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实验中采用Ti6Al4V钛合金样件的成分如表 1所示,其物理性能参数如表 2所示。将钛合金小块(50 mm×30 mm×10 mm)依次经过400#、800#、1200#砂纸进行打磨,然后使用抛光机对其进行抛光处理,最后将抛光之后的样品放入无水乙醇中进行超声清洗。
表 1 Ti6Al4V钛合金化学成分
Table 1. Ti6Al4V titanium alloy chemical composition
element Al V Fe C N Ti mass fraction/% ≤6 ≤4 ≤0.12 ≤0.01 ≤0.09 balance -
实验中使用光纤激光打标机对样品进行加工,激光波长1064 nm,最大平均功率30 W,脉宽120 ns,光斑直径50 μm,扫描速率0 mm/s~5000 mm/s,输出光束为高斯光束。激光束的扫描移动通过控制光纤激光打标机的X/Y振镜转动实现,激光束的功率和频率由激光发生器控制,利用上述激光器在室温空气环境下开展加工试验;利用正交实验法和单因素实验法得到不同扫描速率、激光功率、扫描线间距的加工结果。对于加工后的样件,先使用超声波清洗机清洗10 min,再通过3-D显微镜和激光共聚焦显微镜对加工后的表面形貌及粗糙度值进行测量,得到最佳加工参数。最后,利用最佳加工参数加工阵列沟槽结构,验证本研究的有效性。加工区激光加工扫描路径如图 1所示。
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正交实验法可以通过部分实验获得多个因素对加工结果的影响规律,进而优选出较好的工艺参数。在本研究中,影响激光加工质量的参数较多,本文中选取激光扫描速率、激光功率、扫描线间距3个参数作为因素,每个因素设置4个水平,设计共16组实验,具体正交实验参数及测量结果如表 3所示,每组实验加工面积均为30 mm×20 mm的长方形区域,扫描加工次数均为2次;加工完成后检测加工表面形貌见图 2所示。
表 3 正交实验参数及测量结果
Table 3. Orthogonal experimental parameters and measurement results
serial number scanning speed/ (mm·s-1) laser power/W line spacing/ mm surface roughness/μm 1 500 6 0.01 2.272 2 500 12 0.025 1.953 3 500 18 0.05 15.975 4 500 24 0.1 11.000 5 1000 6 0.025 2.573 6 1000 12 0.01 1.847 7 1000 18 0.1 4.587 8 1000 24 0.05 5.237 9 1500 6 0.05 1.913 10 1500 12 0.1 4.778 11 1500 18 0.01 1.375 12 1500 24 0.025 2.565 13 2000 6 0.1 1.940 14 2000 12 0.05 6.604 15 2000 18 0.025 3.046 16 2000 24 0.01 1.398 对比第1、6、11、16组发现,当线间距为0.01 mm时,加工表面较为平整均匀,粗糙度相对较小;对比第4、7、10、13组发现,当线间距为0.1 mm时,加工表面呈现连续条状的凹槽结构,凹槽间存在明显的非加工区,材料未被连续去除,表面粗糙度相对较大。对比第1~4组和第13~16组加工形貌图发现,在速率一定的情况下,既存在较为平整的加工形貌也存在沟槽形貌,表面的凹凸度不一致,无法明确速率对加工形貌的影响规律;对比第1、5、9、13组和第4、8、12、16组加工形貌发现,当功率为6 W和24 W时,均存在平整均匀加工形貌和沟槽形貌,表面存在较大的凹凸,导致表面质量粗糙,无法明确功率对加工质量的影响规律。因此,为了明确激光功率、扫描速率、线间距对加工后表面质量的影响规律,需进一步开展单因素实验研究。
钛合金表面沟槽结构纳秒激光加工实验研究
Experimental study on nanosecond laser processing of surface groove structure of titanium alloy
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摘要: 为了在钛合金表面加工高质量的微小结构,探究不同因素对表面质量的影响规律,利用纳秒激光开展钛合金Ti6Al4V加工实验研究。通过3维显微镜和共聚焦显微镜测量了不同参数下的钛合金工件加工表面形貌,利用正交实验和单因素分析法探究扫描速率、激光功率、扫描线间距对加工形貌和粗糙度值的影响规律。结果表明,在低功率、高速率、大线间距条件下,材料去除不连续,加工表面呈现间断的凹坑结构;随着功率的增加、加工速率的降低和线间距的减小,材料去除逐渐连续,加工后材料表面质量得到明显改善;选择激光功率24 W、扫描速率2000 mm/s、线间距0.01 mm的参数在钛合金表面成功加工出宽度500 μm、深度140 μm的阵列微沟槽结构。该研究对激光加工钛合金表面微小结构具有较好的实用价值。Abstract: In order to process high-quality microstructures on the surface of titanium alloys and to investigate the influence of different factors on the surface quality, the nanosecond laser was used in the experimental research on the processing of titanium alloy Ti6Al4V. The surface morphology of titanium alloy workpieces processed under different parameters was measured by three-dimensional microscope and confocal microscope. Further, orthogonal experiments and one-way analysis of factors were used to investigate the effects of scanning speed, laser power and scanning line spacing on the processing morphology and roughness values. The results show that under the conditions of low power, high speed, and large line spacing, the material removal is discontinuous and the processed surface shows intermittent pit structure; with the increase of power, the decrease of processing speed and the reduction of line spacing, the material removal is gradually continuous and the processed surface quality is improved. The parameters of laser power 24 W, scanning speed 2000 mm/s, and line spacing 0.01 mm were selected to successfully process the array microgroove structure with a width of 500 μm and a depth of 140 μm on the surface of titanium alloy. This study has good practical value for laser processing of the surface microstructure of titanium alloys.
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Key words:
- laser technique /
- microgroove structure /
- laser ablation /
- surface topography
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表 1 Ti6Al4V钛合金化学成分
Table 1. Ti6Al4V titanium alloy chemical composition
element Al V Fe C N Ti mass fraction/% ≤6 ≤4 ≤0.12 ≤0.01 ≤0.09 balance elongation ≥8% density 4420 kg/m3 Poisson's ratio 0.31 hardness 195 HB heat conductivity 7.955 W/(m·K) specific heat 0.612 J/(g·K) 表 3 正交实验参数及测量结果
Table 3. Orthogonal experimental parameters and measurement results
serial number scanning speed/ (mm·s-1) laser power/W line spacing/ mm surface roughness/μm 1 500 6 0.01 2.272 2 500 12 0.025 1.953 3 500 18 0.05 15.975 4 500 24 0.1 11.000 5 1000 6 0.025 2.573 6 1000 12 0.01 1.847 7 1000 18 0.1 4.587 8 1000 24 0.05 5.237 9 1500 6 0.05 1.913 10 1500 12 0.1 4.778 11 1500 18 0.01 1.375 12 1500 24 0.025 2.565 13 2000 6 0.1 1.940 14 2000 12 0.05 6.604 15 2000 18 0.025 3.046 16 2000 24 0.01 1.398 -
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