WO2020062341A1

WO2020062341A1 - Laser additive apparatus and additive manufacturing method therefor

Info

Publication number: WO2020062341A1
Application number: PCT/CN2018/110197
Authority: WO
Inventors: 任旭东; 童照鹏; 周王凡; 陈兰; 焦加飞
Original assignee: 江苏大学
Priority date: 2018-09-28
Filing date: 2018-10-15
Publication date: 2020-04-02
Also published as: CN109175364B; CN109175364A

Abstract

Provided is a laser additive apparatus, comprising a rotary light beam laser system, a high-frequency short-pulse laser system and an auxiliary current system, wherein the rotary light beam laser system outputs rotary continuous lasers for melting and depositing wires on the surface of a base material (13); the high-frequency short-pulse laser system outputs high-frequency short-pulse lasers for inputting a pulse laser beam into a molten pool (10); the auxiliary current system is used for enabling the wires and the molten pool (10) to form a current loop for enabling strong electromagnetic force to be directly generated in the molten pool (10); the rotary light beam laser system comprises a continuous laser generator (1), a first high-precision mechanical arm (2) and a continuous laser device laser head (9); and the high-frequency short-pulse laser system comprises a high-frequency short-pulse laser generator (3), a high-frequency short-pulse laser head (4) and a second high-precision mechanical arm (5). Further disclosed is a method for manufacturing a laser additive. The rotary laser beam enables the liquid in the molten pool to be stirred uniformly, and the strong electromagnetic force promotes the rapid flow of the liquid in the molten pool, which avoid the defects that element segregation is likely to be caused, gas cannot be exhausted, the organization is nonuniform, heat stress is concentrated, etc. in the molten pool.

Description

Laser additive device and method for additive manufacturing

Technical field

The invention relates to the technical field of laser additive manufacturing, in particular to a laser additive device and a method for additive manufacturing thereof.

Background technique

Additive manufacturing technology, also known as 3D printing technology, has attracted wide attention of many scholars in recent years, and is called the "third industrial revolution." Among the many additive manufacturing methods, laser additive manufacturing (LAM) is a more advanced manufacturing method for producing net-shaped metal components with excellent performance. It has been widely used in automobiles, aerospace, military equipment, and medical fields. . At present, many scholars at home and abroad have made great progress in the field of laser additive manufacturing technology research, and have successfully prepared alloy components of nickel-based alloys, titanium alloys, stainless steel and other materials with good performance by using this technology.

However, in the process of laser additive manufacturing components, there are usually some common problems, such as incomplete melting, pore inclusions, pores, cracks, coarse grain structure and other metallurgical defects in the interior of the additive component; due to its " The characteristics of "quick cooling and hot heating" can also cause large residual tensile stress and element segregation inside the component; therefore, with the development of laser composite processing technology, many scholars have adopted an external energy field to assist laser additive manufacturing methods to Improve the comprehensive performance of additive components. According to the existing research and reports at home and abroad, it is common to use an external cross magnetic field to refine the microstructure in the molten pool; however, this magnetic field is a static form, and the magnetic field energy remains unchanged during operation and cannot be adjusted in real time. Moreover, the magnetic field and the molten pool are non-contact, which has a limited effect on the interior of the molten pool. At present, the beams used in laser additive manufacturing are all direct laser beams. The uneven energy distribution within the linear laser beam will cause the melt channel. The boundaries are unclear and irregular, the flatness of the deposited layer is poor, and the bonding strength between layers is low, which further seriously affects the mechanical properties of the components.

Laser processing technology parameters and laser equipment are important factors affecting the performance of additive components. In order to obtain laser additive components with excellent comprehensive performance, usually after trying many process parameters, the post-test comparison of the prepared additive components is preferred. The best one. Laser additive cost is relatively high. Through a large number of sample detection, it is bound to be time-consuming, labor-intensive and greatly increase production costs.

Through the retrieval of domestic and foreign literature, many researchers have focused on regulating the microstructure performance of components through the application of electric or magnetic fields.

Summary of the Invention

Aiming at the shortcomings in the prior art, the present invention provides a laser additive device and a method for additive manufacturing thereof, which can solve defects such as easy element segregation, gas cannot be discharged, uneven organization, and thermal stress concentration in the molten pool. .

The present invention achieves the above technical objectives through the following technical means.

A laser additive device includes a rotating beam laser device and a high-frequency short-pulse laser device;

The rotating beam laser device outputs a rotating continuous laser, and the continuous laser is used for melting and depositing a filament on a surface of a substrate;

The high-frequency short-pulse laser device outputs a high-frequency short-pulse laser, and the high-frequency short-pulse laser is used to input a pulsed laser beam into a molten pool.

Furthermore, the auxiliary current device is further included; the auxiliary current device is used to form a current loop between the wire and the molten pool, and is used to directly generate a strong electromagnetic force inside the molten pool.

Further, the rotating beam laser device includes a continuous laser generator, a first high-precision mechanical arm, and a continuous laser laser head; the continuous laser generator is connected to the continuous laser laser head; and the continuous laser laser head is installed at the first high On a precision mechanical arm; a wire feeder is used to feed the filament into the continuous laser laser head.

Further, the continuous laser laser head has a built-in optical rotation module for generating a rotating beam.

Further, the high-frequency short-pulse laser device includes a high-frequency short-pulse laser generator, a high-frequency short-pulse laser head, and a second high-precision robot arm; the high-frequency short-pulse laser generator and the high-frequency short-pulse laser The high-frequency short-pulse laser head is mounted on a second high-precision robotic arm; the high-frequency short-pulse laser head is located beside the continuous laser laser head, and the high-frequency short-pulse laser head is aligned A quasi-melt pool on the surface of the substrate is used to continuously provide a pulsed laser beam into the molten pool.

Further, the auxiliary current device includes a power supply device and an additional rolling electrode; one end of the power supply device is connected to the wire, the other end of the power supply device is connected to an additional rolling electrode, and the additional rolling electrode is located at the rear side of the molten pool, It is in contact with the surface of the deposited layer to form a current loop.

Further, it also includes an information acquisition system; the information acquisition system includes a high-speed camera, an illumination device, a spectrometer probe, a spectrometer, and a synchronization signal generator; the high-speed camera is located near a molten pool, and the spectrometer probe is used to measure the inside of the molten pool For the generated plasma / metal vapor, the spectrometer is used to collect data measured by the spectrometer probe; the high-speed camera, lighting device, and spectrometer are connected to a synchronous signal generator to ensure that when the high-speed camera collects images, the spectrometer The lighting device is in a lighting state and ensures that the high-speed camera and the spectrometer collect data at the same time.

Further, it further comprises a high-frequency induction heating system; the high-frequency induction heating system includes a high-frequency induction heating coil and a high-frequency induction heating power source, the high-frequency induction heating coil is located at the bottom of the substrate, the high-frequency induction heating power source and A high-frequency induction heating coil is connected for heating the substrate.

A method for a laser additive device for additive manufacturing includes the following steps:

The rotating beam laser device outputs a continuous continuous laser to melt and deposit the filament on the surface of the substrate;

Input high-frequency short-pulse laser into the molten pool through a high-frequency short-pulse laser device;

Furthermore, it includes the following steps:

Generate electromagnetic inside the molten pool: By forming a current loop between the wire and the molten pool, a strong electromagnetic force is directly generated inside the molten pool;

Preheating the substrate: Preheat the substrate through a high-frequency induction heating system;

On-line monitoring of the quality of the deposited layer: real-time detection of the plasma / metal vapor generated in the molten pool through an information acquisition system, judgment of the quality of the deposited layer, and the control computer dynamically adjusts the rotating beam laser device, high-frequency short-pulse laser device and auxiliary current according to the judgment result Device parameters.

The beneficial effects of the present invention are:

1. The laser additive device of the present invention uses a built-in optical rotation module in the continuous laser laser head to rotate the beam during the additive manufacturing process, ensuring that the internal energy and temperature field of a single molten pool are uniformly distributed, and the energy distribution of the linear beam is solved. Uniformity leads to unclear and irregular borders of the melt channel, poor flatness of the deposited layer, and low bonding strength between layers.

2. In the laser additive device of the present invention, continuous beam rotation can ensure the uniform distribution of energy and temperature fields within a single molten pool, which is beneficial to the current generation of a uniform electromagnetic field inside the molten pool, and the metal liquid inside the molten pool follows the focal point. Rotate and rotate to achieve full and uniform stirring inside the molten pool.

3. The laser additive device of the present invention provides auxiliary current to the molten pool through additional electrodes, which directly generates strong electromagnetic force inside the molten pool, and the current is not easy to be lost through the matrix material, which promotes the rapid Control the flow to achieve the purpose of heat balance distribution.

4. The laser additive device according to the present invention directly applies the high-frequency short-pulse laser beam inside the molten pool to cause cavitation and crushing effects inside the molten pool, and cooperates with the effect of electromagnetic force and rotating beam on the molten pool. The coupling is used to stir the molten pool uniformly and fully to achieve the purpose of eliminating or suppressing various metallurgical defects inside the component and releasing thermal stress.

5. The laser additive method according to the present invention proposes to determine the quality of the deposited layer based on the state of the plasma / metal vapor in the molten pool. Use high-speed cameras and spectrometers to collect the plasma / metal vapor information in the molten pool, transfer the collected information to the control computer, learn the internal conditions of the molten pool based on the plasma / metal vapor information, and judge the quality performance of the deposited layer. As a result, the high-frequency short-pulse laser parameters, continuous laser parameters, auxiliary power parameters, and beam rotation parameters are adjusted in real time, and the entire device forms a closed-loop system, which realizes systematization, automation, and intelligence, saving preparation time and cost, improving efficiency and quality.

6. The laser additive device of the present invention uses a high-frequency short-pulse laser and a high-density current to rotate the laser beam in conjunction with the molten pool to stir the molten pool at the same time. The high-speed camera and spectrometer are used to plasma / metal vapor in the molten pool. The information is collected, the collected information is transmitted to the control computer, the internal conditions of the molten pool are known according to the plasma / metal vapor information, the quality performance of the deposited layer is judged, and the high-frequency short-pulse laser parameters and continuous laser parameters are adjusted in real time based on the judgment results The auxiliary power source parameters and beam rotation parameters can achieve the purpose of suppressing metallurgical defects, optimizing microstructure, and improving the mechanical properties of additive components.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a laser additive device according to the present invention.

FIG. 2 is a partial plan view of a laser additive device according to the present invention.

FIG. 3 is a comparison diagram of the residual stress of an additive member prepared by different methods.

FIG. 4 is a comparison diagram of tensile strength of an additive member prepared by different methods.

5 is a microstructure morphology of a titanium alloy component prepared by a laser additive manufacturing method in the prior art.

FIG. 6 is a microstructure morphology of a titanium alloy component prepared by the present invention.

In the picture:

1-continuous laser generator; 2-first high precision robot arm; 3-high frequency short pulse laser generator; 4-high frequency short pulse laser head; 5-second high precision robot arm; 6-wire feeder; 7-power supply device; 8-additional rolling electrode; 9-continuous laser head; 10-melt pool; 11-high frequency induction heating coil; 12-deposition layer; 13-substrate; 14-high frequency induction heating power supply; 15 -Control computer; 16-speed camera; 17- sync signal generator; 18- spectrometer; 19- plasma / metal vapor; 20- lighting device; 21- spectrometer probe.

detailed description

The present invention is further described below with reference to the drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

As shown in FIGS. 1 and 2, the laser additive device according to the present invention includes a rotating beam laser device, a high-frequency short-pulse laser device, an auxiliary current device, an information acquisition system, a high-frequency induction heating system, and a control computer 15.

The rotating beam laser device includes a continuous laser generator 1, a first high-precision robotic arm 2, a wire feeder 6, and a continuous laser laser head 9; the continuous laser generator 1 is connected to the continuous laser laser head 9 and provides it with A continuous laser light source; a built-in optical rotation module is built into the continuous laser laser head 9, and the laser beam generates a rotating beam during the emission process; the continuous laser laser head 9 is mounted on the first high-precision robot arm 2; the wire feeder The 6-direction rotating continuous laser beam conveys the material wire to the center of the substrate and is deposited on the surface of the substrate. It is a coaxial coaxial wire feed. Through the built-in optical rotation module in the continuous laser laser head 9, the beam is rotated during the additive manufacturing process to ensure single melting. The internal energy and temperature fields of the pool 10 are evenly distributed, which solves the problems of uneven energy distribution of the linear beam, which leads to unclear and irregular boundaries of the melt channel, poor flatness of the deposited layer, and low bonding strength between layers.

The high-frequency short-pulse laser device includes a high-frequency short-pulse laser generator 3, a high-frequency short-pulse laser head 4, and a second high-precision robot arm 5. The high-frequency short-pulse laser generator 3 is connected to the high-frequency short-pulse laser. The pulsed laser head 4 is connected to provide a pulsed laser light source. The high-frequency short-pulse laser head 4 is mounted on a second high-precision robot arm 5; the high-frequency short-pulse laser head 4 is located on the continuous laser laser head 9 On the side, aim at the molten pool 10, and continuously provide a pulsed laser beam into the molten pool 10; the high-frequency short-pulse laser beam directly acts on the inside of the molten pool 10, so that the inside of the molten pool 10 produces cavitation and crushing effects, and cooperates The effect of electromagnetic force and rotating beam on the molten pool, the three are coupled to evenly and fully stir the molten pool to achieve the purpose of eliminating or suppressing various metallurgical defects inside the component and releasing thermal stress.

The auxiliary current device includes a power source device 7 and an additional rolling electrode 8. One output stage of the power supply device 7 is connected to the wire, and the other output stage is connected to an additional rolling electrode 8 located on the rear side of the molten pool 10 and in contact with the surface of the deposition layer. The current passes through the molten pool to form a current loop. The additional rolling electrode 8 is fixed on the side of the continuous laser laser head 9 and does not interfere with the high-frequency short-pulse laser head 4; an auxiliary current is supplied to the molten pool through the additional electrode, which directly generates the inside of the molten pool. Strong electromagnetic force, and the current is not easy to be lost through the matrix material, and promote the rapid and controllable flow of liquid metal inside the molten pool to achieve the purpose of heat balance distribution.

The information acquisition system includes a high-speed camera 16, a lighting device 20, a spectrometer probe 21, a spectrometer 18, and a synchronization signal generator 17 located beside the molten pool 10. A spectrometer probe 21 disposed near the molten pool 10 is aligned with the plasma / metal vapor 19, and a spectrometer 18 is connected to the spectrometer probe 21 to collect data measured by the spectrometer probe 21; the high-speed camera 16, The lighting device 20 and the spectrometer 18 are connected to a synchronization signal generator 17 to ensure that when the high-speed camera 16 collects images, the lighting device 20 is in an illuminated state, and that the high-speed camera 16 and the spectrometer 18 collect data at the same time. It is proposed to use the state of the plasma / metal vapor 19 in the molten pool 10 as a criterion to determine the quality of the deposited layer. The high-speed camera 16 and the spectrometer 18 are used to collect the plasma / metal vapor 19 information in the molten pool 10, and the collected information is transmitted to the control computer 15, and the internal conditions of the molten pool 10 are known and judged based on the plasma / metal vapor 19 information. According to the judgment results, the quality and performance of the deposited layer 12 are adjusted in real time according to the high-frequency short-pulse laser parameters, continuous laser parameters, auxiliary power parameters, and beam rotation parameters. The entire device forms a closed-loop system, which realizes systemization, automation, and intelligence, saving Preparation time and cost improve efficiency and quality. The high-speed camera 16 of the information acquisition system has a shooting speed of up to 40,000 frames per second and a dynamic range of 160 dB. The spectrometer 18 can measure a wavelength range of 200-1100 nm and a maximum resolution of 0.04 nm.

The high-frequency induction heating system includes a high-frequency induction heating coil 11 and a high-frequency induction heating power source 14. The high-frequency induction heating power source 14 is connected to the high-frequency induction heating coil 11 to provide power for heating the substrate 13 placed on a high-precision two-dimensional mobile platform; the high-precision two-dimensional mobile platform may be horizontal Move in the X and Y directions or coordinate the X and Y directions in the plane.

The rotating beam laser device, high-frequency short-pulse laser device, auxiliary current device, information acquisition system, high-frequency induction heating system, and high-precision two-dimensional mobile platform are all connected to the control computer 15. The information acquisition system feeds back the obtained information to the control computer 15, and the control computer 15 adjusts the process parameters of the rotating beam laser device, the high-frequency short-pulse laser device, the wire feeding system, and the auxiliary current device in real time to complete the material deposition.

In the following, laser additive manufacturing of titanium alloy is used as an example, and a laser additive method in the present invention is used. The schematic diagram of the equipment is shown in FIG. 1. Specific steps include:

A. Establish a three-dimensional model of the additive component in the control computer 15, slice the model using built-in software, obtain the profile information of the section of the component, and complete the continuous laser beam scanning path in the control computer 15 according to the shape information;

B. Initialize the high-precision two-dimensional mobile platform, continuous laser generator 1, high-frequency short-pulse laser generator 3;

C. Turn on the high-frequency induction heating power supply 14 and set the temperature value of the high-frequency induction heating coil 11 to preheat the substrate so that the substrate temperature reaches 300 ° C;

D. After the substrate is preheated to the specified temperature, turn on the high-speed camera 16, the lighting device 20, the spectrometer probe 21, the spectrometer 18, and the synchronization signal generator 17;

E. Turn on the continuous laser generator 1, high-frequency short-pulse laser generator 3, wire feeder 6, and power supply device 7 to achieve high-frequency short-pulse laser-current coupling assisted rotating beam laser additive manufacturing processing; initial continuous laser generator The parameters are set as follows: the laser power is 1500W, the spot diameter is 2mm, the overlap rate is 50%, and the powder feed rate is 25g / min; the optical rotation module is set as: a rotation evaluation rate of 1500min ^-1 , a beam deflection angle of 3 °, and a rotating beam The path radius is 1.5mm; the initial high-frequency short-pulse laser generator parameters are set as follows: the center wavelength is 1030nm, the maximum output power is 80W, the pulse output energy is 80μJ, and the pulse width is 100fs. The initial wire feed speed is 900mm / min; the initial power supply current is set to 100A.

F. During the additive manufacturing process, based on the plasma / metal vapor 19 information obtained by the high-speed camera 16 and the spectrometer probe 21, determine the quality of the deposited layer 12 and adjust the continuous laser generator 1, high-frequency short-pulse laser generator 3 in real time , Process parameters of wire feeder 6 and power supply unit 7.

G. Turn off all equipment after the end of the additive manufacturing process.

Measurements of residual stress and tensile strength of bulk titanium alloy samples prepared using ordinary laser additive manufacturing, electromagnetic-assisted laser additive manufacturing, and the method of the present invention are shown in Figures 3 and 4, respectively. The titanium alloy prepared by the device and method has the lowest residual stress and the largest tensile strength; observation of the microstructure shows that. In Figures 3 and 4, the rightmost figure is a titanium alloy sample made according to the method of the present invention.

As shown in Figure 5, the titanium alloy prepared by the ordinary laser additive manufacturing method has coarse grains, uneven grain distribution, anisotropy, and obvious defects such as pores and cracks; as shown in Figure 6, In the laser additive method of the present invention, the titanium alloy prepared by combining high-frequency short-pulse laser, high-density current, and co-rotating the laser beam is used to assist the laser additive manufacturing to produce a compact and uniform titanium alloy with fine grains and no pores. , Cracks and other defects can significantly improve the comprehensive mechanical properties of titanium alloys.

The embodiment is a preferred implementation of the present invention, but the present invention is not limited to the above-mentioned embodiments. Without departing from the essence of the present invention, any obvious improvement, replacement, or Variations belong to the protection scope of the present invention.

Claims

A laser additive device characterized by comprising a rotating beam laser device and a high-frequency short-pulse laser device;

The rotating beam laser device outputs a rotating continuous laser, and the continuous laser is used for melting and depositing a filament on a surface of a substrate (13);

The high-frequency short-pulse laser device outputs a high-frequency short-pulse laser, and the high-frequency short-pulse laser is used to input a pulsed laser beam into the molten pool (10).
The laser additive device according to claim 1, further comprising the auxiliary current device; the auxiliary current device is used to form a current loop between the filament and the molten pool (10), and is used to make the molten pool ( 10) Strong electromagnetic force is generated directly inside.
The laser additive device according to claim 1, characterized in that the rotating beam laser device comprises a continuous laser generator (1), a first high-precision robot arm (2), and a continuous laser laser head (9); The continuous laser generator (1) is connected to a continuous laser laser head (9); the continuous laser laser head (9) is mounted on a first high-precision robot arm (2); a wire feeder (6) is used to The continuous laser head (9) conveys material filaments.
The laser additive device according to claim 3, wherein the continuous laser laser head (9) has a built-in optical rotation module for generating a rotating beam.
The laser additive device according to claim 1, wherein the high-frequency short-pulse laser device comprises a high-frequency short-pulse laser generator (3), a high-frequency short-pulse laser head (4), and a second high-precision A robot arm (5); the high-frequency short-pulse laser generator (3) is connected to the high-frequency short-pulse laser head (4); the high-frequency short-pulse laser head (4) is installed on a second high-precision machine On the arm (5); the high-frequency short-pulse laser head (4) is located beside the continuous laser laser head (9), and the high-frequency short-pulse laser head (4) is aligned with the surface of the substrate (13) A quasi-melt pool (10) for continuously supplying a pulsed laser beam into the melt pool (10).
The laser additive device according to claim 2, characterized in that the auxiliary current device comprises a power supply device (7) and an additional rolling electrode (8); one end of the power supply device (7) is connected to a wire, and The other end of the power supply device (7) is connected to an additional rolling electrode (8), which is located on the rear side of the molten pool (10) and is in contact with the surface of the deposition layer (12) to form a current loop.
The laser additive device according to any one of claims 1-6, further comprising an information acquisition system; the information acquisition system comprises a high-speed camera (16), a lighting device (20), and a spectrometer probe (21) , Spectrometer (18) and synchronization signal generator (17); the high-speed camera (16) is located near the molten pool (10), and the spectrometer probe (21) is used to measure the plasma generated in the molten pool (10) Body / metal vapor (19), the spectrometer (18) is used to collect data measured by the spectrometer probe (21); the high-speed camera (16), lighting device (20) and spectrometer (18) and synchronization signals The generator (17) is connected to ensure that when the high-speed camera (16) collects images, the lighting device (20) is in an illuminated state, and that the high-speed camera (16) and the spectrometer (18) collect data at the same time.
The laser additive device according to any one of claims 1-6, further comprising a high-frequency induction heating system; the high-frequency induction heating system comprises a high-frequency induction heating coil (11) and high-frequency induction heating A power source (14), the high-frequency induction heating coil (11) is located at the bottom of the substrate (13), the high-frequency induction heating power source (14) and the high-frequency induction heating coil (11) are connected for heating the substrate ( 13).
The method for additive manufacturing of a laser additive device according to claim 1, further comprising the following steps:

The rotating beam laser device outputs a continuous continuous laser to melt and deposit the filaments on the surface of the substrate (13);

Input a high-frequency short-pulse laser into the molten pool (10) through a high-frequency short-pulse laser device;
The method for additive manufacturing of a laser additive device according to claim 9, further comprising the following steps:

Electromagnetic generation inside the molten pool (10): By forming a current loop between the filament and the molten pool (10), a strong electromagnetic force is directly generated inside the molten pool (10);

Preheating the substrate (13): preheating the substrate (13) through a high-frequency induction heating system;

On-line monitoring of the quality of the deposited layer (12): real-time detection of the plasma / metal vapor (19) generated in the molten pool (10) through an information acquisition system, judgment of the quality of the deposited layer (12), and control of the computer (15) based on the judgment result Dynamically adjust the parameters of the rotating beam laser device, high-frequency short-pulse laser device and auxiliary current device.