阅读说明：本技术 一种光内同轴送粉双束环形激光沉积加工方法及加工头 (Optical inner coaxial powder feeding double-beam annular laser deposition processing method and processing head ) 是由 陈永雄 王荣 孔令超 梁秀兵 胡振峰 王浩旭 陈珂玮 于 2020-12-31 设计创作，主要内容包括：本公开提供了一种光内同轴送粉双束环形激光沉积加工方法及加工头,由第一束和第二束经过准直的激光得到第一并合环形光束和第二并合环形光束；第一并合环形光束和第二并合环形光束通过聚焦透镜后形成同轴、在深度方向上彼此分离且向中央汇聚的第一聚焦环形光束和第二聚焦环形光束；送粉管依次穿过第五折向平面反射镜的第四通孔、光束并合模块的第五通孔、聚焦透镜的中心孔后与粉末喷嘴连接,粉末喷嘴喷出的粉末束流与第一聚焦环形光束和第二聚焦环形光束都同轴；同等质量条件下,沉积材料总体吸收的热量大大减小,加工头可以相对基体进行高速的移动,沉积效率大为提高,因热沉积过程产生的残余应力和变形减小,故而显著提高了成形精度和涂层质量。(The invention provides a processing method and a processing head for optical inner coaxial powder feeding double-beam annular laser deposition, wherein a first combined annular light beam and a second combined annular light beam are obtained by collimated lasers of a first beam and a second beam; the first and second combined annular light beams form a first focusing annular light beam and a second focusing annular light beam which are coaxial, are separated from each other in the depth direction and converge towards the center after passing through a focusing lens; the powder feeding pipe sequentially penetrates through a fourth through hole of the fifth deflecting plane reflector, a fifth through hole of the light beam combining module and a central hole of the focusing lens and then is connected with the powder nozzle, and the powder beam current sprayed by the powder nozzle is coaxial with the first focusing annular light beam and the second focusing annular light beam; under the condition of the same mass, the heat absorbed by the overall deposited material is greatly reduced, the processing head can move at a high speed relative to the substrate, the deposition efficiency is greatly improved, and the forming precision and the coating quality are obviously improved because the residual stress and the deformation generated in the thermal deposition process are reduced.)

1. An optical inner coaxial powder feeding double-beam annular laser deposition processing method is characterized in that: the method comprises the following steps:

the first beam of collimated laser reaches the first W-shaped conical reflector after passing through the first through hole of the first deflecting plane mirror, and reflected light is emitted to the reflecting surface of the first deflecting plane reflector to be turned by 90 degrees to form a hollow first annular light beam;

the second beam of collimated laser reaches a second W-shaped conical reflector after passing through a second through hole of a second deflecting plane mirror, reflected light irradiates the reflecting surface of the second deflecting plane reflector to be turned for 90 degrees, and a hollow second annular light beam is formed after passing through a third through hole of the first deflecting plane mirror;

the first split annular light beam and the second split annular light beam are deflected by 90 degrees through a fifth deflection plane mirror and then generate a first combined annular light beam and a second combined annular light beam which are coaxial and combined towards the middle through a light beam combining module;

the first and second combined annular light beams form a first focusing annular light beam and a second focusing annular light beam which are coaxial, are separated from each other in the depth direction and converge towards the center after passing through a focusing lens;

the powder feeding pipe sequentially penetrates through a fourth through hole of the fifth deflecting plane reflector, a fifth through hole of the light beam combining module and a central hole of the focusing lens and then is connected with the powder nozzle, and powder conveyed by compressed gas sequentially passes through the powder feeding pipe and the powder nozzle to form a powder beam coaxial with the first focusing annular light beam and the second focusing annular light beam and then is sprayed to the surface of the substrate.

2. The in-light coaxial powder-feeding double-beam annular laser deposition processing method as claimed in claim 1, characterized in that:

the second focusing annular light beam heats the matrix surface material of the focusing spot area to a molten or semi-molten state, the powder beam is heated after being intersected with the first focusing annular light beam, and then is intersected with the second focusing annular light beam to be heated for the second time so as to achieve the molten or semi-molten state.

3. The in-light coaxial powder-feeding double-beam annular laser deposition processing method as claimed in claim 1, characterized in that:

before the formed first split annular light beam and the second split annular light beam reach the fifth deflecting plane mirror, the powder conveying pipe penetrates through the middle gap area of the first split annular light beam and the second split annular light beam without blocking light;

alternatively, the first and second electrodes may be,

the focusing lens is of a plano-convex structure with a through hole in the center along the light transmission direction, the convex surface is formed by a composite surface formed by an inner ring and an outer ring with different focal lengths, the inner ring is a spherical surface or an aspherical surface, and the outer ring is an aspherical surface;

alternatively, the first and second electrodes may be,

the focal depth length of a focusing spot converged by the first combined annular light beam after passing through the outer ring of the focusing lens is 2-20 mm, and the focal depth length of a focusing spot converged by the second combined annular light beam after passing through the inner ring of the focusing lens is 0.2-2 mm;

alternatively, the first and second electrodes may be,

the focal length of the focusing light spot corresponding to the first combined annular light beam is smaller than that of the focusing light spot corresponding to the second combined annular light beam, and the distance between focal planes of the first combined annular light beam and the second combined annular light beam is 1-50 mm;

alternatively, the first and second electrodes may be,

the first laser and the second laser are divided into two laser beams by the beam splitter from the same optical fiber laser and then are accessed to the laser input interface through the optical fiber;

alternatively, the first and second electrodes may be,

the first laser beam and the second laser beam are respectively accessed to the laser input interface from two mutually independent fiber lasers through optical fibers;

alternatively, the first and second electrodes may be,

the inner diameter of the hollow first annular light beam is larger than or equal to the outer diameter of the hollow second annular light beam, and the inner diameter of the hollow second annular light beam is larger than the outer diameter of the powder feeding pipe;

alternatively, the first and second electrodes may be,

the diameter range of the powder beam current intersected with the laser is 0.1-5 mm, the outer diameter range of the first focusing light spot and the second focusing light spot is 0.1-8 mm, and the diameter of the powder beam current is smaller than or equal to the outer diameter of the first focusing light spot and the outer diameter of the second focusing light spot;

alternatively, the first and second electrodes may be,

the beam splitting module comprises a light splitting rhombic reflector, a third folding plane reflector and a fourth folding plane reflector, the direction of a ridge edge of the light splitting rhombic reflector is opposite to the incidence direction of the hollow first annular beam and the hollow second annular beam, and two adjacent side surfaces of the ridge edge of the light splitting rhombic reflector are respectively parallel to the reflecting surfaces of the third folding plane reflector and the fourth folding plane reflector;

alternatively, the first and second electrodes may be,

the light beam combining module comprises a light combining rhombic reflector, a sixth refraction plane reflector and a seventh refraction plane reflector, the direction of a ridge edge of the light combining rhombic reflector is the same as the incidence direction of the first split annular light beam and the second split annular light beam, and two adjacent side surfaces of the ridge edge of the light combining rhombic reflector are parallel to the reflection surfaces of the sixth refraction plane reflector and the seventh refraction plane reflector respectively.

4. The utility model provides a coaxial powder double-beam annular laser deposition processing head that send in light which characterized in that:

at least comprises the following steps: the device comprises a first W-shaped conical surface reflector, a first refracting plane reflector, a second W-shaped conical surface reflector, a second refracting plane reflector, a fifth refracting plane reflector, a focusing lens, a light beam splitting module and a light beam combining module;

the first folding plane reflector is provided with a first through hole and a third through hole, the second folding plane reflector is provided with a second through hole, the axis of the first through hole is superposed with the central axis of the first W-shaped conical surface reflector, and the axis of the second through hole is superposed with the central axis of the second W-shaped conical surface reflector;

the first collimated laser beam passes through a first through hole of a first folding plane mirror and then sequentially passes through a first W-shaped conical reflector, a first folding plane reflector, a beam splitting module, a fifth folding plane reflector and a beam merging module to obtain a first parallel ring-shaped beam;

the collimated laser beam passes through a second through hole of a second deflecting plane mirror and then sequentially passes through a second W-shaped conical reflector, a second deflecting plane reflector, a beam splitting module, a fifth deflecting plane reflector and a beam combining module to obtain a second combined annular beam;

the first and second combined annular light beams form a first focusing annular light beam and a second focusing annular light beam which are coaxial, are separated from each other in the depth direction and converge towards the center after passing through a focusing lens;

and the powder feeding pipe sequentially passes through a fourth through hole of the fifth deflecting plane reflector, a fifth through hole of the light beam combining module and a central hole of the focusing lens and then is connected with the powder nozzle, and the powder beam current sprayed by the powder nozzle is coaxial with the first focusing annular light beam and the second focusing annular light beam.

5. The in-light coaxial powder feeding dual-beam ring laser deposition processing head as claimed in claim 4, wherein:

the focusing lens is a plano-convex structure with a through hole in the center along the light transmission direction, the convex surface is formed by a composite surface formed by an inner ring and an outer ring with different focal lengths, the inner ring is a spherical surface or an aspheric surface, and the outer ring is an aspheric surface.

6. The in-light coaxial powder feeding dual-beam ring laser deposition processing head as claimed in claim 4, wherein:

the focal depth length of a focusing spot converged by the first combined annular light beam after passing through the outer ring of the focusing lens is 2-20 mm, and the focal depth length of a focusing spot converged by the second combined annular light beam after passing through the inner ring of the focusing lens is 0.2-2 mm;

alternatively, the first and second electrodes may be,

the focal length of the focusing light spot corresponding to the first combined annular light beam is smaller than that of the focusing light spot corresponding to the second combined annular light beam, and the distance between focal planes of the first combined annular light beam and the second combined annular light beam is 1-50 mm.

7. The in-light coaxial powder feeding dual-beam ring laser deposition processing head as claimed in claim 4, wherein:

the first laser and the second laser are divided into two laser beams by the beam splitter from the same optical fiber laser and then are accessed to the laser input interface through the optical fiber;

alternatively, the first and second electrodes may be,

the first laser beam and the second laser beam are respectively connected to the laser input interface from two independent fiber lasers through optical fibers.

8. The in-light coaxial powder feeding dual-beam ring laser deposition processing head as claimed in claim 4, wherein:

the inner diameter of the hollow first annular light beam is larger than or equal to the outer diameter of the hollow second annular light beam, and the inner diameter of the hollow second annular light beam is larger than the outer diameter of the powder feeding pipe;

alternatively, the first and second electrodes may be,

the diameter range of the powder beam current intersected with the laser is 0.1-5 mm, the outer diameter range of the first focusing light spot and the second focusing light spot is 0.1-8 mm, and the diameter of the powder beam current is smaller than or equal to the outer diameter of the first focusing light spot and the outer diameter of the second focusing light spot.

9. The in-light coaxial powder feeding dual-beam ring laser deposition processing head as claimed in claim 4, wherein:

the beam splitting module comprises a light splitting rhombic reflector, a third folding plane reflector and a fourth folding plane reflector, the direction of a ridge edge of the light splitting rhombic reflector is opposite to the incidence direction of the hollow first annular beam and the hollow second annular beam, and two adjacent side surfaces of the ridge edge of the light splitting rhombic reflector are respectively parallel to the reflecting surfaces of the third folding plane reflector and the fourth folding plane reflector;

alternatively, the first and second electrodes may be,

the light beam combining module comprises a light combining rhombic reflector, a sixth refraction plane reflector and a seventh refraction plane reflector, the direction of a ridge edge of the light combining rhombic reflector is the same as the incidence direction of the first split annular light beam and the second split annular light beam, and two adjacent side surfaces of the ridge edge of the light combining rhombic reflector are parallel to the reflection surfaces of the sixth refraction plane reflector and the seventh refraction plane reflector respectively.

10. The in-light coaxial powder feeding dual-beam ring laser deposition processing head as set forth in claim 4, wherein:

the second focusing annular light beam heats the matrix surface material of the focusing spot area to a molten or semi-molten state, the powder beam current is heated after being intersected with the first focusing annular light beam, and then is intersected with the second focusing annular light beam to generate secondary heating so as to achieve the molten or semi-molten state;

alternatively, the first and second electrodes may be,

before the formed first split annular light beam and the second split annular light beam reach the fifth deflecting plane mirror, the powder conveying pipe penetrates through the middle gap area of the first split annular light beam and the second split annular light beam without blocking light.

Technical Field

The disclosure relates to the technical field of laser deposition additive manufacturing, in particular to an optical inner coaxial powder feeding double-beam annular laser deposition processing method and a processing head.

Background

The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art.

Laser melting deposition (LMD, also known as laser cladding) is an outstanding representative of metal additive manufacturing technology developed based on the micro-area liquid phase welding idea, plays an increasingly important role in the 3D printing industry, and has been deeply applied to the fields of aerospace, biomedical, industrial molds and the like. However, there are still many technical problems and challenges to be solved in this technique, the laser heats the material to a molten state and forms a molten pool on the surface to be deposited, resulting in high heat input, large residual stress, coarsening of the material structure, low moving speed of the machining head relative to the part, low additive forming efficiency, and the like.

In addition to metal additive manufacturing techniques based on liquid phase welding principles, additive manufacturing techniques based on thermal spray principles also provide alternative solutions, wherein laser spray additive manufacturing represents one of the technologies. In the laser spraying, metal powder is heated to a molten or semi-molten state by laser, and powder particles are conveyed at a high speed by compressed gas, so that partial energy of the laser can be used for heating the surface of a matrix, and reliable deposition and forming of the sprayed particles on the surface of the matrix are realized. During the laser spraying process, the action of the laser does not cause the surface to be deposited to produce a molten pool which levels without significant overlap. Compared with laser metal deposition additive manufacturing technologies based on a liquid phase welding principle, such as laser cladding, laser spraying can improve the deposition efficiency by dozens or even hundreds of times, and can also effectively avoid the phenomena of oxidation, ablation, grain growth and the like brought to materials by liquid phase welding. However, in view of the current state of development, the following disadvantages severely restrict the progress of the technology: (1) the laser beam of the laser spraying process is mostly arranged laterally relative to the spraying jet flow, so that the moving direction of a processing head (or called a spray gun) is severely limited, laser spots and powder deposition spots are difficult to completely coincide, the accelerating synergistic effect of the sprayed powder is not ideal, the powder splashes seriously, and the process uniformity is poor; (2) the powder deposition spots are large, the application in the field of additive manufacturing is not facilitated, the diameter of a laser focusing spot used for laser spraying is more than 4mm, even a rectangular spot is used, the quality of a light beam is generally not high, the diameter of an outlet of a powder spray pipe is 2-12 mm, and high-precision additive forming is difficult to realize; (3) the forming redundant heat is more, which is not beneficial to improving the processing efficiency and the quality.

The coaxial powder feeding of the additive manufacturing process of laser melting deposition and laser spraying (hereinafter, collectively referred to as laser deposition) can be divided into two modes of coaxial powder feeding from the outside of light to the inside of light and coaxial powder feeding from the center of light. Researchers try to adopt a laser spraying scheme of coaxially feeding powder outside the light, and the scheme has the risks of insufficient acceleration of the powder, large deposited spots, severe material splashing and the like due to the limited acceleration action distance of high-pressure gas jet on the powder, so that the exertion of the advantages of the laser spraying technology is limited to a certain extent. For the coaxial powder feeding of the optical center, a central powder feeding/wire feeding laser cladding technical scheme that a plurality of beams of laser are uniformly distributed in the circumferential direction and converged towards the center is adopted, and a laser cladding scheme that a hollow annular converged light beam is formed through a light path conversion design is also adopted. However, the focused laser mostly forms a focused focal spot with a small focal depth, the focal spot is mainly used for heating a substrate to form a molten pool, powder is mainly melted by the convection heat transfer of the molten pool to realize deposition, and the molten pool is inevitably required to have enough surplus heat to enable the materials to be metallurgically bonded. Therefore, the focusing optical design of converging laser energy on a single focal spot cannot meet the development requirements of high-precision and high-quality laser spraying or laser cladding additive manufacturing and processing, and the fine adjustment of the laser energy required for depositing micro-area materials is difficult to realize.

Disclosure of Invention

In order to solve the defects of the prior art, the disclosure provides an optical inner coaxial powder feeding double-beam annular laser deposition processing method and a processing head, which can generate a first annular focused laser beam with a long focal depth or a conventional short focal depth, so that a powder beam coaxially fed from an optical inner center is highly matched with the first annular focused laser beam and sufficiently absorbs laser energy to reach a semi-melting state or a full melting state; and meanwhile, a second annular focusing laser beam with a longer focal length and a conventional short focal depth and coaxial with the first annular focusing laser beam is generated so as to be focused on a to-be-deposited area on the surface of the substrate to realize heating, and the energy of the two laser beams can be finely adjusted in a large-scale interval in a mutually independent and non-interfering manner.

In order to achieve the purpose, the following technical scheme is adopted in the disclosure:

the first aspect of the disclosure provides an optical coaxial powder feeding double-beam annular laser deposition processing method.

An optical inner coaxial powder feeding double-beam annular laser deposition processing method comprises the following steps:

the first beam of collimated laser reaches the first W-shaped conical reflector after passing through the first through hole of the first deflecting plane mirror, and reflected light is emitted to the reflecting surface of the first deflecting plane reflector to be turned by 90 degrees to form a hollow first annular light beam;

the second beam of collimated laser reaches a second W-shaped conical reflector after passing through a second through hole of a second deflecting plane mirror, reflected light irradiates the reflecting surface of the second deflecting plane reflector to be turned for 90 degrees, and a hollow second annular light beam is formed after passing through a third through hole of the first deflecting plane mirror;

the first split annular light beam and the second split annular light beam are deflected by 90 degrees through a fifth deflection plane mirror and then generate a first combined annular light beam and a second combined annular light beam which are coaxial and combined towards the middle through a light beam combining module;

the first and second combined annular light beams form a first focusing annular light beam and a second focusing annular light beam which are coaxial, are separated from each other in the depth direction and converge towards the center after passing through a focusing lens;

the powder feeding pipe sequentially penetrates through a fourth through hole of the fifth deflecting plane reflector, a fifth through hole of the light beam combining module and a central hole of the focusing lens and then is connected with the powder nozzle, and powder conveyed by compressed gas sequentially passes through the powder feeding pipe and the powder nozzle to form a powder beam coaxial with the first focusing annular light beam and the second focusing annular light beam and then is sprayed to the surface of the substrate.

A second aspect of the disclosure provides an in-light coaxial powder feed dual-beam ring laser deposition processing head.

An optical coaxial powder feeding double-beam annular laser deposition processing head at least comprises: the device comprises a first W-shaped conical surface reflector, a first refracting plane reflector, a second W-shaped conical surface reflector, a second refracting plane reflector, a fifth refracting plane reflector, a focusing lens, a light beam splitting module and a light beam combining module;

the first folding plane reflector is provided with a first through hole and a third through hole, the second folding plane reflector is provided with a second through hole, the axis of the first through hole is superposed with the central axis of the first W-shaped conical surface reflector, and the axis of the second through hole is superposed with the central axis of the second W-shaped conical surface reflector;

the first collimated laser beam passes through a first through hole of a first folding plane mirror and then sequentially passes through a first W-shaped conical reflector, a first folding plane reflector, a beam splitting module, a fifth folding plane reflector and a beam merging module to obtain a first parallel ring-shaped beam;

the collimated laser beam passes through a second through hole of a second deflecting plane mirror and then sequentially passes through a second W-shaped conical reflector, a second deflecting plane reflector, a beam splitting module, a fifth deflecting plane reflector and a beam combining module to obtain a second combined annular beam;

the first and second combined annular light beams form a first focusing annular light beam and a second focusing annular light beam which are coaxial, are separated from each other in the depth direction and converge towards the center after passing through a focusing lens;

and the powder feeding pipe sequentially passes through a fourth through hole of the fifth deflecting plane reflector, a fifth through hole of the light beam combining module and a central hole of the focusing lens and then is connected with the powder nozzle, and the powder beam current sprayed by the powder nozzle is coaxial with the first focusing annular light beam and the second focusing annular light beam.

Compared with the prior art, the beneficial effect of this disclosure is:

1. according to the optical inner coaxial powder feeding double-beam annular laser deposition processing method and the processing head, surplus heat absorbed by a deposition material is small, the moving speed of the processing head is high, residual stress and deformation caused by a forming process are small, and forming efficiency is high. The first focusing light spot heats the powder material to a molten or semi-molten state, the second focusing light spot is mainly used for heating a deposition spot area on the surface of the substrate to a semi-molten (softened) or molten state, and the heating depth of the substrate irradiated by laser is shallow, so that the laser energy is accurately utilized, and the required redundant energy is less; the effect of the comprehensive effect is that under the same quality condition, the heat absorbed by the overall deposited material is greatly reduced, the processing head can move at high speed relative to the substrate, the deposition efficiency is greatly improved, and the forming precision and the coating quality are obviously improved because the residual stress and the deformation generated in the thermal deposition process are reduced.

2. According to the optical inner coaxial powder feeding double-beam annular laser deposition processing method and the processing head, the laser beam and the particle jet flow are good in matching performance, and the particle jet flow is high in adjustment flexibility. By adopting a coaxial powder feeding mode, the focusing light spot and the particle jet flow can be absolutely coaxial, so that the deposition material is uniformly and fully heated, the splashing is less, and the deposition angle and the moving direction are not limited; furthermore, by adjusting the diameter of the excircle of the annular focusing light spot and the caliber of the powder nozzle, the diameter of the deposited spot of the particle jet can be as low as hundreds of microns magnitude and can also be as high as several millimeters magnitude, so that the process adjustment flexibility and the application range are greatly improved.

3. The in-light coaxial powder feeding double-beam annular laser deposition processing method and the processing head can achieve the effect of high-speed laser cladding or laser spraying as required, and have wide process adaptability. By adjusting the power of the laser, the heating temperature of the powder particles and the surface of the matrix is changed in a large range, and parameters such as the flight speed of the powder particles are adjusted, so that high-quality laser cladding or laser spraying can be realized, the process flexibility is good, and the parameter adjusting window range is wide.

Advantages of additional aspects of the disclosure will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the disclosure.

Drawings

The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.

Fig. 1 is a schematic diagram of a dual-beam ring laser deposition processing head structure and optical path transmission provided in an embodiment of the present disclosure.

Fig. 2 is a schematic diagram of an optical lens arrangement and a focusing spot of a dual-beam ring laser deposition processing head according to an embodiment of the disclosure.

Fig. 3 is a schematic view of a collecting lens profile provided by an embodiment of the present disclosure.

Fig. 4 is a schematic diagram of a long focal depth structure of an outer ring of a focusing lens according to an embodiment of the present disclosure.

1. A first beam of laser light; 2. a first collimating mirror; 3. a first fold plane mirror; 4. a first W-shaped conical reflector; 5. a hollow first annular beam;

6. a second beam of laser light; 7. a second collimating mirror; 8. a second fold plane mirror; 9. a second W-shaped conical reflector; 10. a hollow second annular beam;

100. a prismatic mirror for light splitting; 101. a third fold plane mirror; 102. a fourth, redirecting, planar mirror;

11. a first split annular beam; 12. a second split annular beam; 13. a fifth deflecting plane mirror;

200. a light-combining prismatic mirror; 201. a sixth redirecting plane mirror; 202. a seventh fold plane mirror;

14. a first parallel loop-shaped light beam; 15. a second merged annular beam; 16. a focusing lens; 17. a first focused annular beam; 18. a second focused annular beam;

19. a powder feeding pipe; 20. a powder nozzle;

300. a central bore; 301. an inner ring; 302. and an outer ring.

Detailed Description

The present disclosure is further described with reference to the following drawings and examples.

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

Example (b):

as shown in fig. 1, the present embodiment provides an in-light coaxial powder feeding dual-beam ring laser deposition processing head, which includes: the device comprises a first collimating mirror 2, a first W-shaped conical reflector 4, a first folding plane reflector 3, a second collimating mirror 6, a second W-shaped conical reflector 9, a second folding plane reflector 8, a beam splitting prismatic reflector 100, a third folding plane reflector 101, a fourth folding plane reflector 102, a fifth folding plane reflector 13, a beam combining prismatic reflector 200, a sixth folding plane reflector 201, a seventh folding plane reflector 202 and a focusing lens 16;

after forming collimated light through the first collimating mirror 2, the first beam of laser 1 passes through a first through hole arranged on the first refracting planar reflector 3 without shielding, then is emitted to the first W-shaped conical reflector 4, and then is emitted to the reflecting plane of the first refracting planar reflector 3 to generate 90-degree steering, so that a hollow first annular light beam 5 is formed;

after forming collimated light by the second collimating mirror 7, the second laser beam 6 passes through a second through hole arranged on the second refraction plane reflector 8 without shielding, then is emitted to the second W-shaped conical surface reflector 9, then is emitted to the reflecting plane of the second refraction plane reflector 8 to generate 90-degree turning, then passes through a third through hole arranged on the first refraction plane reflector 3 without shielding, and then forms a hollow second annular light beam 10 coaxial with the first hollow annular light beam 5;

the hollow first annular light beam 5 and the hollow second annular light beam 10 respectively emit to the prismatic light splitting reflector 100, the third folding plane reflector 101 and the fourth folding plane reflector 102 to form a first split annular light beam 11 and a second split annular light beam 12 which are coaxial and have a gap in the middle; then the light beam is emitted to a fifth refraction plane reflector 13 to be emitted to a light-combining prism reflector 200, a sixth refraction plane reflector 201 and a seventh refraction plane reflector 202 respectively after being deflected by 90 degrees, and then a first combined annular light beam 14 and a second combined annular light beam 15 which are coaxial and combined towards the middle are formed; the first and second merged annular beams 14, 15 pass through a focusing lens 16 to form first and second focused annular beams 17, 18 which are concentric but separated from each other in the depth direction and converge towards the center;

the powder feeding pipe 19 sequentially passes through the fourth through hole of the fifth deflecting plane mirror 13, the fifth through hole of the light-combining prismatic mirror 200 and the central hole 300 of the focusing lens 16 and then is connected with the powder nozzle 20, and the powder conveyed by the compressed gas sequentially passes through the powder feeding pipe and the powder nozzle to form a powder beam coaxial with the first focusing annular beam 17 and the second focusing annular beam 18 and then is sprayed to the surface of the substrate.

In this embodiment, the beam splitting module is composed of the beam splitting rhomboid reflector 100, the third turning plane reflector 101 and the fourth turning plane reflector 102, the ridge of the beam splitting rhomboid reflector 100 faces the direction opposite to the incident direction of the hollow first annular light beam 5 and the hollow second annular light beam 10, and two adjacent side surfaces of the ridge of the beam splitting rhomboid reflector are parallel to the reflecting surfaces of the third turning plane reflector and the fourth turning plane reflector respectively;

in this embodiment, the light combining rhombus reflector 200, the sixth deflecting plane reflector 201, and the seventh deflecting plane reflector 202 constitute a light beam combining module, the direction of the ridge of the light combining rhombus reflector 200 is the same as the incident direction of the first split annular light beam 11 and the second split annular light beam 12, and two adjacent side surfaces of the ridge of the light combining rhombus reflector 200 are parallel to the reflecting surfaces of the sixth deflecting plane reflector and the seventh deflecting plane reflector, respectively.

In this embodiment, the focusing lens 16 is a plano-convex structure with a through hole at the center along the light transmission direction, wherein the convex surface is formed by a composite surface formed by an inner circle 301 and an outer circle 302 with different focal lengths, the inner circle 301 is a spherical surface or an aspherical surface, and the outer circle 302 is an aspherical surface.

Specifically, the focusing lens is a plano-convex structure with a through hole in the center along the light transmission direction, as shown in fig. 3, wherein the convex surface is formed by a composite surface consisting of an inner circle 301 and an outer circle 302 with different focal lengths.

The first and second merged annular beams 14, 15 pass through the outer and inner circles 302, 301, respectively, of the focusing lens 16. The outer ring of the focusing lens is usually aspheric, because when the powder particle flow flies from the central axis of the ring laser to the surface of the substrate, the powder particle flow will first intersect with the focusing spot formed by the first parallel ring-shaped light beam passing through the outer ring of the focusing lens, and the particles are heated. When a focusing light spot with relatively long focal depth (generally 2-20 mm is required) interacts with particle flow and the diameter of the light spot is not greatly fluctuated within the focal depth range, the particles are heated more sufficiently and uniformly, and the high-quality deposition of powder particles is facilitated. Therefore, the surface shape parameters of the aspheric surface need to be designed according to the requirements.

As a typical method, an arbitrary point P (r) on the aspherical surface_p,z_p) Can be obtained according to the following formula (seeFigure 4):

in the formula, R₀Is the first converging annular beam inner diameter, R₁Is the outer diameter of the first combined annular beam, r is the coordinate value of the horizontal axis (radius) of the cylindrical coordinate system, z is the coordinate value of the vertical axis of the cylindrical coordinate system, n is the refractive index of the lens, and delta_fIs depth of focus, f₀Is the beam inner diameter R₀The distance from the focal point of the light to the origin of coordinates (focal length).

The inner ring of the focusing lens usually adopts a conventional spherical surface, and the second combined annular light beam 15 forms a focusing light spot near the surface of the substrate after passing through the focusing lens 16, and is mainly used for heating the substrate material in the area, and the focal depth length of the focusing light spot formed by convergence is usually 0.2 mm-2 mm, so that the requirement can be met, the focusing can be realized by using a focusing means of the conventional spherical lens, and the realization cost is lower. Of course, the conventional short-focal-depth aspheric surface can be used as the inner ring surface shape, and the method is not limited. Obviously, the focal length of the outer circle of the focusing lens is smaller than that of the inner circle, and the focal plane distance between the two is (i.e. the first parallel-ring beam inner diameter R)₀The distance between the focal point of the light and the focal point formed by the second combined annular light beam passing through the spherical surface of the inner ring of the lens) ranges from 1mm to 50 mm. The reason is that when the particles are intersected with the first focusing annular beam, although the time from the photon energy absorption of the particles to the temperature rise is very short, for the particles in a flight state, especially for the particles flying at high speed, the time difference cannot be ignored, the first focusing light spot and the second focusing light spot are separated, the particle beam is intersected with the first focusing light spot firstly and then reaches the surface of the substrate, a certain time is required for the powder particles to emit heat after absorbing the photon energy through light irradiation, and the heating of the flying particles reaching the surface of the substrate can be ensured to reach the required temperature. Moreover, the higher the particle flight velocity, the greater the depth of focus of the first concentrated annular beam is generally required.

In this embodiment, the inner diameter of the light beam forming the first hollow annular light beam is not smaller than the outer diameter of the second hollow annular light beam, so that the two light beams respectively pass through the outer ring and the inner ring of the focusing lens, and then two focal spots with different focal lengths are formed; the diameter range of the powder beam current intersected with the laser is 0.1-5 mm, the outer diameter range of the first focusing light spot and the second focusing light spot is 0.1-8 mm, and the diameter of the powder beam current is not more than the outer diameter of the first focusing light spot and the second focusing light spot.

In this embodiment, before the formed first split annular light beam and the second split annular light beam reach the fifth deflecting plane mirror, the powder feeding pipe passes through the middle gap region of the first split annular light beam and the second split annular light beam without blocking light.

Specifically, the powder feeding tube is inserted into the center of the ring laser according to the position shown in fig. 1 without any light blocking, in order to realize this, the hollow first ring beam and the second ring beam pass through the mirrors 100, 101, 102 and then become split ring beams, and the formed gap is that the light cannot shine on the surface of the tube when the powder feeding tube is inserted; when the powder feeding tube is inserted into the center of the annular light and the light is coaxial, the mirrors 200, 201 and 202 are needed to change the split annular light into the combined annular light (i.e. the gap in the middle of the annular light is removed), and then the light is focused by the lens.

In this embodiment, the size of the opening in the middle of the fifth deflecting plane mirror 13, the light-combining prism mirror 200 and the focusing lens 200 is smaller than the inner diameter of the second combined ring beam 15, i.e. the opening cannot be too large, so as to prevent the ring beam from leaking out of the opening. Obviously, the inner diameter of the second annular beam forming the hollow is larger than the outer diameter of the powder feeding tube, so that the second combined annular beam to be formed later does not impinge on the outer surface of the powder feeding tube.

In this embodiment, the focal depth length of the focusing spot converged by the first merging annular light beam 14 after passing through the outer ring 302 of the focusing lens 16 is 2mm to 20mm, preferably 10mm, and those skilled in the art can select the focal depth within a range of 2mm to 20mm according to specific working conditions, which is not described herein again.

In this embodiment, the focal depth length of the focusing spot formed by converging the second combined annular light beam 15 after passing through the inner ring 301 of the focusing lens 16 is 0.2mm to 2mm, preferably 0.5mm, and those skilled in the art can select the focal depth within the range of 0.2mm to 2mm according to specific working conditions, which is not described herein again.

In this embodiment, the focal length of the focusing spot corresponding to the first merged annular light beam 14 is smaller than the focal length of the focusing spot corresponding to the second merged annular light beam 15, and the focal plane distance between the two is 1mm to 50mm, preferably 25mm, and those skilled in the art can select the focusing spot within the range of 1mm to 50mm according to specific working conditions, which is not described herein again.

The first focusing light spot and the second focusing light spot need to have a certain spacing distance, the purpose is to enable the particle beam to be intersected with the first focusing light spot and then reach the surface of the substrate, the powder particles absorb photon energy through light irradiation until the powder particles generate heat, a certain time is needed, the second focusing light spot is mainly used for heating the surface of the substrate, the particle beam and the intersection are only incidental, and the deposition process requires that the particle is heated and reaches the required temperature when reaching the surface of the substrate.

The first laser beam 1 and the second laser beam 6 are divided into two laser beams by a beam splitter from the same optical fiber laser and then are connected to the laser input interface of the processing head through optical fibers, or the two laser beams which are independent of each other are respectively connected to the laser input interface of the processing head through optical fibers.

Specifically, when the laser input scheme of one fiber laser is adopted, the ratio of the laser powers of the two lasers output by the beam splitter is relatively fixed, the complexity and the cost of the device are relatively low, but the energy of the formed first focused annular beam 17 and the second focused annular beam 18 can only be increased or reduced at the same time in a fixed ratio, which is also generally satisfied for the additive manufacturing of most materials; when the laser input scheme of two fiber lasers is adopted, two beams of laser are independent from each other, so that the energy distributions of the formed first focusing annular beam 17 and the second focusing annular beam 18 are also independent from each other, and the laser power can be adjusted independently without influencing each other, so that the process adjustment of the method is more flexible, and the generated materials and process adaptability are wider.

The second focused annular beam 18 heats the matrix surface material of the focused spot region to a molten or semi-molten state; the powder beam is heated after being intersected with the first focusing annular beam 17, and then is intersected with the second focusing annular beam 18 to generate secondary heating to reach a melting or semi-melting state, so that the powder beam is reliably deposited on the surface of a heated substrate and is continuously superposed and thickened to realize additive manufacturing.

In particular, the powder stream is subjected to a first focused annular beam 17 as the primary heating means and a second focused annular beam 18 as the secondary, incidental heating means. When the surface material of the substrate is heated to a molten state by the laser, a molten pool or a micro-molten pool is formed on the surface of the substrate, and the process of laser cladding is realized substantially. But it is different from the conventional laser cladding, because the powder particles are fully heated before reaching the molten pool, the laser processing head can move at high speed relative to the substrate to realize high-quality cladding deposition, and the moving speed is generally improved by dozens of times or even hundreds of times compared with the traditional laser cladding. When the laser heats the substrate surface material to a semi-molten state (i.e., a state where the substrate surface material temperature in the deposition region does not reach its melting point temperature but has softened), it is generally desirable that the particles have a high flight speed, which substantially enables the additive manufacturing process of laser spraying.

The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure, and various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.