Formation and Characteristics of Through Holes with Picosecond-Laser Helical Drilling on Alloy Material

Precision drilling can improve the microhole quality by yielding a reduced recast layer thickness and no heat-affected zone. We evaluate the quality of the helical drilled holes, e.g., the recast layer, microcracks, and circularity by scanning electron microscopy. We investigate the overlap rate of the laser beam and find its influence on the efficiency of through-hole machining. The microhole entrance, exit, and side walls are smooth, without an accumulation of spattering material and the formation of a recast layer and microcracks. Optimum parameters for drilling through holes on alloy material GH2132 are a thickness of 500 μm, a laser fluence of 3.06 · 10−2 J/mm2, a pulse repetition rate of 100 kHz, and a helical speed of 60 rev/s. The tapering phenomenon can be avoided by using a helical system with a rotating stage, and the hole circularity is fairly good. Picosecond laser helical drilling can be effective for manufacturing microholes with a high quality. The development of high-power picosecond laser would promote picosecond laser drilling with future industrial relevance.