Product Code: ICA13_M305

Sequential Colorization of Steel Surface by Ps Laser Texturing
Authors:
Peixun Fan, Tsinghua University; Beijing Peoples Republic of China
Minlin Zhong, Tsinghua University; Beijing Peoples Republic of China
Cheng Lin, Tsinghua University; Beijing Peoples Republic of China
JIangyou Long, Tsinghua University; Beijing Peoples Republic of China
Hongjun Zhang, Tsinghua University; Beijing Peoples Republic of China
Presented at ICALEO 2013

Intrinsically, most metals are gray or silvery white in appearance. However, to render metal surfaces to various desirable colors without changing their chemical composition is necessary and important in many applications including decoration, marking, data storage, and anti counterfeiting. Some previous reported work has been conducted on utilizing femtosecond lasers to transform highly reflective metals to either totally absorptive or reflective to a certain color of light, creating the so-called black metals and colorized metals, e.g., gold aluminum, blue titanium, etc. However, the flexibility to produce diverse colors on metal surfaces in a controllable way is still unsatisfactory. For one aspect, the diversity of the colors produced by a femtosecond laser is insufficient, only limited kinds of colors can be induced. For another aspect, a complicated modulation procedure of different fs laser processing parameters is usually needed. In addition, manufacturing of this kind of color metals by simply focusing femtosecond light to metal surfaces is rather time-consuming, making fabrication of large area of the colorized metals unaffordable.
In this paper, we report a surface micro/nano structuring technique by utilizing a high power (with an average power up to 100 W) and high repetition rate (with a maximum of 2 MHz) picosecond laser beam to colorize metal surfaces. Sequential colors varying from golden to green were realized on steel surfaces by simply changing the ps laser scanning speeds. Systematic analyses on the spectral response and micro/nano structure characterization were reported. Spectrum shifting effect corresponding to color change was explained through surface plasmon resonance mechanism. The current research demonstrates that a high power and high repetition rate ps laser is capable of forming sequential colors on steel surfaces with a processing speed up to several meters per second, making this technology an efficient and affordable candidate for practical industrial applications. The research can pave the way for ps laser surface structuring technique to be applied to colorize conventional engineering materials.