Nanosecond Pulsed Laser Irradiation of Titanium Alloy Substrate: Effects of Periodic Patterned Topography on the Optical Properties of Colorizing Surfaces

Most of the current works based on surface treatments of metals by laser marking technology are focused on the modification of the color tonality of flat surfaces, or the development of specific topography features, but the combination of both processes is not usually evaluated, mainly due to the complexity of controlling the optical properties on rough surfaces. This research presents an analysis of the influence of the micro-geometrical characteristics of periodic patterned laser tracks on the chromaticity and reflectance of Ti6Al4V substrates. The samples were irradiated with an infrared nanosecond pulsed laser in air atmosphere, taking as the control parameter the scan speed of the beam. A roughness evaluation, microscopic inspection, and absorption and chromaticity examination were conducted. Although micro-crack growth was detected in an isolated case (10 mm/s), the possibility of adjusting the result color was demonstrated by controlling the heat-affected zone thickness of the textures. The results of rough/colored combined textures allow new perspectives in industrial design to open, particularly in aesthetic applications with special properties.