scholarly journals Study on the Characteristics of a TBC System Containing a PVD-Al Interlayer under Isothermal Loading

Coatings ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 887
Author(s):  
Ibrahim Ali ◽  
Paweł Sokołowski ◽  
Lech Pawłowski ◽  
Daniel Wett ◽  
Thomas Grund ◽  
...  
Keyword(s):  
Bond Coat ◽  
Physical Vapor Deposition ◽  
Crack Formation ◽  
Yttria Stabilized Zirconia ◽  
Atmospheric Plasma ◽  
Slow Heating ◽  
Thermal Barrier ◽  
Oxide Formation ◽  
Stabilized Zirconia ◽  
Isothermal Exposure

In this work, the oxidation behavior of an atmospheric plasma-sprayed thermal barrier coating (TBC) system with a thin Al physical vapor deposition (PVD) film deposited over the bond coat is discussed. The TBC consisted of: (i) CoNiCrAlY bond coat sprayed on the Inconel 600 substrate; (ii) a thin Al interlayer deposited by direct current DC magnetron sputtering; and (iii) yttria-stabilized zirconia (YSZ) sprayed as the top coat. Such thermal barrier coatings (Al-TBC) were isothermally oxidized at 1150 °C with different holding times, and then they were compared with the reference TBC (R-TBC) systems without an Al interlayer (R-TBC). Scanning electron microscopy with energy-dispersive X-ray analysis was used to study the oxide formation along the bond coat (BC) and top coat (TC) interface, as well as crack formation in the yttria-stabilized zirconia top coat. Then, using Image Analysis, the oxide formation and crack formation were characterized in all specimens after a slow heating and cooling cycle, and after 100, 300, and 600 h of isothermal exposure. The results showed that the Al-TBC system proposed here exhibits higher oxidation resistance at the bond coat and top coat interface, less crack formation in the YSZ top coat, and enhanced mechanical stability compared to the conventional TBCs. It was found that enrichment of the bond coat and top coat interface with Al limited the formation of detrimental transition metal oxides during isothermal loading. Finally, the corresponding failure caused by thermally grown oxide (TGO) phenomena is “mixed failure mode” for both studied TBCs.

scholarly journals Isothermal Oxidation Behavior of Gadolinium Zirconate (Gd2Zr2O7) Thermal Barrier Coatings (TBCs) produced by Electron Beam Physical Vapor Deposition (EB-PVD) technique

2018 ◽  
Vol 16 (1) ◽  
pp. 986-991 ◽  
Author(s):  
Kadir Mert Doleker ◽  
Yasin Ozgurluk ◽  
Hayrettin Ahlatci ◽  
Abdullah Cahit Karaoglanli
Keyword(s):  
Electron Beam ◽  
Thermal Barrier Coatings ◽  
Vapor Deposition ◽  
Bond Coat ◽  
Physical Vapor Deposition ◽  
Isothermal Oxidation ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Barrier Coatings ◽  
X Ray

AbstractThermal Barrier Coatings (TBCs) provide thermal insulation for gas turbine components operating at high temperatures. Generally, TBCs were produced on a MCrAlY bond coat with 7-8% Yttria Stabilized Zirconia (YSZ) using Atmospheric Plasma Spray (APS) technique. In this study, Inconel 718 substrate material was coated with CoNiCrAlY bond coat using high velocity oxygen fuel (HVOF) technique. Afterward, Gd2Zr2O7 was deposited on samples using Electron Beam Physical Vapor Deposition (EB-PVD) technique. Produced TBCs were exposed to isothermal oxidation tests at 1000°C for 8 h, 24 h, 50 h and 100 h in muffle furnace. Scanning electron microscopy-energy distribution X-ray (SEM-EDX) spectroscopy was used to investigate thermally grown oxide (TGO) layer and TGO growth behavior of TBCs. In addition, X-ray Diffractometer (XRD) analysis was performed to TBCs to understand whether phase transformation occurs or not before and after oxidation.

Transmission Electron Microscopy Investigations of an As-Processed Yttria-Stablilized zirconia on Platinum Aluminide Bond Coat

2000 ◽  
Vol 645 ◽  
Author(s):  
Judith C. Yang ◽  
Noel T. Nuhfer
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Bond Coat ◽  
Physical Vapor Deposition ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
Hollow Cone ◽  
X Ray ◽  
Platinum Aluminide ◽  
Transmission Electron

ABSTRACTWe examined an as-processed yttria-stabilized zirconia (YSZ) on platinum aluminide bond coat (BC), produced by electron beam physical vapor deposition, with transmission electron microscopy, including energy dispersive X-ray spectroscopy and hollow-cone diffraction. Columnar α-Al2O3 grains (∼100nm) formed at the interface between the BC and YSZ. A thin intermix (∼50nm) region was observed between the α-Al2O3 and YSZ. Hollow cone diffraction showed that the α-Al2O3 grains and the small-grained (∼10nm) YSZ near the α-Al2O3 are randomly oriented, without preferential texturing. No evidence of spinel formation was noted.

scholarly journals Effect of La2O3 on Microstructure and Thermal Conductivity of La2O3-Doped YSZ Coatings

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2966 ◽  
Author(s):  
Xiaojie Guo ◽  
Chucheng Lin ◽  
Jimei Zhang ◽  
Ziwei Liu ◽  
Caifen Jiang ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Barrier Coatings ◽  
Lattice Parameter ◽  
Atmospheric Plasma Spraying ◽  
Yttria Stabilized Zirconia ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Co Doped

Enhancing the properties of thermal barrier coatings (TBCs) by doping with rare earth elements has been a hot topic for a while. La2O3 and Y2O3 co-doped ZrO2 (La-YSZ) TBCs and yttria-stabilized zirconia (YSZ) TBCs were deposited by atmospheric plasma spraying (APS), and the comprehensive effects of La3+ on the microstructure and property were investigated. The thermal conductivity and microstructure were investigated and were compared with YSZ. The recrystallized fraction components of all TBCs were quantified. It is clearly found that the component of “recrystallized” and “deformed” grains for La-YSZ TBCs is much higher than that for YSZ TBCs. This could be due to La3+ doping enlarging the lattice parameter of YSZ and thus increasing the melting index, which in turns leads to the smaller grain size of La-YSZ TBCs. As a result, the thermal conductivities of La-YSZ TBCs were distinctly lower than those of YSZ TBCs.

Failure Mechanism of Yttria Stabilized Zirconia Atmospheric Plasma Sprayed Thermal Barrier Coatings Subjected to Calcia-Magnesia-Alumino-Silicate Environmental Attack

2017 ◽  
Vol 270 ◽  
pp. 39-44 ◽  
Author(s):  
Ladislav Čelko ◽  
David Jech ◽  
Pavel Komarov ◽  
Michaela Remešová ◽  
Karel Dvořák ◽  
...  
Keyword(s):  
Thin Layer ◽  
Thermal Barrier Coatings ◽  
Yttria Stabilized Zirconia ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Alumino Silicate ◽  
Plasma Sprayed ◽  
Environmental Attack

The contribution focuses on the description of failure mechanism of atmospheric plasma sprayed multilayer thermal barrier coatings subjected to calcia-magnesia-alumino-silicate (CMAS) environmental attack. To identify exothermic and endothermic reactions which occurred during heating/cooling by means of calorimetry was also utilized initial yttria stabilized zirconia (YSZ) powder subsequently used for thermal spraying of multilayer thermal barrier coating system (TBCs), CMAS powder later on utilized for thin layer deposition and its mixture. Atmospheric plasma spray technique was used to produce the TBCs on a grit blasted nickel-based superalloy substrates, where CoNiCrAlY powder was used for deposition of a bond coat and YSZ powder was sprayed as a top coat. In accordance to the aerospace standard the thin layer of CMAS was deposited on as sprayed TBCs samples surface from its colloidal solution by paint brush method. Burner-rig test, utilizing direct propane-oxygen flame, was used for thermal cyclic exposition of the multilayer coated samples at the temperature of 1150 °C. Samples after thermal cyclic exposure test were investigated by means of materialographic analysis approaches. The significant reduction in life-time of CMAS coated YSZ top coat was observed due to lower melting point phase formation and molten silicate crystallization within the pores providing the spallation identified as a major mechanism of TBCs failure.

scholarly journals Effect of Different Types of Pores on Thermal Conductivity of YSZ Thermal Barrier Coatings

Coatings ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 138 ◽  
Author(s):  
Yiling Huang ◽  
Ningning Hu ◽  
Yi Zeng ◽  
Xuemei Song ◽  
Chucheng Lin ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermal Barrier Coatings ◽  
Cross Section ◽  
Quantitative Relationship ◽  
Yttria Stabilized Zirconia ◽  
Atmospheric Plasma ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Different Types

Atmospheric plasma spray (APS) yttria-stabilized zirconia coatings have a complex microstructure with a variety of pores that significantly reduce the thermal conductivity. APS thermal barrier coatings (TBCs) with a similar monoclinic phase were prepared. The pore sizes and distributions of the coatings were obtained by scanning their cross-section via SEM; the scanned areas were over 1 mm × 2 mm and more than 23,000 pores for each coating were analyzed. Multiple linear regression was used to analyze the porosity data and then to determine the quantitative relationship between different types of pores and thermal conductivity. Results revealed that the different pores have different effects on decreasing the thermal conductivity. The small, vertical pores have the biggest effect, while the horizontal pores also play a significant role in decreasing the thermal conductivity.

scholarly journals The Effects on Thermal Efficiency of Yttria-Stabilized Zirconia and Lanthanum Zirconate-based Thermal Barrier Coatings on Aluminum Heating Block for 3d Printer

Coatings ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 792
Author(s):  
Hasan Demir
Keyword(s):  
Temperature Distribution ◽  
Heat Loss ◽  
Yttria Stabilized Zirconia ◽  
Thermal Barrier ◽  
Print Quality ◽  
Stabilized Zirconia ◽  
Coating Materials ◽  
Lanthanum Zirconate ◽  
Barrier Coating ◽  
Coating Method

Fused filament fabrication is an important additive manufacturing method, for which 3D printers are the most commonly used printing tools. In this method, there are many factors that affect the printing quality, chief among which is temperature. The fusion temperature of the material is created by an aluminum heating block in the extruder. Stability and a constant temperature for the aluminum heating block are inevitable requirements for print quality. This study aims to use the thermal barrier coating method to increase the thermal efficiency and stability of the aluminum heating block by reducing heat loss. Furthermore, it aims to perform steady-state thermal analysis using finite element analysis software. The analyses are carried out in stagnant air environment and at the printing temperature of acrylonitrile butadiene styrene material. In order to examine the effects of different coating materials, blocks coated with two different coating materials, as well as uncoated blocks, were used in the analyses. The coating made with yttria-stabilized zirconia and pyrochlore-type lanthanum zirconate materials, together with the NiCRAl bond layer, prevent temperature fluctuation by preventing heat loss. The effects of the coating method on average heat flux density, temperature distribution of blocks, and temperature distribution of the filament tube hole were investigated. Additionally, changes in flow velocity were determined by examining the effects of the thermal barrier coating method on temperature distribution. The average heat flux density in the coated blocks decreased by 10.258%. Throughout the investigation, the temperature distributions in the coated blocks became homogeneous. It was also observed that both coating materials produce the same effect. This article performs a steady-state thermal analysis of a conventional model and thermal-barrier-coated models to increase print quality by reducing heat loss from the aluminum heating block.

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