A method and apparatus for additive manufacturing nitridation enhancement and nitrided additive

Abstract

The application discloses a kind of additive manufacturing nitriding enhancement method and device and nitriding additive, the method includes using continuous heat source to form molten pool and local high temperature field on substrate under nitrogen atmosphere;Metal powder is sprayed to molten pool through local high temperature field, while introducing pulse laser to form molten pool oscillation, and nitriding layer is punched into molten pool inside, to realize additive manufacturing nitriding enhancement.Compared with additive manufacturing technology, introduce an additional pulse laser to form molten pool oscillation and punch the nitriding layer falling to the surface of molten pool into the molten pool, break through the problem that original nitriding layer depth is limited.And combined with mechanical arm to build double laser composite additive manufacturing platform, in one-dimensional, curved surface and three-dimensional and other complex working conditions, real-time nitriding is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a method and device for nitriding enhancement in additive manufacturing, and a nitriding additive. Background Art

[0002] With the rapid development of industry, the performance of metal components in various large aircraft, ships, and automobiles needs to meet higher requirements. Researchers have gradually shifted their research focus to improving the mechanical properties of metal components, such as hardness, wear resistance, and corrosion resistance.

[0003] At present, traditional methods include carburizing, nitriding, carbonitriding and other heat treatment processes, which improve the surface properties by forming carbon-rich or nitrogen-hardened layers of varying thickness on the surface of solid metal parts. However, the process is complex, the bonding strength between the surface coating and the substrate is low, and it is prone to falling off. In addition, the depth of the surface coating is limited, which is a technical problem that needs to be solved urgently. Summary of the Invention

[0004] In order to solve the problems existing in the prior art, the present invention forms a local high-temperature field during the additive manufacturing process, utilizes protective nitrogen gas to perform real-time nitriding in the air with the falling metal powder, and simultaneously introduces an additional pulsed laser to form a molten pool oscillation to drive the nitride layer that falls to the surface of the molten pool into the interior of the molten pool. Due to the intensified convection inside the molten pool, the uniform nitriding effect is further improved. The problem of the original limited depth of the nitriding layer is overcome by applying laser shock to the molten pool to assist in the nitriding process. In addition, a dual-laser composite additive manufacturing platform is built in combination with a robotic arm to enhance nitriding in real time under complex working conditions such as one-dimensional, curved and three-dimensional conditions, thereby achieving flexible additive manufacturing of metal parts.

[0005] In order to achieve the above object, the present invention provides a method for nitriding enhancement in additive manufacturing, comprising:

[0006] In a nitrogen atmosphere, a molten pool and a local high-temperature field are formed on the substrate through heat treatment, and a nitride layer is formed on the surface of the molten pool;

[0007] The metal powder is sprayed into the molten pool through a local high-temperature field. At this time, the metal powder is nitrided. At the same time, a pulsed laser is introduced to form molten pool oscillation, and the nitrided metal powder and the nitrided layer are driven into the molten pool to achieve additive manufacturing nitriding enhancement.

[0008] Furthermore, the nitrogen atmosphere is provided by nitrogen at a flow rate of 5 to 10 L / min, wherein the nitrogen flow rate should not be too large. If it exceeds 10 L / min, the metal powder may be blown away and cannot be formed.

[0009] Furthermore, the formation of a molten pool and a local high-temperature field on the substrate through heat treatment is achieved by irradiating the substrate with a continuous heat source.

[0010] Furthermore, the temperature of the local high temperature field is higher than 1000°C.

[0011] Furthermore, the powder feeding rate of the metal powder is 1 to 3 g / min, wherein the powder feeding rate should not be too large, and exceeding 3 g / min may cause powder accumulation;

[0012] The main components of the metal powder include one or both of Ti and Al;

[0013] The substrate material includes stainless steel, 45# steel or titanium alloy.

[0014] Furthermore, the parameters of the pulse laser are: pulse width 0-1 ms, pulse energy 0.1 mJ-100 J, and repetition frequency 1 Hz-10 MHz.

[0015] The present invention also provides a device for implementing the above method, comprising a dual-laser composite additive manufacturing platform and a moving component;

[0016] The dual-laser composite additive manufacturing platform consists of a protective gas circuit, a pulsed laser, a scraper pneumatic powder feeder and a continuous laser;

[0017] A first fixing block and a second fixing block are provided on both sides of the continuous laser, the first fixing block is used to fix the pulse laser on the continuous laser, and the second fixing block is used to fix the protective gas path on the continuous laser;

[0018] A scraper pneumatic powder feeder is fixed to the laser outlet end of the continuous laser;

[0019] The moving component includes a mechanical arm and a servo drive motor, and the arm end of the mechanical arm is fixed to the continuous laser;

[0020] The servo drive motor is used to drive the movement of the robotic arm, and the robotic arm is used to drive the continuous laser to move, thereby driving the scraper pneumatic powder feeder, the protective gas circuit and the pulse laser to move together.

[0021] Furthermore, the robotic arm is a five-axis linkage robotic arm.

[0022] Furthermore, the continuous laser includes a solid laser, a semiconductor laser or a continuous laser, etc., which can provide a local temperature field higher than 1000°C.

[0023] Furthermore, the pulse laser includes one of a nanosecond laser, a microsecond laser or a millisecond laser.

[0024] The present invention also provides a nitrided additive material, which is prepared using the above method.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) Compared with traditional nitriding technology, nitrogen is used as a protective gas in the additive manufacturing process to nitride the falling metal powder in real time in the air;

[0027] (2) Compared with additive manufacturing technology, an additional pulsed laser is introduced to form a molten pool oscillation, which drives the nitride layer that falls to the surface of the molten pool into the interior of the molten pool, breaking through the problem of limited depth of the original nitride layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 The figure shows a schematic structural diagram of the nitriding enhancement device for additive manufacturing in Example 1 of the present invention;

[0030] Figure 2 The working path of the five-axis linkage robot arm of the present invention is shown;

[0031] Figure 3 The following is a comparison of the morphology and Vickers hardness of metal parts manufactured by AlCrCoFeNiTi metal additive manufacturing on the surface of 45 steel substrate in Example 2 of the present invention and Comparative Example 1; Figure 3 (a) is the product of Comparative Example 1; Figure 3 (b) is the product obtained in Example 2;

[0032] Description of reference numerals:

[0033] 1. Robotic arm; 2. Servo drive motor; 3. Scraper pneumatic powder feeder; 4. Continuous laser; 5. Shielding gas line; 6. Pulsed laser. DETAILED DESCRIPTION

[0034] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to form one or more new numerical ranges, and these numerical ranges should be considered to be specifically disclosed in the present invention.

[0035] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the specific embodiments of the present invention and the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0036] Example 1

[0037] like Figure 1 As shown, an additive manufacturing nitriding enhancement device includes a dual-laser composite additive manufacturing platform and moving parts; the dual-laser composite additive manufacturing platform consists of a protective gas circuit 5, a pulse laser 6, a scraper pneumatic powder feeder 3 and a continuous laser 4; the protective gas circuit 5 is used to provide nitrogen to form a nitrogen atmosphere; the pulse laser 6 is used to introduce pulse laser to form a molten pool oscillation, and to drive nitride metal powder and a nitride layer into the molten pool; the scraper pneumatic powder feeder 3 is used to spray metal powder into the molten pool through a local high-temperature field; the continuous laser 4 is used to provide continuous laser to form a continuous heat source to form a molten pool and a local high-temperature field on the substrate.

[0038] A first fixing block and a second fixing block are provided on both sides of the continuous laser 4. The first fixing block is used to fix the pulse laser 6 on the continuous laser 4, and the second fixing block is used to fix the protective gas path 5 on the continuous laser 4. A scraper pneumatic powder feeder 3 is fixed to the laser outlet end of the continuous laser 4.

[0039] The moving part includes a robotic arm 1 and a servo drive motor 2, and the arm end of the robotic arm 1 is fixed to the continuous laser 4; the servo drive motor 2 is used to drive the robotic arm 1 to move, and the robotic arm 1 is used to drive the continuous laser 4 to move, thereby driving the scraper pneumatic powder feeder 3, the protective gas circuit 5 and the pulse laser 6 to move together.

[0040] Preferably, the continuous laser 4 is a 1kW fiber continuous laser.

[0041] Preferably, the pulse laser 6 is a nanosecond pulse laser.

[0042] Preferably, the robot arm 1 is a five-axis linkage robot arm, such as Figure 3 As shown, based on the flexibility of the five-axis linkage robotic arm, the dual-laser composite additive manufacturing platform built on it can enhance nitriding in real time under complex working conditions such as one-dimensional, curved and three-dimensional, thereby achieving the purpose of flexible additive manufacturing of parts.

[0043] For the main raw materials and related parameters involved in Examples 2 to 4, please refer to Table 1.

[0044] Table 1 Main raw materials and related parameters involved in Examples 2 to 4

[0045]

[0046] Example 2

[0047] A method for nitriding enhancement in additive manufacturing is provided, based on the apparatus of Example 1, wherein the metal powder is the widely used AlCrCoFeNiTi metal powder with a particle size of 20 to 50 μm and good fluidity, and the experimental substrate is the common 45 steel, comprising the following steps:

[0048] Step 1: Fix the 45# steel substrate; add the AlCrCoFeNiTi metal powder to be manufactured into the scraper pneumatic powder feeder 3, and set the powder feeding rate to 2g / min; set the power of the fiber continuous laser to 1000W and the scanning pitch to 0.8mm; set the nitrogen flow rate in the protective gas path 5 to 10L / min; set the pulse width of the nanosecond pulse laser to 10ns, the pulse energy to 0.5J, and the repetition rate to 20Hz; set the processing path and scanning speed of the five-axis linkage robot to 4mm / s;

[0049] Step 2: Simultaneously activate the five-axis linkage robot, fiber continuous laser, shielding gas circuit 5, nanosecond pulsed laser, and scraper pneumatic powder feeder. At this point, shielding gas circuit 5 creates a nitrogen atmosphere on the substrate surface. The fiber continuous laser irradiates the substrate, forming a molten pool and a localized high-temperature field, while a nitride layer forms on the surface of the molten pool. The scraper pneumatic powder feeder 3 sprays AlCrCoFeNiTi metal powder through the localized high-temperature field into the molten pool, nitriding the metal powder. Simultaneously, a pulsed laser is introduced to oscillate the molten pool, driving the nitrided metal powder and nitride layer into the molten pool. The five-axis linkage robot completes the pre-set processing path, completing the additive manufacturing and nitridation enhancement of AlCrCoFeNiTi metal on the 45-grade steel substrate.

[0050] Example 3

[0051] A method for nitriding enhancement in additive manufacturing is provided, based on the apparatus of Example 1, wherein the metal powder is the widely used AlCrCoFeNi metal powder with a particle size of 20 to 50 μm and good fluidity, and the experimental substrate is the common 45 steel, comprising the following steps:

[0052] Step 1: Secure the 45# steel substrate; add the AlCrCoFeNi metal powder to be manufactured into the scraper pneumatic powder feeder 3, and set the powder feed rate to 1.5g / min; set the fiber continuous laser power to 900W and the scanning pitch to 1mm; set the nitrogen flow rate in the protective gas path 5 to 9L / min; set the nanosecond pulse laser pulse width to 10ns, the pulse energy to 1J, and the repetition rate to 15Hz; set the five-axis linkage robot arm processing path and scanning speed to 6mm / s;

[0053] Step 2: Simultaneously activate the five-axis linkage robot, fiber continuous laser, shielding gas circuit 5, nanosecond pulsed laser, and scraper pneumatic powder feeder. At this point, shielding gas circuit 5 creates a nitrogen atmosphere on the substrate surface. The fiber continuous laser irradiates the substrate, forming a molten pool and a localized high-temperature field, while a nitride layer forms on the surface of the molten pool. The scraper pneumatic powder feeder 3 sprays AlCrCoFeNi metal powder through the localized high-temperature field into the molten pool, nitriding the metal powder. Simultaneously, a pulsed laser is introduced to oscillate the molten pool, driving the nitrided metal powder and nitride layer into the molten pool. The five-axis linkage robot completes the pre-set processing path, completing the additive manufacturing and nitridation enhancement of AlCrCoFeNi metal on the 45-grade steel substrate.

[0054] Example 4

[0055] A method for nitriding enhancement in additive manufacturing is provided, based on the apparatus of Example 1, wherein the metal powder is the widely used CrCoFeNi metal powder with a particle size of 20 to 50 μm and good fluidity, and the experimental substrate is the common 45 steel, comprising the following steps:

[0056] Step 1: Secure the 45# steel substrate; add the CrCoFeNi metal powder to be manufactured into the scraper pneumatic powder feeder 3, and set the powder feed rate to 1g / min; set the fiber continuous laser power to 800W and the scanning pitch to 1.5mm; set the nitrogen flow rate in the protective gas path 5 to 8L / min; set the nanosecond pulse laser pulse width to 10ns, pulse energy to 3J, and repetition rate to 10Hz; set the five-axis linkage robot arm processing path and scanning speed to 10mm / s;

[0057] Step 2: Simultaneously activate the fixed five-axis linkage robot arm, fiber continuous laser, shielding gas circuit 5, nanosecond pulse laser, and scraper pneumatic powder feeder. At this point, shielding gas circuit 5 creates a nitrogen atmosphere on the substrate surface. The fiber continuous laser irradiates the substrate to form a molten pool and a localized high-temperature field, while a nitride layer forms on the surface of the molten pool. The scraper pneumatic powder feeder 3 sprays CrCoFeNi metal powder through the localized high-temperature field into the molten pool, where the metal powder is nitrided. Simultaneously, a pulsed laser is introduced to oscillate the molten pool, driving the nitrided metal powder and nitride layer into the molten pool. The five-axis linkage robot arm completes the preset processing path, completing the additive manufacturing and nitridation enhancement of CrCoFeNi metal on the 45-grade steel substrate.

[0058] Comparative Example

[0059] An additive manufacturing method is based on the apparatus of Example 1 (the nanosecond pulse laser is turned off and the gas in the shielding gas path 5 is replaced with argon). The metal powder uses widely used AlCrCoFeNiTi metal powder with a particle size of 20 to 50 μm and good fluidity. The experimental substrate uses common 45 steel. The method includes the following steps:

[0060] Step 1: Secure the 45# steel substrate; add the AlCrCoFeNiTi metal powder to be manufactured into the scraper pneumatic powder feeder 3, and set the powder feed rate to 2g / min; set the fiber continuous laser power to 1000W and the scanning pitch to 0.8mm; set the argon flow rate in the protective gas path 5 to 10L / min; set the processing path and scanning speed of the five-axis linkage robot arm to 4mm / s;

[0061] Step 2: Simultaneously activate the five-axis robotic arm, fiber CW laser, shielding gas circuit 5, and scraper-type pneumatic powder feeder. At this point, shielding gas circuit 5 creates an argon atmosphere on the substrate surface. The fiber CW laser irradiates the substrate, forming a molten pool and a localized high-temperature field. The pneumatic powder feeder 3 sprays AlCrCoFeNiTi metal powder through the localized high-temperature field into the molten pool. The five-axis robotic arm completes the pre-set machining path, completing the additive manufacturing of AlCrCoFeNi metal on the 45-gauge steel substrate.

[0062] Figure 3 The following is a comparison of the morphology and Vickers hardness of metal parts manufactured by AlCrCoFeNiTi metal additive manufacturing on the surface of 45# steel substrate in Example 1 of the present invention and Comparative Example 1. Figure 3 (a) is the product of Comparative Example 1; Figure 3 (b) is the product obtained in Example 2.

[0063] Comparison shows that the substrate surface of the product produced in Comparative Example 1 appears silvery white, with no nitride layer formed. In contrast, the substrate surface of the product produced in Example 1 appears yellowish brown, indicating that nitrides have been fully formed in the metal component. Vickers hardness testing of three samples each from Comparative Example 1 and Example 2 revealed that, under the same compressive load of 300g, the average Vickers hardness of the product in Comparative Example 1 was 745.1 HV. 0.3 The mechanical properties of the product obtained in Example 2 are improved, and its average Vickers hardness is 939.7HV 0.3 .

[0064] In summary, the present invention forms a local high-temperature field during the additive manufacturing process, utilizes protective nitrogen gas to perform real-time nitriding with the falling metal powder in the air, and simultaneously introduces an additional pulsed laser to form a molten pool oscillation to drive the nitride layer that falls to the surface of the molten pool into the interior of the molten pool. Due to the intensified convection inside the molten pool, the uniform nitriding effect is further improved. The problem of the original limited depth of the nitrided layer is overcome by applying laser shock to the molten pool to assist in the nitriding process. In addition, a dual-laser composite additive manufacturing platform is built in combination with a robotic arm to enhance nitriding in real time under complex working conditions such as one-dimensional, curved and three-dimensional conditions, thereby achieving flexible additive manufacturing of metal parts.

[0065] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A nitriding enhancement method for additive manufacturing, characterized in that: include, In a nitrogen atmosphere, a molten pool and a local high-temperature field are formed on the substrate through heat treatment, and a nitride layer is formed on the surface of the molten pool; The metal powder is sprayed into the molten pool through a local high temperature field. At this time, the metal powder is nitrided. At the same time, a pulsed laser is introduced to form molten pool oscillation, and the nitrided metal powder and nitrided layer are driven into the molten pool to achieve additive manufacturing nitriding enhancement. The molten pool and the local high-temperature field are formed by continuous laser irradiation; The temperature of the local high temperature field is higher than 1000°C; The metal powder feeding rate is 1-3 g / min; The metal powder contains one or both of Ti and Al; The substrate material includes stainless steel, 45 steel or titanium alloy; The parameters of the pulse laser are: pulse width 0-1 ms, pulse energy 0.1 mJ-100 J, and repetition frequency 1 Hz-10 MHz.

2. The additive manufacturing nitriding enhancement method according to claim 1, characterized in that: The nitrogen atmosphere was provided by nitrogen gas at a flow rate of 5 to 10 L / min.

3. A nitriding additive, characterized in that: The method according to claim 1 or 2 is used for preparation.

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