Cold laser micromachining efficiency in nickel-yttrium stabilised zirconia cermets was studied as a function of cermet composition. Nickel oxide-yttrium stabilised zirconia ceramic plates obtained via tape casting technique were machined using 8–25ns pulses of a Nd: YAG laser at the fixed wavelength of 1.064μm and a frequency of 1kHz. The morphology of the holes, etched volume, drill diameter, shape and depth were evaluated as a function of the processing parameters such as pulse irradiance and of the initial composition. The laser drilling mechanism was evaluated in terms of laser-material interaction parameters such as beam absorptivity, material spallation and the impact on the overall process discussed. By varying the nickel oxide content of the composite the optical absorption (-value is greatly modified and significantly affected the drilling efficiency of the green state ceramic substrates and the morphology of the holes. Higher depth values and improved drilled volume upto 0.2mm3 per pulse were obtained for substrates with higher optical transparency (lower optical absorption value). In addition, a laser beam self-focussing effect is observed for the compositions with less nickel oxide content. Holes with average diameter from 60μm to 110μm and upto 1mm in depth were drilled with a high rate of 40ms per hole while the final microstructure of the cermet obtained by reduction of the nickel oxide-yttrium stabilised zirconia composites remained unchanged.
|Journal||Materials Research Bulletin|
|Publication status||Published - 2009|