Surface Modification Of Some Metals Treated By Excimer Laser

Along with innovations of the traditional industry technology and advances of modern industry,the trends of industrial development are focusing on the saving of energy and resource, and what ismore, the pursuit of sustainable development. Materials are required to have higher performance, andthe invalidation of metalsis also taken seriously. By applying the laser surface modificationtechnology, the wear resistance, corrosion resistance and other properties can be improved. Suchadvantages will extend the service life of materials, contributing to a great economic benefit.KrF excimer laser (wavelength of248nm, pulse duration of20ns) has been taken to perform asurface treatment on AISI304stainless steel and superalloy GH4169in ambient air. A variety ofdifferent morphologies are produced by the change of the laser power density, laser frequency andpulse number. By means of microscope, microhardness tester and X-ray photoelectron spectroscopy(XPS), we investigate the microstructure, phase, hardness and compositional changes after lasertreatment. The main research results are as follows:1. The treated surfaces are featured by stripe structure and granular morphology with differentirradiation pulses. No obvious cracks, impurities or other defects are observed after surface treatments.XPS results show that excimer laser can effectively eliminate carbides implying a cleaning effect onsurfaces. After laser treatments, the steel surface is mainly characterized by iron and chrome oxideswhich can enhance corrosion resistance. Excimer laser does not seem to obviously improve thesurface hardness. The hardness of the treated areas is reduced to175HV0.3from187HV0.3. The laserprocessing initially causes a stress-induced softening.2. Excimer laser surface treatment on superalloy GH4169exhibits a micro-polishing effect in ourstudy. The results show that surface roughness is reduced significantly with the followingexperimental parameters:5pulses,22KV working voltage, and10Hz laser frequency. The mechanicsof laser micro polishing are analyzed. During the process, both photothermal and light pressure actionare taken into account to explain the material melting and solidification.In summary, surface modification experiments on AISI304stainless steel and superalloyGH4169have been performed by means of excimer laser. The relationship between modificationeffects and laser parameters has been investigated. The research provides valuable data for both theapplication of laser surface modification and the theoretical investigation of mechanics of surfacetreatment.