Effect of laser treatment modes on metal surface marking color

Abstract

The laser beam marking process is considered to be a subject to important scientific research. In this area, there are insufficiently studied problems and concepts requiring their experimental validation and determining the solutions. Upon laser action, the effect of metal surface coloration can be caused by different processes. The most probable is formation of thin oxidic films, although formation of the other compounds is not unlikely as well [1–2]. Under actual values of luminous flux density, however, scanning with laser beam results in occurrence of regular surface roughness. Therefore, the analysis of diffraction effect impact on the image color is also necessary [3–4]. The color images on the metal surface were assessed based on range of colors RAL “Reich Ausschluß für Lieferbedingungen”. In this system, the color space is divided to ranges with identification of each color by its unique index number. When doing research of the metal surface composite regular relief [5] obtained using laser marker, the depth of microroughnesses in differently colored samples was determined. The was performed using non-contact VICWU profilometer. Due to the method of measurement technological specificity, this equipment does not have destructive effect on the object under study. The roughness values (Rz and Ra) of the surfaces under study were measured based on acceptably small areas, thereat the base lines were selected in such way that to consider the surface waviness effect on the roughness values Rz and Ra [6]. The research results demonstrated that change of surface roughness values Ra and Rz by 1.5 times (owing to change of the surface laser treatment mode), changes the specimen metal surface coloration drastically.