CN117102514A - Ultrasonic and laser impact in-situ reinforced selective laser melting equipment and method - Google Patents
Ultrasonic and laser impact in-situ reinforced selective laser melting equipment and method Download PDFInfo
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- 238000002844 melting Methods 0.000 title claims abstract description 94
- 230000008018 melting Effects 0.000 title claims abstract description 94
- 238000011065 in-situ storage Methods 0.000 title claims abstract description 56
- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000005728 strengthening Methods 0.000 claims abstract description 67
- 230000035939 shock Effects 0.000 claims abstract description 47
- 239000000463 material Substances 0.000 claims abstract description 43
- 239000000779 smoke Substances 0.000 claims abstract description 12
- 239000000428 dust Substances 0.000 claims abstract description 9
- 230000002787 reinforcement Effects 0.000 claims abstract description 8
- 239000000843 powder Substances 0.000 claims description 45
- 239000007789 gas Substances 0.000 claims description 34
- 239000000758 substrate Substances 0.000 claims description 28
- 230000008569 process Effects 0.000 claims description 26
- 229910052751 metal Inorganic materials 0.000 claims description 25
- 239000002184 metal Substances 0.000 claims description 25
- 230000003287 optical effect Effects 0.000 claims description 21
- 238000007789 sealing Methods 0.000 claims description 19
- 238000012545 processing Methods 0.000 claims description 18
- 239000000654 additive Substances 0.000 claims description 13
- 230000000996 additive effect Effects 0.000 claims description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 11
- 238000003860 storage Methods 0.000 claims description 10
- 239000013078 crystal Substances 0.000 claims description 8
- 238000010309 melting process Methods 0.000 claims description 8
- 238000010438 heat treatment Methods 0.000 claims description 7
- 229910052757 nitrogen Inorganic materials 0.000 claims description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 6
- 230000001681 protective effect Effects 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 5
- 229910001069 Ti alloy Inorganic materials 0.000 claims description 4
- 229910000838 Al alloy Inorganic materials 0.000 claims description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 3
- 229910000990 Ni alloy Inorganic materials 0.000 claims description 3
- 230000003213 activating effect Effects 0.000 claims description 3
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- 239000010949 copper Substances 0.000 claims description 3
- 238000011049 filling Methods 0.000 claims description 3
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
- B22F12/40—Radiation means
- B22F12/44—Radiation means characterised by the configuration of the radiation means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/20—Direct sintering or melting
- B22F10/28—Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/50—Treatment of workpieces or articles during build-up, e.g. treatments applied to fused layers during build-up
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
- B22F12/60—Planarisation devices; Compression devices
- B22F12/67—Blades
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y10/00—Processes of additive manufacturing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
Abstract
The invention provides ultrasonic and laser impact in-situ reinforced selective laser melting equipment and a method. The invention comprises a selective laser melting material adding system, a laser impact strengthening system, an ultrasonic in-situ strengthening system, a gas protection system, a smoke dust purifying system and the like; the selective laser melting material adding system is used for three-dimensional forming of the part; the invention aims to improve the wear resistance and fatigue performance of SLM formed parts through in-situ ultrasonic strengthening and laser shock strengthening. The invention enhances the mechanical properties such as yield strength, tensile strength and the like of the forming material by ultrasonic in-situ strengthening selective laser melting. The beneficial 800-1000 mu m deep compressive stress layer is introduced through laser shock reinforcement, and the tensile residual stress which damages the fatigue performance of the part and causes the part to crack is eliminated, so that the geometric precision, microhardness, plasticity and fatigue resistance of the part are improved.
Description
Technical Field
The invention relates to the field of additive manufacturing, in particular to ultrasonic and laser impact in-situ reinforced selective laser melting equipment and method.
Background
The selective laser melting technology, SLM (Selective laser melting), uses high-energy laser beam as energy source, and adopts selective area to melt metal powder layer by layer, and utilizes layer by layer superposition to make metal parts, so that it is favourable for making parts with arbitrary complex geometric shapes. However, the SLM parts have the problem of high porosity and residual tensile stress during the construction process, and the tensile residual stress can significantly reduce the fatigue life of the parts, distort the parts, cause cracking of the parts, and even cause delamination of the parts during the SLM construction process, resulting in process failure. Geometric deformation of the part increases the subsequent processing effort, while cracking of SLM formed parts limits its potential applications. It is difficult to eliminate the above-described forming defects only by optimizing the process parameters, so various compound processing processes and post-treatment processes are currently used to cope with the residual tensile stress and crack problems, but the effects so far are very little.
In the case of post-treatment processes, the heat treatment reduces the tensile residual stress by up to 70%, and the hot isostatic pressing treatment eliminates the residual tensile stress and existing porosity, thereby improving fatigue life. The post-treatment process refines the microstructure of the material by controlling grain growth after recrystallization, but cannot solve the problems of cracking and layering of the part in the selective laser melting construction process. In the composite processing technology, each layer after selective laser melting and forming is subjected to laser remelting, so that the composite processing technology can be used as in-situ heat treatment, the accumulation of tensile residual stress can be reduced, and 70% of tensile residual stress can be reduced, but the processing time can be obviously increased by scanning each layer again by laser, and the processing efficiency is reduced. In addition, the part after selective laser melting and forming can also be subjected to composite rolling forging or ultrasonic impact strengthening and other strengthening processes, and the tensile residual stress of the part is reduced by introducing compressive residual stress into the surface layer and reducing the porosity, so that the fatigue life of the part is prolonged, and the hardness of the surface area can be increased. However, such a composite processing process is time-consuming, expensive, and has limited improvement in the performance of the part in the depth direction, so a method for conveniently and efficiently controlling the residual tensile stress of the SLM-formed part is needed.
Disclosure of Invention
Aiming at the problems of part cracking, distortion, reduction of fatigue life and the like caused by tensile residual stress in the existing additive manufacturing process of SLM formed parts, the invention provides ultrasonic and laser impact in-situ strengthening selective laser melting equipment and a method, and aims to improve the wear resistance and fatigue performance of the SLM formed parts through in-situ ultrasonic strengthening and laser impact strengthening. The invention adopts the following technical means:
an ultrasonic and laser impact in-situ strengthening selective laser melting device comprises a selective laser melting material adding system, a laser impact strengthening system, an ultrasonic in-situ strengthening system, a gas protection system and a smoke dust purifying system,
the selective laser melting material adding system is used for three-dimensional forming of the part;
the laser shock strengthening system is used for carrying out laser shock strengthening on the formed part of the part after the material addition is preset, and introducing pre-compression stress;
the ultrasonic in-situ strengthening system is used for stirring the melt by acoustic cavitation in the selective laser melting and forming process, activating naturally-occurring crystal nuclei in the metal and refining crystal grains;
the gas protection system is used for filling protection gas into the selective laser melting material adding system in the selective laser melting forming process;
the smoke dust purifying system is used for filtering impurities generated in the selective laser melting material adding system in the laser melting process.
Further, the material adding system for selective laser melting comprises a sealing chamber, a scraper, a powder cylinder, a substrate, a forming cylinder and a first laser output system, wherein the material adding processing part of the material adding system for selective laser melting is arranged in the sealing chamber, the output end of the first laser output system is connected to the sealing chamber, the powder cylinder and the forming cylinder are of adjustable height, the powder cylinder is provided with a movable scraper, metal powder is arranged inside the powder cylinder, the substrate is arranged above the forming cylinder, a part to be formed is arranged above the substrate, and the metal powder is spread on the substrate through the scraper.
Further, a heating coil is arranged below the substrate.
Further, the first laser output system comprises a first x-y scanning galvanometer system, a first F-theta focusing lens, a second reflecting mirror, a second collimating lens, a second optical gate and a continuous laser, wherein the continuous laser emits continuous laser, and after passing through the second optical gate, the second collimating lens, the second reflecting mirror, the first x-y scanning galvanometer system and the first F-theta focusing lens, the continuous laser is focused on a current forming layer to carry out selective laser melting on a powder layer.
Further, the laser shock enhancement system comprises a pulse laser, a first optical gate, a first collimating lens, a first reflecting mirror, a second x-y scanning galvanometer system and a second F-theta focusing lens, wherein pulse laser generated by the pulse laser is focused on a current shock layer through the first optical gate, the first collimating lens, the first reflecting mirror, the second x-y scanning galvanometer and the second F-theta focusing lens by pulse beams.
Further, the ultrasonic in-situ reinforcement system comprises an ultrasonic generator, an ultrasonic transducer and an amplitude transformer, wherein the ultrasonic generator emits ultrasonic waves, the ultrasonic waves are transmitted to the amplitude transformer through the ultrasonic transducer, and the amplitude transformer is connected with the bottom of the substrate.
Further, an air inlet and an air outlet are respectively arranged at two ends of the sealing chamber, the air inlet is connected with the gas storage tank, protective gas nitrogen is input into the sealing chamber from the gas storage tank, and the air outlet is connected with the smoke dust purifying system.
The invention also discloses a processing method of the ultrasonic and laser impact in-situ reinforced selective laser melting equipment, which comprises the following steps:
step one: carrying out layering slicing treatment on three-dimensional data of the part through additive manufacturing software, and guiding the treated program data into ultrasonic and laser impact in-situ strengthening selective laser melting equipment;
step two: the powder cylinder rises, the forming cylinder descends, the scraper pushes metal powder from the cylinder to the forming cylinder substrate, the metal powder spreads uniformly on the surface of the metal powder, the continuous laser emits continuous laser, the second optical gate is opened, the continuous light passes through the second optical gate, the second collimating lens, the second reflecting mirror, the first x-y scanning vibrating mirror and the first F-theta focusing lens respectively and then is focused on the surface of preset metal powder, and selective laser melting is carried out according to a planned path according to the slice contour shape of the part, in the selective laser melting process, the ultrasonic auxiliary equipment of the ultrasonic in-situ strengthening system keeps an on state, and after the selective laser melting is finished, the ultrasonic auxiliary equipment of the ultrasonic in-situ strengthening system stops working;
step three: after each formed 10-20 layers are melted by the selective laser, a laser shock strengthening system is opened, high-power pulse laser is used as a follow beam to carry out laser shock strengthening in a laser shock strengthening window period, or after the current layer is formed, the laser shock strengthening is carried out according to a path planned by the shape of the formed layer, and residual compressive stress is input on the surface of the part;
step four: and performing next round of ultrasonic in-situ strengthening selective laser melting and laser shock strengthening until the additive forming of the part is completed.
Further, the substrate is preheated before selective laser melting, and the preheating temperature is 100-500 ℃.
Further, the selective laser melting material comprises titanium alloy, aluminum alloy, nickel alloy and stainless steel, wherein a forming laser is selected as a continuous laser with rated power of 200W-1000W, the laser wavelength is 1064nm, and the diameter of a focusing light spot is 70-100 mu m;
when the selective laser melting material is copper/gold material, the forming laser is a continuous laser with rated power of 200W-500W, the laser wavelength is 532nm, and the diameter of the focusing light spot is 70-100 mu m.
In the second step, the ascending height of the powder cylinder is 50-80 mu m each time, the descending height of the forming cylinder is 20-50 mu m each time, and the laser processing technological parameters in selective laser melting forming are determined according to materials;
in the third step, in the laser shock strengthening process, the energy of a laser is 0-20J, the laser wavelength is 532nm/1064nm, the pulse width is 5-15ns, the diameter of a focusing light spot is 1-5mm, and the repetition frequency is 1-10Hz;
in the third step, after the selected area laser is melted and formed into 10-20 layers, high-power pulse laser is used for impact reinforcement, and pulse laser is used as follow laser of continuous laser in the selected area laser melting, and is inserted in a reinforced window period or is inserted singly after the 10-20 layers are formed; when the laser is used for following laser, the scanning path is the same as the selective laser path; when the laser beam is singly inserted, the scanning path is required to be set according to the section shape and the diameter of the light spot;
in the second step, the power of the ultrasonic in-situ strengthening system and the ultrasonic generator is 800-2000w, the frequency is 15-30kHz, and the amplitude is 15-30 mu m;
in the whole part processing process, protective gas nitrogen is input into the sealing chamber from the gas storage tank, the gas passes through the surface of the processed part, and the gas protection device determines that the gas source is nitrogen or argon according to the forming material.
The invention has the following advantages:
1. columnar crystals growing along the forming direction in a molten pool are subjected to ultrasonic in-situ reinforced selective laser melting, and the molten pool is stirred by ultrasonic cavitation, bubble formation, bubble growth and bubble blasting, so that naturally-existing crystal nuclei in the alloy are activated, and the crystal grains are refined. Thereby improving the mechanical properties of the forming material such as yield strength, tensile strength and the like.
2. The beneficial 800-1000 mu m deep compressive stress layer is introduced through laser shock reinforcement in the third method step, and the tensile residual stress which damages the fatigue performance of the part and causes the part to crack is eliminated, so that the geometric precision, microhardness, plasticity and fatigue resistance of the part are improved. The laser shock peening and the selective laser melting are alternately performed, the in-situ peening is performed, the strengthening layer is not only limited to the surface of the formed part, but also the whole mechanical property of the part is improved.
3. The ultrasonic in-situ strengthening and the laser impact strengthening are simultaneously carried out, the strengthening depth in the part is deeper, the grain refinement is smaller, the working efficiency is high, and a large amount of post-treatment time is saved while the strengthening effect is achieved, so that the part processing cost is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to the drawings without inventive effort to a person skilled in the art.
FIG. 1 is a schematic diagram of an ultrasonic and laser shock in-situ reinforced selective laser melting apparatus according to the present invention.
FIG. 2 is a schematic diagram of an ultrasonic in-situ enhanced selective laser melting apparatus according to the present invention.
FIG. 3 is a schematic diagram of an ultrasonic and laser shock in-situ enhanced selective laser melting process according to the present invention.
FIG. 4 is a graph showing the results of the residual stress test before and after the ultrasonic and laser shock in-situ reinforcement module of the present invention is turned on. (a) Measuring the residual stress of the sample surface formed by selective laser melting; (b) And measuring the residual stress on the surface of the ultrasonic and laser shock in-situ reinforced selective laser melting sample.
In the figure: the device comprises a 1-protective gas storage tank, a 2-sealing chamber, a 3-scraper, 4-metal powder, a 5-powder cylinder, a 6-first X-y scanning galvanometer system, a 7-first F-theta focusing lens, an 8-continuous laser beam, a 9-part to be formed, a 10-substrate, an 11-heating coil, a 12-second X-y scanning galvanometer system, a 13-second F-theta focusing lens, a 14-pulse beam, a 15-amplitude transformer, a 16-forming cylinder, a 17-air outlet, a 18-smoke dust purifying system, a 19-first reflecting mirror, a 20-first collimating lens, a 21-first optical shutter, a 22-high-power pulse laser, a 23-second reflecting mirror, a 24-second collimating lens, a 25-second optical shutter, a 26-continuous laser, a 27-ultrasonic transducer and a 28-ultrasonic generator.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As shown in fig. 1-3, the embodiment of the invention discloses ultrasonic and laser impact in-situ reinforced selective laser melting equipment, which comprises a selective laser melting material adding system, a laser impact reinforcing system, an ultrasonic in-situ reinforcing system, a gas protection system and a smoke dust purifying system,
the selective laser melting material adding system is used for three-dimensional forming of the part;
the laser shock strengthening system is used for carrying out laser shock strengthening on the formed part of the part after the material is added for a preset condition, generally after 10-20 layers of material are added, residual tensile stress of the formed part is eliminated, high-power pulse laser follows continuous laser formed in a selected area in a window period, or laser shock strengthening is carried out on the formed part independently, and residual compressive stress is introduced, so that the overall stress state of the part is changed, the fatigue life is prolonged, and the initiation and the expansion of cracks are inhibited;
the ultrasonic in-situ strengthening system is used for stirring the melt by acoustic cavitation in the selective laser melting and forming process, activating naturally occurring crystal nuclei in the metal, refining grains and improving the mechanical properties of the alloy;
the gas protection system is used for filling protection gas in the selective laser melting forming process;
the smoke dust purifying system is used for filtering impurities such as slag, oxide particles and the like generated in the laser melting process.
Specifically, the district-selecting laser melting material-increasing system comprises a sealing chamber 2, a scraper 3, a powder material cylinder 5, a substrate 10, a forming cylinder 16 and a first laser output system, wherein an material-increasing processing part of the district-selecting laser melting material-increasing system is arranged in the sealing chamber, the output end of the first laser output system is connected to the sealing chamber, the powder material cylinder and the forming cylinder are of adjustable height, the movable scraper is arranged on the powder material cylinder, metal powder 4 is arranged in the powder material cylinder, the substrate is arranged above the forming cylinder, a part 9 to be formed is arranged above the substrate, and the metal powder is spread on the substrate through the scraper.
A heating coil 11 is arranged below the base plate.
The first laser output system comprises a first x-y scanning galvanometer system 6, a first F-theta focusing lens 7, a second reflecting mirror 23, a second collimating lens 24, a second optical shutter 25 and a continuous laser 26, wherein the continuous laser emits a continuous laser beam 8, and the continuous laser beam is focused on a current forming layer after passing through the second optical shutter, the second collimating lens, the second reflecting mirror, the first x-y scanning galvanometer system and the first F-theta focusing lens to perform selective laser melting on the powder layer.
The laser shock peening system includes: the second x-y scanning galvanometer system 12, the second F-theta focusing lens 13, the first reflecting mirror 19, the first collimating lens 20, the first optical gate 21 and the pulse laser 22, wherein the pulse laser 14 generated by the pulse laser is focused on the current impact layer by the pulse beam after passing through the first optical gate, the first collimating lens, the first reflecting mirror, the second x-y scanning galvanometer and the second F-theta focusing lens.
The laser scanning path is determined by controlling the first x-y scanning galvanometer and the second x-y scanning galvanometer by a computer.
The ultrasonic in-situ reinforcement system comprises an amplitude transformer 15, an ultrasonic transducer 27 and an ultrasonic generator 28, wherein the ultrasonic generator transmits ultrasonic waves to the amplitude transformer through the ultrasonic transducer, and the amplitude transformer is connected with the bottom of the substrate.
The two ends of the sealing chamber are respectively provided with an air inlet and an air outlet, the air inlet is connected with the protective gas storage tank 1, protective gas nitrogen is input into the sealing chamber from the gas storage tank, and the air outlet 17 is connected with the smoke purification system 18.
The invention also discloses a processing method of the ultrasonic and laser impact in-situ reinforced selective laser melting equipment, which comprises the following steps:
step one: the three-dimensional data of the part is subjected to layering slicing treatment through additive manufacturing software, and the treated program data is led into ultrasonic and laser impact in-situ reinforced selective laser melting equipment, in particular to an integral industrial personal computer;
step two: the powder cylinder rises, the forming cylinder descends, the scraper pushes metal powder from the cylinder to the forming cylinder substrate, the metal powder spreads uniformly on the surface of the metal powder, the continuous laser emits continuous laser, the second optical gate is opened, the continuous light passes through the second optical gate, the second collimating lens, the second reflecting mirror, the first x-y scanning vibrating mirror and the first F-theta focusing lens respectively and then is focused on the surface of preset metal powder, and selective laser melting is carried out according to a planned path according to the slice contour shape of the part, in the selective laser melting process, the ultrasonic auxiliary equipment keeps an on state, and after the selective laser melting is finished, the ultrasonic auxiliary equipment stops working;
step three: after each formed 10-20 layers are melted by the selective laser, a laser shock strengthening system is opened, high-power pulse laser is used as a follow beam to carry out laser shock strengthening in a laser shock strengthening window period, or after the current layer is formed, the laser shock strengthening is carried out according to a path planned by the shape of the formed layer, and residual compressive stress is input on the surface of the part;
step four: and performing next round of ultrasonic in-situ strengthening selective laser melting and laser shock strengthening until the additive forming of the part is completed.
Before selective laser melting, the substrate is preheated at 100-500 ℃.
The selective laser melting material comprises titanium alloy, aluminum alloy and nickel alloy, wherein a forming laser is a continuous laser with rated power of 200W-1000W, the laser wavelength is 1064nm, and the diameter of a focusing light spot is 70-100 mu m;
when the selective laser melting material is copper/gold material and other materials with higher laser reflectivity, the forming laser is a continuous laser with rated power of 200W-1000W, the laser wavelength is 532nm, and the diameter of the focusing light spot is 70-100 mu m.
The ascending height of the powder cylinder is 50-80 mu m each time, the descending height of the forming cylinder is 20-50 mu m each time, and the laser processing technological parameters in selective laser melting forming are determined according to the materials;
in the laser shock strengthening process, the energy of a laser is 0-20J, the laser wavelength is 532nm/1064nm, the pulse width is 5-15ns, the diameter of a focusing light spot is 1-5mm, and the repetition frequency is 1-10Hz;
after the selected area laser is melted and formed into 10-20 layers, high-power pulse laser is used for impact reinforcement, and the pulse laser is used as follow laser of continuous laser in the selected area laser melting, is inserted in a reinforced window period, or is inserted singly after the formed 10-20 layers; when the laser is used for following laser, the scanning path is the same as the selective laser path; when the laser beam is singly inserted, the scanning path is required to be set according to the section shape and the diameter of the light spot;
the power of the ultrasonic generator of the ultrasonic in-situ strengthening system is 800-2000w, the frequency is 15-30kHz, and the amplitude is 15-30 mu m;
the gas protection device determines that the gas source is nitrogen or argon according to the forming material.
Example 1
In this example, a formed titanium alloy (TC 4) cylindrical part is taken as an example, and the diameter of the cylinder is 30mm and the height thereof is 3mm. Firstly, three-dimensional data of a part is subjected to layering slicing treatment by using additive manufacturing professional software such as Magics, a treated program code is led into ultrasonic and laser impact in-situ reinforced selective laser melting equipment, a heating coil 11 preheats a substrate 10 to 150 ℃, a powder cylinder 5 rises by 60 mu m, a forming cylinder 16 descends by 30 mu m, a scraper 3 uniformly spreads metal powder 4 on the surface of the substrate 10, a continuous laser 26 emits infrared light with the wavelength of 1064nm, and the infrared light passes through a second optical shutter 25, a second collimating lens 24, a second reflecting mirror 23, a first x-y scanning vibrating mirror system 6 and a first F-theta focusing lens 7 and then is focused on a current forming layer by a continuous light beam 8 to perform selective laser melting on the powder layer. The rated power of the selected laser is 500W, the power is 80-200W, the scanning speed is 600-1500mm/s, and the scanning interval is 0.09-0.13mm. In the selective laser melting process, the ultrasonic in-situ strengthening system is kept in an on state, the ultrasonic generator 28 emits ultrasonic waves at the power of 1000W and the frequency of 20kHz, the ultrasonic waves are transmitted to the amplitude transformer 15 through the ultrasonic transducer 27, finally the ultrasonic waves are transmitted to the substrate 10 in the amplitude reduction of 15-30 mu m, and the ultrasonic strengthening is carried out in the selective laser melting process, so that grains are refined. After the laser melting of each layer of selected area is finished, the ultrasonic auxiliary equipment pauses.
The laser shock strengthening is to use high-power pulse laser 22 as following light after 10-20 layers are melted by selective laser, intervene in the window period of forming by selective laser melting (in this embodiment, the window period is 0.11 s-0.43 s after continuous laser melting metal powder), or re-plan the pulse light shock path according to the contour shape of the current layer after the current layer is formed by selective laser melting, and perform laser shock strengthening on the formed part of the part. The pulsed laser passes through a first shutter 21, a first collimating lens 20, a first reflecting mirror 19, a second x-y scanning galvanometer 12 and a second F-theta focusing lens 13, and is focused on the current impact layer by a pulsed light beam 14. The energy of the laser is 5-20J, the laser wavelength is 1064nm, the pulse width is 5-10ns, the diameter of the focusing light spot is 1-5mm, the repetition frequency is 1-10Hz, and the scanning speed is 50-500mm/s. The ultrasonic and laser impact in-situ strengthening system is closed, the residual stress on the upper surface of the cylinder formed by selective laser melting is tensile stress, the numerical value is 68.5+/-13.1 MPa, and the measurement result is shown in fig. 4 (a). Ultrasonic and laser impact strengthening are carried out while the selective laser melting forming cylinder, the residual stress on the upper surface of the cylinder is compressive stress, and the numerical value is-354.3 +/-17.4 MPa, as shown in fig. 4 (b).
In the whole part processing process, protective gas nitrogen is input into a sealing chamber 2 from a gas storage tank 1, the gas passes through the surface of a processed part, slag and oxide particles generated by selective laser melting are taken away, and then enter a smoke purification system 18 through an air outlet 17, wherein the oxygen content is required to be kept below 1% in the processing process.
The ultrasonic in-situ reinforced selective laser melting and laser impact forced crossing are carried out until the whole additive manufacturing of the part is completed, and the process flow is shown in figure 3.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.
Claims (10)
1. The ultrasonic and laser impact in-situ strengthening selective laser melting equipment is characterized by comprising a selective laser melting material adding system, a laser impact strengthening system, an ultrasonic in-situ strengthening system, a gas protection system and a smoke dust purifying system,
the selective laser melting material adding system is used for completing three-dimensional forming manufacturing of the part;
the laser shock strengthening system is used for carrying out laser shock strengthening on the formed part of the part after the preset condition of material addition, and introducing pre-compression stress;
the ultrasonic in-situ strengthening system is used for stirring the melt by acoustic cavitation in the selective laser melting and forming process, activating naturally-occurring crystal nuclei in the metal and refining crystal grains;
the gas protection system is used for filling protection gas into the selective laser melting material adding system in the selective laser melting forming process;
the smoke dust purifying system is used for filtering impurities generated in the selective laser melting material adding system in the laser melting process.
2. The ultrasonic and laser shock in-situ reinforced selective laser melting equipment according to claim 1, wherein the selective laser melting additive system comprises a sealing chamber, a scraper, a powder cylinder, a substrate, a forming cylinder and a first laser output system, wherein an additive processing part of the selective laser melting additive system is arranged in the sealing chamber, the output end of the first laser output system is connected to the sealing chamber, the powder cylinder and the forming cylinder are adjustable in height, the movable scraper is arranged on the powder cylinder, metal powder is arranged in the powder cylinder, a substrate is arranged above the forming cylinder, a part to be formed is arranged above the substrate, and the metal powder is spread on the substrate through the scraper.
3. The ultrasonic and laser shock in-situ reinforced selective laser melting equipment according to claim 2, wherein a heating coil is arranged below the substrate.
4. The ultrasonic and laser shock in-situ enhanced selective laser melting equipment according to claim 2, wherein the first laser output system comprises a continuous laser, a second optical gate, a second collimating lens, a second reflecting mirror, a first x-y scanning galvanometer system and a first F-theta focusing lens, wherein the continuous laser emits continuous laser, and the continuous laser is focused on the current forming layer by continuous beams after passing through the second optical gate, the second collimating lens, the second reflecting mirror, the first x-y scanning galvanometer system and the first F-theta focusing lens to perform selective laser melting on the powder layer.
5. The ultrasonic and laser shock in-situ reinforced selective laser melting apparatus of claim 1, wherein the laser shock peening system comprises: the pulse laser device comprises a pulse laser, a first optical gate, a first collimating lens, a first reflecting mirror, a second x-y scanning galvanometer system and a second F-theta focusing lens, wherein pulse laser generated by the pulse laser is focused on a current impact layer through the pulse laser after passing through the first optical gate, the first collimating lens, the first reflecting mirror, the second x-y scanning galvanometer and the second F-theta focusing lens.
6. The ultrasonic and laser shock in-situ reinforced selective laser melting equipment according to claim 1, wherein the ultrasonic in-situ reinforcing system comprises an ultrasonic generator, an ultrasonic transducer and an amplitude transformer, wherein the ultrasonic generator emits ultrasonic waves, the ultrasonic waves are transmitted to the amplitude transformer through the ultrasonic transducer, and the amplitude transformer is connected with the bottom of the substrate.
7. The ultrasonic and laser shock in-situ reinforced selective laser melting equipment according to claim 2, wherein the two ends of the sealing chamber are respectively provided with an air inlet and an air outlet, the air inlet is connected with a gas storage tank, protective gas is input into the sealing chamber from the gas storage tank, and the air outlet is connected with a smoke purification system.
8. The processing method of the ultrasonic and laser shock in-situ reinforced selective laser melting equipment according to any one of claims 1 to 7, comprising the following steps:
step one: carrying out layering slicing treatment on three-dimensional data of the part through additive manufacturing software, and guiding the treated program data into ultrasonic and laser impact in-situ strengthening selective laser melting equipment;
step two: the method comprises the steps of controlling a powder cylinder to ascend, a forming cylinder to descend, pushing metal powder from the cylinder to a forming cylinder substrate by a scraper, uniformly spreading the metal powder on the surface of the forming cylinder substrate, controlling a continuous laser to emit continuous laser, opening a second optical gate, respectively passing through the second optical gate, a second collimating lens, a second reflecting mirror, a first x-y scanning vibrating mirror and a first F-theta focusing lens, focusing the continuous light on the surface of preset metal powder by using continuous light beams, and carrying out zone selection laser melting according to a planned path according to the slice contour shape of a part, wherein in the process of zone selection laser melting, ultrasonic auxiliary equipment of an ultrasonic in-situ strengthening system keeps an on state, and after the zone selection laser melting is finished, the ultrasonic auxiliary equipment of the ultrasonic in-situ strengthening system pauses working;
step three: after the selected area laser is melted under the preset condition of material addition, a laser shock strengthening system is opened, high-power pulse laser is used as a follow beam to carry out laser shock strengthening in a laser shock strengthening window period, or after the current layer is formed, laser shock strengthening is carried out according to a path planned by the shape of a formed layer, and residual compressive stress is input on the surface of the part;
step four: and performing next round of ultrasonic in-situ strengthening selective laser melting and laser shock strengthening until the additive forming of the part is completed.
9. The method of claim 8, wherein the substrate is preheated prior to selective laser melting at a temperature of 100-500 ℃.
10. The method of claim 8, wherein the selective laser melting material comprises titanium alloy, aluminum alloy, nickel alloy, stainless steel, and the continuous laser with the rated power of forming laser of 200W-1000W is selected, the laser wavelength is 1064nm, and the diameter of focusing light spot is 70-100 μm;
when the selective laser melting material is copper/gold material, forming a continuous laser with rated power of 200W-500W, laser wavelength of 532nm and focused spot diameter of 70-100 μm;
in the second step, the ascending height of the powder cylinder is 50-80 mu m each time, the descending height of the forming cylinder is 20-50 mu m each time, and the laser processing technological parameters in selective laser melting forming are determined according to materials;
in the third step, in the laser shock strengthening process, the energy of a laser is 0-20J, the laser wavelength is 532nm/1064nm, the pulse width is 5-15ns, the diameter of a focusing light spot is 1-5mm, and the repetition frequency is 1-10Hz;
in the third step, after the selected area laser is melted and formed into 10-20 layers, high-power pulse laser is used for impact reinforcement, and pulse laser is used as follow laser of continuous laser in the selected area laser melting, and is inserted in a reinforced window period or is inserted singly after the 10-20 layers are formed; when the laser is used for following laser, the scanning path is the same as the selective laser path; when the laser beam is singly inserted, a scanning path is set according to the cross section shape and the diameter of the light spot;
in the second step, the power of the ultrasonic in-situ strengthening system and the ultrasonic generator is 800-2000w, the frequency is 15-30kHz, and the amplitude is 15-30 mu m;
in the whole part processing process, shielding gas is input into the sealing chamber from the gas storage tank, the gas passes through the surface of the processed part, and the gas shielding device determines that the gas source is nitrogen or argon according to the forming material.
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