Comparison of volumetric and surface heating sources in the modeling of laser melting of ceramic materials

It is known that laser beam absorption length for ceramic materials is several orders of magnitude larger than that of metallic materials. Therefore the use of surface heating source in the modeling of laser melting of ceramics may not be correct. In this paper, thermal fields have been modeled with both a volumetric heating source and a surface heating source to predict the melt cross-sections of an Al2O3-based refractory during CO2 laser treatment. Three-dimension quasi-steady state heat conduction equations are solved by applying the Green function method, while the singularities associated with the numerical integration are dealt with using a linear interpolation method. It has been experimentally confirmed that the model incorporating the volumetric heating source is more accurate than that incorporating the surface heating source. The melt depths and widths predicted from the model using the volumetric heating source are in excellent agreement with the experimental data. The predicted cross-sectional profiles of the melt/solid interfaces are also consistent with the experimental results for smaller melt cross-sections. However, increasing discrepancy has been observed with the increase in size of the melt cross-section.