Influence of long time post annealing on thermal stability and thermophysical properties of plasma sprayed La2Zr2O7 coatings

Erdoğan, Garip; Üstel, Fatih; Bobzin, Kirsten; Öte, Mehmet; Linke, Thomas; Zhao, Lei

doi:10.1016/j.jallcom.2016.10.328

Cited by 22 publications

(3 citation statements)

References 34 publications

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“…Additionally, selective corrosion and structural destruction of the pyrochlore phase were also observed [ 16 ]. The literature data [ 26 , 27 , 28 , 29 ] describes generally the effect of thermal decomposition of single-phase TBC systems of La 2 Zr 2 O 7 . However, the presented problem showed that mutual chemical inertness between phases co-existed in TBC systems such as 8YSZ and different types of rare earth zirconates should be explained, and a conception of mutual inner thermal barrier coatings (MITBC) is a good direction of investigation.…”

Section: Discussionmentioning

confidence: 99%

Oxidation Behavior of the Monolayered La2Zr2O7, Composite La2Zr2O7 + 8YSZ, and Double-Ceramic Layered La2Zr2O7/La2Zr2O7 + 8YSZ/8YSZ Thermal Barrier Coatings

et al. 2020

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The degradation process of thermal barrier coatings (TBCs) such as monolayered La2Zr2O7, composite 50% La2Zr2O7 + 50% 8YSZ, and double-ceramic layer (DCL) La2Zr2O7/50% La2Zr2O7 + 50% 8YSZ/8YSZ was investigated. Coatings were deposited using the atmospheric plasma spraying (APS) process (ceramic layer and bond-coat) on the Ni-based superalloy substrate with Ni-22Cr-10Al-1Y bond-coat. The thickness of the ceramic top-coats in all cases were 300 µm. In the case of La2Zr2O7/8YSZ, the internal sublayer was built from 8YSZ powder whereas the outer from La2Zr2O7. Between both sublayers’ “composite” a 50% La2Zr2O7 + 50% 8YSZ zone was present. The “composite” 50% La2Zr2O7 + 50% 8YSZ TBC system was sprayed from two different feedstock powders with equal weight ratios. In the first part of the investigation, the microstructural characterization of the TBCs was presented. The main goals were related to the characterization of the degradation processes in different TBC systems with special emphasis on the phenomenon in the thermally grown oxide (TGO) zone related to oxidation, and the phenomenon related to phase stability in ceramic top-coats as related to temperature influence. The oxidation test was carried out in air at 1100 °C for 500 h. In the second step of the investigation, the numerical simulation of the monolayered TBC 8YSZ and La2Zr2O7 systems was analyzed from the stress distribution point of view. Additionally, the two-layered TBC coating of the DCL type was also analyzed.

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Section: Discussionmentioning

confidence: 99%

Oxidation Behavior of the Monolayered La2Zr2O7, Composite La2Zr2O7 + 8YSZ, and Double-Ceramic Layered La2Zr2O7/La2Zr2O7 + 8YSZ/8YSZ Thermal Barrier Coatings

et al. 2020

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“…Previous studies have reported that plasma-sprayed coatings will be significantly sintered within a few hours of thermal shock, resulting in a decrease in the porosity of the coatings [32,33]. The sintering rate of the coating is related to the size of the pores in the coating, in which the large pores are difficult to be healed by sintering [34][35][36]. From the microstructure of the coating, it can be seen that the pores in the coating prepared by fine YSZ powder are finer than those of coarse YSZ powder, so the coating is easier to be sintered.…”

Section: Microstructure and Fracture Toughness Of Coatingmentioning

confidence: 99%

Cracking Behavior of Atmospheric Plasma-Sprayed 8YSZ Thermal Barrier Coatings during Thermal Shock Test

Huang

Sun²,

Huang³

et al. 2023

Coatings

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The failure of plasma-sprayed thermal barrier coatings (TBCs) during service is usually related to the cracking behavior. In this study, plasma-sprayed TBCs were prepared with two kinds of agglomerated sintered yttria-stabilized zirconia (YSZ) powders with different particle sizes. The evolution of mechanical properties and crack propagation behavior of the coatings during the whole life stage were studied by a thermal shock test. The effect of powder particle size on the cracking behavior of the TBCs during thermal shock was analyzed from the aspect of pore structure, mechanical properties, and stress state of the coatings. The crack propagation and coalescence in the direction parallel to the substrate in the coating is the main factor leading to the spalling failure of the coating during thermal shock. Although the coating prepared by fine YSZ has higher fracture toughness, the lower strain tolerance will increase the cracking driving force on the crack tip of the coating during thermal shock, and the cracks in the coating propagate merge at a faster rate during thermal shock. The larger porosity and pore size of the coating prepared by coarse YSZ help the coating suffer less thermal stress during thermal shock. Although the existence of pores reduces the fracture toughness of the coating to a certain extent, the increase of strain tolerance reduces the crack growth rate in the coating, so the coating has a longer life.

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“…Rare-earth zirconates (Ln 2 Zr 2 O 7 , Ln = La, Nd, Sm, Eu, Gd and Dy) with low thermal conductivities, high thermal stability and a low sintering rate are considered as the promising candidates for the topcoat materials [7][8][9]. The thermal expansion coefficients of Ln 2 Zr 2 O 7 are much lower than that of YSZ, which could result in higher misfit stress during thermal cycling and eventually lead to delamination of the TBCs [10,11]. Therefore, tremendous efforts have been devoted to increasing the thermal expansion coefficient of the Ln 2 Zr 2 O 7 .…”

Section: Introductionmentioning

confidence: 99%

Effect of CaO and CeO₂ co-doping on thermo-physical properties of La₂Z₂O₇

Luo

Xu²,

Chang³

et al. 2020

Journal of Asian Ceramic Societies

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Ce 4+ and Ca 2+ modified La 2 Zr 2 O 7 samples, La 2 Zr 2 O 7 , (La 0.8 Ce 0.2) 2 (Zr 0.7 Ce 0.3) 2 O 7.2 and (La 0.6 Ce 0.2 Ca 0.2) 2 (Zr 0.7 Ce 0.3) 2 O 7 , were prepared by the co-precipitation method to obtain enhanced thermos-physical properties. Compared with La 2 Zr 2 O 7 , (La 0.8 Ce 0.2) 2 (Zr 0.7 Ce 0.3) 2 O 7.2 and (La 0.6 Ce 0.2 Ca 0.2) 2 (Zr 0.7 Ce 0.3) 2 O 7 both exhibited better sintering resistance, lower thermal conductivities, and higher thermal expansion coefficients. The underlying mechanism of the improved thermo-physical performance of La 2 Zr 2 O 7 induced by Ce 4+ and Ca 2+ doping was discussed. The thermal conductivity and thermal expansion coefficient of (La 0.6 Ce 0.2 Ca 0.2) 2 (Zr 0.7 Ce 0.3) 2 O 7 were 1.165 W•m −1 •K −1 at 1450°C and 10.91 × 10 −6 K −1 , respectively, making it a promising material for the thermal barrier coatings (TBCs).

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Influence of long time post annealing on thermal stability and thermophysical properties of plasma sprayed La2Zr2O7 coatings

Cited by 22 publications

References 34 publications

Oxidation Behavior of the Monolayered La2Zr2O7, Composite La2Zr2O7 + 8YSZ, and Double-Ceramic Layered La2Zr2O7/La2Zr2O7 + 8YSZ/8YSZ Thermal Barrier Coatings

Oxidation Behavior of the Monolayered La2Zr2O7, Composite La2Zr2O7 + 8YSZ, and Double-Ceramic Layered La2Zr2O7/La2Zr2O7 + 8YSZ/8YSZ Thermal Barrier Coatings

Cracking Behavior of Atmospheric Plasma-Sprayed 8YSZ Thermal Barrier Coatings during Thermal Shock Test

Effect of CaO and CeO₂ co-doping on thermo-physical properties of La₂Z₂O₇

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Influence of long time post annealing on thermal stability and thermophysical properties of plasma sprayed La2Zr2O7 coatings

Cited by 22 publications

References 34 publications

Oxidation Behavior of the Monolayered La2Zr2O7, Composite La2Zr2O7 + 8YSZ, and Double-Ceramic Layered La2Zr2O7/La2Zr2O7 + 8YSZ/8YSZ Thermal Barrier Coatings

Oxidation Behavior of the Monolayered La2Zr2O7, Composite La2Zr2O7 + 8YSZ, and Double-Ceramic Layered La2Zr2O7/La2Zr2O7 + 8YSZ/8YSZ Thermal Barrier Coatings

Cracking Behavior of Atmospheric Plasma-Sprayed 8YSZ Thermal Barrier Coatings during Thermal Shock Test

Effect of CaO and CeO2 co-doping on thermo-physical properties of La2Z2O7

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Effect of CaO and CeO₂ co-doping on thermo-physical properties of La₂Z₂O₇