RECENT PROGRESS IN LASER-SURFACE TREATMENT .1. IMPLICATIONS OF LASER WAVELENGTH

The coupling mechanisms of laser radiation and the mechanisms of heat transport in the workpiece are considered. Starting from the well-know n basics of Fresnel absorption - valid only for smooth and clean surfa ces - further effects of coupling are examined. Studies on the effects of surface modifications inherent to all industrial parts and process conditions are presented. The more appropriate term coupling rate is introduced: This describes the ratio of the total energy coupled into the workpiece (regardless of the particular mechanisms) to the supplie d laser power. For negligible radiation and convectional heat losses, it describes the energy available for the process. The heat, correspon ding to the coupled laser energy, is distributed within the workpiece by conduction and convection. The three-dimensional development of the temperature field in the solid materials and in the melt pool as a fu nction of the intensity distribution in the laser beam will be discuss ed in Part II of this calibration together with more practical aspects of hardening and cladding.