Laser-Induced Iridescent Steel Surfaces with Moderate Reflectance

Laser-induced coloration on metallic surfaces has emerged as a clean technology to prepare visual designs. After laser processing, the metallic surface is covered by typical periodically repeated microstructures, which interact with visible light and bring iridescent appearance to the laser markings due to the structural color effect. Although many studies have focused on this topic, the necessity of iridescent surfaces with moderate optical reflectance still needs to be addressed. In general, structural colors are shiny with high brightness. There are troubles in certain cases because shiny markings with excessive reflectance may be harmful to human eyes. In this work, we prepared iridescent an AISI444 stainless steel surface via femtosecond laser processing. By studying the influence of surface microstructures on the coloration and reflectance, suitable laser parameters for producing markings with moderate reflectance were discussed. The contribution of intrinsic colors of the chemical compositions in the surface was further analyzed.