Effects of Laser Texturing on Technical Surfaces
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Effects of Laser Texturing on Technical Surfaces 1
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Y. Gerbig , G. Dumitru , V. Romano , V. Spassov , H. Haefke 1 CSEM Swiss Center for Electronics and Microtechnology Inc., Neuchâtel, Switzerland 2 Institute of Applied Physics, University of Berne, Switzerland ABSTRACT Different laser beam techniques were applied to AISI M3 steel samples in order to produce well-defined surface microtextures consisting of pores, which can act as lubricant pockets (reservoir) as well as traps for wear debris. Both effects contribute to improve the tribological performance of textured functional surfaces. The tribological performance of lasertetxures was studied as function of the pore depth and diameter in unidirectional sliding tests under starved lubrication. The lasertetxured surfaces tested under those conditions were produced by a wellestablished ns laser technique using a Q switched Nd:YAG laser. The topographical microstructures of these laser-induced textures were characterized by optical and scanning electron microscopy as well as replica technique. A significant change in friction behavior as compared to untextured tool surfaces was observed when using microtextured surfaces. In another part of the study, the influence of new-developed fs laser technique of the tool steel was investigated. The fs laser texturing of the steel results in a change of the metallographic structure of the laser-affected zone, which is clearly detectable in cross-section samples. The structure of the material and chemical composition of the laser-affected, pore-near region was analyzed by transmission electron microscopy with combined EDX analysis. It could be shown that the laser-affected zone seems to consist of an amorphous or nanocrystalline material in opposite to the ‘macrocrystalline’ steel substrate. Nanoindentations revealed a two times higher hardness of the laser-affected zone than the steel bulk phase. INTRODUCTION The role of surface topographic features in friction, wear and lubrication has been emphasized by many researchers, engineers and industrialists. It has been known that the functional performance of tools and components can vary depending on what surface features are present or dominate. Microtexturing of tool surfaces offers the opportunity to reduce friction and wear during the processes, increase the tool life and reduce the amount of lubricants. For environmental and economical reasons the latter is a pronounced need in metal forming industry, where large amounts of lubricants (so-called ‘flooded lubrication’) are used. There are various methods with which surface functionality can be improved. Mechanical processes, such as grinding, polishing, milling and engraving have been used for quite sometime now for surface texturing. This is also the case for chemical methods like chemical etching and electrochemical routes; an exception is the photochemical route that grew out of advances in the semiconductor industry. A promising and emerging technology for microstructuring to enhance surface functionalit
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