A high-efficiency linear spot laser additive manufacturing method instead of a circular spot

Abstract

This invention discloses a high-efficiency linear laser spot additive manufacturing method that replaces circular laser spots, comprising the following steps: Step 1: forming a linear cross-section powder flow; Step 2: the linear powder flow ejected from the powder nozzle absorbs energy, heats up, and melts, reaching the workpiece surface in the form of small liquid droplets; Step 3: forming a metallurgical bonding cladding layer of a certain thickness; Step 4: obtaining a single-pass double-layer additive layer; and testing and comparing the macroscopic and microscopic forming and performance under different process parameters; Step 5: applying it to subsequent actual laser additive manufacturing processes; Step 6: obtaining a well-formed single-pass double-layer laser additive manufacturing process, and processing under these parameters; Step 7: determining whether the overall performance meets the target requirements. This invention achieves ultra-high-speed linear laser spot cladding, enabling high efficiency improvement with relatively low cost.

Description

Technical Field

[0001] This invention relates to the field of high-efficiency laser additive manufacturing technology, and specifically to a high-efficiency linear laser additive manufacturing method that replaces circular laser spots. Background Technology

[0002] Additive manufacturing technology can accumulate raw materials layer by layer through melting and solidification based on an imported three-dimensional digital model until the desired three-dimensional part is formed. This technology is widely applicable to various material systems such as metals, ceramics, polymers, and composite materials, among which laser additive manufacturing technology is the most mature.

[0003] Traditional circular laser spot additive manufacturing technology has a relatively low single-pass processing width, only reaching a size comparable to the diameter of the laser spot. It requires repeated sweeping in the same direction to complete a single layer. Furthermore, during single-layer processing, a robotic arm drives the laser processing head in reciprocating motion, repeatedly changing its direction, which significantly hinders the smoothness of the processing and limits the overall processing speed. Both of these factors severely limit the processing efficiency of laser additive manufacturing. In addition, during single-layer laser additive manufacturing, the circular spot repeatedly sweeps the same area of ​​the workpiece surface, leading to excessive heat absorption and abnormal grain growth, or even oxidation, thus weakening the overall performance of the final product. Moreover, after completing the single-layer forming, the final product has a multi-pass reciprocating surface, exhibiting a macroscopic undulating morphology with overlapping single passes. This results in performance differences and even defects at different locations on the formed workpiece surface, which will become the first areas to fail during service, thus weakening the overall performance of the workpiece and affecting its normal service use. Furthermore, in traditional laser cladding, both the laser focus and the powder focus are located on the surface of the substrate to be processed, resulting in insufficient laser energy directly acting on the powder particles, thus failing to achieve full melting of the powder particles and ultimately causing low powder utilization. Summary of the Invention

[0004] To overcome the shortcomings of the existing technology, this invention proposes a high-efficiency linear laser additive manufacturing method that replaces the circular laser spot. This method changes the shape of the copper mirror used to change the laser beam path and the powder conveying channel by replacing the laser processing head connected to the laser generator. This makes the shape of the laser spot projected onto the workpiece surface and the shape of the powder flow cross section both become slender rectangular linear shapes, which serve as the heat source in the laser additive manufacturing process. This enables ultra-high-speed linear laser cladding, achieving a high efficiency improvement with a relatively low cost.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A high-efficiency linear laser additive manufacturing method that replaces circular laser spots includes the following steps;

[0007] Step 1: Forming a powder flow with a linear cross-section;

[0008] Step 2: The linear powder stream ejected from the powder nozzle absorbs energy, heats up, and melts, reaching the workpiece surface in the form of small liquid droplets;

[0009] Step 3: After the droplets formed by the powder flowing in the air reach the surface of the workpiece, part of the laser energy will also directly act on the surface layer of the workpiece. After the laser spot moves away, the molten pool cools down and solidifies, forming a metallurgical bonding cladding layer of a certain thickness at the same position.

[0010] Step 4: A single-pass, single-layer linear laser additive manufacturing layer is obtained on the substrate surface, and the above process is repeated on the basis of the single-pass, single-layer layer to obtain a single-pass, double-layer additive layer; the macroscopic and microscopic forming and performance under different process parameters are tested and compared, and the process parameters of single-pass linear laser additive manufacturing are explored through experiments.

[0011] Step 5: After completing the above-mentioned experiment on the process parameters of single-pass additive manufacturing, process parameters with good forming are obtained and will be applied to laser additive manufacturing processing under subsequent actual processing conditions.

[0012] Step Six: Based on the well-formed single-layer process parameters obtained in Step Five, further explore the multi-layer cumulative forming law to obtain a well-formed single-layer double-layer laser additive manufacturing process, and perform processing under these parameters:

[0013] Step 7: Test the metallographic and chemical composition of the laser additive manufacturing product obtained in Step 6, and conduct Charpy impact test, grooved hammer fracture test and hardness test to determine whether its comprehensive performance meets the target requirements.

[0014] In step one, the powder of the target cladding layer composition is used as raw material. Under the action of the powder feeding gas, the powder is transported to the linear spot laser processing head through the powder feeding pipe and sprayed onto the workpiece surface by the linear powder nozzle on it. The powder of the target cladding layer composition is spherical powder of the target 316L austenitic stainless steel cladding layer composition.

[0015] The 316L austenitic stainless steel spherical powder is composed of the following components by mass percentage: C≤0.030%, Si≤0.75%, Mn≤2.00%, P≤0.035%, S≤0.015%, 10.00%≤Ni≤14.00%, 16.00%≤Cr≤18.00%, 2.00%≤Mo≤3.00%, N≈0.10%; the remainder is Fe.

[0016] In step two, while the powder stream is sprayed onto the surface of the workpiece to be processed, the laser is emitted from the laser generator through an optical fiber into the laser processing head. After the laser beam is shaped by the integrating copper mirror, it finally converges and is projected onto the workpiece surface to form a slender rectangular linear laser spot. This spot acts on the linear powder stream ejected from the powder nozzle, causing it to absorb energy, heat up, and melt, reaching the workpiece surface in the form of small liquid droplets. The workpiece is an X80M pipeline steel substrate, which is composed of the following components by mass percentage: C≤0.12%, Si≤0.45%, Mn≤1.85%, P≤0.02%, S≤0.004%, Cu≤0.50%, Ni≤1.00%, Cr≤0.50%, Mo≤0.50%, and the total amount of V, Nb, and Ti ≤0.15%; the remainder is Fe.

[0017] Step two employs ultra-high-speed laser cladding. By rationally readjusting the relative positions of the laser focus, powder focus, and substrate to be processed, the focal points of the laser and powder flow coincide, and both are located above the substrate to be processed, thus achieving full pre-melting of the powder particles in the air above the substrate to be processed.

[0018] The X80M pipeline steel has a yield strength of not less than 555 MPa, a tensile strength of not less than 625 MPa, and an elongation after fracture of approximately 13.60%. The laser additive manufacturing of 316L bulk material has a yield strength of not less than 392.40 MPa, a tensile strength of not less than 656.79 MPa, and an elongation after fracture of approximately 44-55%.

[0019] In step two, before laser additive manufacturing, the surface of the X80M pipeline steel substrate to be processed needs to be cleaned with acetone, then ground until smooth, and finally sandblasted. This is to improve the laser energy absorption rate of the substrate surface material.

[0020] In steps one and two, during the actual laser additive manufacturing process, all groups use the same process parameters, except for the laser power, powder feeding speed, and scanning speed, which are controlled differently: powder feeding gas pressure is 0.1–0.5 MPa, powder feeding gas flow rate is 4–10 L / min, protective gas pressure is 0.2–0.8 MPa, and protective gas flow rate is 0.25–1.5 m³ / min. 3 / h, working distance is 15~20mm.

[0021] Step three specifically involves:

[0022] When the powder flows through the air and forms droplets, heat is conducted from the high-temperature droplets to the low-temperature surface after reaching the workpiece surface. At the same time, some of the laser energy will also directly act on the workpiece surface, causing a certain thickness of the surface layer to melt and form a small molten pool. Finally, after the laser spot moves away, the molten pool cools down and solidifies, forming a metallurgical bonding cladding layer of a certain thickness at the same location.

[0023] Step four specifically involves:

[0024] As the above processing continues and the laser processing head moves horizontally, a single-pass, single-layer linear laser additive manufacturing layer with a certain length along the laser scanning direction will eventually be obtained on the substrate surface, and the above process will be repeated on the basis of the single-pass, single-layer.

[0025] Step six specifically involves:

[0026] In the actual laser additive manufacturing process, the workpiece to be processed is an X80M pipeline steel. First, a section of the surface of the X80M pipeline steel to be laser additive manufactured is selected for milling to create a trapezoidal groove with a regular shape. Inside the processed trapezoidal groove, 316L austenitic stainless steel additive manufacturing layers are added one by one. Since the width of the trapezoidal groove increases linearly with the number of layers, the number of single-layer cladding passes during the processing will also increase linearly. At the same time, the overlap between single passes must be kept constant until the entire trapezoidal groove is filled with additive manufacturing. Then, the parts of its surface that are higher than the standard shape are mechanically removed to complete the entire laser additive manufacturing process.

[0027] The beneficial effects of this invention are:

[0028] This invention enables the additive manufacturing of 316L austenitic stainless steel onto an X80M pipeline steel substrate. While ensuring the basic mechanical properties of the substrate, it improves the plasticity and toughness of the material to a certain extent, effectively preventing cracking during processing and use. It also partially enhances corrosion resistance, effectively extending its service life.

[0029] This invention uses a slender rectangular linear laser spot instead of a traditional circular laser spot. The laser additive manufacturing layer is formed uniformly and densely, without obvious cracks or defects. At the same time, the bonding strength between the laser additive manufacturing layer and the substrate meets the basic requirements for service and is not prone to falling off.

[0030] Based on the traditional circular laser spot, this invention modifies the integrating copper mirror in the laser processing head to reshape the laser beam path, so that the laser spot projected onto the surface of the substrate to be processed appears as a slender rectangular linear spot. This significantly increases the single-scan width of the laser spot on the substrate surface, thereby increasing the processing width of a single laser additive manufacturing process and effectively improving the processing efficiency of laser additive manufacturing.

[0031] This invention changes the original circular laser spot projected onto the surface of the substrate to a slender rectangular linear spot, thereby rationally adjusting the laser energy distribution, reducing unnecessary energy output loss, and effectively improving the utilization rate of laser energy. At the same time, it avoids the macroscopic morphology of a single-pass cladding layer that is high in the middle and low on both sides.

[0032] This invention employs ultra-high-speed laser cladding technology. Compared with traditional laser cladding, by rationally adjusting the relative positions of the laser focus, powder focus, and the substrate to be processed, pre-melting of powder particles in the air above the substrate to be processed is achieved, thereby effectively improving powder utilization. Attached Figure Description

[0033] Figure 1 This is a flowchart illustrating the method of the present invention.

[0034] Figure 2 This is a schematic diagram of the structure of the laser additive manufacturing of 316L austenitic stainless steel-X80M pipeline steel dissimilar materials using linear spot laser additive manufacturing, which is a schematic diagram of the laser additive manufacturing of 16 according to the present invention.

[0035] Figure 3 This is a schematic diagram and macroscopic morphology of the trapezoidal groove milled on the surface of the X80M pipeline steel substrate for laser additive manufacturing 16 according to the present invention.

[0036] Figure 4 This invention describes the specific overlapping and post-processing methods and processing procedures for the laser additive manufacturing of 316L austenitic stainless steel-X80M pipeline steel dissimilar materials using linear laser spot laser additive manufacturing.

[0037] Figure 5 The macroscopic morphology of the linear spot laser additive manufacturing of dissimilar materials of 316L austenitic stainless steel-X80M pipeline steel in single-pass single-layer 1 to single-pass double-layer 14 according to the present invention.

[0038] Figure 6 This is a SEM image of the linear spot laser additive manufacturing of dissimilar materials, specifically 316L austenitic stainless steel and X80M pipeline steel, using a single-pass, single-layer, 15mm laser. Figure 6 (a) is a low-magnification SEM image of the entire cladding layer. Figure 6 (b) Figure 6 (c) and Figure 6 (d) are high-magnification SEM images of the top of the cladding layer, the inside of the cladding layer, and the interface between the cladding layer and the substrate, respectively.

[0039] Figure 7 The macroscopic morphology of the linear spot laser additive manufacturing of dissimilar materials, 316L austenitic stainless steel-X80M pipeline steel, for the laser additive manufacturing of 16 according to the present invention.

[0040] Figure 8 The image shows the macroscopic morphology of the weld layer cross-section after corrosion in the laser additive manufacturing of 316L austenitic stainless steel-X80M pipeline steel dissimilar materials using linear spot laser additive manufacturing according to the present invention.

[0041] Figure 9 The images show the microstructure (OM) of the weld, heat-affected zone, and base material of the dissimilar material 316L austenitic stainless steel-X80M pipeline steel produced by laser additive manufacturing of 316L austenitic stainless steel-X80M pipeline steel using linear spot laser additive manufacturing, as described in this invention.

[0042] Figure 10 The macroscopic morphology of the side crack propagation path of the impact specimen manufactured by laser additive manufacturing of dissimilar materials such as 316L austenitic stainless steel and X80M pipeline steel using linear spot laser additive manufacturing according to the present invention.

[0043] Figure 11 The macroscopic morphology of the fracture surface of the impact specimen manufactured by laser additive manufacturing of dissimilar materials such as 316L austenitic stainless steel and X80M pipeline steel using linear spot laser additive manufacturing, which is the subject of this invention.

[0044] Figure 12 The macroscopic morphology of the fracture surface of a grooved hammer fracture sample manufactured by laser additive manufacturing of dissimilar materials such as 316L austenitic stainless steel-X80M pipeline steel using linear spot laser additive manufacturing according to the present invention.

[0045] Figure 13 This is a schematic diagram of the Vickers hardness test indentation location for the laser additive manufacturing of 316L austenitic stainless steel-X80M pipeline steel dissimilar materials using linear laser spot manufacturing according to the present invention. Detailed Implementation

[0046] The following is a further explanation with reference to the accompanying drawings.

[0047] like Figure 1 As shown: A high-efficiency linear laser additive manufacturing method that replaces circular laser spots includes the following steps;

[0048] Step 1: The powder of the target cladding layer composition is used as raw material. Under the action of the powder feeding gas, the powder is transported to the linear spot laser processing head through the powder feeding pipe, and sprayed onto the workpiece surface by the linear powder nozzle on it to form a linear cross-section powder flow.

[0049] Step Two: While the powder stream is being sprayed onto the surface of the X80M pipeline steel workpiece to be processed, a laser beam is emitted from the laser generator through an optical fiber into the laser processing head. After being shaped by the integrating copper mirror, the laser beam converges and is projected onto the surface of the X80M pipeline steel substrate, forming a slender rectangular linear laser spot. This spot acts on the linear powder stream ejected from the powder nozzle, causing it to absorb energy, heat up, and melt, reaching the workpiece surface in the form of small liquid droplets. The X80M pipeline steel substrate is composed of the following components by mass percentage: C≤0.12%, Si≤0.45%, Mn≤1.85%, P≤0.02%, S≤0.004%, Cu≤0.50%, Ni≤1.00%, Cr≤0.50%, Mo≤0.50%, and the total amount of V, Nb, and Ti ≤0.15%; the remainder is Fe.

[0050] Step 3: When the powder flows in the air and forms droplets, heat will be conducted from the high-temperature droplets to the low-temperature surface after reaching the surface of the X80M pipeline steel. At the same time, some of the laser energy will also directly act on the surface of the workpiece, causing a certain thickness of the surface layer to melt and form a small molten pool. Finally, after the laser spot moves away, the molten pool cools down and solidifies, forming a metallurgical bonding cladding layer of a certain thickness at the same location.

[0051] Step 4: As the above processing continues and the laser processing head moves horizontally, a single-pass, single-layer linear laser additive manufacturing layer with a certain length along the laser scanning direction will be obtained on the surface of the X80M pipeline steel substrate. The above process will be repeated on the basis of the single-pass, single-layer layer to obtain a single-pass, double-layer additive layer. The macroscopic and microscopic forming and performance under different process parameters will be tested and compared to conduct an experimental study on the process parameters of single-pass linear laser additive manufacturing.

[0052] Step 5: After completing the above-mentioned experiment on the process parameters of single-pass additive manufacturing, process parameters with good forming are obtained and will be applied to laser additive manufacturing processing under subsequent actual processing conditions.

[0053] Step Six: Based on the well-formed single-layer process parameters obtained in Step Five, further explore the multi-layer cumulative forming law to obtain a well-formed single-layer double-layer laser additive manufacturing process. Under these parameters, perform the following processing:

[0054] Taking the additive manufacturing of 316L austenitic stainless steel on the surface of X80M pipeline steel as an example, in the actual laser additive manufacturing process, the workpiece to be processed is an X80M pipeline steel.

[0055] First, a section of the X80M pipeline steel to be laser additively manufactured is selected and milled to create a regularly shaped trapezoidal groove, which is beneficial for laser additive manufacturing. Inside the trapezoidal groove, 316L austenitic stainless steel additive manufacturing layers are added one by one. Since the width of the trapezoidal groove increases linearly with the number of layers, the number of single-layer cladding passes during the processing will also increase linearly. At the same time, the overlap between single passes must be kept constant until the entire trapezoidal groove is filled with additive manufacturing. Then, the parts of the surface that are higher than the standard shape are mechanically removed to complete the entire laser additive manufacturing process.

[0056] Step 7: Test the metallographic and chemical composition of the laser additive manufacturing product obtained in Step 6, and conduct Charpy impact test, grooved hammer fracture test and hardness test to determine whether its comprehensive performance meets the target requirements.

[0057] Laser spots typically exhibit a Gaussian thermal distribution that is low at both ends and high in the middle. When a conventional circular laser spot sweeps across a workpiece surface in a specific direction, the uneven distribution of laser energy and the width distribution of the circular spot along the scanning direction (narrow at both ends and wide in the middle) result in the actual laser energy projected onto the workpiece surface also exhibiting a distribution that is low at both ends and high in the middle. In this case, because the laser energy at the center of the single-pass laser additive manufacturing layer is relatively high, when it irradiates the powder stream ejected from the laser processing head and the workpiece surface, a larger amount of powder at this central location is heated and melted into droplets, leading to the formation of a larger molten pool. More droplets enter the molten pool at this location and eventually cool and solidify together with the molten pool to form a relatively thicker laser additive manufacturing layer. Conversely, the laser additive manufacturing layers formed at both ends of this central location are relatively thinner, resulting in a macroscopic morphology of a single-pass additive manufacturing layer that is high in the middle and low at both ends. The distribution of laser energy in the above situation is obviously unreasonable, and some of the energy is not effectively utilized, resulting in a decrease in energy utilization. This defect will be effectively improved in linear spot laser additive manufacturing.

[0058] When using a linear laser processing head, the laser beam, after being redirected by an integrating copper mirror, converges into a slender rectangular linear spot and is projected onto the workpiece surface. This results in a uniform distribution of laser energy along the length of the spot, with all the energy received by the substrate being used to form a laser additive manufacturing layer with more uniform height and surface morphology. Furthermore, because the relatively higher laser energy at the center of a single-pass laser additive layer in traditional circular laser spot additive manufacturing is redistributed to a more efficient location within the linear spot, energy utilization is significantly improved. Given a fixed laser power requirement for the material system, the power of the laser generator can be appropriately reduced, effectively lowering energy consumption and manufacturing costs associated with high-power laser generators. Simultaneously, the size of the laser generator can be reduced to some extent, alleviating transportation difficulties.

[0059] Step two employs ultra-high-speed laser cladding. By rationally readjusting the relative positions of the laser focus, powder focus, and substrate to be processed, the focal points of the laser and powder flow coincide, and both are located above the substrate to be processed. This ensures sufficient laser energy directly acting on the powder particles, achieving full pre-melting of the powder particles in the air above the substrate to be processed, thereby effectively improving powder utilization.

[0060] The additive manufacturing matrix material selected in step two is X80M pipeline steel, and the additive manufacturing powder selected in step one is 316L austenitic stainless steel spherical powder.

[0061] The high Mo content in the 316L austenitic stainless steel spherical powder can prevent the formation of a Mo-depleted zone at the interface between the laser additive manufacturing layer and the X80M pipeline steel substrate, and is conducive to the formation of acicular ferrite, which can effectively prevent crack propagation and help improve the plasticity and toughness of the final processed product.

[0062] The X80M pipeline steel has a yield strength of not less than 555 MPa, a tensile strength of not less than 625 MPa, and an elongation after fracture of approximately 13.60%. The laser additive manufacturing of 316L bulk material has a yield strength of not less than 392.40 MPa, a tensile strength of not less than 656.79 MPa, and an elongation after fracture of approximately 44-55%.

[0063] Comparative analysis shows that the yield strength of 316L bulk materials manufactured using laser additive manufacturing is slightly lower than that of X80M pipeline steel, while its elongation after fracture is approximately 3 to 4 times higher. Furthermore, their tensile strengths are roughly equivalent, resulting in similar overall mechanical properties. Due to the excellent plasticity and toughness of 316L austenitic stainless steel, it is less prone to cracking after laser additive manufacturing. Additionally, it exhibits good corrosion resistance at room temperature. Therefore, it demonstrates excellent overall performance in laser additive manufacturing on X80M pipeline steel substrates.

[0064] In step two, before laser additive manufacturing, the surface of the X80M pipeline steel substrate to be processed needs to be cleaned with acetone, then ground until smooth, and finally sandblasted. This is to improve the laser energy absorption rate of the substrate surface material.

[0065] In steps one and two, during the actual laser additive manufacturing process, all groups use the same process parameters, except for the laser power, powder feeding speed, and scanning speed, which are controlled differently: powder feeding gas pressure is 0.1–0.5 MPa, powder feeding gas flow rate is 4–10 L / min, protective gas pressure is 0.2–0.8 MPa, and protective gas flow rate is 0.25–1.5 m³ / min. 3 / h, working distance is 15~20mm.

[0066] In this invention, an additive manufacturing method is adopted that uses a slender rectangular linear laser spot as an alternative to the traditional circular laser spot.

[0067] The X80M pipeline steel matrix material selected in this invention is composed of the following components by mass percentage: C≤0.12%, Si≤0.45%, Mn≤1.85%, P≤0.02%, S≤0.004%, Cu≤0.50%, Ni≤1.00%, Cr≤0.50%, Mo≤0.50%, V, Nb, and Ti total ≤0.15%, with the remainder being Fe. The 316L austenitic stainless steel spherical powder used in additive manufacturing is composed of the following components by mass percentage: C≤0.030%, Si≤0.75%, Mn≤2.00%, P≤0.035%, S≤0.015%, 10.00%≤Ni≤14.00%, 16.00%≤Cr≤18.00%, 2.00%≤Mo≤3.00%, N≈0.10%, with the remainder being Fe. The chemical compositions of the two materials are shown in Table 1.

[0068] Table 1. Chemical composition (wt%) of X80M pipeline steel and 316L austenitic stainless steel powder

[0069]

[0070] The X80M pipeline steel used in this invention has a yield strength of not less than 555 MPa, a tensile strength of not less than 625 MPa, and an elongation after fracture of approximately 13.60%. The additively manufactured 316L austenitic stainless steel spherical powder, produced by laser additive manufacturing, yields a bulk material with a yield strength of not less than 392.40 MPa, a tensile strength of not less than 656.79 MPa, and an elongation after fracture of approximately 44-55%. The mechanical properties of these two materials are shown in Table 2.

[0071] Table 2 Mechanical properties of additively manufactured blocks of X80M pipeline steel and 316L austenitic stainless steel

[0072] Material Yield strength / MPa Tensile strength / MPa Elongation after fracture / % X80M 555～705 625～825 13.60 (6.4mm diameter tensile sample) LMD 316L block 392.40～539.49 656.79～725.28 44～55

[0073] In this invention, the detailed preparation process of the laser additive manufacturing embodiments in all groups is as follows:

[0074] This invention relates to a process in which all forming processes are carried out under an inert protective gas, with a pressure of 0.2–0.8 MPa and a flow rate of 0.25–1.5 m³ / s. 3 / h; In this invention, the powder is transported to the substrate surface through the powder flow channel in the laser processing head under the action of the powder feeding gas, wherein the powder feeding gas pressure is 0.1~0.5MPa and the powder feeding gas flow rate is 4~10L / min. The working distance of the laser processing head in this invention is 15~20mm.

[0075] Single-lane single-layer 1:

[0076] Step 1: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0077] Step 2: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to the powder flow channel. While a 4.8kW laser beam is emitted onto the workpiece surface, the mixed powder is transported to the workpiece surface through the powder flow channel by the powder feeding airflow and the powder feeding speed is controlled at 43.2g / min. After absorbing part of the laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs part of the laser energy irradiated on the surface, causing partial melting of the surface to form a molten pool. As the robot moves at a scanning speed of 2m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory to form a single-pass single-layer 1.

[0078] Single-lane single-layer 2:

[0079] Step 1: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0080] Step 2: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to the powder flow channel. While a 4.8kW laser beam is emitted onto the workpiece surface, the mixed powder is transported to the workpiece surface through the powder flow channel by the powder feeding airflow and the powder feeding speed is controlled at 43.2g / min. After absorbing part of the laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs part of the laser energy irradiated on the surface, causing partial melting of the surface to form a molten pool. As the robot moves at a scanning speed of 4m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory to form a single-pass single-layer 2.

[0081] Single-lane single-layer 3:

[0082] Step 1: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0083] Step 2: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to the powder flow channel. While a 4.8kW laser beam is emitted onto the workpiece surface, the mixed powder is transported to the workpiece surface through the powder flow channel by the powder feeding airflow and the powder feeding speed is controlled at 57.6g / min. After absorbing part of the laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs part of the laser energy irradiated on the surface, causing partial melting of the surface to form a molten pool. As the robot moves at a scanning speed of 4m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory to form a single-pass single-layer 3.

[0084] Single-lane single-layer 4:

[0085] Step 1: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0086] Step 2: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to the powder flow channel. While a 4.8kW laser beam is emitted onto the workpiece surface, the mixed powder is transported to the workpiece surface through the powder flow channel by the powder feeding airflow and the powder feeding speed is controlled at 57.6g / min. After absorbing part of the laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs part of the laser energy irradiated on the surface, causing partial melting of the surface to form a molten pool. As the robot moves at a scanning speed of 2m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory to form a single-pass single-layer 4.

[0087] Single lane, single layer 5:

[0088] Step 1: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0089] Step 2: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to the powder flow channel. While a 4.2kW ​​laser beam is emitted onto the workpiece surface, the mixed powder is transported to the workpiece surface through the powder flow channel by the powder airflow and the powder feeding speed is controlled at 43.2g / min. After absorbing part of the laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs part of the laser energy irradiated on the surface, causing partial melting of the surface to form a molten pool. As the robot moves at a scanning speed of 2m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory to form a single-pass single-layer 5.

[0090] Single lane, single layer 6:

[0091] Step 1: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0092] Step 2: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to the powder flow channel. While a 4.2kW ​​laser beam is emitted onto the workpiece surface, the mixed powder is transported to the workpiece surface through the powder flow channel by the powder feeding airflow and the powder feeding speed is controlled at 43.2g / min. After absorbing part of the laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs part of the laser energy irradiated on the surface, causing partial melting of the surface to form a molten pool. As the robot moves at a scanning speed of 2m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory to form a single-pass single-layer 6.

[0093] Single-lane double-layer 7:

[0094] Step 1: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0095] Step Two: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to a powder flow channel. Simultaneously, a 4.2kW ​​laser beam is emitted onto the workpiece surface. Through the action of the powder feed airflow and with the powder feed rate controlled at 43.2g / min, the mixed powder is transported from the powder flow channel to the workpiece surface. After absorbing some laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs some of the laser energy irradiated on its surface, causing partial melting to form a molten pool. As the robotic arm moves at a scanning speed of 2m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory. After completing the single-layer laser additive manufacturing, the above steps are repeated, and the laser power is adjusted to 3.3kW for the second layer additive manufacturing, forming a single-pass double-layer 7.

[0096] Single-lane double-layer 8:

[0097] Step 1: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0098] Step Two: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to a powder flow channel. Simultaneously, a 4.2kW ​​laser beam is emitted onto the workpiece surface. Through the action of the powder feed airflow and with the powder feed rate controlled at 43.2g / min, the mixed powder is transported from the powder flow channel to the workpiece surface. After absorbing some laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs some of the laser energy irradiated on its surface, causing partial melting to form a molten pool. As the robotic arm moves at a scanning speed of 3m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory. After completing the single-layer laser additive manufacturing, the above steps are repeated, and the laser power is adjusted to 3.3kW for the second layer additive manufacturing, forming a single-pass double-layer 8.

[0099] Single lane, single layer 9:

[0100] Step 1: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0101] Step 2: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to the powder flow channel. While a 2.4kW laser beam is emitted onto the workpiece surface, the mixed powder is transported to the workpiece surface through the powder flow channel by the powder feeding airflow and the powder feeding speed is controlled at 21.6g / min. After absorbing part of the laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs part of the laser energy irradiated on the surface, causing partial melting of the surface to form a molten pool. As the robot moves at a scanning speed of 2m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory to form a single-pass single-layer 9.

[0102] Single lane, single layer, 10:

[0103] Step 1: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0104] Step 2: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to the powder flow channel. While a 3.6kW laser beam is emitted onto the workpiece surface, the mixed powder is transported to the workpiece surface through the powder flow channel by the powder feeding airflow and the powder feeding speed is controlled at 21.6g / min. After absorbing part of the laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs part of the laser energy irradiated on the surface, causing partial melting of the surface to form a molten pool. As the robot moves at a scanning speed of 2m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory to form a single-pass single-layer 10.

[0105] Single lane, single layer 11:

[0106] Step 1: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0107] Step 2: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to the powder flow channel. While a 3.6kW laser beam is emitted onto the workpiece surface, the mixed powder is transported to the workpiece surface through the powder flow channel by the powder airflow and the powder feeding speed is controlled at 43.2g / min. After absorbing part of the laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs part of the laser energy irradiated on the surface, causing partial melting of the surface to form a molten pool. As the robot moves at a scanning speed of 2m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory to form a single-pass single-layer 11.

[0108] Single lane, single layer, 12:

[0109] Step 1: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0110] Step 2: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to the powder flow channel. While a 3.6kW laser beam is emitted onto the workpiece surface, the mixed powder is transported to the workpiece surface through the powder flow channel by the powder feeding airflow and the powder feeding speed is controlled at 64.8g / min. After absorbing part of the laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs part of the laser energy irradiated on the surface, causing partial melting of the surface to form a molten pool. As the robot moves at a scanning speed of 2m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory to form a single-pass single-layer 12.

[0111] Single lane, single layer, 13:

[0112] Step 1: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0113] Step 2: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to the powder flow channel. While a 3.6kW laser beam is emitted onto the workpiece surface, the mixed powder is transported to the workpiece surface through the powder flow channel by the powder feeding airflow and the powder feeding speed is controlled at 64.8g / min. After absorbing part of the laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs part of the laser energy irradiated on the surface, causing partial melting of the surface to form a molten pool. As the robot moves at a scanning speed of 1m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory to form a single-pass single-layer 13.

[0114] Single-lane double-layer 14:

[0115] Step 1: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0116] Step Two: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to the powder flow channel. Simultaneously, a 3.6kW laser beam is emitted onto the workpiece surface. Through the action of the powder feed airflow and with the powder feed speed controlled at 64.8g / min, the mixed powder is transported from the powder flow channel to the workpiece surface. After absorbing some laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs some of the laser energy irradiated on its surface, causing partial melting to form a molten pool. As the robotic arm moves at a scanning speed of 1m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory. After completing the single-layer laser additive manufacturing, the above steps are repeated, maintaining the laser power at 3.6kW for the second layer additive manufacturing, forming a single-pass double-layer 14.

[0117] Single lane, single layer, 15:

[0118] Step 1: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0119] Step 2: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to the powder flow channel. While a 3.6kW laser beam is emitted onto the workpiece surface, the mixed powder is transported to the workpiece surface through the powder flow channel by the powder airflow and the powder feeding speed is controlled at 72g / min. After absorbing part of the laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs part of the laser energy irradiated on the surface, causing partial melting of the surface to form a molten pool. As the robot moves at a scanning speed of 1m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory to form a single-pass single-layer 15.

[0120] Laser Additive Manufacturing 16:

[0121] Step 1: On the surface of the X80M pipeline steel substrate to be processed, a trapezoidal groove with a regular shape is milled. The schematic diagram and macroscopic morphology of the resulting trapezoidal groove are shown below. Figure 3 As shown;

[0122] Step 2: Place the 316L austenitic stainless steel spherical powder in a vacuum drying oven and dry it at 80℃ for 10 hours until the moisture is completely removed. Then, thoroughly mechanically mix it in a planetary ball mill to obtain the desired laser additive manufacturing powder.

[0123] Step 3: A certain mass of mixed laser additive manufacturing powder is placed in a powder feeder connected to the powder flow channel. While a 3.6kW laser beam is emitted onto the workpiece surface, the mixed powder is transported to the workpiece surface through the powder flow channel by the powder feeding airflow and the powder feeding speed is controlled at 64.8g / min. After absorbing part of the laser energy, the powder melts into droplets. Upon reaching the workpiece surface, heat is transferred to the workpiece, and the workpiece absorbs part of the laser energy irradiated on the surface, causing partial melting of the surface to form a molten pool. As the robot moves at a scanning speed of 1m / min, the molten mixed powder and part of the matrix gradually cool, alloy, and solidify along a preset trajectory.

[0124] Step 4: After completing the single-pass laser additive manufacturing described above, control the laser processing head to move 1mm parallel to the direction perpendicular to the scanning speed, and repeat the above steps while keeping the laser power at 3.6kW to perform single-layer multi-pass laser additive manufacturing until the trapezoidal groove at the current horizontal height is completely filled.

[0125] Step 5: After completing the single-layer additive manufacturing, repeat the same multi-layer additive manufacturing process layer by layer upwards. Each single-layer solid sheet is built up layer by layer within the trapezoidal groove. As the width of the trapezoidal groove increases linearly with the number of layers, the number of single-layer cladding passes during processing will also increase linearly. Simultaneously, the overlap between single passes must be kept constant until the entire trapezoidal groove is filled. Then, any parts of the material surface that are higher than the standard shape after additive manufacturing are mechanically removed. Specific overlap and post-processing methods and processing procedures are as follows: Figure 4 As shown. The final trapezoidal groove internally fabricated to obtain an inverted trapezoid with a cross-section of 14.68 mm high, 7.98 mm long at the bottom, and 39.5 mm long at the top, with a total length of 130 mm. A schematic diagram of its dimensions is shown below. Figure 2 As shown.

[0126] In this invention, the macroscopic morphology of linear spot laser additive manufacturing of dissimilar materials such as 316L austenitic stainless steel-X80M pipeline steel with single-pass single-layer 1 to single-pass double-layer 14 is as follows: Figure 5 As shown.

[0127] In this invention, the SEM image of the linear spot laser additive manufacturing of dissimilar materials such as single-pass, single-layer 15mm 316L austenitic stainless steel-X80M pipeline steel is shown below. Figure 6 As shown, where Figure 6 (a) is a low-magnification SEM image of the entire cladding layer. Figure 6 (b) Figure 6 (c) and Figure 6 (d) are high-magnification SEM images of the top of the cladding layer, the inside of the cladding layer, and the interface between the cladding layer and the substrate, respectively.

[0128] In this invention, the macroscopic morphology of the dissimilar material 316L austenitic stainless steel-X80M pipeline steel linear spot laser additive manufacturing 16 is as follows: Figure 7 As shown.

[0129] In this invention, samples were taken from the laser additive manufacturing process 16 and the base material. The microstructure and macroscopic morphology of the samples and welded joints were tested and analyzed using the GB / T 13298-2015 test standard. The results showed that the microstructure in the center of the laser cladding zone was austenite, and the microstructures of the coarse-grained and fine-grained regions in the heat-affected zone were B... 粒 The microstructure of the PF+MA and X80M parent material is B. 粒 The macroscopic morphology of the weld layer cross-section of the sample after corrosion is as follows: Figure 8 As shown, the microstructure of the weld, heat-affected zone, and base metal is as follows: Figure 9 As shown.

[0130] In this invention, after sampling from the laser additive manufacturing 16 and the parent material, and testing and analyzing the chemical composition of the samples using an ARL4460 direct-reading spectrometer and the GB / T 4336-2016 test standard, the results showed that the C content in the laser cladding area was 0.049%, which was higher than the GB / T 20878-2007 standard requirement for S31603, while the contents of other elements were within the requirements of the standard. The chemical composition analysis results are shown in Table 3.

[0131] Table 3. Chemical composition analysis results (wt%)

[0132]

[0133] In this invention, samples were taken from the laser additive manufacturing process 16 and the base material. The impact performance of the samples was tested and analyzed using a PIT752D-2 impact testing machine (201312006) and the GB / T229-2007 test standard. The results showed that the impact energy of the sample containing the laser cladding zone at 0℃ was in the range of 44J to 71J, with an average value of 54J, which was generally less than the impact energy of the X80M base material. The Charpy impact test results are shown in Table 4. However, the fracture morphology of the base material area and the cladding zone of the impact sample differed significantly. The cladding zone exhibited a brittle fracture, breaking along the fusion line, while the base material area showed a ductile fracture. The side crack propagation path and macroscopic fracture morphology of the impact sample are shown in Table 4. Figure 10 , Figure 11 As shown;

[0134] Table 4. Results of Charpy Impact Test

[0135]

[0136] In this invention, samples were taken from the laser additive manufacturing process 16 and the base material. The fracture morphology of the grooved hammer fracture samples was analyzed using an SHT4106 testing machine and the GB / T 31032-2014 testing standard. The results showed that no defects exceeding the standard were found on the fracture surface of the grooved hammer fracture test results of the samples containing laser cladding. The grooved hammer fracture test results are shown in Table 5. However, the fracture morphology of the base material area and the cladding area of ​​the hammer-fractured samples differed significantly. The cladding area exhibited a brittle fracture, breaking along the fusion line, while the base material area showed a ductile fracture. The macroscopic morphology of the hammer-fractured samples is shown in Table 5. Figure 12 As shown;

[0137] Table 5 Results of Grooved Hammer Fracture Test

[0138]

[0139] In this invention, samples were taken from the laser additive manufacturing process 16 and the parent material, and the Vickers hardness values ​​of the samples were determined using a KB30BVZ-FA hardness tester and the GB / T 4340.1-2009 test standard. The indentation location distribution was as follows: Figure 13 The test analysis results show that the hardness of the laser cladding center area is less than 220HV10, and there is a high hardness anomaly of 232HV10 in the heat-affected zone, which is greater than the Vickers hardness requirement of 220HV10 in GB / T24511-2017 standard for S31603. This indicates that the hardness of the heat-affected zone of the laser cladding is too high. The Vickers hardness test results of the samples are shown in Table 6.

[0140] Table 6. Vickers hardness test results

[0141]

[0142] Compared to traditional circular laser spots, the linear laser spot of this invention boasts advantages such as high scanning speed, high single-scan width, high powder utilization, and more rational laser energy distribution. It is widely used in the preparation of ultra-thin, high-performance laser cladding coatings, achieving a significant breakthrough in processing efficiency in the field of material surface processing and possessing broad development prospects. Furthermore, realizing a linear laser spot only requires replacing the laser processing head on top of a circular spot, changing the shape of the copper mirror used to alter the laser path, and modifying the shape of the powder delivery channel. This transforms the circular spot projected onto the workpiece surface into a slender rectangular linear spot, which acts on the linearly cross-sectional powder flow transported through the slender rectangular linear channel, achieving ultra-high-speed linear laser cladding. This allows for high efficiency improvements with relatively low cost, thus exhibiting significant advantages in the field of material surface modification.

[0143] When linear laser spot is applied to laser additive manufacturing, this technology can provide a huge impetus for the future development of additive manufacturing technology due to its many considerable advantages, such as high single-pass processing width, fast scanning speed, small heat input to the substrate and the previous additive layer, small impact on material properties, high powder utilization rate, and high production efficiency.

Claims

1. A high-efficiency linear laser additive manufacturing method for replacing circular laser spots, characterized in that, Includes the following steps; Step 1: Forming a powder flow with a linear cross-section; Step 2: While the powder stream is being sprayed onto the surface of the workpiece to be processed, the laser is emitted from the laser generator through the optical fiber into the laser processing head. After the laser beam is shaped by the integrating copper mirror, it finally converges and is projected onto the workpiece surface to form a thin, rectangular linear laser spot. This spot acts on the linear powder stream ejected from the powder nozzle, causing it to absorb energy, heat up, and melt, reaching the workpiece surface in the form of small liquid droplets. The workpiece is an X80M pipeline steel matrix, which is composed of the following components by mass percentage: C≤0.12%, Si≤0.45%, Mn≤1.85%, P≤0.02%, S≤0.004%, Cu≤0.50%, Ni≤1.00%, Cr≤0.50%, Mo≤0.50%, and the total amount of V, Nb, and Ti ≤0.15%; the remainder is Fe. Step 3: After the droplets formed by the powder flowing in the air reach the surface of the workpiece, part of the laser energy will also directly act on the surface layer of the workpiece. After the laser spot moves away, the molten pool cools down and solidifies, forming a metallurgical bonding cladding layer of a certain thickness at the same position. Step 4: As the processing continues and the laser processing head moves horizontally, a single-pass, single-layer linear laser additive manufacturing layer with a certain length along the laser scanning direction will eventually be obtained on the substrate surface. The above process will be repeated on the basis of the single-pass, single-layer layer to obtain a single-pass, double-layer additive manufacturing layer. The macroscopic and microscopic forming and performance under different process parameters were tested and compared, and the process parameters of single-channel linear spot laser additive manufacturing were explored. Step 5: After completing the above-mentioned experiments on the process parameters of single-pass additive manufacturing, process parameters with good forming are obtained and will be applied to laser additive manufacturing processing under subsequent actual processing conditions. Step Six: In the actual laser additive manufacturing process, the workpiece to be processed is an X80M pipeline steel. First, a part of the surface of the X80M pipeline steel to be laser additive manufactured is selected for milling to create a trapezoidal groove with a regular shape. Then, 316L austenitic stainless steel additive manufacturing layers are added layer by layer inside the processed trapezoidal groove. Since the width of the trapezoidal groove increases linearly with the number of layers, the number of single-layer cladding passes during the processing will also increase linearly. At the same time, the overlap between single passes must be kept constant until the entire trapezoidal groove is filled with additive manufacturing. Then, the parts of its surface that are higher than the standard shape are mechanically removed to complete the entire laser additive manufacturing process. Step 7: Test the metallographic and chemical composition of the laser additive manufacturing product obtained in Step 6, and conduct Charpy impact test, grooved hammer fracture test and hardness test to determine whether its comprehensive performance meets the target requirements. In step one, the powder of the target cladding layer composition is used as raw material. Under the action of powder feeding gas, the powder is transported to the linear spot laser processing head through the powder feeding pipe and sprayed onto the workpiece surface by the linear powder nozzle on it. The powder of the target cladding layer composition is 316L austenitic stainless steel spherical powder. The 316L austenitic stainless steel spherical powder is composed of the following components by mass percentage: C≤0.030%, Si≤0.75%, Mn≤2.00%, P≤0.035%, S≤0.015%, 10.00%≤Ni≤14.00%, 16.00%≤Cr≤18.00%, 2.00%≤Mo≤3.00%, N≈0.10%; the remainder is Fe. All forming processes were carried out under an inert protective gas pressure of 0.2~0.8MPa and a flow rate of 0.25~1.5m³. 3 / h; Under the action of the powder feeding gas flow, the powder is transported to the workpiece to be processed through the powder flow channel in the laser processing head, wherein the powder feeding gas pressure is 0.1~0.5MPa and the powder feeding gas flow rate is 4~10L / min; the working distance of the laser processing head is 15~20mm.

2. The high-efficiency linear spot laser additive manufacturing method for replacing circular spots according to claim 1, characterized in that, In step two, before laser additive manufacturing, the surface of the X80M pipeline steel substrate to be processed needs to be cleaned with acetone, and then its surface is polished to a smooth surface before sandblasting.

3. The high-efficiency linear spot laser additive manufacturing method for replacing circular spots according to claim 1, characterized in that, Step three specifically involves: When the powder flows through the air and forms droplets, heat is conducted from the high-temperature droplets to the low-temperature surface after reaching the workpiece surface. At the same time, some of the laser energy will also directly act on the workpiece surface, causing a certain thickness of the surface layer to melt and form a small molten pool. Finally, after the laser spot moves away, the molten pool cools down and solidifies, forming a metallurgical bonding cladding layer of a certain thickness at the same location.

4. The high-efficiency linear spot laser additive manufacturing method for replacing circular spots according to claim 1, characterized in that, Step two employs ultra-high-speed laser cladding. By rationally readjusting the relative positions of the laser focus, powder focus, and workpiece, the focal points of the laser and powder flow coincide, and both are located above the workpiece, thus achieving full pre-melting of the powder particles in the air above the workpiece.

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