Ultrasound-assisted pulsed laser drilling for fabricating high quality microholes

Ultrasound-assisted pulsed laser drilling is one recently-developing laser drilling technique. In this study, nickel-based superalloy GH4037 sheets were drilled using the self-developed ultrasound-assisted pulsed Nd:YAG laser precision drilling system, which incorporated the self-designed ultrasonic vibration system and the pulsed laser precision drilling system as one integrated laser processing system. Effects of ultrasonic vibration on microhole morphology and microhole wall quality were analyzed through corresponding comparisons. Decrease degree for the drilled microhole recast layer using ultrasonic wave was also disclosed. It was shown that the axial ultrasonic vibration might enhance and accelerate the ejection of the material melted/vaporized by the laser beam from the drilling hole, which might reduce the molten material spattering around the drilling microhole wall to solidify as the recast layer. Compared with the laser drilling without ultrasonic assistance, the ultrasound-assisted laser drilling technique might improve the drilled microhole wall quality in terms of relatively clean, uniform, and better-profiled microhole wall surface with fine crystal grains, less defects, and less residual stress.