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Superhydrophobic surfaces have received extensive attention owing to their excellent properties. In this study, yttria stabilized zirconia (YSZ) surfaces with micro-nano composite structures were prepared by one-step laser texturing. Laser texturing greatly improved the hydrophobicity of YSZ surface. Contact angle of the surface increased from 86.7° to 151.8°, indicating the transition from hydrophilic to superhydrophobic surface. Surface chemical analysis indicated that the enhancement of surface hydrophobicity can be attributed to the decrease in surface polarity, caused by changes in the ratio of chemical components adsorbed from the air and the formation of micro-nano composite structures. Laser texturing effectively regulated the hydrophobicity of YSZ surface, thereby providing promising strategy for corrosion resistance research of thermal barrier coatings. [ABSTRACT FROM AUTHOR]

Computational study related to thermal stress and hole formation in laser percussion drilling of thermal barrier coated nickel alloy based on a thermal-mechanical coupled model, combined with experimental work, was conducted in this paper. The effects of laser parameters (pulse duration and laser power) and material property (elastic modulus) on delamination were discussed based on thermal stress analysis. Laser drilling with higher peak power density (>1e11W/m 2 ) can quickly get a through-hole of 2.3 mm within 10 pulses. Stress mutation and thermal stress shock near the interfaces are responsible for the crack formation. For the case with low peak power density, solidification rate and solidification sequence between materials should also be considered. Under the same pulse duration, the thermal stress would be enhanced with increasing of laser power. With the same pulse energy, a more intense thermal stress shock in pulse cycles can be produced under a longer pulse duration. And this shock effect near the interfaces can be alleviated when laser source is far from the interfaces. Heat accumulating effect induced by stagnation phenomenon, mainly due to lower peak power, can contribute to crack extension along the interfaces. Thus, breaking through the first two layers with high drilling efficiency is an effective way to restrain/prevent the delamination and viable parameters are also determined in the paper. Furthermore, it would offer great benefits for delamination prevention that make sure the elastic modulus of TBC and BC close to each other along the thickness with a gradually approaching method in their preparations. [ABSTRACT FROM AUTHOR]

• An analysis of the effect of beam polarization on polarization removal is proposed. • The periodic structure at TBC layer has a strong dependence on the beam polarization. • Microstructures at BC and substrate layers are independent of the beam polarization. • Charge carriers at TBC layer may remember the polarization state due to low mobility. A high-pulse-energy femtosecond pulsed Ti:sapphire laser was employed to perform laser drilling of 2.4-mm-thick thermal barrier coated In718. The influences of polarization on hole profile and morphology of periodic structures on the sidewall of drilled holes were explored. Based on Fresnel formula, combined with the effects of multiple reflections and energy-trapping, a comprehensive analysis of the effect of polarization on polarization removal was proposed. The microstructures on the sidewall of drilled holes for different layers under different polarizations were compared. The fabricated structures on the thermal barrier coating (TBC) layer showed a strong dependence on the polarization state of the laser beam. The structures with ball-like profile were generated under circular polarization while pine needle-like periodic structures were produced under linear polarization. However, for both the bond coat and substrate layers, the microstructures of the sidewall were independent of the polarization state of the laser beam. For TBC layer the interaction between the resonance of charge carriers and the second harmonic of the surface contributed to a corrugated structure in harmony with the polarization state. Thereinto, the charge carriers may remember the polarization state of the light beam and maintain this information because of the low mobility. [ABSTRACT FROM AUTHOR]