摘要
针对涂层或镀层金属的激光着色技术以其广泛的应用性和显著优点而备受关注。基于纳秒光纤激光设备,研究了氮化钛镀层不锈钢金属板表面图案的激光直写技术及成色机理。研究了激光参数对金属表面颜色的影响规律,制备了复杂彩色图像,并利用光学观测、能谱分析及光谱分析等手段深入研究了颜色成色机理。结果表明:随着扫描速度、激光功率及扫描间距变化,金属表面颜色表现丰富,并规律性地变化。利用增大扫描间距以及色块单元混合的方法可以获得颜色均匀清楚且较为丰富的图像,并且可以有效增大图案颜色色域,丰富图像效果。所得彩色图案各颜色的波长范围都比较宽,并且出现了相互掺杂的现象,这导致颜色的纯度和饱和度较差。绿色区域存在周期约为1μm的激光诱导表面周期性结构。能谱结果显示图案中存在Cr、Mn、Fe、Ni元素,这说明激光透过氮化钛镀层后作用在不锈钢表面并使其熔化进而向镀层渗透。
Objective In this study,we investigate the laserinduced structural coloring of titanium nitride(TiN)-coated stainless steel substrates via direct laser writing.As a noncontact surface modification method,laser processing offers several advantages over conventional coating techniques,such as ease of operation,high processing efficiency,and ecofriendliness.However,research on the laser processing of thinfilmdeposited metal surfaces is at its early stage and the color formation speed remains slow.Unlike the conventional coating technologies physically depositing film layer,the magnetron sputtering coating technology can form uniform nanoscale films on stainless steel surfaces.We use a nanosecond fiber laser to prepare coloring patterns directly onto a TiNcoated stainless steel surface,creating a distinctive structural color.Through appropriate experiments,the effects of three factors—laser scanning speed,scanning interval,and output power—on pattern colors are assessed independently.The reflectance spectra and energy spectrum of structural color pattern and temperature analysis provide insights into the interaction between the laser and stainless steel surface.The mechanism of the laserinduced structural colors on the coated stainless steel surface is identified.The structural colors are not angledependent.Methods In this study,we investigated the effects of the scanning speed,scanning interval,and output power on the sample surface while setting the other parameters as constant.We calculated and analyzed the variation trends of the pattern color with respect to these three parameters.First,by varying the scanning speed in the range of 100‒300 mm/s,we analyzed its effect on the surface structural color.Second,by setting scanning intervals of 0.02,0.05,0.07,and 0.10 mm,we observed the micronanostructures of the surface and discussed the effect of scanning intervals on the surface structural color.Next,for a fixed focal length of 156 mm,scanning speed of 100 mm/s,repetition frequency of 20 kHz,scanning interval of 0.05 mm,and an output power range of 46%‒66%(in 4%steps),the trend of the structural color changes was investigated and the effects of output power were analyzed.Based on the experimental data,we determined the parameter range of the surface structural colors.By examining the microstructure and energy spectrum of the sample surface,we investigated the mechanism of color formation.Finally,we verified the color stability.Results and Discussions First,we discuss the effect of the laser parameters on the sample surface color.At low scanning speeds,a transition from yellow to violet,then to blue,and finally to silvergray is observed,and the color transition is relatively fast.With the increase in the scanning speed,the color becomes lighter and the color transition speed decreases owing to a decrease in the total laser output energy(Fig.2).Second,at a small scanning interval,the iridescence of surface structures at a scanning interval of 0.02 mm is observed under a microscope(Fig.3).Under the conditions of the other parameters being set as constants while varying the output power,only the color brightness changes with increasing output power(Fig.4),and yellow,violet,and blue are observed.This is the reason why the nonoverlapping laser beam part reduces during pattern marking.Based on the above experiments,different colormixing techniques are used to obtain coloring patterns on the sample surface(Figs.5 and 6).Table 1 summarizes the coloring parameters obtained from the above experiments,and the reflectance spectra of the five colors are measured(Fig.7).Finally,based on the experiments,the microstructure of the sample surface is observed via scanning electron microscopy(Fig.8).According to the elemental content analysis(Table 2),the presence of Cr,Mn,Fe,and Ni in the energy spectroscopy test results confirms the laser radiation penetrating the TiN coating and interacting with the stainless steel surface,which results in the melting of the stainless steel surface and its penetration into the TiN coating(Fig.9).Thus,we conclude that the color formation on a metal surface is primarily dependent on the color of surface oxides or nitrides.Conclusions Basic structural colors are obtained via direct writing on the surface of a TiNcoated stainless steel plate using a nanosecond fiber laser.The results show that the metal surface color changes regularly with the scanning speed,scanning interval,and laser output power.The main colors are yellow,pink,blue,purple,and green.Various colormixing techniques and unique color patterning can be used to produce consistent and clear images.However,the wide range of wavelengths for each color can result in color mixing,which affects the purity and saturation.In the green region,fine patterns obtained by laser scanning are observed,particularly for the laserinduced periodic surface structures(LIPSSs)with a period of approximately 1μm.Subsequent energy spectrum analysis and temperature field calculations imply the presence of Ti,N,O,Cr,Mn,Fe,and Ni on the metal surfaces,which confirms that the laser radiation interacts with the stainless steel surface through the TiN coating,thereby melting and penetrating it.The color of the TiN coating or stainless steel surface under laser irradiation is primarily dependent on the color of surface oxides or nitrides and the LIPSS.The LIPSS occupies a smaller area than the oxide color area and is not the primary coloring mechanism that is affected by the angle or light source.
作者
魏鸿琳
张国伟
Wei Honglin;Zhang Guowei(College of Light Industry Science and Engineering,Tianjin University of Science and Technology,Tianjin 300457,China)
出处
《中国激光》
北大核心
2025年第12期323-330,共8页
Chinese Journal of Lasers
基金
天津技术创新引导专项基金(1900170024)。
关键词
激光直写
氮化钛镀层
不锈钢
结构色
成色机理
laser direct writing
titanium nitride coating
stainless steel
structural colors
coloring mechanism
