Thermocapillary mechanism of deep melting of materials by laser radiation

Formation of a transient crater during laser melting of materials was observed. Three stages of development of the crater, differing in respect of the hydrodynamics of the melt, were distinguished: growth of the crater, excitation of fluctuations in the molten layer on the walls of the crater, and filling of the crater. The results of a model experiment were used to develop a theoretical model of deep melting of materials by laser radiation. A comparison of the results of a calculation based on this model with the experimental results demonstrated that it described satisfactorily the melting of metals. Fluctuations of the thickness of the melt layer at the bottom of the crater were observed when the crater reached its maximum depth. Quantitative and qualitative interpretations of the observed fluctuations were based on excitation of capillary waves.