Pulsed laser treatment of plasma-sprayed thermal barrier coatings: effect of pulse duration and energy input

Pulsed laser treatments of plasma-sprayed thermal barrier coatings can provide good corrosion resistance of protected components without impairing thermal fatigue resistance of the ceramic layers. Laser treatments are performed over a wide range of pulse durations and energy inputs, and their effects on microstructure, crystalline grain size and chemical composition of the remelted thin upper layer are investigated. Particular attention is given to macro and microcracking originating on the surface, gas bubble motion inside the melted layer and consequent surface crater formation. Density, shape, dimension and distribution of craters in the laser-irradiated zone are correlated with pulse duration and energy input of the laser beam. A numerical simulation of temperature distributions and heat phenomena originating in the ceramic coating during laser irradiation is presented, in order to explain the influence of laser characteristics on the quality of the coating surface.