Abstract
The air-plasma-sprayed ceria and yttria-stabilized zirconia (CYSZ) coating was modified by selective laser remelting and Al deposition to enhance hot corrosion resistance. The dotted coating was obtained after selective laser remelting. Magnetron sputtering was used to deposit an Al film on the dotted coating, and a vacuum heat treatment was subsequently performed to produce a dense α-Al2O3 overlay. Hot corrosion behavior of the following three types of coatings was investigated: plasma-sprayed, dotted, and dotted coatings combined with Al deposition (DA). Hot corrosion behaviors were evaluated in a mixture of 55 wt % V2O5 and 45 wt % Na2SO4 molten salts at 1000 °C for 30 h. The hot corrosion reaction between molten salts and zirconia stabilizers (Y2O3 and CeO2) led to the generation of monoclinic zirconia, YVO4, and CeVO4 plate-shaped crystals, and the mineralization of CeO2. The results indicated that the hot corrosion resistance of the DA coating was the best, and the dotted coating had superior hot corrosion resistance in comparison with the plasma-sprayed coating. The minimal surface roughness and dense dotted units improved the hot corrosion resistance of the dotted coating. The dense α-Al2O3 overlay with chemical inertness effectively inhibited the infiltration of molten salts, which led to the optimal hot corrosion resistance of the DA coating.
Highlights
Thermal barrier coatings (TBCs) are finding ever increasing applications in the severe high-temperature environment of gas turbine engines, where they can improve the engine efficiency and decrease undesirable emissions [1,2]
Chang et al [34] fabricated peg-nail structured TBCs by selective laser modification, and the results indicated that the thermal shock resistance of the plasma-sprayed TBCs was enhanced by the peg-nail structured laser modification
A NiCrAlY bondcoat on the superalloy substrate was fabricated by a low-temperature high-velocity oxygen fuel (LT-high velocity oxygen fuel (HVOF)) spraying system (K2, GTV Verschleißschutz GmbH, Luckenbach, Germany), and a ceria and yttria-stabilized zirconia (CYSZ) ceramic coating was sprayed on the bondcoat by an air plasma spray (APS) system
Summary
Thermal barrier coatings (TBCs) are finding ever increasing applications in the severe high-temperature environment of gas turbine engines, where they can improve the engine efficiency and decrease undesirable emissions [1,2]. The typical TBC is a duplex material system that is composed of a ceramic topcoat to provide thermal insulation and an anti-oxidation metallic bondcoat. MCrAlY alloys (M: Ni, Co, and Ni + Co) as the typical bondcoat material are widely used due to their compatible thermal expansion coefficient (TEC) with the metallic substrate [3]. Bondcoats are sprayed on the metallic substrate by air plasma spray (APS) [4], vacuum plasma spray (VPS) [5], low pressure plasma spraying (LPPS) [6], and high velocity oxygen fuel (HVOF) [7], etc. Because of the relatively low costs and high deposition efficiency, APS has been widely accepted in industry [13,14]
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