Short pulse laser milling process for laser deposition part

Abstract

The invention relates to a short pulse laser milling process for a laser deposition part, which belongs to the technical field of micro-nano machining and comprises the following steps: S1, material preparation: selecting a 316 stainless steel plate with the size of 200mm * 200mm * 16mm as a deposition substrate, and ensuring that the surface of the substrate is clean and free of oil stain; s2, a laser deposition process and equipment configuration: selecting a RofinFL040 kilowatt-level fiber laser; s3, a laser cleaning process; s4, carrying out a laser milling process; s5, recording and analyzing data; s6, analyzing a process parameter optimization response surface; s7, result feedback: according to an experimental result, adjusting process parameters to optimize a milling effect; and S8, stability verification and application. According to the method, the material removal rate and the surface quality in the laser milling process can be effectively improved, and the thickness of a recast layer is reduced, so that the bottleneck of a traditional machining method in high-complexity and high-precision part manufacturing is overcome, and the method has wide applicability.

Description

Technical Field

[0001] The invention relates to the technical field of laser processing, and in particular to a short-pulse laser milling process for laser deposited parts. Background Art

[0002] Inconel 718 nickel-based superalloy is widely used in hot end parts of aero engines and industrial gas turbines due to its excellent strength, corrosion resistance and oxidation resistance above 600℃, showing broad application prospects in aerospace and other fields. Traditional manufacturing methods such as casting and forging are costly and have geometric limitations, making it difficult to meet the manufacturing needs of complex parts. In recent years, the demand for lightweight and complex parts in aerospace and related industries has increased, and traditional methods have been difficult to adapt. Laser additive manufacturing technology has become an effective solution due to its high material utilization and low manufacturing cost, but it still needs to be improved in terms of part dimensional accuracy and surface quality, and post-processing processes are usually required. For complex internal surfaces and narrow internal cavity structures, subsequent mechanical processing is extremely challenging, so additive and subtractive composite manufacturing technology has gradually attracted attention. This technology combines additive manufacturing with traditional processing or high-energy beam subtractive technology.

[0003] The research on laser milling of metal materials is gradually increasing. Laser milling technology has the advantages of non-contact processing, no tool wear, high efficiency and precise control, and is suitable for manufacturing complex parts such as microchannels and cooling channels. However, the current research on laser subtraction of metal additive forming parts is still insufficient, and most of it is concentrated on mechanical processing. Therefore, conducting research on laser precision subtraction of metal additive forming parts has important scientific significance and engineering value, which can promote the development of additive and subtractive composite manufacturing technology and solve the manufacturing bottleneck problem of high-complexity and high-precision parts, especially in the field of difficult-to-process materials such as aerospace. The prospects are broad. For this reason, a short-pulse laser milling process for laser deposition parts is proposed. Summary of the invention

[0004] The present invention provides a short-pulse laser milling process for laser deposited parts, which solves the problems raised by the above-mentioned background technology. It can effectively improve the material removal rate and surface quality in the laser milling process and reduce the thickness of the recast layer, thereby overcoming the bottleneck faced by traditional processing methods in the manufacture of high-complexity and high-precision parts, and has wide applicability.

[0005] The present invention solves the above technical problems as follows: a short pulse laser milling process for laser deposited parts, the process method comprises the following steps:

[0006] S1: Select a 316 stainless steel plate with a size of 200mm×200mm×16mm as the deposition substrate, ensure that the substrate surface is clean and oil-free, use Inconel718 nickel-based alloy powder, the average particle size of the powder particles is 50-150μm, and ensure that the chemical composition of the powder meets the standards. The main components include Fe, Cr, Ni, and Nb;

[0007] S2: Use Rofin FL040 kW-class fiber laser with an output power of 4000W, a wavelength of 1070nm, and a spot diameter of 1.5mm to ensure that the cooling system of the laser operates normally to avoid overheating;

[0008] S3: Deposition parameter settings: laser power is set to 1000W, scanning speed is set to 10mm / s, powder feeding rate is 11.3g / min, and shielding gas flow rate is 15L / min;

[0009] S4: Fix the 316 stainless steel substrate on the workbench of the deposition equipment, turn on the laser, and perform layer-by-layer deposition. The thickness of each layer should be controlled between 0.5-1mm until an Inconel718 laser-deposited part with a final size of 17mm×38mm×8mm is formed;

[0010] S5: Use short pulse laser for cleaning, ensure operation in an inert gas environment. Nitrogen or helium can be used as protective gas to prevent oxidation;

[0011] S6: Focus the laser beam on the surface of the deposited part and move it evenly to remove the powder and oxide layer on the surface to achieve a surface roughness Ra of 12.09 μm;

[0012] S7: Laser milling is performed on the surface of the Inconel718 deposited part to mill out multiple microchannels with a size of 1mm×24mm. The local melting and removal of the material are achieved by adjusting the position and movement speed of the laser beam;

[0013] S8: Record the process parameters during milling, including laser power, scanning speed, filling spacing and number of scans, and measure and evaluate the material removal rate (MRR), surface roughness (Ra) and thickness of the recast layer of the milled parts. Detailed observation and characterization can be performed using laser confocal microscopy and scanning electron microscopy (SEM).

[0014] Based on the above technical solution, the present invention can also be improved as follows.

[0015] Furthermore, in S3, when the cleaning parameters are set, they can be adjusted between 50-100 W according to the cleaning needs, and a short pulse laser is used, the pulse width can be set to 72 ns, and the repetition frequency can be set to 100 kHz.

[0016] Furthermore, in S5, RFL-P100M short pulse laser is used for milling.

[0017] Furthermore, in S4, the parameters of the milling process are set as pulse width: 72ns, single pulse energy: 1mJ, maximum power: 100W, focus spot diameter: 70μm, and repetition frequency: 100kHz.

[0018] Further, in S4, the milling parameters are set as follows: the scanning speed is set between 4000-6000 mm / s, and the recommended initial setting is 5000 mm / s; the filling spacing is set to 0.01-0.03 mm, and 0.02 mm can be selected initially; the number of scans is set to 400-800 times, and 600 times can be selected initially.

[0019] Furthermore, in S8, the response surface analysis uses Design-Expert V8.0.6 software to perform statistical analysis and optimize process parameters to ensure the best material removal rate, surface quality and recast layer thickness.

[0020] The beneficial effects of the present invention are as follows: the present invention provides a short pulse laser milling process for laser deposited parts, which has the following advantages:

[0021] 1. Based on response surface analysis, a mathematical model between laser milling parameters material removal rate, surface quality and recast layer was established. Variance analysis and model verification proved that the established model can be used for the prediction of microchannel morphology and process parameter optimization;

[0022] 2. For material removal rate, the number of scans has the most significant effect, followed by the scanning speed. The change of the filling spacing alone has no significant effect on it. However, the interaction between the filling spacing, the scanning speed and the number of scans has an effect on the material removal rate. For surface quality and recast layer, the most significant factor is the scanning speed. The higher the scanning speed, the less recast layer, the fewer defects such as pits and pores at the bottom of the microchannel, and the better the surface quality.

[0023] 3. Through the multi-objective optimization method, the laser milling process parameters are optimized while ensuring the minimum surface roughness and thickness of the recast layer and the material removal rate. The optimization results are compared with the experimental results, and the optimal process parameters for milling microchannels are: scanning speed 6000mm / s, filling spacing 0.02mm, and scanning times 800 times. Under this parameter, the depth of the microgroove is 921.36, the width is 945.84μm, the bottom surface roughness is 4.97μm, and the left and right wall roughnesses are 2.71μm and 8.49μm respectively; the average thickness of the bottom reconstructed layer is 8.44μm, the thickness of the left and right wall recast layers are 2.97μm and 10.84μm respectively, and the material removal rate is 2.37mm3 / min.

[0024] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. The specific implementation of the present invention is given in detail by the following embodiments and their accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 A schematic diagram of a process flow of a short-pulse laser milling process for a laser deposited part provided by an embodiment of the present invention;

[0027] Figure 2 A schematic diagram of the principle of a short-pulse laser milling process for a laser deposited part provided by an embodiment of the present invention;

[0028] Figure 3 A schematic diagram of measuring surface roughness and recast layer in a short pulse laser milling process of a laser deposited part provided by an embodiment of the present invention;

[0029] Figure 4 A diagram showing the influence of process parameters on MRR in a short pulse laser milling process for a laser deposited part provided by one embodiment of the present invention;

[0030] Figure 5 A Vickers hardness diagram of a microchannel along a cross section under optimal milling parameters in a short-pulse laser milling process for a laser deposited part provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The following is combined with Figure 1-5 The principles and features of the present invention are described, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. In the following paragraphs, the present invention is described in more detail by way of example with reference to the accompanying drawings. The advantages and features of the present invention will become clearer according to the following description and claims. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, and are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention.

[0032] It should be noted that when a component is referred to as being "fixed to" another component, it may be directly on the other component or there may also be a component centered. When a component is considered to be "connected to" another component, it may be directly connected to the other component or there may also be a component centered. When a component is considered to be "set on" another component, it may be directly set on the other component or there may also be a component centered. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0034] like Figure 1-5 As shown, the present invention provides a short pulse laser milling process for laser deposited parts, comprising the following steps;

[0035] S1: Material preparation: Select a 316 stainless steel plate with a size of 200mm×200mm×16mm as the deposition substrate, and ensure that the substrate surface is clean and free of oil stains; Powder material preparation: Use Inconel718 nickel-based alloy powder, and confirm that the average particle size of the powder particles is 50-150μm. Ensure that the chemical composition of the powder meets the standards, and the main components include Fe, Cr, Ni, Nb, etc., and meet the following specifications: Cr: 18.72%, Ni: 51.09%, Nb: 5.43%, Mo: 2.88%;

[0036] S2: Laser deposition process, equipment configuration: Rofin FL040 kW-class fiber laser with an output power of 4000W, a wavelength of 1070nm, and a spot diameter of 1.5mm is selected to ensure the normal operation of the laser's cooling system to avoid overheating;

[0037] Deposition parameter settings:

[0038] Laser power: 1000W

[0039] Scanning speed: 10mm / s

[0040] Powder feeding rate: 11.3g / min

[0041] Protective gas flow: 15L / min

[0042] Deposition process: fix the 316 stainless steel substrate on the workbench of the deposition equipment, turn on the laser, and perform layer-by-layer deposition. The thickness of each layer is controlled between 0.5-1mm until the final size of the Inconel718 laser-deposited part with a size of 17mm×38mm×8mm is formed.

[0043] S3: Laser cleaning process

[0044] Equipment configuration: Use short pulse laser for cleaning, ensure operation in an inert gas environment. Nitrogen or helium can be used as protective gas to prevent oxidation.

[0045] Cleaning parameter settings:

[0046] Laser power: Set between 50-100W according to cleaning needs.

[0047] Pulse width: 72ns

[0048] Repetition frequency: 100kHz

[0049] Cleaning process: Focus the laser beam on the surface of the deposited part and move it evenly to remove the powder and oxide layer on the surface, ensuring that the surface roughness Ra is 12.09μm;

[0050] S4: Laser milling process

[0051] Equipment configuration: Use RFL-P100M short pulse laser for milling, the specific parameters are: pulse width: 72ns, single pulse energy: 1mJ, maximum power: 100W, focus spot diameter: 70μm, repetition frequency: 100kHz

[0052] Milling parameter settings:

[0053] Scanning speed: set between 4000-6000mm / s, initially set to 5000mm / s;

[0054] Filling spacing: set to 0.01-0.03mm, initially select 0.02mm;

[0055] Scan times: set to 400-800 times, initially select 600 times;

[0056] Milling process:

[0057] Laser milling was performed on the surface of the Inconel718 deposit to mill out multiple microchannels with a size of 1mm×24mm. The local melting and removal of the material was achieved by adjusting the position and movement speed of the laser beam;

[0058] S5: Data Recording and Analysis

[0059] Record the process parameters during milling, including laser power, scanning speed, filling spacing and number of scans;

[0060] Measuring and evaluating the properties of milled parts:

[0061] Material Removal Rate (MRR)

[0062] Surface roughness (Ra)

[0063] Thickness of recast layer

[0064] Equipment used: Laser confocal microscopy and scanning electron microscopy (SEM) were used for detailed observation and characterization to record the 3D morphology and surface features of the microchannels;

[0065] S6: Response surface analysis for process parameter optimization: Design-Expert V8.0.6 software was used for statistical analysis to optimize process parameters to ensure the best material removal rate, surface quality, and recast layer thickness.

[0066] S7: Result feedback: According to the experimental results, the process parameters are adjusted to optimize the milling effect, with special attention paid to the interactive effects of scanning speed and filling spacing to maximize machining efficiency and surface quality;

[0067] S8: Stability verification and application: Conduct multiple tests to verify the stability of the process to ensure that the expected surface quality and performance requirements can be achieved after each milling. Apply the final prepared Inconel718 laser deposited parts to actual scenarios to evaluate their performance and reliability to verify the practical application value of the process.

[0068] Through the above implementation plan, the short-pulse laser milling process of Inconel718 laser deposited parts can be effectively realized, the processing accuracy and performance of parts can be improved, and the high requirements of aerospace and other fields can be met.

[0069] Figure 1 (a) Short pulse laser milling system; (b) Short pulse laser spot overlap; (c) Schematic diagram of short pulse laser milling;

[0070] Figure 2 (a) surface roughness; (b) recast layer;

[0071] Figure 3 (a) The influence of a single factor on MRR; (b) The influence of AB interaction on MRR; (c) The influence of AC interaction on MRR; (d) The influence of BC interaction on MRR;

[0072] It should be noted that, in this document, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Contents not described in detail in this specification belong to the prior art known to professionals in the field.

[0073] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in the industry can smoothly implement the present invention as shown in the drawings and described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with the profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the technical solution of the present invention.

Claims

1. A short pulse laser milling process for laser deposited parts, characterized in that: The process comprises the following steps: S1: Select a 316 stainless steel plate with a size of 200mm×200mm×16mm as the deposition substrate, ensure that the substrate surface is clean and oil-free, use Inconel718 nickel-based alloy powder, the average particle size of the powder particles is 50-150μm, and ensure that the chemical composition of the powder meets the standards. The main components include Fe, Cr, Ni, and Nb; S2: Use Rofin FL040 kW-class fiber laser with an output power of 4000W, a wavelength of 1070nm, and a spot diameter of 1.5mm to ensure that the cooling system of the laser operates normally to avoid overheating; S3: Deposition parameter settings: laser power is set to 1000W, scanning speed is set to 10mm / s, powder feeding rate is 11.3g / min, and shielding gas flow rate is 15L / min; S4: Fix the 316 stainless steel substrate on the workbench of the deposition equipment, turn on the laser, and perform layer-by-layer deposition. The thickness of each layer should be controlled between 0.5-1mm until an Inconel718 laser-deposited part with a final size of 17mm×38mm×8mm is formed; S5: Use short pulse laser for cleaning, ensure operation in an inert gas environment. Nitrogen or helium can be used as protective gas to prevent oxidation; S6: Focus the laser beam on the surface of the deposited part and move it evenly to remove the powder and oxide layer on the surface to achieve a surface roughness Ra of 12.09 μm; S7: Laser milling is performed on the surface of the Inconel718 deposited part to mill out multiple microchannels with a size of 1mm×24mm. The local melting and removal of the material are achieved by adjusting the position and movement speed of the laser beam; S8: Record the process parameters during milling, including laser power, scanning speed, filling spacing and number of scans, and measure and evaluate the material removal rate (MRR), surface roughness (Ra) and thickness of the recast layer of the milled parts. Detailed observation and characterization can be performed using laser confocal microscopy and scanning electron microscopy (SEM).

2. According to claim 1, a short pulse laser milling process for laser deposited parts is characterized in that: In S3, when setting the cleaning parameters, according to the cleaning needs, it can be adjusted between 50-100W, using short pulse laser, the pulse width can be set to 72ns, and the repetition frequency is 100kHz.

3. The short pulse laser milling process for laser deposited parts according to claim 1, characterized in that: In S5, the milling is performed using an RFL-P100M short pulse laser.

4. The short pulse laser milling process for laser deposited parts according to claim 1, characterized in that: In S4, the parameters of the milling process are set as pulse width: 72ns, single pulse energy: 1mJ, maximum power: 100W, focus spot diameter: 70μm, and repetition frequency: 100kHz.

5. The short pulse laser milling process for laser deposited parts according to claim 1, characterized in that: In S4, the milling parameter settings are: the scanning speed is set between 4000-6000 mm / s, and the recommended initial setting is 5000 mm / s; the filling spacing is set to 0.01-0.03 mm, and 0.02 mm can be selected initially; the number of scans is set to 400-800 times, and 600 times can be selected initially.

6. The short pulse laser milling process for laser deposited parts according to claim 1, characterized in that: In S8, the response surface analysis uses Design-Expert V8.0.6 software to perform statistical analysis and optimize process parameters to ensure the best material removal rate, surface quality and recast layer thickness.

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