CN100432025C - Metal/ ceramic laser sintering product post-processing method - Google Patents

Abstract

The invention discloses a post-processing method for a metal/ceramic laser sintered product. First degrease and high-temperature sinter the metal/ceramic laser sintered parts to be treated; then attach the high-temperature sintered parts to a sheath, and then put them into a cold isostatic pressing furnace for pressure treatment; the method of attaching a sheath It is: immerse the part in the silicone rubber solution, and after a layer of liquid is evenly attached to the surface, heat and dry it to make the liquid form a closed protective film on the surface of the part; finally, carry out subsequent processing on the part obtained by the near-net shape. Make the part geometry and shape meet the requirements. The invention combines the selective laser sintering (SLS) technology and the cold isostatic pressing (CIP) technology in the rapid prototyping technology, and can form complex shape structures and high-performance parts. Using SLS technology, parts with complex shapes and structures can be formed, especially those with complex curved surfaces and internal holes.

Description

A post-processing method for metal/ceramic laser sintered parts

technical field

The invention belongs to the technical field of rapid prototyping, in particular to a post-processing method for metal/ceramic laser sintered parts.

Background technique

Selective laser sintering (SLS) technology is a rapid prototyping technology that has developed very rapidly in recent years. It uses laser to selectively sinter solid powder in layers, and superimposes the solidified layers formed by sintering to generate parts of the desired shape. It can form a variety of powder materials such as metals, ceramics, and polymer materials. SLS technology has the advantages of short processing cycle, the ability to form parts with complex shapes and structures, high material utilization rate (up to 100%), and low cost. When using SLS technology to form metal/ceramic parts, it is necessary to add polymer powder materials with a lower melting point as a binder. Establish an initial connection. After high-temperature sintering, the prototype has certain mechanical properties, but there are still many pores inside, the density is low, and the mechanical properties cannot fully meet the requirements for use. This porous part must be densified to improve its mechanical properties.

Cold isostatic pressing (CIP) technology applies external pressure to cause displacement, deformation or fragmentation of powder particles, shortens the distance between particles, expands the contact area between powder particles, and enhances the degree of mechanical meshing between particles. It has the advantages of good performance, can form compacts of complex shapes, less machining, and saves raw materials. These advantages of cold isostatic pressing technology can be used to post-treat metal/ceramic SLS parts to improve the density and mechanical properties of the parts.

Contents of the invention

The object of the present invention is to provide a post-processing method for metal/ceramic laser sintered parts, the process of the method is simple, easy to implement, low in consumption and high in efficiency.

A post-processing method of a metal/ceramic laser sintered part provided by the invention, the steps are:

(1) Degreasing and high-temperature sintering of the metal/ceramic laser sintered parts to be processed;

(2) Attach a sheath to the high-temperature sintered part, and then put it into a cold isostatic pressing furnace for pressure treatment; the method of attaching a sheath is as follows:

Immerse the workpiece in the silicone rubber solution, and after a layer of liquid is uniformly attached to the surface of the workpiece, the workpiece is heated and dried to make the liquid form a closed protective film on the surface of the workpiece;

(3) Subsequent processing is performed on the parts obtained by the near-net shape, so that the geometric size and shape of the parts meet the requirements.

The present invention combines selective laser sintering (SLS) in rapid prototyping technology with cold isostatic pressing (CIP) technology, and this composite method has the following advantages:

(1) Using SLS technology, parts with complex shapes and structures can be formed, especially parts with complex curved surfaces and internal holes.

(2) After cold isostatic pressing, the workpiece can obtain uniform density.

(3) Because the SLS parts sintered at high temperature already have a certain density and strength, the production efficiency of cold isostatic pressing (CIP) is significantly improved, which can be increased by 50% to 90%.

(4) The sheath used in the cold isostatic pressing (HIP) process is very simple, which eliminates the deviation caused by the design of the sheath.

(5) The technological process is simple and easy, with low consumption and high efficiency.

Description of drawings

Fig. 1 is the process flow diagram of the selective laser-hot isostatic pressing composite manufacturing method of metal/ceramic parts of the present invention, and wherein, Fig. 1 (a) is the powder at the laser scanning section place; Fig. 1 (b) is laser selective Sintered parts; Fig. 1(c) is the part after degreasing and high temperature sintering; Fig. 1(d) is cold isostatic pressing; Fig. 1(e) is the final part.

Detailed ways

Below in conjunction with accompanying drawing and example concrete process of the present invention is described in further detail:

(1) Degreasing and high-temperature sintering of the metal/ceramic laser sintered parts to be treated (ie SLS parts), the purpose of which is to remove the polymer binder in the part, and at the same time establish a connection between the powder particles to improve Density and strength of parts.

(2) After attaching the sheath to the high-temperature sintered SLS part, it can be placed in a cold isostatic pressing furnace for pressure treatment. The design method of the sheath is as follows: the workpiece is immersed in the sheath solution, and after a layer of liquid is evenly attached to the surface of the workpiece, the workpiece is heated and dried to make the liquid form a closed protective film on the surface of the workpiece. It acts as a sheath during isostatic pressing. The liquid material here needs to have the following characteristics: a) It has certain wettability with metal/ceramics, can be attached to the surface of the workpiece, and can be cured to form a closed protective film after heating and drying; b) The formed protective film has a strong Good elasticity and tear resistance, will not break during cold isostatic pressing.

The coating solution adopts a silicone rubber solution, wherein the volume ratio of the silicone rubber to the organic solvent is about 1: (0.8-1.5), and the volume percentage of the curing agent to the silicone rubber solution is 1: 100-2: 100, wherein the organic solvent can be Use any organic solvent such as ethyl acetate that can dissolve the silicone rubber, and the curing agent can be the curing agent used in conventional silicone rubber solutions such as room temperature aliphatic amine curing agent or epoxy resin high temperature resistant curing agent.

(3) Subsequent processing of parts obtained by near-net shape, such as simple machining or surface treatment, so that the geometric size and shape of the parts can fully meet the requirements.

The preparation of metal/ceramic laser sintered parts can adopt the existing technology, and can adopt the following processing steps to carry out:

(1) Use 3D modeling software to design the CAD 3D model of the part, then process it with the slicing software and save it as an STL file, and send the data information of the STL file to the SLS rapid prototyping system.

(2) The powder feeding mechanism spreads a layer of powder to be processed (with a particle size of about 10-60 μm) with a thickness of about 0.02-0.2 mm on the working platform.

(3) Diode-pumped YAG lasers, fiber lasers or _CO2 lasers with a laser power greater than or equal to 50W are used. The laser spot is 10-250μm, the scanning distance is 0.04-0.2mm, and the scanning speed is 500-3000mm/s. Layer sliced powders were subjected to scanning sintering.

(4) Repeat the above steps (2)-(3) until the prototype of the desired shape is made.

The essence of the present invention is to apply cold isostatic pressing (CIP) technology to the field of rapid prototyping, and perform post-processing on metal selective laser sintering (SLS) parts, which can improve the density and strength of the parts. At the same time, the design of the sheath during cold isostatic pressing is simple and easy, which avoids the deviation caused by the design of the sheath. Therefore, combining selective laser sintering (SLS) technology and cold isostatic pressing (CIP) technology, it is possible to form parts with complex shapes and structures and high performance.

Example 1

(1) First, according to the possible deformation of SLM parts after hot isostatic pressing, use 3D modeling software (such as UG, Pro/E, etc.) to design the CAD 3D model of the part before hot isostatic pressing, and then use the slicing software After processing, it is saved as an STL file, and the data information of the STL file is sent to the SLM rapid prototyping system.

(2) The powder feeding mechanism spreads a layer of stainless steel powder (particle size about 20 μm) with a thickness of about 0.1 mm on the working platform. The binder is epoxy resin with a content of about 4%.

(3) Use a diode-pumped YAG laser or fiber laser with a laser power greater than or equal to 50W. The laser spot diameter is about 50μm, the scanning speed is about 2000mm/s, and the scanning distance is about 0.1mm. Scan the sliced powder located in this layer.

(4) Repeat the above steps (2)-(3) until a whole SLS part with the required shape is produced.

(5) Transfer the SLS parts to the vacuum degreasing furnace, vacuumize, and set the degreasing process route as follows: at room temperature, the temperature is raised to 200°C in 1 hour, the temperature is raised to 400°C in 1.5 hours, the temperature is raised to 460°C in 2.5 hours, and 2 hours Raise the temperature to 750°C, then raise the temperature to 950°C in 1 hour, keep warm for half an hour, then cool to room temperature with the furnace, and take it out of the furnace.

(6) Transfer the SLS parts to a vacuum sintering furnace, vacuumize, and set the process route as follows: at room temperature, heat up to 1100°C for 1 hour, hold for 3 hours, then heat up to 1200°C for half an hour, hold for 2 hours, and cool to Bake at room temperature.

(7) Immerse the SLS parts after high-temperature sintering in the silicone rubber solution, so that a layer of silicone rubber is attached to the surface of the parts, transfer the parts to the drying oven, and bake them at 30 ° C to 40 ° C for 7 to 9 hours to make the silicone rubber Form a protective film on the surface of the workpiece. Wherein, the composition of the silicone rubber solution is: the volume fraction of the fatty amine curing agent at room temperature is 1.5%, and the volume ratio of the silicone rubber to ethyl acetate is 1:1.

(8) Check whether the protective film is closed. If it is not completely closed, repeat step (7) until a fully closed protective film is formed on the surface of the workpiece.

(9) Transfer the workpiece with a closed protective film attached to the surface to a cold isostatic pressing furnace, use mixed liquid oil such as kerosene and gasoline as the medium, quickly pressurize to 2GPa, and keep the pressure for 5min. Under the action of pressure, the density and mechanical properties of SLS parts are greatly improved, and the geometric size and shape basically meet the requirements.

(10) Finally, follow-up processing is carried out on the parts obtained by the near net shape, so that the geometric size and shape of the parts fully meet the requirements.

Example 2

(1) First, according to the possible deformation of SLM parts after hot isostatic pressing, use 3D modeling software (such as UG, Pro/E, etc.) to design the CAD 3D model of the part before hot isostatic pressing, and then use the slicing software After processing, it is saved as an STL file, and the data information of the STL file is sent to the SLM rapid prototyping system.

(2) The powder feeding mechanism spreads a layer of ceramic powder with a thickness of about 0.1 mm on the working platform (the main component is alumina, the particle size is about 80 μm), and the binder is epoxy resin. The content is about 5%.

(3) Use a diode-pumped YAG laser or fiber laser with a laser power greater than or equal to 50W. The laser spot is about 50μm, the scanning speed is about 2000mm/s, and the scanning distance is about 0.1mm. Scan the sliced powder located in this layer.

(4) Repeat the above steps (2)-(3) until a whole SLS part with the required shape is produced.

(5) Transfer the SLS parts to a vacuum furnace, vacuumize, degrease and sinter at high temperature. The degreasing process route is set as follows: heat up to 200°C for 1 hour at room temperature, 450°C for 1 hour, 550°C for 1 hour, and 1400°C for 3 hours, and then cool to room temperature with the furnace after 6 hours of heat preservation. .

(6) Immerse the SLS parts after high-temperature sintering in the silica sol solution, so that a layer of silica sol is attached to the surface of the parts, transfer the parts to the drying oven, and bake them at 80 ° C to 100 ° C for 7 to 9 hours to make the silicone rubber Form a protective film on the surface of the workpiece. Wherein, the composition of the silicone rubber solution is: the volume fraction of epoxy resin high temperature resistant curing agent is 1.5%, and the volume ratio of silicone rubber to ethyl acetate is 1:1.

(7) Check whether the protective film is closed. If it is not completely closed, repeat step (7) until a fully closed protective film is formed on the surface of the workpiece.

(8) Transfer the workpiece with a closed protective film attached to the surface to a cold isostatic pressing furnace, use mixed liquid oil such as kerosene and gasoline as the medium, quickly pressurize to 3GPa, and keep the pressure for 6 minutes. Under the action of pressure, the density and mechanical properties of SLS parts are greatly improved, and the geometric size and shape basically meet the requirements.

(9) Finally, follow-up processing is carried out on the parts obtained by the near-net shape, so that the geometric size and shape of the parts fully meet the requirements.

Claims (2)

1, a kind of post-treating method of metal/ceramic laser sintering product, its step comprises:

(1) pending metal/ceramic laser sintering product is carried out skimming treatment and high temperature sintering;

(2) product behind the high temperature sintering is enclosed jacket, put into the isostatic cool pressing stove again, carry out pressure treatment; The method of attached jacket is as follows:

Product is immersed in the silicone rubber solution, after one deck liquid is evenly adhered on the product surface, product is carried out heating, drying handle, make liquid form the protective membrane of sealing on the product surface;

(3) part that near-net-shape is obtained carries out following process, and the part geometry size and dimension is met the requirements.

2, post-treating method according to claim 1 is characterized in that: in the silicone rubber solution, wherein silicon rubber is 1 with the volume of organic solvent ratio: 0.8-1 in the step (2): 1.5, and the volume percent of solidifying agent and silicone rubber solution is 1: 100-2: 100.