large thickness according to claim 7, characterized in that: The scanning speed is 800-1000 mm / s.

10. The method for preparing alloy by high pressure laser selective melting with large thickness according to claim 7, characterized in that: The thickness of the layered powder is 0.01-0.50 mm.

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