Performance of laser-glazed zirconia thermal barrier coatings in cyclic oxidation and corrosion burner rig tests

The performance of laser-glazed zirconia (containing 8 wt.% Y₂O₃) thermal barrier coatings was evaluated in cyclic oxidation and cyclic corrosion tests. Plasma-sprayed zirconia coatings of two thickness (0.02 and 0.04 cm) were partially melted with a CO₂ laser. The power density of the focused lasser beam was varied from 35 to 75W mm^-2, while the scanning speed was about 80 cm min^-1. In cyclic oxidation tests, the specimens were heated in a burner rig for 6 min and cooled for 3 min. The results obtained indicated that the laser-treated samples had the same life as the untreated samples. However, in corrosion tests, in which the burner rig flame contained 100 ppm Na fuel equivalent, the laser-treated samples exhibited a nearly fourfold life improvement over that of the reference samples. In both tests, the lives of the samples varied inversely with the thickness of the laser-melted layer of zirconia.