Plasma deposition and laser remelting composite additive manufacturing method

Abstract

The invention discloses a plasma deposition and laser remelting composite additive manufacturing method, and belongs to the technical field of additive manufacturing. The manufacturing method comprises the processes of plasma deposition, laser densification treatment, laser cutting and the like. Firstly, ceramic, metal or a mixed raw material of ceramic and metal is heated to a molten or semi-molten state through plasma deposition, the molten or semi-molten state is deposited on a substrate through plasma airflow, a forming layer is formed, and in the step, the uniformity and adhesive force of the forming layer are ensured through efficient heat energy transfer and material conveying capacity of the plasma deposition technology. And densifying the forming layer by adopting a selective laser melting mode, and cutting the contour of the forming piece by utilizing a laser cutting process. According to the method, the plasma deposition technology and the laser direct additive manufacturing technology are fused, the method has the advantages of multi-material implementation of the deposition technology and high-precision forming of the laser sintering technology, the material utilization rate and the component performance are improved, and the component manufacturing period is shortened.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic additive manufacturing, and in particular relates to a plasma deposition laser remelting composite additive manufacturing method. Background Art

[0002] In the field of ceramic additive manufacturing, the main technologies for directly manufacturing complex ceramic components include laser selective melting (SLM) and powder feeding laser forming technology. Some companies have used SLM technology with assisted thermal fields to achieve commercial mass production of complex oxide parts. However, powder bed-based SLM technology still faces challenges in the direct forming of high-precision components. On the one hand, it is difficult to clean the powder sticking to the edges and inner flow channels, and on the other hand, this method is difficult to achieve flexible material replacement. Powder feeding laser forming technology is another mainstream direct ceramic additive manufacturing technology, but due to problems such as large powder spot diameter, insufficient laser accuracy, and poor fluidity of ceramic powder, it is still in the research stage of material performance regulation, and it is difficult to achieve direct manufacturing of high-precision ceramic components.

[0003] In the field of indirect additive manufacturing, common technologies include selective laser sintering (SLS), stereolithography (SLA or DLP), binder jet forming (3DP), and powder extrusion-based additive manufacturing (PEP). SLS and 3DP technologies are particularly suitable for manufacturing large-scale ceramic parts with complex structures because they do not require the design of support structures, have high material utilization, and have low thermal stress and shrinkage of the matrix when printing ceramics. The formed ceramic parts have high precision and surface quality. However, these technologies have low density of large-scale ceramic parts after forming, and the post-processing densification process faces the challenges of long cycle and difficulty in density improvement. During the debinding process, the amount of gas evolution is large, and the shrinkage deformation effect during the sintering process is significant, which increases the difficulty of surface quality and crack control. In addition, these technologies usually require additional impregnation or isostatic pressing processes to achieve the preparation of dense ceramics, and these processes have certain restrictions on materials and shapes.

[0004] Although PEP technology has unique advantages in the design and preparation of integral functional gradient materials with continuous gradient layers, it still faces the problems of long preparation cycle, high cost and difficulty in sintering complex shapes. At the same time, the contradiction between printing accuracy and efficiency also limits the application of PEP technology in the preparation of high-precision components. Although photocuring technology is the most widely commercialized indirect additive manufacturing technology, it has high resin content, large green body sintering shrinkage, and difficulty in debinding and sintering. These factors make it challenging to manufacture large-wall thickness, net size and complex components. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a plasma deposition laser remelting composite additive manufacturing method to solve the various problems existing in various methods in the prior art in the additive manufacturing process of ceramic materials, so that additive manufacturing still faces many challenges.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A plasma deposition laser remelting composite additive manufacturing method comprises the following steps: Step 1, outputting a material onto a substrate by plasma deposition, wherein the material is ceramic, metal, or a mixture of ceramic and metal, and the material is in a molten or semi-molten state, and the material forms a solid layer on the substrate; Step 2, subjecting the solid layer to laser sintering, remelting and solidifying the solid layer to form a forming layer; Step 3, cutting the side wall of the forming layer into a target shape and size by pulsed laser; Step 4, repeat steps 1 to 3 until printing is completed to form a process part; Step 5, remove the substrate under the process part to form the final workpiece.

[0007] A further improvement of the present invention is: Preferably, in step 1, during the plasma deposition process, a protective gas is filled into the working chamber.

[0008] Preferably, in step 1, the substrate is preheated before plasma deposition.

[0009] Preferably, in step 1, during the plasma deposition process, the plasma gas flow is 600 m / s to 1200 m / s.

[0010] Preferably, in step 2, during the laser sintering process, the process parameters of the laser sintering are controlled, and the process parameters include spot diameter, laser power, scanning rate and scanning spacing.

[0011] Preferably, in step 2, the substrate is a soluble substrate.

[0012] Preferably, the material of the soluble substrate is magnesium alloy, zinc alloy, zinc-magnesium alloy or soluble inorganic substance.

[0013] Preferably, in step 2, when the material is a mixture of metal and ceramic, the mixed mass ratio of metal and ceramic in the material changes as the forming layer accumulates.

[0014] Preferably, after step 5, the printed part is post-processed, and the post-processing is any one or more of heat treatment, mechanical processing or chemical treatment.

[0015] Preferably, the plasma deposition is any one of PECVD, plasma polymerization or PLD.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a plasma deposition laser remelting composite additive manufacturing method, which includes plasma deposition, laser densification treatment and laser cutting. The present invention first heats the raw materials of ceramic, metal or ceramic and metal mixture to a molten or semi-molten state through plasma deposition, and deposits it on a substrate through a plasma gas flow to form a forming layer. This step utilizes the efficient heat energy transfer and material conveying capabilities of plasma deposition technology to ensure the uniformity and adhesion of the forming layer; the molten or semi-molten material is subjected to a specific temperature field (generally 600~1200℃), and then the forming layer is densified by laser selective melting, and the contour of the formed part is cut out by laser cutting technology. The density and adhesion of the forming layer are improved through the process of melting and rapid solidification, thereby enhancing the overall performance of the component. The present invention integrates plasma deposition and laser direct additive manufacturing technology, and has the advantages of multi-material realization of deposition technology and high-precision forming of laser sintering technology, realizing the precise delivery and melting of ceramic or metal raw materials, which not only improves material utilization and component performance, but also shortens the manufacturing cycle of components, and provides the possibility for the direct design and manufacture of multi-material gradient components of metal ceramics.

[0017] The method of the present invention also has the following advantages: (1) Compared with conventional powder bed laser melting or powder feeding laser melting, the material composition output by the plasma deposition method is more uniform, and because the materials on the substrate are all molten or semi-molten, the material composition state is more uniform, which not only avoids the phenomenon that the powder may not melt due to the presence of unmelted powder inside or on the edge of the molded part, causing cracks or stress concentration; but also provides the possibility for direct laser additive manufacturing of eutectic ceramics. The present invention changes the raw material of additive manufacturing from solid state to molten or semi-molten state for the first time, and uses the ion deposition device as a "feeding device".

[0018] (2) The present invention uses laser cutting technology for forming. The present invention uses pulsed laser technology with a specific wavelength to accurately cut the forming layer according to the preset component contour to form the required complex shape. This step ensures the accuracy and size consistency of the component.

[0019] (3) The application of plasma technology effectively solves the problems of incomplete melting and weak bonding with the matrix during the forming process of traditional ceramic powders, while the precise cutting of pulsed laser technology ensures the consistency of the size and shape of the components, meeting the high standards for the manufacture of complex components. The innovative soluble substrate design further simplifies the post-processing process and reduces manufacturing costs and time. This technology has a wide range of applications, especially in aerospace, medical equipment, automobile manufacturing and other fields. It can produce complex internal gradient structures that are difficult to achieve with traditional processes, greatly expanding the flexibility of design. The environmentally friendly manufacturing process reduces material waste and post-processing requirements, which is in line with the development trend of green manufacturing. In addition, the combination of plasma and laser melting technology not only avoids the problem of uneven overall heating temperature field of the powder bed in traditional laser selective melting technology, but also speeds up the manufacturing speed and improves production efficiency through selective feeding, which is particularly suitable for mass production. In summary, this invention not only improves production efficiency and reduces costs, but also provides a new process method for additive manufacturing of complex ceramic components, especially future ceramic-metal multi-material components. It is particularly suitable for the preparation of complex ceramic components with high density, high strength and excellent surface finish, and has important industrial application value and broad market prospects.

[0020] Furthermore, in the present invention, due to the use of plasma deposition technology, the material in the molten state has better bonding with the substrate. In order to facilitate the removal of the substrate from the molded part, a soluble material is selected as the substrate. It must be a material that can be dissolved under physical or chemical conditions, such as magnesium alloy, zinc alloy or its alloy, and soluble inorganic substances such as calcium oxide, calcium chloride, and magnesium chloride. Such a design allows the substrate to be easily removed after the component is formed without leaving any residue. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a composite cross-section diagram of an alumina high-temperature alloy; Figure 2 This is the surface image of the alumina high-temperature alloy composite macro-part; Figure 3 This is the surface image of aluminum oxide before laser scanning; Figure 4 Laser scanning densification surface image of aluminum oxide. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0023] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0024] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0025] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0026] A first aspect of the present invention discloses a plasma deposition laser remelting composite additive manufacturing method, the method comprising the following steps: Step 1: Using plasma deposition technology to transfer a material onto a substrate to form a solid state, the material is ceramic, metal, or a mixture of metal and ceramic, and the material is in a molten or semi-molten state.

[0027] In the above process, the material becomes molten or semi-molten in the plasma deposition equipment. After the molten material is output by the plasma deposition airflow, it becomes solid after contacting the substrate due to the instantaneous contact with the substrate. This process forms a relatively loose solid on the substrate, but the composition of the solid formed is precisely controlled.

[0028] In this process, the working chamber is first evacuated, and then argon is filled into the working chamber to make the pressure in the chamber reach the target pressure. The substrate is preset, the material is heated to a molten or semi-molten state, and the material is deposited on the substrate through a plasma gas flow to form a forming layer.

[0029] In this process, preheating the substrate in advance can make the blown material and the substrate merge better. It should be noted that the plasma deposition device is loaded with multiple at least two material boxes, which are used to store the powdered materials to be printed. If a single material is printed, the single material is melted and sent out. If a mixed material is output, the mixed powdered material is melted and then flows out. Different powdered materials can also be melted and mixed separately before being output.

[0030] Based on the above-mentioned material that can be output as a mixed material, in some specific embodiments of the present invention, the printout can be a gradient material, that is, as the molding layers accumulate, the ratio between the ceramic material and the metal material, between the ceramic material and the ceramic material, or between the metal material and the metal material can be adjusted.

[0031] The plasma deposition in the present invention can be any one of PECVD (plasma enhanced chemical vapor deposition), plasma polymerization or PLD (high power pulsed laser).

[0032] Step 2: After deposition, the material deposited on the substrate is densified using a laser. After forming a complex block component by stacking layer by layer, the block can be subjected to a subsequent laser sintering and heat preservation process to relieve stress or eliminate defects. The specific laser densification process includes using a laser to melt and rapidly solidify the deposited forming layer to improve the density and adhesion of the forming layer.

[0033] In this process, the laser sintering process is adopted. The specific process parameters include spot diameter, laser power, scanning rate, scanning interval, insulation temperature and insulation environment. The values ​​of specific process parameters are determined according to the actual material of the material.

[0034] It should be understood that when the printed material is a gradient material, the parameters of the corresponding laser sintering process for each layer are adjusted.

[0035] Step 3: Use pulsed laser technology to cut the contour of the formed complex component. Pulsed laser cutting technology includes using a pulsed laser of a specific wavelength to accurately cut the formed layer according to the preset component contour. Pulsed laser technology is to irradiate a high-energy laser beam on the surface of the material, melt or vaporize the material through instantaneous high temperature, so as to achieve the purpose of cutting. Pulsed laser has high forming accuracy and is particularly suitable for process workpieces with uneven edge shapes caused by laser sintering after plasma deposition.

[0036] More specifically, the process is to cut the side wall of the shaping layer so that the structure of the side edge of the shaping layer meets the set size.

[0037] Step 4, repeat the above steps 1 to 3 to complete the deposition of each forming layer until the entire workpiece is prepared.

[0038] In some embodiments, a metal material that is soluble under physical or chemical conditions is used as a substrate; the material that is soluble under physical or chemical conditions as a substrate includes, but is not limited to, magnesium alloy, zinc alloy or its alloy, or soluble inorganic substances such as calcium oxide, calcium chloride, and magnesium chloride.

[0039] The plasma molding surface is large, and ceramics and metals are difficult to remove, so a soluble substrate is used. Some embodiments of the present invention further include post-processing the component to improve the performance of the component, and the post-processing includes heat treatment, mechanical processing or chemical treatment, wherein the heat treatment can further densify the workpiece.

[0040] The workpiece finally formed by the above method has the characteristics of high density, high strength and excellent surface finish.

[0041] The present invention is further described below with reference to the embodiments.

[0042] Embodiment 1, an additive manufacturing material for complex ceramic multi-material components based on a combination of plasma and laser additive manufacturing, includes ceramic powder.

[0043] The powder is zirconium oxide ceramic powder with a particle size of 0.6 μm and a purity greater than 98%.

[0044] The method for manufacturing a complex ceramic multi-material component based on plasma and laser additive manufacturing comprises the following steps: 1) Plasma deposition: Evacuate the working chamber to 10 -3 Pa, and then fill the working chamber with argon gas to make the pressure in the chamber reach 0.1MPa, use calcium oxide as the substrate, and preheat it to 600℃, heat the ceramic powder to a molten or semi-molten state, and deposit it on the calcium oxide substrate at a speed of 600m / s through a plasma gas flow to form a forming layer with a thickness of about 30μm; 2) Laser sintering process: A point light source is used as the energy source for laser sintering, with a spot diameter of 0.05 mm, a laser power of 60 W, a scanning rate of 300 mm / s, a scanning interval of 0.05 mm, and a holding temperature of 600 °C; the corresponding nitrogen or argon pressure is 0.1 MPa.

[0045] 3) Laser cutting: Using pulsed laser technology with a wavelength of 10.6μm and a laser power of 500W, the forming layer is precisely cut according to the preset component contour to form the required complex shape; 4) Repeat the above process 1)-3) until a complex-shaped block is obtained.

[0046] In this embodiment, the complex-shaped blocks are post-processed. The specific processing method is: the complex-shaped blocks prepared as above are placed in a vacuum sintering furnace and processed in an air atmosphere. The sintering temperature is 1350°C and the insulation time is 2 hours, so as to remove defects and stresses that may exist in the laser sintering process inside the material.

[0047] This embodiment effectively solves the problems of incomplete melting and loose bonding with the matrix during the molding process of traditional ceramic powders, and ensures the consistency of the size and shape of the components, with high material utilization, fast molding speed, high efficiency, and reduced production costs.

[0048] Embodiment 2, an additive manufacturing material for complex ceramic multi-material components based on a combination of plasma and laser additive manufacturing, comprising ceramic powder and metal powder.

[0049] The ceramic powder is aluminum oxide, with a particle size of 0.5 μm and a purity greater than 99.9%.

[0050] The metal powder is high temperature alloy GH3536, with a particle size of 30 μm and a purity greater than 99%.

[0051] The method for manufacturing a complex ceramic multi-material component based on plasma and laser additive manufacturing comprises the following steps: 1) Plasma deposition: The working chamber is evacuated to 10-3Pa, and then nitrogen is filled into the working chamber to make the pressure in the chamber reach 0.1MPa. The ceramic powder is heated to a molten or semi-molten state, and is deposited onto the substrate through a plasma gas flow at a speed of 600m / s to form a forming layer with a layer thickness of about 25μm; 2) Laser sintering process: A point light source is used as the energy source for laser sintering, with a spot diameter of 0.05 mm, a laser power of 30 W, a scanning rate of 150 mm / s, a scanning interval of 0.05 mm, and a holding temperature of 600 °C; the corresponding nitrogen pressure is 0.1 MPa.

[0052] 3) Laser cutting: Using pulsed laser technology with a wavelength of 10.6μm and a laser power of 500W, the forming layer is precisely cut according to the preset component contour to form the required complex shape; 4) Repeat the above process and gradually replace the ceramic powder with metal powder, increasing the metal weight ratio by 10% each time, until a complex-shaped block is obtained. The magnesium alloy substrate is removed by immersing it in dilute hydrochloric acid.

[0053] The obtained complex-shaped block is post-processed. The specific post-processing process is to put the complex-shaped block prepared above into a vacuum sintering furnace and treat it under a vacuum atmosphere. The sintering temperature is 1200°C and the insulation time is 2h, so as to remove defects and stresses that may exist in the laser sintering process inside the material.

[0054] See also Figure 1-Figure 4 ,from Figure 3It can be seen that the surface formed by plasma deposition in step 1) still has a large number of holes and the surface flatness is poor. This is because the molten powder particles form a rough surface under the action of the airflow during the plasma deposition process, and the stacking process of the molten particles also makes it difficult for the pores on the surface to be dense. Figure 4 It can be seen that after the laser remelting in step 2), the surface material undergoes secondary short-distance transmission, and the particles that are not completely melted remelt under the action of the laser and undergo a crystallization process to form a dense ceramic layer.

[0055] Example 3 A composite additive manufacturing material for complex ceramic multi-material components based on plasma and laser additive manufacturing, including metal powder.

[0056] The metal powder is a high-temperature alloy GH4169, with a particle size of 20 μm and a purity greater than 99%.

[0057] The manufacturing method based on the combination of plasma and laser additive manufacturing comprises the following steps: 1) Plasma deposition: Evacuate the working chamber to 10 -3 Pa, and then fill the working chamber with argon gas to make the pressure in the chamber reach 0.1MPa, heat the ceramic powder to a molten or semi-molten state, and deposit it on the magnesium oxide substrate through a plasma gas flow at a speed of 300m / s to form a forming layer with a thickness of about 25μm; 2) Laser sintering process: A point light source is used as the energy source for laser sintering, with a spot diameter of 0.05 mm, a laser power of 300 W, a scanning rate of 600 mm / s, a scanning interval of 0.05 mm, and a holding temperature of 400 °C; the corresponding argon pressure is 0.1 MPa.

[0058] 3) Laser cutting: Use a pulsed laser with a wavelength of 1.06μm and a laser power of 500W to accurately cut the forming layer according to the preset component contour to form the required complex shape; 4) Repeat the above process until a complex-shaped component is obtained. After the sample temperature is cooled to room temperature, the magnesium oxide substrate is immersed in deionized water to remove it.

[0059] In this embodiment, the complex-shaped block is post-processed. The specific processing method is: the complex-shaped block prepared as above is placed in a vacuum sintering furnace, and treated under an argon atmosphere. The sintering temperature is 1150°C and the insulation time is 2 hours, so as to remove defects and stresses that may exist in the laser sintering process inside the material.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A plasma deposition laser remelting composite additive manufacturing method, characterized in that: The following steps are involved: Step 1, outputting a material onto a substrate by plasma deposition, wherein the material is ceramic, metal, or a mixture of ceramic and metal, and the material is in a molten or semi-molten state, and the material forms a solid layer on the substrate; Step 2, subjecting the solid layer to laser sintering, remelting and solidifying the solid layer to form a forming layer; Step 3, cutting the side wall of the forming layer into a target shape and size by pulsed laser; Step 4, repeat steps 1 to 3 until printing is completed to form a process part; Step 5, remove the substrate under the process part to form the final workpiece.

2. The plasma deposition laser remelting composite additive manufacturing method according to claim 1, characterized in that: In step 1, during the plasma deposition process, a protective gas is filled into the working chamber.

3. The plasma deposition laser remelting composite additive manufacturing method according to claim 1, characterized in that: In step 1, the substrate is preheated before plasma deposition.

4. The plasma deposition laser remelting composite additive manufacturing method according to claim 1, characterized in that: In step 1, during the plasma deposition process, the plasma gas flow is 600m / s~1200m / s.

5. The plasma deposition laser remelting composite additive manufacturing method according to claim 1, characterized in that: In step 2, during the laser sintering process, the process parameters of the laser sintering are controlled, and the process parameters include spot diameter, laser power, scanning rate and scanning spacing.

6. The plasma deposition laser remelting composite additive manufacturing method according to claim 1, characterized in that: In step 2, the substrate is a soluble substrate.

7. The plasma deposition laser remelting composite additive manufacturing method according to claim 6, characterized in that: The material of the soluble substrate is magnesium alloy, zinc alloy, zinc-magnesium alloy or soluble inorganic matter.

8. The plasma deposition laser remelting composite additive manufacturing method according to claim 1, characterized in that: In step 2, when the material is a mixture of metal and ceramic, as the forming layers are accumulated, the mixed mass ratio of metal and ceramic in the material changes.

9. The plasma deposition laser remelting composite additive manufacturing method according to claim 1, characterized in that: After step 5, the printed part is post-processed, and the post-processing is any one or more of heat treatment, mechanical processing or chemical treatment.

10. The plasma deposition laser remelting composite additive manufacturing method according to claim 1, characterized in that: The plasma deposition is any one of PECVD, plasma polymerization or PLD.

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