Influence of columnar grain microstructure on thermal shock resistance of laser re-melted ZrO2-7wt.% Y2O3 coatings and their failure mechanism

Fan, Zhengjie; Wang, Kedian; Dong, Xia; Duan, Wenqiang; Mei, Xuesong; Wang, Wenjun; Cui, Jianlei; Lv, Jing

doi:10.1016/j.surfcoat.2015.07.036

Cited by 70 publications

(15 citation statements)

References 34 publications

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“…From Figure 5b, the fracture microstructure of the dotted unit presents a structure similar to a columnar structure, a pseudo-columnar structure, which was formed along the heat flow direction owing to the coupling effect of the temperature gradient and solidification rate in laser processing. In fact, it is a columnar structure composed of closely-linked partially melted particles, and a similar structure was also found by others [50]. After Al deposition and vacuum heat treatment, there were still many segmented cracks on the surface of the dotted unit in the DA specimen, as shown in Figure 6a.…”

Section: Characterizationsupporting

confidence: 81%

Effects of Selective Laser Modification and Al Deposition on the Hot Corrosion Resistance of Ceria and Yttria-Stabilized Zirconia Thermal Barrier Coatings

Zhang

et al. 2019

Coatings

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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.

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Section: Characterizationsupporting

confidence: 81%

Effects of Selective Laser Modification and Al Deposition on the Hot Corrosion Resistance of Ceria and Yttria-Stabilized Zirconia Thermal Barrier Coatings

Zhang

et al. 2019

Coatings

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“…The enhanced toughness and decreased porosity and micro-cracks in the nanostructured coating contribute to improvement of thermal shock resistance, which is consistent with what Liang reported [6]. Fan et al discovered the small grain size had a positive influence on thermal fatigue life, and the columnar crystal microstructure had a great effect on thermal shock resistance of TBCs [13]. Wu et al found that the reduction of porosity resulted in increase of thermal diffusivity, suggesting a significant degradation in the thermal barrier effect [14].…”

Section: Introductionsupporting

confidence: 83%

“…Recently, a great deal of research with respect to the effect of microstructure on thermal properties such as thermal shock (oxidation) resistances [6][7][8]12,13] and thermal insulation [9,14], and mechanical properties such as hardness and modulus [5,[14][15][16][17][18][19][20][21][22] have been done. Wang et al found that the nanostructured zirconia coating possessed a better thermal shock resistance than that of the conventional zirconia coating [7].…”

Section: Introductionmentioning

confidence: 99%

Microstructure Observation and Nanoindentation Size Effect Characterization for Micron-/Nano-Grain TBCs

et al. 2020

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Microstructure observation and mechanical properties characterization for micron-/nano-grain thermal barrier coatings were investigated in this article. Scanning electron microscope images demonstrated that both micron-grain coating and nano-grain coating had micrometer-sized columnar grain structures; while the nano-grain coating had the initial nanostructures of the agglomerated powders reserved by the unmelted particles. The mechanical properties (hardness and modulus) of micron-/nano-grain coatings were characterized by using nanoindentation tests. The measurements indicated that the nano-grain coating possessed larger hardness and modulus than the micron-grain coating; which was related to the microstructure of coatings. Nanoindentation tests showed that the measured hardness increased strongly with the indent depth decreasing; which was frequently referred to as the size effect. The nanoindentation size effect of hardness for micron-/nano-grain coatings was effectively described by using the trans-scale mechanics theory. The modeling predictions were consistent with experimental measurements; keeping a reasonable selection of the material parameters.

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“…A graded coating structure consists of the remelted layer and unremelted layer, and the unremelted layer is still the typical pore structure of APS coating. Given the rapid solidification and crystallization from the melt, the microstructure of dense equiaxed and columnar grains could be formed in the remelted layer during laser retreatment 24,25 . However, the net irregular surface cracks and vertical cracks occurred after LR treatment in two cases of laser parameters.…”

Section: Resultsmentioning

confidence: 99%

Research of laser remelting on the thermal‐mechanical behaviors and heat treatment of yttria‐stabilized zirconia coatings

Zhu

Jiang

et al. 2020

Int J Applied Ceramic Tech

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In this study, the thermal and mechanical behaviors were investigated by simulating laser remelting of atmospheric plasma‐sprayed yttria‐stabilized zirconia coatings, and the molten depth and regions of stress concentration were compared between simulation and experiment. The heat treatment process of the remelted coating was also simulated. The crack formation mechanism in the YSZ coating remelted by laser and the heat‐treatment effect on residual stress were investigated. Results showed that the simulated results were consistent with the experimental measurements, and the residual thermal stress was the main cause of cracks formation. The coating remelted by a laser power of 1500 W and a scanning rate of 9 mm/s possessed less residual concentrated stress and segmented cracks. Heat treatment released concentrated stress, which was still accurate for the ceramic coating. If the coatings were slowly heated to demonstrate heat treatment after laser remelting, the cracks in the remelted layer decreased correspondingly.

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Influence of columnar grain microstructure on thermal shock resistance of laser re-melted ZrO2-7wt.% Y2O3 coatings and their failure mechanism

Cited by 70 publications

References 34 publications

Effects of Selective Laser Modification and Al Deposition on the Hot Corrosion Resistance of Ceria and Yttria-Stabilized Zirconia Thermal Barrier Coatings

Effects of Selective Laser Modification and Al Deposition on the Hot Corrosion Resistance of Ceria and Yttria-Stabilized Zirconia Thermal Barrier Coatings

Microstructure Observation and Nanoindentation Size Effect Characterization for Micron-/Nano-Grain TBCs

Research of laser remelting on the thermal‐mechanical behaviors and heat treatment of yttria‐stabilized zirconia coatings

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