Characteristics of spatter formation under the effects of different laser parameters during laser drilling

Laser-drilled holes are known to be inherently associated with the formation of spatter. In this paper, characterisation of the spatter deposited on laser-drilled holes in a Nimonic alloy has been performed and investigated for various laser-processing parameters using a fibre optic delivered Nd:YAG laser. The main findings are: (a) a large proportion of the spatter (approx. >70%) was accumulated due to the initial laser pulses required to drill a through hole; (b) short pulse width, low peak power, high pulse frequency produced smaller spatter areas; (c) at high frequencies, the spatter distribution can be altered due to the interaction between the laser beam and ejected material; (d) focal plane positions between −0.5 and +1.5 mm produced similar spatter areas. In addition, a generic relationship between the spatter area and dentrance/dexit with increasing total laser energy is established.