Investigation into Laser Produced Evaporating Front Characteristics in Relation to Laser Drilling

High power laser heating of metallic surfaces results in non-conduction limited heating. In this case, an irradiated surface evaporates while a cavity is formed in the solid substrate. In the present study, the measurement of the evaporating front velocity distribution across the cavity exit and plume height during the heating pulse. An Nd:YAG laser is used to irradiate a mild steel surface are carried out. Streak photography and Langmuir probe techniques are used in the experiment. It is found that the plume height of 11.2 mm is measured at 250 μs of the heating period. The mean evaporating front velocity is of the order of ∼ 60 m/s and the velocity profile across the cavity exit appears to be almost a fully developed turbulent flow velocity profile as heating progresses.