PERFORMANCE OF LASER-GLAZED PLASMA-SPRAYED (ZRO2-12WT-PERCENT-Y2O3) (NI-22WT-PERCENT-CR-10WT-PERCENT-AL-1WT-PERCENT-Y) THERMAL BARRIER COATINGS IN CYCLIC OXIDATION TESTS

Laser glazing of a plasma-sprayed (ZrO2-12wt.%Y2O3)/(Ni-22wt.%Cr-10wt.%Al-1wt.%Y) thermal barrier coatings (TBCs) was carried out using a pulsed CO2 laser with a cylindrical focal lens. The effects of the laser glazing on the microstructure and thermal cyclic response of these coatings have been evaluated. The results of this investigation showed that the thermal cyclic lifetimes of the plasma-sprayed TBCs were enhanced about fourfold by laser glazing. Laser glazing did not have an evident effect on reducing the oxidation rate of the bond coat. The failure of the TBCs was initiated and propagated mainly within the top coat near the top coat-bond coat interface. Improving the strain accommodation through segmented cracks produced by laser glazing is the major enhancement mechanism for TBC life extension. The microstructures of both as-processed and cycled TBCs were investigated with optical microscopy or scanning electron microscopy. X-ray diffractometry was used to analyze the phases of the top coat.