An Analysis of Crack and Porosity Formation in Laser Surface Treated Magnesia Partially Stabilized Zirconia (MgO-PSZ) and Methods for Alleviation
J. Lawrence and D.W. Evans
Crack formation during the laser surface treatment of materials with low coefficients of thermal conductivity values, such as ceramics, is one of the most intractable problems encountered in the field of laser materials processing. Likewise, porosity formation during the laser surface treatment of ceramics presents a problematic subject. Any analysis, therefore, of these issues would be most informative. It is widely accepted that to prevent cracking in ceramics during laser surface treatment some form of pre- and post-treatment heating must take place. This study examines the formation of cracks and porosities during the CO2 laser surface treatment of a magnesia partially stabilized zirconia (MgO-PSZ) ceramic when pre-treatment heating was applied externally and post treatment heating was achieved using firstly a plain diverging beam, and secondly using a diffractive optical element (DOE) to produce a “tailored” laser beam profile. The results of this study revealed that the pre-treatment heating regime and the laser beam profile played a vital role in determining the occurrence, number and scale of microcracks and porosities in the CO2 laser surface treated MgO-PSZ.