CN100404174C - A preparation method for rapidly manufacturing functionally graded materials - Google Patents

Abstract

The invention discloses a preparation method for rapidly manufacturing functional gradient materials. According to the performance requirements of the prepared functional gradient materials, the method divides the raw material components according to the gradient ratio; The laser processing parameters of each layer; preheat and heat-preserve the prepared powder of each layer above; then spread it on the working platform through the powder feeding device, and scan layer by layer to realize the manufacture of functionally graded materials. The direct production of FGMs by the present invention has the advantages of high productivity, simple process, low manufacturing cost, wide selection of materials, high density, good mechanical properties and the like. For example: when using SLM rapid prototyping technology to manufacture FGMs containing TiC/Ni3Al/Ni components, debonding, high temperature post-treatment and sintering processes are not required, and the production cycle is equivalent to 1/3-1/5 of the SLS method, and the density It can reach 99%, and the manufactured FGMs are resistant to high temperature oxidation and corrosion.

Description

A preparation method for rapidly manufacturing functionally graded materials

technical field

The invention belongs to the field of advanced rapid manufacturing, in particular to a method for rapidly manufacturing functionally gradient materials (Functionally Gradient Materials, referred to as FGMs).

Background technique

FGMs is a new type of functionally graded material, which requires the components or internal structure of the material to be regularly distributed along a certain direction, so that a certain property of the material can produce continuous or gradient changes along this direction. The application fields of FGMs range from a single aerospace to nuclear energy, electronic materials, optical engineering, chemical engineering and biomedicine, and continue to expand. The traditional manufacturing methods of FGMs include: powder metallurgy, electroplating, self-propagating combustion high-temperature synthesis, plasma spraying, electrodeposition, centrifugal casting, etc. For example, the powder metallurgy method is to fully mix powders (metals, ceramics) with a particle size of 10 μm to 100 μm, fill them in layers according to the composition gradient or continuous composition control filling, and sinter to prepare FGMs after compaction. This method should control the powder size of the raw materials And the accuracy of powder filling arrangement, but the low productivity and the difficulty of precisely controlling the material composition and internal structure are its biggest shortcomings. Electroplating is used to manufacture FGMs, which is commonly referred to as DC electroplating. It is an electrochemical process in which a metal (alloy) deposition layer is obtained on a solid surface by electrolysis. The purpose of electroplating is to change the surface characteristics of solid materials. Electroplating can improve the appearance of materials , improve corrosion resistance, wear resistance, and make the surface of the material have magnetic, electrical, optical, thermal and other surface properties, but this method can only prepare FGMs coatings, and the productivity is also low. The self-propagating combustion high-temperature synthesis method uses the large amount of heat released during the sintering of the powder mixture participating in the synthesis reaction to continue the reaction, and the product after the reaction is a new material, but this method is only suitable for systems with high exothermic reactions. The plasma spraying method is to feed the raw material powder into the plasma jet and spray it on the substrate to form a coating in a molten state. The FGMs are prepared by continuously adjusting the spraying ratio and conveying conditions of the raw material powder to control the composition and organization of the coating, but The manufacturing process of this method is complicated, and it is difficult to precisely control the material composition and internal structure. It can be seen from the above that the methods that can directly manufacture FGMs parts are generally limited to the powder metallurgy method, and most of the other methods stay on the preparation of FGMs coatings, and the thickness of the coatings is relatively small. Moreover, these traditional preparation methods are not only complicated in process and difficult in preparation conditions. High, low production efficiency and difficult to precisely control the material composition and internal structure, thus causing the material to be prone to defects. Moreover, a preparation method is often only applicable to a specific material system, and the application range is relatively narrow, such as self-propagating combustion high-temperature synthesis The method is only suitable for systems with high exothermic reactions, and the centrifugal casting method can only produce axisymmetric FGMs, etc.

It can be seen from the above that the use of the above-mentioned traditional manufacturing methods to manufacture FGMs has greatly hindered the large-scale production and application of FGMs. For this reason, several FGMs manufacturing technologies based on rapid prototyping technology have emerged, which overcome some of the defects in the traditional manufacturing methods. But more are obtained through indirect methods. For example, the commonly used rapid prototyping technologies for manufacturing FGMs mainly include three-dimensional printing (Three Dimensional printing, 3DP), fused deposition manufacturing (Fusing Deposition Manufacturing, FDM), and selective laser sintering (Selective Laser Sintering, SLS). Using the 3DP method to manufacture FGMs is to add gradient composition particle slurry to the spray material, spray it to the CAD selection area layer by layer and control it to meet the requirements of the regional gradient composition, so as to manufacture three-dimensional FGMs. FDM is a method in which filamentous thermoplastic materials are melted and deposited layer by layer in selected areas. At present, due to the new technology of adding metal or ceramic particles to thermoplastic materials, this method can directly form metal and ceramic functional gradient prototypes. In foreign countries, the LENS (Laser Engineered NetShaping) system of Sandia National Laboratory, the DMD system of the University of Michigan and the SDM (Shaping Deposition Manufacturing) system of Stanford University are all directly manufactured by three-dimensional laser cladding (ThreeDimensional Laser Cladding, 3DLC) technology. FGMs. The University of Austin in the United States adopts the SLS method to manufacture FGMs by liquid phase sintering. Because it can control the structure and porosity, it is more suitable for the manufacture of FGMs such as biocompatible materials and chemical catalysts. The manufacturing advantage of SLS is that it does not require support and is not limited by complex structures and shapes, but its low density and insufficient strength are major defects. In China, Harbin Institute of Technology uses a combination of laminated molding system (LOM) and self-propagating (SHS) to manufacture TiC/Ni FGMs, in which LOM is used for material forming, and SHS is used for sintering and densification of material blanks. The process is cumbersome and difficult to control.

Practice has proved that it is feasible to fabricate FGMs with existing rapid prototyping techniques, but there are many disadvantages, such as: debonding and high-temperature post-treatment sintering are required, while considering the sintering rates of different phases in the material, it is difficult to avoid shrinkage and deformation, Low density and poor mechanical properties, etc.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a preparation method for rapidly manufacturing functionally graded materials. The FGMs directly produced by the present invention have the characteristics of small shrinkage and deformation, high density, short production cycle and good mechanical properties.

A kind of preparation method of fast manufacturing functional gradient material provided by the present invention, its steps are:

(1) Design the CAD model of FGMs by using 3D modeling software, and then save it as an STL file after being processed by the slicing software, and transfer the data information of the STL file to the selective laser melting rapid prototyping equipment;

(2) According to the performance requirements of the prepared FGMs, carry out graded distribution according to the above CAD model, determine the component ratio of each layer, and determine the laser processing parameters of each layer of powder;

(3) Carry out preheating and heat preservation treatment to each layer of powder prepared above, to reduce the residual stress of each layer of melting and formed parts;

(4) The powder feeding mechanism spreads the first-level distribution material on the working platform, with a layer thickness of 0.1mm to 0.3mm;

(5) Under the protective gas environment, the laser scans the powder according to the laser processing parameters of the layer determined in step (2), and melts the powder material in the laser action area, so that the temperature of the powder melting area is controlled at 30-100°C above the liquidus line Within ℃, the scanning distance is 0.1-0.3mm;

(6) The powder feeding mechanism spreads the next level of distribution material on the working platform according to the same layer thickness;

(7) Repeat the above steps (5)-(6) to scan the powder layer by layer until the task is completed.

Because the composition of FGMs is generally composed of two components, and the composition should be changed in time with the change of thickness in the CAD model during forming to meet the gradient performance requirements, according to the design principle of relieving thermal stress, through the analysis of finite element software with FGMs information Determine the component ratio of each layer, the powder mixing mechanism is controlled by the computer to prepare the powder material composition of each layer, the powder feeding mechanism is controlled by the computer to deliver the component powder corresponding to different positions in the CAD model, and then the powder of each layer is melted by the fiber laser , layer by layer to complete the fabrication of FGMs. No debonding, high-temperature post-treatment and sintering processes are required during processing. The direct production of FGMs by the present invention has the advantages of high productivity, simple process, low manufacturing cost, wide selection of materials, high density, good mechanical properties and the like. For example: when using SLM rapid prototyping technology to manufacture FGMs containing TiC/Ni3Al/Ni components, debonding, high temperature post-treatment and sintering processes are not required, and the production cycle is equivalent to 1/3-1/5 of the SLS method, and the density It can reach 99%, and the manufactured FGMs are resistant to high temperature oxidation and corrosion.

Detailed ways

(1) Use Pro/Engineer, Unigraphic and other three-dimensional modeling software to design the CAD model of FGMs, and then save it as an STL file after being processed by the slicing software, and send the data information of the STL file to the selective laser melting rapid prototyping equipment (ie SLM equipment );

(2) According to the performance requirements of the prepared FGMs, carry out graded distribution according to the above CAD model, determine the component ratio of each layer; and determine the laser processing parameters of each layer of powder, including laser power, scanning speed, layer thickness and scanning distance. The principle of determining the parameters of laser processing is: according to the melting point of the layer composition, the laser power, scanning speed, layer thickness and scanning distance are determined to melt the powder in the laser action area. In order to reduce the surface tension of the liquid surface, the laser action area The temperature should be in the region of 30-100°C above the liquidus of the mixed powder.

For example: TiCN, WC, Co and Ni are used as raw materials to prepare a gradient cermet cutting tool with a hard and wear-resistant TiCN-Ni phase on the surface and a high-strength and toughness WC-Co phase inside. Gradient 5% volume change can cause residual compressive stress greater than 0.45Gpa on the surface of the material, so that the surface can be strengthened and the interior can be toughened, avoiding thermal cracking of the surface layer caused by thermal stress during cutting.

(3) Preheat and heat-preserve the powders of each layer prepared above to reduce the residual stress of each layer melted and the formed part.

(4) The powder feeding mechanism spreads the first-level distribution material on the working platform, with a layer thickness of 0.1mm to 0.3mm;

(5) In the argon or hydrogen protective gas environment, the laser scans the powder according to the laser processing parameters of the layer determined in step (2), and melts the powder material in the laser action area, so that the temperature of the powder melting area is controlled at the liquidus line Above 30-100°C, the scanning distance is 0.1-0.3mm.

(6) The powder feeding mechanism spreads the next level of distribution material on the working platform according to the same layer thickness;

(7) Repeat the above steps (5)-(6) to scan the powder layer by layer until the task is completed. In this way, the fabrication of FGMs is finally realized, and the workpiece can be cooled slowly after fabrication.

The materials adopted above are mainly TiC/Ni3Al/Ni and Ti/ZrO ₂ and so on.

Example 1:

The 20mm thick FGMs containing TiC powder (5μm), Ni3Al powder and Ni powder (5-6μm) components were manufactured by SLM method, the purpose is to manufacture FGMs that are resistant to high temperature and can withstand repeated thermal shocks with large temperature differences. According to the above performance requirements, the composition design rules of FGMs are as follows: one side surface is Ni with a thickness of 1mm, and the other side surface is ^TiC with a thickness of 1mm. The TiC powder decreases layer by layer. Where x is the position coordinate of the gradient layer, d is the total thickness of each gradient layer, which is 20 mm here, and p is the composition distribution index, and the value range here is 1.5-1.8.

This process first uses Pro/Engineer, Unigraphic and other three-dimensional modeling software to design the solid shape of FGMs, and then it is processed by slicing software and saved as an STL file, and the data information of the STL file is sent to the rapid prototyping system of SLM. For the requirements of components and properties, a series of batching is carried out through the function (x/d) ^p of the powder composition changing with the processing position, and then preheated to 1250°C under the protection of an argon atmosphere, and kept for 8 hours, and the powder feeding mechanism is controlled by a computer. The ingredients are spread on the working platform, the minimum thickness of each layer is 0.1mm, the TiC powder used is about 5μm, the particle size of Ni3Al powder and Ni powder is about 5μm~6μm; finally, the fiber laser is used, and the scanning speed (200mm/s-500mm /s), scanning layer thickness (0.1mm-0.3mm) and scanning distance (0.1mm--0.2mm), melting the scanning layer powder material, layer by layer stacking, to realize the manufacture of FGMs of TiC, Ni3Al and Ni, and the workpiece is manufactured Then slowly cool to room temperature. After testing: the range of residual stress close to the TiC side is -200Mpa-200Mpa, and the manufactured FGMs are resistant to high temperature and can withstand large temperature difference thermal shock.

Example 2:

The FGMs of 16mm thick Ti/ _ZrO2 are manufactured by the SLM method. Firstly, the solid shape of the FGMs is designed with 3D modeling software such as Pro/Engineer and Unigraphic, and then processed by the slicing software and saved as an STL file. The data information of the STL file is sent to In the rapid prototyping system of SLM, according to the composition and performance requirements of the prepared FGMs, the functional relationship of the powder composition with the change of the processing position is analyzed through the CAD/CAM software with FGMs information, such as the volume ratio of Ti/ZrO ₂ is 10% The gradient increases for a series of batching, and then preheated to 1100°C under the protection of argon atmosphere, and kept for 8 hours. The powder feeding mechanism is controlled by the computer according to the functional relationship between the feeding amount required by the above FGMs and the processing position. On the working platform, the minimum thickness of each layer is 0.1mm, and the particle size of W powder and Cu powder used is about 0.5μM; finally, fiber laser is used, scanning speed (200mm/s-500mm/s), scanning layer thickness (0.1 mm-0.3mm) and scanning distance (0.1mm-0.2mm), the powder material of the scanning layer is melted and stacked layer by layer to realize the manufacture of FGMs of Ti/ _ZrO2 , and the workpiece is slowly cooled to room temperature after the workpiece is manufactured. Through experimental calculation and analysis, both sides of pure Ti and ZrO ₂ are subjected to compressive stress, which are about -10Mpa and -60Mpa respectively, and most of the middle is in a state of tensile stress. Such a stress state is conducive to improving the strength characteristics of the material and has a relatively Good thermal stress relief properties.

Claims (1)

1. A preparation method for rapidly manufacturing functionally graded materials, the steps of which are: (1) Design the CAD model of FGMs by using 3D modeling software, and then save it as an STL file after being processed by the slicing software, and transfer the data information of the STL file to the selective laser melting rapid prototyping equipment; (2) According to the performance requirements of the prepared FGMs, carry out graded distribution according to the above CAD model, determine the component ratio of each layer, and determine the laser processing parameters of each layer of powder; (3) Carry out preheating and heat preservation treatment to each layer of powder prepared above, to reduce the residual stress of each layer of melting and formed parts; (4) The powder feeding mechanism spreads the first-level distribution material on the working platform, with a layer thickness of 0.1mm to 0.3mm; (5) Under the protective gas environment, the laser scans the powder according to the laser processing parameters of the layer determined in step (2), and melts the powder material in the laser action area, so that the temperature of the powder melting area is controlled at 30-100°C above the liquidus line Within ℃, the scanning distance is 0.1-0.3mm; (6) The powder feeding mechanism spreads the next level of distribution material on the working platform according to the same layer thickness; (7) Repeat the above steps (5)-(6) to scan the powder layer by layer until the task is completed.