In Part I of this contribution, energy coupling and transport mechanisms were considered in detail. The second part concentrates on the effect of the spatial distribution of the energy in the laser beam, which will be discussed in connection with applications of laser surface technologies. Along these lines, a variety of beam shaping facilities is presented for laser hardening and cladding. Their purpose is to adapt the irradiated area to the workpiece geometry in order to achieve optimum energy coupling and processing quality. As an example, the use of beam combining optics permits of pre- and postheating, thereby offering interesting variations in the process. Means and techniques to enhance quality by controlling the process are also demonstrated. The principles discussed are practically independent of the laser wavelength, so that this aspect will not be treated explicitly.

The coupling mechanisms of laser radiation and the mechanisms of heat transport in the workpiece are considered. Starting from the well-known basics of Fresnel absorption -valid only for smooth and clean surfaces -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 supplied laser power. For negligible radiation and convectional heat losses, it describes the energy available for the process. The heat, corresponding 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 function of the intensity distribution in the laser beam will be discussed in Part II of this calibration together with more practical aspects of hardening and cladding.

No abstract

No abstract

No abstract