The effects of process parameters on spatter deposition in laser percussion drilling

This paper reports on the characterisation and analysis of spatter deposition during laser drilling in Nimonic 263 alloy for various laser processing parameters using a fibre-optic delivered 400 W Nd:YAG laser. The principal findings are a large proportion of the spatter(approx. >70%) was deposited due to the initial laser pulses (before beam breakthrough) required to drill a through-hole. Short pulse widths, low peak powers and high pulse frequencies generated smaller spatter deposition areas. At high pulse frequencies, the spatter distribution/thickness can he altered as a result of laser-ejected material interaction. Focal plane positions between -0.5 and +1.5 mm produced relatively similar spatter areas of about 14 mm(2). As a result of the reduction in the material removed per pulse, a longer focal length of 160 mm generated smaller areas of spatter deposition in comparison to a shorter focal length of 120 mm. In addition, a generic relationship between the spatter area and d(entrance)/d(exit) with increasing total laser energy has been established. (C) 2000 Elsevier Science Ltd. All rights reserved.