Laser‐Induced Color Marking of Titanium: A Modeling Study of the Interference Effect and the Impact of Protective Coating

Abstract

Laser-induced color marking of metals, due to numerous advantages, including inter alia the high quality, resolution, durability, and noncontact methodology of surface marking, seems to be attractive for use in various applications. In this method, the resulting color is mainly evident from the interference effect. Therefore, one of the still unsolved problems on titanium is the color change after imposition of an additional layer (fingerprints, grease, etc.). In this paper, a computer simulation based on the theoretical thin layers model was presented. The results of the modeling study revealed that theoretically a thin protective coating of a known refractive index can be applied while still maintaining the target color. In this case, as a protective layer, an amphiphobic coating has been taken into consideration with its ability to resist surface contamination. The study was performed for titanium (grade 2). The model utilizes the real data derived from the spectrophotometer, as well as from the ellipsometry measurements of laser-induced samples.

Review on Experimental and Theoretical Investigations of Ultra-Short Pulsed Laser Ablation of Metals with Burst Pulses

“…Laser coloring was intensively investigated for ns pulse processing where oxide layers are formed [167][168][169][170]. Alternatively, ultra-short pulsed lasers can be used.…”

Comment on “Bioinspired Reversible Switch between Underwater Superoleophobicity/Superaerophobicity and Oleophilicity/Aerophilicity and Improved Antireflective Property on the Nanosecond Laser-Ablated Superhydrophobic Titanium Surfaces”

“…As shown by several authors, 7 , 12 , 13 the laser texturing of a metallic surface in an oxygen-containing atmosphere does not result only in modified surface topography but also in surface oxidation. On a microscopic scale, this manifests as a change of surface color 13 , 14 and results in modified surface wettability. 15 − 17 After the laser texturing, the surfaces may become superhydrophilic in a saturated Wenzel regime (θ = 0°).…”

“…Again, they neglected the interference effects even though—as evident from the theoretical calculations in Figure 3 a, d—they should not be neglected. As explained in the section S9 of the Supporting Information , the reflectivity for an electric field in case of a double thin-film layer (DTF) system can be calculated as 14 where indices 1, 2, 3, and 4 stand for air, water, TiO 2 , and titanium, respectively (see Figure S32 ), and the phase change due to light propagation in water δ w is calculated similarly as phase change due to light propagation within the oxide film in eq 2 .…”

“…As shown by several authors, ,, the laser texturing of a metallic surface in an oxygen-containing atmosphere does not result only in modified surface topography but also in surface oxidation. On a microscopic scale, this manifests as a change of surface color , and results in modified surface wettability. − After the laser texturing, the surfaces may become superhydrophilic in a saturated Wenzel regime (θ = 0°). − However, this regime is not stable and the superhydrophilic-to-superhydrophobic transition usually occurs over the course of several weeks or months if these surfaces are exposed to atmospheric air. ,,, Although the underlying mechanisms for this transition are still under debate, several experimental observations ,− convincingly endorse contamination as one of the most likely reasons.…”

Effect of Laser Parameters on Colour Marking of Ti6Al4V Titanium Alloy

“…The oxide layer will repeatedly reflect the beam from the surface of both oxide and metal. Research by Łȩcka et al [3] said that the effect of colour can be observed and controlled if the oxide thicknesses on the surface are increased.…”