Research On Technology Of Laser Colorful Marking On Metal

Although laser colorful marking on metal has not been wildly used as a result of restriction on complexity of processing, applicability of material and laser performance, its enormous potential market is waiting for us to breeding and developing. In order to explore essence of laser colorful marking on metal, this paper introduces the mechanism of laser colorful marking on stainless steel and titanium and the mechanism of color generation of film processed by laser colorful marking on stainless steel and titanium.First of all, the spot size in different defocused position of laser colorful marking system after laser focused and propagated has been evaluated, and then, the approach of scanning region has been introduced to achieve colorful marking. The analysis of results of scanning surface of metal in different affecting factor such as laser power density, spot overlap on travel scanning and line overlap indicates that the mechanism of laser colorful marking on metal is determined by different way on laser energy input. The mechanism of laser colorful marking on metal is that the optical film, which is oxide and nitride coated on surface of metal, is generated by controlling ways on laser energy input and using the approach of scanning region.Single color marking can be achieved by scanning a closed region, and colorful marking can be achieved by combining with several single color marking.The research goal is to find the mechanism of color generating of film after laser scanning. The film is analyzed by X-Ray Diffraction. It can be found that the film coating on surface of stainless steel contains ferric oxides and nitrides and the film coating on surface of titanium contains titanium oxides and nitrides. The composition of films with different color is different in term of substance. The thickness with several hundred nanometers of films on stainless steel or titanium is observed on cross-section of films by Scanning Electronic Microscope. Holes with size of several microns can also be observed between the film and the substrate of titanium. With the understanding of the film, the mechanism of color generating can be explained by thin film interference. The calculation on reflection rate of single layer medium under ideal condition indicates the face that the film is subject to the optical layer which presents color.