激光除漆对铝合金基材表面质量的影响

Effect of Laser Paint Removal on Surface Quality of Aluminum Alloy Substrate

目的研究激光除漆后对铝合金基材表面阳极氧化膜的损伤情况。方法采用纳秒脉冲激光器对涂覆复合漆层的2A12铝合金表面进行激光清洗试验。采用超景深显微镜对清洗后表面形貌与横截面进行观察,利用扫描电子显微镜与能谱仪观察清洗后的微观形貌,并利用维氏硬度计对表面显微硬度进行检测。结果选择合适的激光参数能够完全除去复合漆层,当激光功率过高或激光扫描速度较低时,会发生过度清洗现象,清洗后表面的阳极氧化膜层发生损伤,甚至被去除的情况。在激光功率为450、400 W,扫描速度为4.5 mm/s时,清洗后表面的阳极氧化膜层发生破损;在激光功率为450、400 W,扫描速度为4 mm/s时,清洗后表面的阳极氧化膜层已经被去除。在激光功率为500 W,扫描速度为5.5 mm/s,与激光功率为450 W,扫描速度为5 mm/s时,完全去除复合漆层后的阳极氧化膜层表面的平均维氏硬度分别约为211HV与242HV,在工艺参数为450 W、4.5 mm/s时,表面平均维氏硬度约为168HV。结论在激光除漆的过程中,采用合适的激光工艺参数彻底去除漆层后,铝合金表面阳极氧化膜层的显微硬度并未受到影响。在发生过度清洗时,铝合金表面的阳极氧化膜层会发生烧蚀损伤以及弹性振动剥离。

This is an experimental and test analysis of the damage to an anodic oxide film on the surface of 2A12 aluminum alloy substrate after laser removal of the composite paint layer.The purpose of laser paint removal is to totally remove the paint layer without damaging the substrate surface.However,when excessive laser cleaning occurs,the anodic oxide film on the substrate surface is damaged.Since the anodic oxide film can be recreated,there is also a process where the laser removes the paint layer while also completely removing the oxide film,thus re-preparing the oxide film.The work aims to investigate the damage to the anodic oxide layer caused by laser paint removal and the removal process.Aluminum alloy samples were anodized and later coated with a composite paint layer.The laser power range was 500 W to 400 W,the laser scanning speed was 5.5 mm/s to 4 mm/s,the pulse width was 70 ns,and a square spot with a spot length of 1.5 mm was selected for the laser cleaning experiments.After the experiments,the surface morphology and cross-section of the cleaned samples were observed by OLYMPUS-DSX1000 super depth-of-field microscope,the cleaned surface was observed and the elemental content was measured by MIRA3 scanning electron microscope and energy spectrometer,and the microhardness of the cleaned sample surface was tested by HV-1000 Vickers hardness tester.It was found that by choosing appropriate laser parameters,the composite coating could be completely removed.When the laser power was too high or the laser scanning speed was low,over-cleaning occurred and the anodic oxide film on the cleaned surface could be damaged or even removed.With laser power of 450 W and scanning speed of 4.5 mm/s and laser power of 400 W and scanning speed of 4.5 mm/s,the anodic oxide film on the cleaned surface was damaged.At laser power of 450 W,400 W and scanning speed of 4 mm/s,the composite paint layer as well as the anodic oxide film on the specimen surface could be completely removed.The average microhardness of the anodic oxide film surface after complete removal of the composite paint layer was about 211HV and 242HV,respectively.When the laser power was 500 W and the scanning speed was 5.5 mm/s,and when the laser power was 450 W and the scanning speed was 5 mm/s,the average Vickers hardness of the cleaned sample surface was about 168HV at laser parameters of 450 W and 4.5 mm/s.The microhardness of the surface anodized film is not affected during the laser removal of the composite paint layer,which can be completely removed by a laser process with suitable parameters.The anodic oxide film can be completely removed at high laser power or low scanning speed.It has also been found that over-cleaning can cause ablation damage,and elastic vibrational stripping of anodized film on aluminum alloy surfaces.When the anodized film is completely removed,the microhardness of the surface of the aluminum alloy substrate is similar to that of the raw material surface,and no hardening layer is produced.