Influence of assist gases on pulsed laser drilling of nickel-based superalloy

Abstract

Assist gases, including combustion-supporting gas and shielding gas, can greatly affect laser drilling process and drilled hole quality. In this study, oxygen and argon were used for assisting pulsed laser drilling of nickel-based superalloy plates. Influential mechanisms for oxygen and argon on pulsed laser drilling processes were discussed. Effects of oxygen and argon on drilled microhole entry, hole wall quality (defects, morphology, surface roughness), and drilling efficiency were analyzed. It was shown that oxygen-assisted laser drilling could achieve higher drilling efficiency (threshold of pulse number for argon-assisted laser drilling is relatively high). Different from argon-assisted laser drilling, the melted material might combust with oxygen during oxygen-assisted laser drilling process, leading to some black brittle oxides around the drilled hole wall/entry (these oxides could be easily removed due to their poor adhesion to hole entry surface). When using oxygen-assisted laser drilling, many microscale depressions and cracks were found around the drilled microhole wall. Moreover, compared with oxygen-assisted laser drilling (on the same other conditions), surface roughness and microcracks of the microhole wall drilled using argon-assisted pulsed laser were obviously reduced.