Quantitative assessment of structural and compositional colors induced by femtosecond laser: A case study on 301LN stainless steel surface

• Published in: Applied surface science 2019-08, Vol.484, p.655-662
• Main Authors: Shi, Xinying, Huang, Zhongjia, Laakso, Miku J., Niklaus, Frank, Sliz, Rafal, Fabritius, Tapio, Somani, Mahesh, Nyo, Tun, Wang, Xiao, Zhang, Meng, Wang, Gang, Kömi, Jukka, Huttula, Marko, Cao, Wei
• Format: Article
• Language: English
• Subjects: Chemical analysis; Chemical state analysis; Color; Compositional color; Femtosecond laser machining; Femtosecond laser marking; Femtosecond lasers; Laser coloration; Marking machines; Microalloyed steel; Periodic surface structures; Quantitative assessments; Quantitative determinations; Quantitative separation; State-of-the-art techniques; Structural color; Structural metals
• ISSN: 0169-4332; 1873-5584; 1873-5584
• DOI: 10.1016/j.apsusc.2019.04.147

The topic of durable coloration and passivation of metal surfaces using state-of-the-art techniques has gained enormous attention and devotion with unremitting efforts of researchers worldwide. Although femtosecond laser marking has been performed on many metals, the related coloration mechanisms are mainly referred to structural colors produced by the interaction of visible light with periodic surface structures. Yet, general quantitative determination of the resulting colors and their origins remain elusive. In this work, we realized quantitative separations of structural colors and compositional pigmentary colors on 301LN austenitic stainless steel surfaces that were treated by femtosecond laser machining. The overall color information was extracted from surface reflectance, with structural color given by numerical simulations, and oxide compositions by chemical state analysis. It was shown that the laser-induced apparent colors of 301LN steel surfaces were combinations of structural and compositional colorations, with the former dominating the angular response and the latter setting up the brownish bases. In addition to the quantification of colors, the analysis method in this work may be useful for the generation and specification of tailored color palettes for practical coloration on metal surfaces by femtosecond laser marking. [Display omitted] •Iridescent colors were successfully generated on 301LN stainless steel surfaces by using femtosecond laser irradiation.•Chemical compositions on steel surface and the resulting colors were calculated by quantitative XPS analysis.•The laser coloration mechanism was confirmed as the combination of structural and compositional colors.