Method for controlling powder sticking phenomenon of porous metal in laser additive manufacturing

Abstract

The invention discloses a method for controlling a powder sticking phenomenon of a porous metal implant in laser additive manufacturing, which comprises the following steps of: optimally designing a macroscopic pore structure through a computer, selecting powder spreading in each pass by adopting selective laser melting according to the optimally designed macroscopic pore structure, and carrying out laser sintering treatment for multiple times, and the porous metal implant which does not stick powder and has a macroscopic pore structure is prepared. According to the method, after gradient optimization design is carried out on the laser energy density in the printing process, the powder sticking phenomenon of the porous structure is effectively improved, the porosity and modulus which are most similar to those of a theoretical design and good connectivity of the porous metal implant can be obtained by adjusting the powder sticking phenomenon in pores of the porous structure, and therefore the porous metal implant can be manufactured. Meanwhile, the problem that the powder adheres to the surface of the implant and falls off due to friction, body fluid corrosion and the like after the implant is implanted into the human body can be effectively solved, dissolution of harmful metal ions is reduced, and the long-term use safety of the implant is improved.

Description

Technical Field

[0001] The present invention belongs to the fields of laser additive manufacturing technology and 3D printing medical technology, and specifically relates to a method for controlling powder sticking phenomenon of porous metals in laser additive manufacturing. Background Art

[0002] With the continued growth of healthcare needs, bone tissue repair and regeneration have become a major challenge in the field of biomedical engineering. As the main load-bearing organ of the human body, bones not only need to meet complex mechanical support requirements, but also undertake active biological functions such as cell adhesion, angiogenesis, and tissue repair. Although traditional metal implants have excellent mechanical properties and biocompatibility, their dense structure and high stiffness often lead to problems such as stress shielding, bone resorption, and insufficient biointegration, which affect long-term clinical effects. In recent years, the rise of metal additive manufacturing (AM) technology has made it possible to construct porous bone implants with precise pore structures. This not only allows the elastic modulus and mechanical distribution of the implant to be regulated, but also provides an ideal microenvironment for cell activity and angiogenesis, showing great application potential. Although additive manufacturing of porous implants has made positive progress in improving the biological and mechanical properties, the printing process of porous structures still suffers from powder sticking due to the high laser energy, which has a significant impact on printing accuracy. Therefore, eliminating the powder sticking phenomenon during the printing of porous structures has always been a focus of attention.

[0003] Regarding the powder sticking phenomenon, there are currently two main approaches: post-printing processing and printing process processing. In terms of post-printing processing, the invention patent with publication number CN118023540A specifically discloses a 3D-printed porous metal implant with a rough surface that is free of powder sticking and its manufacturing method. This method proposes that after the porous mesh metal implant is purified by vibration, water washing, air blowing, ultrasound, and plasma polishing, the unmelted metal powder remaining on the surface and inside the implant mesh skeleton can be efficiently removed. The invention patent with publication number CN117139642A specifically discloses a powder removal method for additively manufactured medical porous titanium alloys and its application. This method first immerses the medical porous titanium alloy in an acidic etching solution and removes it; then, the treated medical porous titanium alloy is cleaned using ultrasound; then, the treated medical porous titanium alloy is immersed in the acidic etching solution again, removed and cleaned again using ultrasound, and the above steps are repeated, maintaining a total etching time of 2 to 20 minutes. This invention adopts a method of graded chemical etching combined with ultrasonic cleaning, which can quickly and thoroughly remove most of the sticky powder in medical porous titanium alloys without reducing the mechanical properties of the molded parts, solving the current problem of being unable to meet the powder removal effect and mechanical performance requirements at the same time. In addition, the invention patent with publication number CN115488351A mentioned the use of high-pressure gas or ultrasound to remove sticky powder on the surface of parts in a critical β-type titanium-tantalum alloy and additive manufacturing method. Similarly, the invention patent with publication number CN110000382A specifically discloses a method for removing support structures in titanium alloys for additive manufacturing. In this method, a strategy of using a solution with a volume ratio of hydrofluoric acid, nitric acid and water of 1 to 5: 2 to 10: 1 to 10, and / or a full nitric acid solution to treat the surface of the molded part to remove sticky powder on the surface is mentioned.

[0004] In terms of printing process processing, there are still relatively few solutions disclosed so far. The invention patent with publication number CN109590468A specifically discloses a method for controlling powder sticking on the surface of austenitic stainless steel components during laser direct additive manufacturing. This method conducts quasi-continuous laser direct additive manufacturing experiments on austenitic stainless steel powder based on a single-factor method, and obtains the influence of pulse frequency and duty cycle on sample surface powder sticking; based on the experimental data, the pulse frequency and duty cycle range that can effectively suppress surface powder sticking are determined. This method can effectively control the serious problem of surface powder sticking when laser direct additive manufacturing austenitic stainless steel components; however, this method is mainly aimed at dealing with the surface powder sticking phenomenon after the printing of the solid model, and there is no feasible example for powder sticking inside the pore structure of porous structures. In addition, the invention patent with publication number CN113953531A specifically discloses a method for reducing powder sticking on the surface of laser additively manufactured parts. This method achieves the purpose of reducing powder sticking on the surface of parts by modifying the powder feeding and powder return paths of the equipment, but this method is also limited to eliminating the powder sticking phenomenon on the surface of the solid material.

[0005] In summary, many scholars in the field are committed to solving the problem of powder sticking phenomenon of additive manufacturing parts, and the disclosed invention patents have enriched and developed the processing method of powder sticking phenomenon of additive manufacturing parts. However, most of the methods are mainly post-processing, and most of them are surface powder sticking treatment of solid parts, so it is very meaningful to solve the powder sticking phenomenon of additive manufacturing porous metal from the printing process. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a control method for laser additive manufacturing porous metal powder sticking phenomenon in view of the shortcomings of the prior art. The method effectively improves the powder sticking phenomenon of the porous structure by optimizing the gradient of the laser energy density in the printing process. By adjusting the powder sticking phenomenon in the pores of the porous structure, the porous metal implant can obtain the most similar porosity, modulus and better connectivity to the theoretical design. At the same time, the solution of the powder sticking phenomenon in the internal pore structure of the porous structure can effectively avoid the problem of powder falling off from the surface of the implant due to friction and body fluid corrosion after the implant is implanted into the human body, reduce the dissolution of harmful metal ions, and improve the long-term use safety of the implant.

[0007] To solve the above technical problems, the technical scheme adopted by the present application is: a control method for laser additive manufacturing porous metal powder sticking phenomenon, characterized in that the method optimizes the macro-pore structure by computer, and according to the optimized macro-pore structure, the laser selective melting selects multiple laser sintering treatment after each pass of powder laying, to prepare a porous metal implant without powder sticking and with macro-pore structure.

[0008] The present application optimizes the macro-pore structure by computer, and according to the characteristics of bone growth and nutrient substance transmission, designs the macro-pore structure most suitable for orthopedic implants, so that it is suitable for cell adhesion and proliferation, and at the same time regulates the mechanical properties of the porous metal implant. In order to ensure the accuracy of the macro-pore structure, laser selective melting is used to select multiple laser sintering treatment after each pass of powder laying, to prevent powder sticking phenomenon and realize the preparation of a porous metal implant without powder sticking and with macro-pore structure.

[0009] The present application adopts the strategy of single powder laying and multiple laser sintering, and according to the formula E v =P / VHL, in which E v , P, V, H, L represent laser energy density, laser power, scanning speed, scanning interval and powder layer thickness respectively. By energy segmentation, the total energy of laser sintering is divided into multiple small energy inputs in proportion, the depth and width of the molten pool and the range of the surrounding heat affected zone are reduced, the formation of sintering neck between powders in the heat affected zone around the molten pool is reduced, and the powder sticking phenomenon of the porous structure in the printing process is reduced.

[0010] The above-mentioned method for controlling powder sticking phenomenon of porous metal in laser additive manufacturing is characterized in that the method comprises the following steps:

[0011] Step 1: Select spherical powder for 3D printing; the composition of the spherical powder for 3D printing is medical zinc alloy, medical titanium alloy or medical tantalum metal;

[0012] Step 2: Based on the design criteria of the porous metal implant, the macro-pore structure is optimized and designed by computer modeling to obtain the macro-pore structure of the porous metal implant;

[0013] Step 3: The spherical powder for 3D printing selected in Step 1 is subjected to laser additive manufacturing by selective laser melting according to the macroscopic pore structure of the porous metal implant obtained in Step 2. During the laser additive manufacturing process, two or three laser sintering steps are performed after each powder spreading pass to obtain a preform;

[0014] Step 4: After the preform obtained in step 3 is cooled, it is ultrasonically cleaned in anhydrous ethanol and dried to obtain a porous metal implant.

[0015] The present invention is applicable to spherical powders for 3D printing of different materials. Medical zinc alloys, medical titanium alloys or medical metal tantalum are typical representatives of materials used for medical orthopedic implants and are applicable to the use of various porous metal implants.

[0016] The aforementioned method for controlling powder sticking in laser additive manufacturing of porous metals is characterized in that the particle size of the spherical powder for 3D printing in step 1 is between 15 μm and 53 μm. By controlling the particle size of the spherical powder for 3D printing, the present invention ensures the smooth preparation of macroporous structures while also maintaining the performance of porous metal implants.

[0017] The aforementioned method for controlling powder sticking in laser additive manufacturing of porous metals is characterized in that the medical zinc alloy and medical titanium alloy described in step 1 are pre-alloyed powders or physically doped powders; the physically doped powders are obtained by mechanically mixing elemental metal powders in a biaxial horizontal mixer at a speed of 180 to 240 rpm for 3 hours, using a 10 mm diameter and 20 mm long short rod of the same material as a stirring rod, with a rod-to-material ratio of 10:1, and the vacuum level in the mixing tank is less than 50 Pa. In the present invention, the pre-alloyed powder is prepared by first melting the alloy and then forming a spherical powder for 3D printing. The physically doped powder is prepared by mechanically mixing elemental metal powders in a biaxial horizontal mixer to obtain the desired spherical powder for 3D printing. The physically doped powder is selected based on production requirements, and the performance of the physically doped powder is guaranteed by controlling the preparation parameters of the physically doped powder.

[0018] The control method for the powder sticking phenomenon of laser additive manufacturing of porous metal has the characteristics that in step two, the macro-pore structure optimization design is to establish a gradient macro-pore structure, a negative Poisson's ratio structure or a three-period minimal surface biomimetic structure, and the porosity is controlled to be 60% to 90%. The gradient macro-pore structure and the negative Poisson's ratio structure are used to achieve specific mechanical properties, the three-period minimal surface biomimetic structure is used to promote cell adhesion and proliferation, and the porosity is controlled according to actual requirements, so that the mechanical properties are adjusted and the transmission of nutrients and bone ingrowth are ensured, and the functions cannot be effectively realized when the porosity is less than 60%.

[0019] The control method for the powder sticking phenomenon of laser additive manufacturing of porous metal has the characteristics that in step three, the thickness of each pass of powder laying is 30 microns, the scanning angle in the laser additive manufacturing is 67 degrees, and the scanning strategy is a strip mode. The thickness of the powder laying, the scanning angle and the scanning strategy are controlled to ensure the forming effect of the porous metal implant and better realize the regulation of the laser energy density and reduce the variables in the operation.

[0020] The control method for the powder sticking phenomenon of laser additive manufacturing of porous metal has the characteristics that in step three, the ratio of the laser energy density in the two-time laser sintering is 60%:40%, and the ratio of the sintering laser energy density in the three-time laser sintering is 40%:30%:30%. The total energy of the laser sintering is divided into multiple small energy inputs in proportion through energy segmentation, and the laser energy density of each laser sintering is limited, so that the powder sticking phenomenon is further prevented. It should be noted that in the energy distribution process, in order to ensure structure shaping, the first laser energy density is higher, and the subsequent energy density is slightly lower, which is used for heat compensation and defect repair.

[0021] The control method for the powder sticking phenomenon of laser additive manufacturing of porous metal has the characteristics that in step three, when the melting point of the selected spherical powder for 3D printing is less than 2000 degrees Celsius, two-time laser sintering is performed, and when the melting point is greater than or equal to 2000 degrees Celsius, three-time laser sintering is performed. The number of times of laser sintering is determined according to the melting point of the spherical powder for 3D printing. Since the melting points of the spherical powder for 3D printing are different, the forming characteristics are different, and too many times of sintering are not suitable for low-melting-point alloys, which can easily cause a large amount of spatter and evaporation, resulting in a decrease in material composition accuracy. Multiple sintering of high-melting-point alloys can provide effective heat compensation through subsequent sintering, which can control the powder sticking while reducing defects and improving product quality.

[0022] Compared with the prior art, the present application has the following advantages:

[0023] 1. The purpose of the present invention is to control the width and depth of the molten pool and the range of the heat-affected zone around the molten pool by gradient design of the input laser energy density, thereby reducing the heat input of the powder around the pores of the porous structure, preventing the formation of metallurgical sintering necks between the surrounding powder and the molten pool, and between powders, thereby effectively preventing the occurrence of internal powder sticking in the porous structure, further improving the molding quality and printing accuracy of additively manufactured parts, and ensuring the realization of the biological functions and mechanical properties of porous metal implants.

[0024] 2. The present invention is different from the existing technology for preparing porous metals, which causes serious powder sticking between pores. This method effectively limits the range of the heat-affected zone by regulating the heat input, reduces the formation of sintering necks between powders in the heat-affected zone around the molten pool, and reduces the powder sticking phenomenon of the porous structure during the printing process.

[0025] 3. Unlike the prior art, which is prone to forming printing defects such as pores and unfused parts after printing, the present invention can thermally compensate for the defects formed by a single laser sintering through multiple laser sintering, thereby eliminating pores and unfused parts and improving the printing quality of porous metal implants.

[0026] 4. The present invention uses input laser energy regulation to effectively regulate the powder sticking phenomenon inside the macroscopic pore structure of the porous metal implant. At the same time, secondary sintering can provide effective thermal compensation, reduce the generation of defects such as pores and unfused parts during the printing process, and improve the printing quality.

[0027] 5. The present invention can make the porous metal implant obtain the porosity, modulus and better connectivity that are closest to the theoretical design by adjusting the powder sticking phenomenon in the pores of the porous structure. At the same time, solving the powder sticking phenomenon inside the pore structure can effectively avoid the problem of powder adhering to the implant surface falling off due to friction and body fluid corrosion after implantation in the human body, reduce the dissolution of harmful metal ions, and improve the long-term safety of the implant.

[0028] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a morphology diagram of the porous metal implant prepared by double laser sintering in Example 1 of the present invention.

[0030] Figure 2 This is a morphology diagram of the porous metal implant prepared by single laser sintering in Comparative Example 1 of the present invention.

[0031] Figure 3 Schematic diagram of the distribution of the molten pool and heat-affected zone of double laser sintering and single laser sintering in Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0032] Example 1

[0033] This embodiment includes the following steps:

[0034] Step 1: Mechanically mix the zinc powder and manganese powder in a double-shaft horizontal mixer at a speed of 200 rpm for 3 hours. A zinc rod with a diameter of 10 mm and a length of 20 mm is added as a stirring rod. The rod-to-material ratio is 10:1. The vacuum degree in the mixing tank is less than 50 Pa to obtain a spherical powder for medical zinc alloy 3D printing with a particle size of 15 μm to 53 μm and a manganese mass content of 0.6%;

[0035] Step 2: Based on the design criteria of the porous metal implant, computer modeling is used to optimize the macroscopic pore structure, establish a negative Poisson's ratio structure, and control the porosity to 90%, thereby obtaining the macroscopic pore structure of the porous metal implant;

[0036] Step 3: The medical zinc alloy 3D printing spherical powder selected in step 1 is subjected to laser additive manufacturing by laser selective melting according to the macroscopic pore structure of the porous metal implant obtained in step 2. The single layer powder thickness is 30 μm, the laser rotation angle is 67°, the scanning strategy is strip mode, and the input laser energy density is set to 120 J / mm 3 In the laser additive manufacturing process, two laser sintering processes are performed after each powder laying process. The laser energy density of the first laser sintering process is 72J / mm 3 The laser energy density of the second laser sintering is 48J / mm 3 , obtaining a preform with a size of 10 mm × 10 mm × 10 mm (length × width × height);

[0037] Step 4: After the preform obtained in step 3 is cooled, it is ultrasonically cleaned in anhydrous ethanol and dried to obtain a porous metal implant.

[0038] Figure 1 The morphology of the porous metal implant prepared by multiple laser sintering in this embodiment is shown in FIG. Figure 1 It can be seen from the figure that the negative Poisson's ratio porous structure of the porous metal implant prepared by multiple laser sintering in this embodiment has good formability, a regular surface, clear pore struts, and no powder sticking phenomenon.

[0039] In this embodiment, the rotation speed of the mechanical mixing can also be 180 rpm or 240 rpm.

[0040] Comparative Example 1

[0041] This comparative example comprises the following steps:

[0042] Step one, the zinc powder and manganese powder are mechanically mixed on a double-shaft horizontal mixer, the rotation speed of mechanical mixing is 200 rpm, the mixing time is 3 h, a zinc rod with a diameter of 10 mm and a length of 20 mm is added as a stirring rod, the rod ratio is 10:1, the vacuum degree in the mixing tank is less than 50 Pa, the particle size of the medical zinc alloy 3D printing spherical powder obtained is 15 μm-53 μm, and the mass content of manganese is 0.6%;

[0043] Step two, based on the design criteria of the porous metal implant, the macroscopic pore structure is optimized by computer modeling, a negative Poisson's ratio structure is established, and the porosity is controlled to be 90%, and the macroscopic pore structure of the porous metal implant is obtained;

[0044] Step three, the medical zinc alloy 3D printing spherical powder selected in step one is subjected to laser additive manufacturing by laser selective melting according to the macroscopic pore structure of the porous metal implant obtained in step two, the single-layer powder thickness is 30 μm, the laser rotation angle is 67°, the scanning strategy is the strip mode, the input laser energy density is set to 120 J / mm 3 , and a preform with a size of 10 mm×10 mm×10 mm (length×width×height) is obtained;

[0045] Step four, after the preform obtained in step three is cooled, it is ultrasonically cleaned in anhydrous ethanol and dried to obtain a porous metal implant.

[0046] Figure 2 The morphology of the porous metal implant prepared by single laser sintering in the present comparative example can be seen from Figure 2 , the negative Poisson's ratio structure of the porous metal implant prepared by single laser sintering in the present comparative example is rough, covered with a thick powder sticking layer, the pore structure uniformity is poor, and there are a large number of powder sticking on the pore edges, and the powder sticking thickness is also uneven.

[0047] Figure 3 The schematic diagram of the molten pool and heat affected zone distribution of multiple laser sintering and single laser sintering in the present embodiment 1 and comparative example 1 can be seen from Figure 3 , it can be seen that multiple sintering can effectively reduce the range of the molten pool and the range of the heat affected zone, and at the same time, multiple sintering reduces the heat input of each pass, not only reduces the possible powder sticking range, but also the lower heat input greatly reduces the sintering and necking of the powder in the heat shadow area, prevents the formation of metallurgical bonding between powder particles, thereby greatly reducing the powder sticking phenomenon.

[0048] By comparing Example 1 and Comparative Example 1, it can be seen that Example 1 performs a gradient design on the input laser energy density to regulate the width and depth of the molten pool brought about by each heat input and the range of the heat-affected zone around the molten pool, thereby reducing the heat input of the powder around the pores of the porous structure, preventing the formation of metallurgical sintering necks between the surrounding powder and the molten pool, and between powders, thereby effectively preventing the occurrence of internal powder sticking in the porous structure, further improving the molding quality and printing accuracy of additively manufactured parts, and ensuring the realization of biological functions and mechanical properties of porous metal implants.

[0049] Example 2

[0050] This embodiment includes the following steps:

[0051] Step 1: Select spherical powder for medical TLE titanium alloy pre-alloy 3D printing;

[0052] Step 2: Based on the design criteria of the porous metal implant, computer modeling is used to optimize the macro-pore structure, establish a radial density gradient pore structure, and control the porosity to 80%, thereby obtaining the macro-pore structure of the porous metal implant;

[0053] Step 3: The spherical powder for medical TLE titanium alloy pre-alloy 3D printing selected in step 1 is subjected to laser additive manufacturing by laser selective melting according to the macroscopic pore structure of the porous metal implant obtained in step 2. The single layer powder thickness is 30 μm, the laser rotation angle is 67°, the scanning strategy is strip mode, and the input laser energy density is set to 160 J / mm 3 In the laser additive manufacturing process, two laser sintering processes are performed after each powder laying process. The laser energy density of the first laser sintering is 96J / mm 3 The laser energy density of the second laser sintering is 64J / mm 3 , obtaining a preform with a size of 10 mm × 10 mm × 10 mm (length × width × height);

[0054] Step 4: After the preform obtained in step 3 is cooled, it is ultrasonically cleaned in anhydrous ethanol and dried to obtain a porous metal implant.

[0055] Example 3

[0056] This embodiment includes the following steps:

[0057] Step 1: Select spherical powder for medical tantalum metal 3D printing;

[0058] Step 2: Based on the design criteria of the porous metal implant, computer modeling is used to optimize the macroscopic pore structure, establish a three-periodic minimal surface biomimetic structure, and control the porosity to 60%, thereby obtaining the macroscopic pore structure of the porous metal implant;

[0059] Step 3: The spherical powder for medical TLE titanium alloy pre-alloy 3D printing selected in step 1 is subjected to laser additive manufacturing by laser selective melting according to the macroscopic pore structure of the porous metal implant obtained in step 2. The single layer powder thickness is 30 μm, the laser rotation angle is 67°, the scanning strategy is strip mode, and the input laser energy density is set to 210 J / mm 3 In the laser additive manufacturing process, two laser sintering processes are performed after each powder laying process. The laser energy density of the first laser sintering process is 84J / mm 3 The laser energy density of the second laser sintering is 63J / mm 3 The laser energy density of the third laser sintering is 63J / mm 3 , obtaining a preform with a size of 10 mm × 10 mm × 10 mm (length × width × height);

[0060] Step 4: After the preform obtained in step 3 is cooled, it is ultrasonically cleaned in anhydrous ethanol and dried to obtain a porous metal implant.

[0061] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the technical essence of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for controlling powder sticking phenomenon in laser additive manufacturing of porous metal, characterized in that: This method uses computer optimization to design a macro-pore structure, and adopts laser selective melting to select multiple laser sintering processes after each powder spreading process based on the optimized macro-pore structure to prepare a porous metal implant that is non-sticky and has a macro-pore structure.

2. The method for controlling powder sticking phenomenon in laser additive manufacturing of porous metal according to claim 1, characterized in that: The method comprises the following steps: Step 1: Select spherical powder for 3D printing; the composition of the spherical powder for 3D printing is medical zinc alloy, medical titanium alloy or medical tantalum metal; Step 2: Based on the design criteria of the porous metal implant, the macro-pore structure is optimized and designed by computer modeling to obtain the macro-pore structure of the porous metal implant; Step 3: The spherical powder for 3D printing selected in Step 1 is subjected to laser additive manufacturing by selective laser melting according to the macroscopic pore structure of the porous metal implant obtained in Step 2. During the laser additive manufacturing process, two or three laser sintering steps are performed after each powder spreading pass to obtain a preform; Step 4: After the preform obtained in step 3 is cooled, it is ultrasonically cleaned in anhydrous ethanol and dried to obtain a porous metal implant.

3. The method for controlling powder sticking phenomenon in laser additive manufacturing of porous metal according to claim 2, characterized in that: The particle size of the spherical powder for 3D printing described in step 1 is 15 μm to 53 μm.

4. The method for controlling powder sticking phenomenon in laser additive manufacturing of porous metal according to claim 2, characterized in that: The medical zinc alloy and medical titanium alloy described in step one are pre-alloyed powder or physically doped powder; the physically doped powder is obtained by mechanically mixing elemental metal powder on a biaxial horizontal mixer, the mechanical mixing speed is 180rpm~240rpm, the mixing time is 3h, and elemental metal powder with a diameter of 10mm and a length of 20mm is added together with a short rod of the same material as a stirring rod, the rod-to-material ratio is 10:1, and the vacuum degree in the mixing tank is less than 50Pa.

5. The method for controlling powder sticking phenomenon in laser additive manufacturing of porous metal according to claim 2, characterized in that: The macro-pore structure optimization design in step 2 is to establish a gradient macro-pore structure, a negative Poisson's ratio structure or a three-periodic minimal surface bionic structure, and control the porosity to be 60% to 90%.

6. The method for controlling powder sticking phenomenon in laser additive manufacturing of porous metal according to claim 2, characterized in that: The thickness of each powder spreading in step 3 is 30 μm, the scanning angle in the laser additive manufacturing is 67°, and the scanning strategy is strip mode.

7. The method for controlling powder sticking phenomenon in laser additive manufacturing of porous metal according to claim 2, characterized in that: In step 3, when the laser sintering is performed twice, the ratio of laser energy density is 60%:40%. When the laser sintering is performed three times, the ratio of laser energy density is 40%:30%:30%.

8. The method for controlling powder sticking phenomenon in laser additive manufacturing of porous metal according to claim 2, characterized in that: When the melting point of the spherical powder for 3D printing selected in step 3 is less than 2000° C., laser sintering is performed twice; when the melting point is greater than or equal to 2000° C., laser sintering is performed three times.

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