Ablation Characteristics of Alumina and Zirconia Ceramics on Ultra-short Pulsed Laser Machining

Ultra-short pulsed laser manufacturing gives a unique route to ablate hard-to-machine materials and enables little thermal impact. A comparative study on an alumina-toughened zirconia (ATZ) composite and pure alumina is presented. Single- and multi-pulse ablation of 1030nm and 515nm wavelength with sub picosecond pulses reveal an abrupt increase of the material removal rate. Pockets with 5 mu m beam distance and 15 layers rotated by 23 degrees are generated to attain the multi-pulse ablation rate. The threshold fluence gives 0.1J/cm(2) and 0.11J/cm(2) for green wavelength and the ATZ and alumina, respectively. Single pulse ablation with 7J/cm(2) energy density point to the sharp ablation limit and an electron microscopy assessment reveals a step-like behavior. Subsequent Raman spectroscopy studies prove the persistence of the tetragonal morphology of zirconia. These findings enable laser manufacturing of microstructures on ceramic specimen with a 2.5D and quasi-tangential strategy.