“…In the case of Quadlayer coating, GZO column tops were successfully covered by protective dense YAG “caps” but deeper and narrower intercolumnar gaps were not filled by YAG, thus retaining the desirable strain tolerance of the columnar GZO. It may be noted that deposition rates and microstructures of individual sublayers correspond well to our previous studies with single-layered top-coats where their microstructural features are discussed in more details (Ref 13 , 15 ). Fig.…”
Section: Resultssupporting
confidence: 86%
“…Deposition of individual sublayers consisted of several deposition cycles (each consisting of 3 up and down torch strokes) interrupted by cooling periods to prevent overheating of the samples. Further details on deposition procedure are provided in Ref 12 , 13 , 15 . Spraying parameters are surveyed in Table 1 .…”
Section: Methodsmentioning
confidence: 99%
“…Due to the high plasma enthalpy, considerable feed rates (more than 100 mL of liquid per minute) may be processed with high deposition efficiency (DE). For example, at ~ 100 mL/min feed rates, DE of around 55-60% is commonly achieved by WSP-H torch for YSZ spraying from suspension or solution and around 75% for spraying of YAG from suspension (Ref 12 , 13 ). TBCs with both NiCrAlY bond-coat and single-layer YSZ or GZO top-coats were already successfully deposited from powder, suspension, and solution and benchmarked by thermal cycling fatigue (TCF) test repeatedly exposing coatings to 1100 °C for 1 h. Please note that this test is in the literature also denoted as furnace cycle test (acronym FCT) and due to its relatively low cost, simplicity, and high throughput is often used for initial screening of thermal fatigue resistance of newly developed TBCs.…”
High-enthalpy hybrid water/argon-stabilized plasma (WSP-H) torch may be used for efficient deposition of coatings from dry powders, suspensions, and solutions. WSP-H torch was used to deposit two complete thermal barrier coatings (TBCs) with multilayered top-coat. NiCrAlY was used as bond
-
coat and deposited on nickel-based superalloy substrates. Top-coat consisted of up to three sublayers: (i) yttria-stabilized zirconia (ZrO
2
-8 wt.%Y
2
O
3
-YSZ) deposited from solution, (ii) gadolinium zirconate (Gd
2
Zr
2
O
7
-GZO) deposited from suspension, and (iii) optional yttrium aluminum garnet (Y
3
Al
5
O
12
-YAG) overlayer deposited from suspension. Each of the sublayers was intended to provide different functionalities, namely improved fracture toughness, low thermal conductivity, and high erosion resistance, respectively. High-temperature performance and thermal shock resistance of the deposited coatings were tested by thermal cycling fatigue “TCF” test (maximum temperature 1100 °C, 1 h dwell per cycle) and “laser-rig” test (maximum temperature ~ 1530 °C, 5 min dwell per cycle) exposing samples to isothermal and gradient thermal conditions, respectively. In both tests, coatings endured around 800 test cycles which shows great potential for further development of these layers and their application in demanding thermal conditions. Analysis of the samples after the test showed microstructural changes and identified reason of ultimate coating failure.
“…In the case of Quadlayer coating, GZO column tops were successfully covered by protective dense YAG “caps” but deeper and narrower intercolumnar gaps were not filled by YAG, thus retaining the desirable strain tolerance of the columnar GZO. It may be noted that deposition rates and microstructures of individual sublayers correspond well to our previous studies with single-layered top-coats where their microstructural features are discussed in more details (Ref 13 , 15 ). Fig.…”
Section: Resultssupporting
confidence: 86%
“…Deposition of individual sublayers consisted of several deposition cycles (each consisting of 3 up and down torch strokes) interrupted by cooling periods to prevent overheating of the samples. Further details on deposition procedure are provided in Ref 12 , 13 , 15 . Spraying parameters are surveyed in Table 1 .…”
Section: Methodsmentioning
confidence: 99%
“…Due to the high plasma enthalpy, considerable feed rates (more than 100 mL of liquid per minute) may be processed with high deposition efficiency (DE). For example, at ~ 100 mL/min feed rates, DE of around 55-60% is commonly achieved by WSP-H torch for YSZ spraying from suspension or solution and around 75% for spraying of YAG from suspension (Ref 12 , 13 ). TBCs with both NiCrAlY bond-coat and single-layer YSZ or GZO top-coats were already successfully deposited from powder, suspension, and solution and benchmarked by thermal cycling fatigue (TCF) test repeatedly exposing coatings to 1100 °C for 1 h. Please note that this test is in the literature also denoted as furnace cycle test (acronym FCT) and due to its relatively low cost, simplicity, and high throughput is often used for initial screening of thermal fatigue resistance of newly developed TBCs.…”
High-enthalpy hybrid water/argon-stabilized plasma (WSP-H) torch may be used for efficient deposition of coatings from dry powders, suspensions, and solutions. WSP-H torch was used to deposit two complete thermal barrier coatings (TBCs) with multilayered top-coat. NiCrAlY was used as bond
-
coat and deposited on nickel-based superalloy substrates. Top-coat consisted of up to three sublayers: (i) yttria-stabilized zirconia (ZrO
2
-8 wt.%Y
2
O
3
-YSZ) deposited from solution, (ii) gadolinium zirconate (Gd
2
Zr
2
O
7
-GZO) deposited from suspension, and (iii) optional yttrium aluminum garnet (Y
3
Al
5
O
12
-YAG) overlayer deposited from suspension. Each of the sublayers was intended to provide different functionalities, namely improved fracture toughness, low thermal conductivity, and high erosion resistance, respectively. High-temperature performance and thermal shock resistance of the deposited coatings were tested by thermal cycling fatigue “TCF” test (maximum temperature 1100 °C, 1 h dwell per cycle) and “laser-rig” test (maximum temperature ~ 1530 °C, 5 min dwell per cycle) exposing samples to isothermal and gradient thermal conditions, respectively. In both tests, coatings endured around 800 test cycles which shows great potential for further development of these layers and their application in demanding thermal conditions. Analysis of the samples after the test showed microstructural changes and identified reason of ultimate coating failure.
“…This surface view allows to show the cauliflower-like structure typically built-up during SPS process [28]. As reported in the literature, this cauliflower structure relates to the columnar structure observable through the cross-sectional area of thick SPS coatings [29,30]. As observed, the stand-off distance exerts an important influence on the formation and growth of cauliflower-like structure because at shorter distance particles impact almost completely melted on the substrate.…”
Section: Suspension Feedstock Preparation and Characterisationmentioning
confidence: 53%
“…give rise after injection to a large amount of droplets with fewer particles inside [30]. Therefore, during water evaporation particles receive less energy to melt remaining isolated in the centre and periphery of the torch.…”
Section: Suspension Feedstock Preparation and Characterisationmentioning
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