Abstract
Laser scanning modification was applied to secondarily melt the top ceramic coating surface of lanthanum zirconate/yttria-stabilized zirconia double ceramic thermal barrier coatings (LZO/YSZ TBCs) to reduce the gas oxygen diffusion and improve the TBCs service life. Isothermal oxidations with different times were carried out on the as-sprayed (AS) TBCs and laser-remolten (LR) TBCs at 1100 °C to investigate thermally growth oxide (TGO)growth mechanisms and isothermal oxidation behaviors. The results showed that the laser-remolten top-ceramic-coating dense layer with a columnar crystal structure of LR TBCs presented a 96.3% and 59.1% lower surface roughness and porosity, respectively, than those of the top ceramic coating of AS TBCs, and the TGO growth rate of LR TBCs decreased by 46.2% compared to that of AS TBCs. The mixed-oxides appearance time of LR TBCs (50 h) was later than that of AS TBCs (25 h). After 100 h of isothermal oxidation, the total TGO thickness of LR TBCs was only 77.2% of that of AS TBCs, and the effects of the laser-remolten TBCs on gas oxygen diffusion inhibition and high-temperature oxidation resistance were promising in LZO/YSZ TBCs.
Highlights
Thermal barrier coatings (TBCs) are widely used in hot end components of gas turbines, such as combustion chambers and high-pressure nozzles, to protect hot end components from oxidation, thermal corrosion, erosion wear, and even touch-friction between blades
Typical TBCs are composed of ceramic coatings, metallic bonding coatings, superalloy substrates, and thermally growth oxide (TGO) layers
Ahmadi-Pidani et al [32] and Fretias [33] used pulsed lasers to treat plasma-sprayed ceria and yttria-stabilized zirconia (CYSZ) TBCs, and the effects of laser remelting on the microstructure and thermal shock resistance of the coatings were evaluated; the results showed that the lifetime of the laser-treated TBCs was enhanced about fourfold
Summary
Thermal barrier coatings (TBCs) are widely used in hot end components of gas turbines, such as combustion chambers and high-pressure nozzles, to protect hot end components from oxidation, thermal corrosion, erosion wear, and even touch-friction between blades. Ahmadi-Pidani et al [32] and Fretias [33] used pulsed lasers to treat plasma-sprayed ceria and yttria-stabilized zirconia (CYSZ) TBCs, and the effects of laser remelting on the microstructure and thermal shock resistance of the coatings were evaluated; the results showed that the lifetime of the laser-treated TBCs was enhanced about fourfold This is attributable to the formation of a continuous network of segmented cracks perpendicular to the surface and the increase in strain accommodation. Laser scanning for remelting modification on LZO/YSZ doubleceramic-layer TBCs was carried out, and the remelting effects on the microstructure, TGO growth behavior, and oxidization mechanism were investigated, to explore the sealing feasibility to reduce oxygen transport and improve the high-temperature service life of LZO/YSZ double-ceramic-layer APS TBCs
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