Process modelling of laser ablating ferrous materials

Abstract

Based on experimental results, a qualitative process model for reactive ablation of ferrous materials is suggested, which includes the absorption of the radiation to the workpiece, oxidation of the workpiece material, formation of a chip or wedge and removal of the oxide by bending perpendicular to the workpiece. The superior role is ascribed to the exothermal reaction of the matrix material by increasing the absorption and thus initiating a stationary process of either chip or wedge formation. The model is verified by different experiments, comparing the ablation results of steels with varying carbon content and therefore different heat conductivities, the importance to the process of which becomes obvious in the phenomenon of the sudden transition from chip removal to wedge removal. The influence of impurities on the formation of the chip is explained as well as the mechanism of chip bending.

Laser milling

“…Another mechanism of laser ablation can take place under the following conditions: oxygen environment, low scanning speeds and nanosecond-to-microsecond laser pulses. This mechanism involves four steps [12]:…”

“…This was the layout adopted in the ®rst laser milling machines [12] where conventional CNC milling platforms were integrated with lasers. This design provides accurate positioning and precise toolpaths, but is limited to low scanning speeds due to the machine dynamics.…”

Patterning of amorphous and polycrystalline Ni78B14Si8 with a focused-ion-beam

“…There is a group of energy-assisted processes, e.g., ultra-short pulse laser ablation, electro discharge, e-beam and ion beam machining that could provide the required high fluence [J/cm 2 ]. Using multi-photon ablation or focused-ion-beam (FIB) sputtering, it is possible to sublimate amorphous Ni-based alloys directly at such high specific processing energy without significant thermal effects [4][5][6].…”