Dross-free submerged laser cutting of AZ31 Mg alloy for biodegradable stents

Submerged cutting of AZ31 Mg alloy was studied with ns-pulsed green fiber laser and three different submersion liquids, namely, water, alcohol-water solution, and paraffin based oil. Compared to conventional laser cutting with coaxial process gas, differences due to optical, chemical, and mechanical effects were identified. An analytical solution was introduced to assess the fluence decay due to beam enlargement and absorption in the submersion liquid. The chemical reactions between the Mg alloy and submersion liquid were defined, and weight loss due to chemical effects was studied in static immersion tests. The mechanical instability related to liquid breakdown was studied to reveal the threshold levels for the liquids. The interaction of these mechanisms was studied within process. The results showed dross-free cutting is achievable by submerging the Mg alloy in 0.5 mm alcohol-water solution, which shows a processing condition that enables chemical dissolution of dross without excessive fluence loss or liquid instability. The cut quality of the optimized conditions was comparable to fs-pulsed laser cutting of the same material.