Abstract
Two types of segmentation-crack structured yttria-stabilized zirconia (YSZ) thick thermal barrier coatings (>500 μm, TTBCs) were deposited onto the stainless steel substrates using atmospheric plasma spraying (APS) and suspension plasma spraying (SPS) process, respectively. In this work, thermal aging behaviors, such as the microstructures, phase compositions, grain growth, and mechanical properties of APS TTBCs and SPS TTBCs, were systematically investigated. Results showed that both as-sprayed TTBCs exhibited a typical segmentation-crack structure in the through-thickness direction. APS coatings mainly comprised of larger columnar crystals, while a large number of smaller equiaxed grains existed in SPS coatings. Both of the coatings underwent tetragonal-monoclinic phase transformation after 155 °C/40 h heat treatment. The poorer phase stability of SPS TTBCs may have a connection with smaller grain size. Thermal-aged APS and SPS coatings exhibited a significant increase in H and E values with the rising of thermal aging temperature, and for the samples that thermal aged at 1550 °C, the H and E values increased sharply during initial stage then decreased after 80 h due to the phase decomposition. The segmented APS coatings had weak bonding between the lamellaes during thermal exposure, which caused the mean Vickers hardness value of APS TTBCs to be much lower than that of SPS TTBCs.
Highlights
Plasma-sprayed yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) have been increasingly used in aero- and land-based gas turbines to effectively protect the high-temperature components against hot oxidation and corrosion, which improves work efficiency and prolongs the serve life [1,2,3,4]
A typical TBC system consists of a superalloy substrate, an oxidation-resistant bond coat, and a thermal insulating ceramic topcoat
Considering the low thermal conductivity and high thermal expansion coefficient close to that of the metallic substrate, 6–8 wt.% YSZ is widely used as the ceramic topcoat of TBCs [5]
Summary
Plasma-sprayed yttria-stabilized zirconia (YSZ) thermal barrier coatings (TBCs) have been increasingly used in aero- and land-based gas turbines to effectively protect the high-temperature components against hot oxidation and corrosion, which improves work efficiency and prolongs the serve life [1,2,3,4]. A typical TBC system consists of a superalloy substrate, an oxidation-resistant bond coat, and a thermal insulating ceramic topcoat. Considering the low thermal conductivity and high thermal expansion coefficient close to that of the metallic substrate, 6–8 wt.% YSZ is widely used as the ceramic topcoat of TBCs [5]. The thickness of traditional YSZ TBCs is generally less than. Measures should be taken to further improve the thermal insulation performance of TBCs to meet the increasing working temperature requirements of gas turbines.
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