Atmospheric plasma-sprayed (APS) ZrO2–8%WtY2O3 thermal barrier coatings (TBCs) were subjected to a CO2 continuous
wave laser-glazing process in order to generate an external dense layer produced by different processing parameters. For that
purpose, different beam scanning speeds and track overlapping were chosen.
Surface roughness has been reduced significantly after laser-glazing. Despite the surface crack network, all laser-glazed
specimens presented a fully dense and porous free external layer with a columnar microstructure. Surface cracks along the
densified layer were found to have tendency to be oriented in two perpendicular directions, one in the direction of the laser beam
travel, the other perpendicular to it. Moreover, the cracks parallel to the beam moving direction are found to be on the
overlapping zone, coinciding with the edge of the subsequent track. The cracks along the densified layer are vertical and tend to
branch and deviate from the vertical direction within the porous PS coating. The largest overlapping allied to the smallest amount
of irradiated energy generated the most uniform layer with the shortest crack branches within the PS coating. For the as-sprayed
coating, the XRD results revealed mainly t0 non-transformable tetragonal zirconia with a small percentage of residual
monoclinic zirconia. All glazed coatings presented only t0 non-transformable tetragonal zirconia with some variations on
preferable crystal orientation.
thermal barrier coating , Laser-glazing , zirconia , PLASMA SPRAYING