阅读说明：本技术 3d打印方法及3d打印件 (3D printing method and 3D printed piece ) 是由 李长鹏 周忠娇 陈国锋 于 2018-09-04 设计创作，主要内容包括：本发明提供了3D打印方法及3D打印件,其中,包括如下步骤：S1,根据3D打印模型对打印材料进行激光扫描,使得所述打印材料自下而上地逐层开始烧结为预设形状的打印件；S2,在3D打印装置中通入处理气体,并且对所述打印件的局部区域执行激光扫描,使得所述处理气体与所述打印件的局部区域表面反应形成硬化层,其中,所述步骤S1和所述步骤S2交替执行,直至构成具有局部硬化层的打印件。本发明通过调整气体环境使得选择性激光熔化设备制造的元件具有耐磨耐腐蚀的表面氮化层,并保持中心区域的预期延展性。氮化层具有理想的晶格结构。本发明不需要设置额外的表面处理步骤,因此功耗更低,花费更少。本发明提供的原位氮化制程精确地控制了氮化梯度。(The invention provides a 3D printing method and a 3D printed product, wherein the method comprises the following steps: s1, performing laser scanning on the printing material according to the 3D printing model, so that the printing material starts to be sintered into a printing piece with a preset shape layer by layer from bottom to top; and S2, introducing a processing gas into the 3D printing device, and performing laser scanning on the local area of the printed material, so that the processing gas and the local area of the printed material are subjected to surface reaction to form a hardened layer, wherein the step S1 and the step S2 are alternately performed until the printed material with the locally hardened layer is formed. The invention enables the selective laser melting equipment to manufacture components with wear-resistant and corrosion-resistant surface nitrided layers by adjusting the gas environment and maintains the expected ductility of the central area. The nitride layer has an ideal lattice structure. The invention does not need to arrange an additional surface treatment step, thereby having lower power consumption and lower cost. The in-situ nitridation process provided by the present invention precisely controls the nitridation gradient.)

The 3D printing method comprises the following steps:

s1, performing laser scanning on the printing material according to the 3D printing model, so that the printing material starts to be sintered into a printing piece with a preset shape layer by layer from bottom to top;

s2, introducing processing gas into the 3D printing device, and performing laser scanning on the local area of the printed matter to enable the processing gas to react with the surface of the local area of the printed matter to form a hardened layer,

wherein the step S1 and the step S2 are alternately executed until a printed matter having a locally hardened layer is constituted.

2. The 3D printing method according to claim 1, wherein the process gas comprises ammonia gas.

3. The 3D printing method according to claim 2, wherein the 3D printing method further comprises the steps of:

the step S1 and the step S2 are alternately executed until a printed matter having hardened layers disposed at intervals is constituted so that the printed matter has a desired hardness.

4. The 3D printing method according to claim 1, wherein the 3D printing method further comprises the steps of:

adjusting the internal elastic modulus and the surface hardness of the print by adjusting the volume ratio of the material layer and the hardened layer of the print.

5. The 3D printing method according to claim 1, wherein the 3D printing method further comprises the steps of:

the thicknesses of the material layer and the hardened layer are adjusted by adjusting the amounts of the process gas and the protective gas and the transport time, thereby adjusting the internal elastic modulus and the surface hardness of the printed material.

6. The 3D printing method according to claim 1, wherein the laser scanning step comprises a rotary laser scanning or a partial laser scanning.

7. The 3D printing method according to claim 1, wherein a protective gas is introduced into the 3D printing apparatus when the step S1 is executed, wherein the protective gas is an inert gas.

8. The 3D printing method according to claim 7, wherein the shielding gas comprises nitrogen or argon.

9. The 3D printing method according to claim 1, wherein the 3D printing method further comprises the steps of:

and sending the printing material forming the material from the forming cylinder of the 3D device to a recovery cylinder for recovery.

A 3D print, characterized in that the 3D print is manufactured by the 3D printing method as provided in any of claims 1 to 9.

Technical Field

The invention relates to the field of additive manufacturing, in particular to a 3D printing method and a 3D printed piece.

Background

Additive Manufacturing process (Additive Manufacturing) is now one of the rapidly evolving high-level Manufacturing technologies in the world, which shows broad application prospects. Selective Laser Melting (SLM) is one of Additive manufacturing (Additive manufacturing) technologies that can rapidly manufacture the same parts as a CAD model by means of Laser sintering. Currently, selective laser melting processes are widely used. Unlike conventional material removal mechanisms, additive manufacturing is based on the completely opposite material additive manufacturing principle (materials additive manufacturing philosophy), in which selective laser melting utilizes a high-power laser to melt metal powder and build up parts/components layer by layer through a 3D CAD input, which can successfully manufacture components with complex internal channels. Additive manufacturing techniques can offer a unique potential for arbitrarily fabricating complex structural elements that cannot generally be readily fabricated by conventional processes.

In addition to the above-mentioned advantages of additive manufacturing processes, higher capital investment and lower printing rates have prevented their widespread use. Custom designed, low-throughput, and complex-structured components may be more suitable than conventional fabrication techniques for utilizing additive manufacturing processes, based on cost considerations. One typical application is a sealing element.

However, additive manufacturing techniques still have some technical bottlenecks, such as relatively low corrosion and wear resistance. In order to solve the above problems, the prior art would select a high loss material, such as a carbide material, as the sealing element. However, carbide materials are generally more difficult to use in additive manufacturing processes because the materials tend to crack and other defects upon rapid heating and cooling by the laser. Binder Jetting Technology followed by a sintering process can be used to fabricate hard metal components. However, the high shrinkage rate caused during sintering is not easily predictable and controllable, preventing its application to sealing elements requiring high dimensional accuracy.

Disclosure of Invention

The invention provides a 3D printing method in a first aspect, which comprises the following steps: s1, performing laser scanning on the printing material according to the 3D printing model, so that the printing material starts to be sintered into a printing piece with a preset shape layer by layer from bottom to top; and S2, introducing a processing gas into the 3D printing device, and performing laser scanning on the local area of the printed material, so that the processing gas and the local area of the printed material are subjected to surface reaction to form a hardened layer, wherein the step S1 and the step S2 are alternately performed until the printed material with the locally hardened layer is formed.

Further, the process gas includes ammonia.

Further, the 3D printing method further includes the steps of: the step S1 and the step S2 are alternately executed until a printed matter having hardened layers disposed at intervals is constituted so that the printed matter has a desired hardness.

Further, the 3D printing method further includes the steps of: adjusting the internal elastic modulus and the surface hardness of the print by adjusting the volume ratio of the material layer and the hardened layer of the print.

Further, the 3D printing method further includes the steps of: the thicknesses of the material layer and the hardened layer are adjusted by adjusting the amounts of the process gas and the protective gas and the transport time, thereby adjusting the internal elastic modulus and the surface hardness of the printed material.

Further, the laser scanning step includes a rotation laser scanning or a partial laser scanning.

Further, when the step S1 is executed, a protective gas is introduced into the 3D printing apparatus, wherein the protective gas is an inert gas.

Further, the shielding gas comprises nitrogen or argon.

Further, the 3D printing method further includes the steps of: and sending the printing material forming the material from the forming cylinder of the 3D device to a recovery cylinder for recovery.

The invention provides a 3D printing piece in a second aspect, wherein the 3D printing piece is manufactured by the 3D printing method provided by the first aspect of the invention.

The present invention also maintains the desired ductility in the central region by adjusting the gas environment so that the components produced by the selective laser melting apparatus have a wear and corrosion resistant surface nitrided layer. Wherein the nitride layer has an ideal lattice structure. And the invention does not need to arrange an additional surface treatment step, so the power consumption is lower and the cost is less. The in-situ nitridation process provided by the present invention precisely controls the nitridation gradient.

Drawings

FIG. 1 is a schematic view of a selective laser melting apparatus;

FIG. 2a is a cross-sectional view of a 3D printing method provided by the invention implemented in a selective laser melting apparatus according to an embodiment of the invention, wherein the 3D printing piece is provided with 3D printing pieces, and the 3D printing pieces are respectively provided with hardened layers on the upper surface and the lower surface;

FIG. 2b is a cross-sectional view of a 3D printing method provided by the present invention performed in a selective laser melting apparatus according to yet another embodiment of the present invention, configured with a 3D print, wherein the 3D print has a plurality of spaced hardened layers;

fig. 2c is a cross-sectional view of a 3D printing method provided by the present invention performed in a selective laser melting apparatus according to another embodiment of the present invention, configured with a 3D print, wherein the 3D print has a hardened region in the central region.

Detailed Description

The following describes a specific embodiment of the present invention with reference to the drawings.

The invention provides a 3D printing method, which simultaneously executes a laser scanning step and a hardening step in the same 3D printing equipment to form a 3D printing piece with any local hardening layer. Compared with single nitriding treatment, the formed hardened layer can accurately adjust hardness gradient and hardening depth without forming a surface over-hardened layer due to reaching enough hardening depth, so that an over-hardened layer removing step is not needed, the local hardened layer is not easy to crack, and the hardening degree can be adjusted according to requirements.

Wherein the invention is preferably performed in a selective laser melting device. Wherein, different printing materials such as metal, ceramic, plastic, sand and the like are arranged in the selective laser melting equipment. The present invention will be explained below using metal powder as a printing material.

The present invention also maintains the desired ductility in the central region by adjusting the gas environment so that the components produced by the selective laser melting apparatus have a wear and corrosion resistant surface nitrided layer. Wherein the nitride layer has an ideal lattice structure. And the invention does not need to arrange an additional surface treatment step, so the power consumption is lower and the cost is less. The in-situ nitridation process provided by the present invention precisely controls the nitridation gradient.

FIG. 1 is a schematic view of a selective laser melting apparatus. As shown in FIG. 1, selective laser melting apparatus 100 includes a laser source 110, a mirror scanner 120, a prism 130, a powder feed cylinder 140, a forming cylinder 150, and a recovery cylinder 160. Therein, a laser source 110 is disposed above the selective laser melting apparatus 100, serving as a heating source for metal powder, i.e., melting the metal powder for 3D printing.

Wherein, the powder feeding cylinder 140 has a first piston (not shown) at a lower portion thereof, which can move up and down, and the spare metal powder is placed in a cavity space above the first piston of the powder feeding cylinder 140, and the metal powder is fed from the powder feeding cylinder 140 to the molding cylinder 150 in accordance with the up and down movement of the first piston. A 3D print placing table 154 is provided in the forming cylinder 150, a 3D print C is held above the placing table 154, and a second piston 152 is fixed below the placing table 154, wherein the second piston 152 and the placing table 154 are vertically provided. During 3D printing, the second piston 152 moves from top to bottom to form a printing space in the forming cylinder 220. The laser source 110 for laser scanning should be disposed above the forming cylinder 150 of the selective laser melting apparatus, and the mirror scanner 120 adjusts the position of the laser by adjusting the angle of one prism 130, and determines which region of the metal powder is melted by the laser by adjusting the prism 130. The powder feeding cylinder 140 further includes a roller (not shown), and the metal powder P is stacked on an upper surface of the first piston, which vertically moves from bottom to top to transfer the metal powder to an upper portion of the powder feeding cylinder 140. The roller may roll on the metal powder P to feed the metal powder P into the forming cylinder 150. And continuously performing laser scanning on the metal powder, decomposing the metal powder into a powder matrix, and continuously performing laser scanning on the powder matrix until the powder matrix is sintered into a printing piece C with a preset shape from bottom to top.

Wherein the selective laser melting apparatus 100 further comprises a gas supply device 170. The gas supply device 170 includes first and second gas inlet conduits 172 and 174, and a gas outlet conduit 176. A first valve 173 is further provided in the first intake pipe 172, and a second valve 175 is provided in the second intake pipe 174. A control device 171 is connected to the first valve 173 and the second valve 175 for controlling the opening and closing of the first intake conduit 172 and the second intake conduit 174.

The 3D printing method provided by the invention comprises the following steps:

and step S1, performing laser scanning on the printing material according to the 3D printing model, so that the printing material starts to be sintered into a printing piece with a preset shape layer by layer from bottom to top. According to a preferred embodiment of the present invention, the 3D printing model is a digital model, and the printing material is metal powder. Specifically, laser scanning is continuously performed on metal powder, the metal powder is decomposed into a powder matrix, and the powder matrix is continuously subjected to laser scanning until the powder matrix is sintered into a preset shape layer by layer from bottom to top. During the laser scan, the first valve 173 of the first gas inlet line 172 is opened to deliver shielding gas into the selective laser melting apparatus 100. At the same time, the second valve 175 of the second intake pipe 174 is closed, and the process gas ammonia NH is cut off₃Into the selective laser melting apparatus 100 to form a protective gas environment for laser scanning.

And step S2, introducing processing gas into the 3D printing device, and performing laser scanning on the local area of the printed matter, so that the processing gas and the local area of the printed matter react to form a hardened layer. Wherein, according to a preferred embodiment of the present invention, the 3D printing apparatus is a selective laser melting device 100 as shown in fig. 1. Specifically, as shown in FIG. 1, the first intake conduit 172 is usedFor delivering the shielding gas, the second gas inlet pipe 174 is used for delivering the processing gas. In particular, the protective gas is in particular an inert gas, such as nitrogen or argon. The treatment gas is ammonia NH₃. When a partially hardened layer or a partially hardened region needs to be formed based on the 3D printing model, the first valve 173 of the first gas inlet pipe 172 is closed to shut off the supply of the shielding gas into the selective laser melting apparatus 100. And the second valve 175 of the second gas inlet line 174 is opened to open the process gas ammonia NH₃Into selective laser melting apparatus 100. Ammonia NH adjacent to the forming cylinder 150₃Will decompose into ions and react with metallic material (metallic material), ammonia NH₃The decomposed ions diffuse and the metallic material of the print produces a thin hardened layer.

Wherein the step S1 and the step S2 are alternately performed until a 3D printed matter having a locally hardened layer is constructed. The 3D printing method provided by the present invention is specifically described below in conjunction with different print shapes/configurations.

As shown in fig. 2a, according to the digital model, the first 3D print 200 should have a metal body 220, and a hardened layer needs to be provided on both upper and lower surfaces of the metal body 220, respectively, a first hardened layer 210 provided on the upper surface of the metal body 220 and a second hardened layer 230 provided on the lower surface of the metal body 220. The direction of the arrows in fig. 2a shows the printing direction, i.e. the vertical printing direction from bottom to top. Specifically, the hardening step S2 is first performed to print the second hardened layer 230, at which time the second valve 175 of the second air inlet pipe 174 is opened and the process gas ammonia NH is opened₃Into selective laser melting apparatus 100. At the same time, the first valve 173 of the first gas inlet conduit 172 is closed to shut off the supply of shielding gas to the selective laser melting apparatus 100. After the second hardened layer 230 is formed, the laser scanning step S1 is performed, specifically, the first valve 173 of the first air inlet pipe 172 is opened to deliver the shielding gas to the selective laser melting apparatus 100. At the same time, the second valve 175 of the second intake pipe 174 is closed, and the process gas ammonia NH is cut off₃Into selective laser melting apparatus 100. To be processed into the metal body 220When the process is completed, the hardening step S2 is performed to print the first hardened layer 210, wherein the second valve 175 of the second air inlet pipe 174 is opened, and the process gas, ammonia NH, is opened₃Into selective laser melting apparatus 100. At the same time, the first valve 173 of the first gas inlet conduit 172 is closed to shut off the supply of shielding gas to the selective laser melting apparatus 100. The laser scanning step S1 and the hardening step S2 are alternately performed so far until the first 3D printed matter 200 is formed.

Further, the invention also comprises the following steps: the step S1 and the step S2 are alternately executed until a printed matter having hardened layers disposed at intervals is constituted so that the printed matter has a desired hardness.

As shown in fig. 2b, the second 3D print 300 has hardening layers arranged at intervals according to the digital model. Specifically, the second 3D print 300 is provided with a first hardened layer 310, a first material layer 360, a second hardened layer 320, a second material layer 370, a third hardened layer 330, a third material layer 380, a fourth hardened layer 340, a fourth material layer 390, and a fifth hardened layer 350 in this order from below. According to a variant of the specific embodiment shown in fig. 2a, the laser scanning step S1 and the hardening step S2 are repeatedly performed alternately a plurality of times. The direction of the arrows in fig. 2b shows the printing direction, i.e. the vertical printing direction from bottom to top. Specifically, the hardening step S2 is first performed to print the first hardened layer 310, at which time the second valve 175 of the second air inlet pipe 174 is opened and the process gas ammonia NH is opened₃Into selective laser melting apparatus 100. At the same time, the first valve 173 of the first gas inlet conduit 172 is closed to shut off the supply of shielding gas to the selective laser melting apparatus 100. After the first hardened layer 310 is formed, the laser scanning step S1 is performed, specifically, the first valve 173 of the first air inlet pipe 172 is opened to deliver the shielding gas to the selective laser melting apparatus 100. At the same time, the second valve 175 of the second intake pipe 174 is closed, and the process gas ammonia NH is cut off₃Into selective laser melting apparatus 100. Similarly, the hardening step S2 and the laser scanning step S1 are repeated a plurality of times, thereby forming the second hardened layer 320, the second material layer 370, and the third hardened layer 320, 370A layer 330, a layer 380 of a third material, a layer 340 of a fourth hardening layer, a layer 390 of a fourth material, a layer 350 of a fifth hardening layer until a second 3D print 300 is formed.

As shown in fig. 2c, the third 3D print 400 has a material area 420, in accordance with the digital model, and a hardening area 410 is provided in a central area of the material area 420. The present embodiment needs to adopt a local scanning strategy, specifically, first, the laser scanning is performed vertically from bottom to top according to the printing direction shown by the arrow in fig. 2c, i.e. the laser scanning step S1 is performed, and the material region 420 with the predetermined thickness is formed. The hardening zone 410 is then constituted in the central region of the material zone 420, i.e. the hardening step S2 is performed. Therein, when the scanning step S1 is performed, the first valve 173 of the first gas inlet conduit 172 is opened to deliver the shielding gas to the selective laser melting apparatus 100. At the same time, the second valve 175 of the second intake pipe 174 is closed, and the process gas ammonia NH is cut off₃Into selective laser melting apparatus 100. In the hardening step S2, the second valve 175 of the second gas inlet pipe 174 is opened, and the process gas, ammonia NH, is opened₃Into selective laser melting apparatus 100. At the same time, the first valve 173 of the first gas inlet conduit 172 is closed to shut off the supply of shielding gas to the selective laser melting apparatus 100.

In addition, the invention also comprises the following steps: and sending the printing material forming the material from the forming cylinder of the 3D device to a recovery cylinder for recovery. In this embodiment, the metal powder forming the material region 420 may be recovered and recycled. Specifically, as shown in fig. 1, after printing is completed, the second piston 152 below the placement table 154 of the molding cylinder 150 is vertically moved from bottom to top, and the used metal powder is fed into the recovery cylinder 160.

Wherein the laser scanning step comprises rotary laser scanning or partial laser scanning.

The present invention is also advantageous in that the internal modulus of elasticity and the surface hardness of the printed material can be adjusted. Alternatively, the present invention can adjust the internal elastic modulus and the surface hardness of the print by adjusting the volume ratio of the material layer and the hardened layer of the print. Optionally, the present invention further adjusts the thicknesses of the material layer and the hardened layer by adjusting the amounts of the process gas and the protective gas and the transport time, thereby adjusting the internal elastic modulus and the surface hardness of the print.

Specifically, in executing step S2, the heat of laser scanning causes ammonia NH₃The decomposition into atomic states N and H causes nitriding of the surface material of the printed article. Assuming that the material of the print is steel, the surface of the steel will produce a wear and corrosion resistant compound layer. If the laser is used to generate NH under the action of the laser in step S2₃The decomposition is as follows:

the nitrogen atoms N penetrating into the steel form iron nitride with different nitrogen contents with iron in the material steel on one hand, and combine with alloy elements in the steel to form various alloy nitrides, particularly aluminum nitride and chromium nitride on the other hand.

In addition, NH can be introduced into the reactor₃And CO₂Mixed gas of (2) to make NH₃And CO₂The mixed gas and the surface of the material steel are subjected to a thermal decomposition reaction to generate activated carbon and nitrogen atoms. The activated carbon and nitrogen atoms are absorbed by the surface of the printing piece and permeate into the surface layer of the printing piece through diffusion, so that a carbonitriding layer mainly containing nitrogen is obtained, carbonitriding is realized, and better hardening quality and material toughness are obtained.

Wherein the thickness of the compound layer is about 0.05-1.0 mm, and the compound layer has extremely hard property and the hardness can reach 1000-1200 HV.

The second aspect of the invention also provides a 3D print, the 3D print being manufactured by the 3D printing method provided above.

Compared with the prior art, the combination of nitriding treatment and 3D printing is realized in the prior art. The hardened layer formed by nitriding treatment has a high hardness gradient, which is equivalent to an excessively hard layer on the outermost surface and then has a decreasing hardness gradient from the excessively hard layer to the material layer. In this case, the hard layer on the outer surface is cracked and embrittled due to excessive hardness. Therefore, mechanical processing such as surface polishing is often required after 3D printing to grind off or remove the over-hard layer. The gradient effect of the hardened layer formed by nitriding treatment in the prior art is difficult to control, and the mechanical treatment such as surface polishing makes the process complicated. The 3D printing has the advantages of integral forming and weakening the advantages due to complicated processes. In addition, some 3D printed materials cannot be subjected to subsequent mechanical processing such as surface polishing, and these printed materials have a complicated internal structure or surface voids, etc., and the dimensions change after surface polishing.

The present invention performs a nitridation process during 3D printing by precisely controlling the inert gas and NH₃The mixing ratio of the process gases controls the degree of nitridation. Wherein the nitridation gradient of the selective laser melting device can be easily controlled to obtain a thick nitride layer without over-nitridation of the surface. Furthermore, the nitridation process is performed to ensure that the device has a hard surface layer while maintaining a ductile central region. Different lattice-structured elements with nitrided interlayers can also guarantee a high wear resistance and at the same time a satisfactory ductility.

The present invention is not only applicable to in-situ nitridation processes during selective laser melting processes, but is also applicable to performing other processes with printing gas environment processing. Since the nitridation process is only on NH₃This occurs near the forming cylinder when the process gas has a sufficiently high decomposition temperature that the other metal powder is not affected and is well circulated to ensure high utilization of the untreated powder material.

While the present invention has been described in detail with reference to the preferred embodiments, it should be understood that the above description should not be taken as limiting the invention. Various modifications and alterations to this invention will become apparent to those skilled in the art upon reading the foregoing description. Accordingly, the scope of the invention should be determined from the following claims. Furthermore, any reference signs in the claims shall not be construed as limiting the claim concerned; the word "comprising" does not exclude the presence of other devices or steps than those listed in a claim or the specification; the terms "first," "second," and the like are used merely to denote names, and do not denote any particular order.