scholarly journals Thermoelastic Characteristics in Thermal Barrier Coatings with a Graded Layer between the Top and Bond Coats

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Seokchan Kim ◽  
Jaegwi Go ◽  
Yeon-Gil Jung ◽  
Je-Hyun Lee
Keyword(s):  
Temperature Distribution ◽  
Longitudinal Direction ◽  
Thermomechanical Properties ◽  
Thermal Barrier ◽  
Bond Coats ◽  
Barrier Coating ◽  
Thermoelastic Characteristics ◽  
Volume Method ◽  
Thermoelastic Theory ◽  
Symmetric Temperature

A graded layer was introduced at the interface between the top and bond coats to reduce the risk of failure in a thermal barrier coating (TBC) system, and the thermoelastic behavior was investigated through mathematical approaches. Two types of TBC model with and without the graded layer, subject to a symmetric temperature distribution in the longitudinal direction, were taken into consideration to evaluate thermoelastic behaviors such as temperature distribution, displacement, and thermal stress. Thermoelastic theory was applied to derive two governing partial differential equations, and a finite volume method was developed to obtain approximations because of the complexity. The TBC with the graded layer shows improved durability in thermoelastic characteristics through mathematical approaches, in agreement with the experimental results. The results will be useful in discovering technologies for enhancing the thermomechanical properties of TBCs.

scholarly journals Progress in Novel Electrodeposited Bond Coats for Thermal Barrier Coating Systems

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4214
Author(s):  
Kranthi Kumar Maniam ◽  
Shiladitya Paul
Keyword(s):  
Gas Turbine ◽  
Thermal Barrier Coating ◽  
Gas Turbines ◽  
High Performance ◽  
Turbine Engines ◽  
Thermal Barrier ◽  
Gas Turbine Engines ◽  
Potential Cost ◽  
Bond Coats ◽  
Barrier Coating

The increased demand for high performance gas turbine engines has resulted in a continuous search for new base materials and coatings. With the significant developments in nickel-based superalloys, the quest for developments related to thermal barrier coating (TBC) systems is increasing rapidly and is considered a key area of research. Of key importance are the processing routes that can provide the required coating properties when applied on engine components with complex shapes, such as turbine vanes, blades, etc. Despite significant research and development in the coating systems, the scope of electrodeposition as a potential alternative to the conventional methods of producing bond coats has only been realised to a limited extent. Additionally, their effectiveness in prolonging the alloys’ lifetime is not well understood. This review summarises the work on electrodeposition as a coating development method for application in high temperature alloys for gas turbine engines and discusses the progress in the coatings that combine electrodeposition and other processes to achieve desired bond coats. The overall aim of this review is to emphasise the role of electrodeposition as a potential cost-effective alternative to produce bond coats. Besides, the developments in the electrodeposition of aluminium from ionic liquids for potential applications in gas turbines and the nuclear sector, as well as cost considerations and future challenges, are reviewed with the crucial raw materials’ current and future savings scenarios in mind.

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.

Examples of the Use of Optical Spectroscopy to Detect Damage of Thermal Barrier Coatings During Cyclic Oxidation

2012 ◽  
Author(s):  
Claudia Rinaldi ◽  
Ada del Corno ◽  
Francesco Enrichi
Keyword(s):  
Thermal Cycling ◽  
Compressive Stress ◽  
Optical Spectroscopy ◽  
Residual Life ◽  
Phase Changes ◽  
Thermal Barrier ◽  
Bond Coats ◽  
Barrier Coating ◽  
Automatic Mapping ◽  
Temperature Exposure

This paper describes some examples of the use of two optical spectroscopy techniques to study thermal barrier coating (TBC) degradation preceeding failure. The first part describes photoluminescence piezospectroscopy (PLPS) results obtained on a series of specimens with EB-PVD TBC and Pt -aluminised bond coats. The monotonic decrease of the alumina compressive stress level with ageing and thermal cycling confirms that TGO compressive stress levels can be used as residual life indicators in this type of coating. The automatic mapping system implemented by RSE (Ricerca sul Sistema Energetico) provides precise and reliable results about the level of damage at the BC/TBC interface, well before failure; mapping provides data regarding the precise positions where the first macroscopic detachment (a few millimeters wide) occurs. As PLPS is not applicable to thermal-sprayed APS TBCs, the second part of the paper describes some examples of the contribution that Raman spectroscopy can provide to detect phase changes due to degradation preceeding failure of the TBCs. Possible problems relating to the presence of undesired RE elements in the ceramic layer due to strong fluorescence are also described; solutions are proposed. Finally, examples of how innovative confocal microRaman produces maps evidencing areas where high temperature exposure and thermal cycling-produced phase transformation of the Yttria partially stabilised Zirconia from tetragonal to monoclinic (which typically occurs during cracking processes preceeding final TBC failure) are provided.

scholarly journals Effect of Plasma Pretreatment on Thermal Durability of Thermal Barrier Coatings in Cyclic Thermal Exposure

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Sang-Won Myoung ◽  
Zhe Lu ◽  
Yeon-Gil Jung ◽  
Byung-Koog Jang ◽  
Young-Soo Yoo ◽  
...  
Keyword(s):  
Bond Coat ◽  
Thermal Exposure ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Bond Coats ◽  
Thermal Durability ◽  
Thermomechanical Characteristics ◽  
Barrier Coating ◽  
Plasma Pretreatment ◽  
Surface Modified

Plasma pretreatment on the top and bond coats was performed and its influence on the thermal durability of thermal barrier coating (TBC) system was investigated through cyclic thermal exposure. Two types of bond coat were prepared by different methods, namely, air plasma spray (APS) and high-velocity oxy-fuel (HVOF), and two kinds of feedstock powder were employed for preparing the top coat in APS process. The better thermal durability was achieved in the vertically cracked TBC with the surface modified bond coat or with the bond coat prepared by APS process. The hardness and fracture toughness values of TBCs increased because of densification of the top coat during cyclic thermal exposure, and the bond coat prepared by HVOF process showed higher values than that by APS process. The TBCs with the surface modified bond coat were more efficient in improving adhesive strength than those without plasma pretreatment on the bond coat. The relationship between microstructure evolution and thermomechanical characteristics of TBCs with plasma pretreatment was discussed in cyclic thermal exposure.

Formation of discontinuous Al2O3 layers during high-temperature oxidation of RuAl alloys

2006 ◽  
Vol 21 (1) ◽  
pp. 276-286 ◽  
Author(s):  
P.J. Bellina ◽  
A. Catanoiu ◽  
F.M. Morales ◽  
M. Rühle
Keyword(s):  
High Temperature Oxidation ◽  
Oxidation Behavior ◽  
Microstructural Characterization ◽  
Isothermal Oxidation ◽  
Thermal Barrier ◽  
Interface Instability ◽  
Temperature Oxidation ◽  
Bond Coats ◽  
Barrier Coating ◽  
Transmission Electron

Bond coats play a crucial role in the performance of thermal barrier coating systems. Ru alloys have been identified as promising candidates; therefore, systematic studies were performed on the oxidation behavior of bulk RuAl (50–50 at.%). Isothermal oxidation and thermogravimetric analyses were performed at 1100 °C for different times ranging from 0.1 h to 500 h. Microstructural characterization was performed by scanning and transmission electron microscopy. The results showed the formation of an α–Al2O3 layer on top of a δ–Ru layer. Interface instability between these layers and evaporation of gaseous Ru-oxides lead to the formation of large elongated cavities and alternating α–Al2O3/δ–Ru layers.

Ru-Based Bond Coats Used for High Temperature Applications

2015 ◽  
Vol 1114 ◽  
pp. 229-232
Author(s):  
Amalia Soare ◽  
Ioana Csáki ◽  
Cristina Oprea ◽  
Sorin Soare ◽  
Cristian Predescu ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermal Barrier Coating ◽  
Electric Furnace ◽  
Induction Furnace ◽  
Thermal Barrier ◽  
Bond Coats ◽  
Barrier Coating ◽  
Before And After ◽  
Materials Used ◽  
Microscopy Techniques

The main objective of this work is the development of new Ru-based Bond Coats (BC) as part of Thermal Barrier Coating Systems (TBC).So far, Ru-based systems have not been investigated in detail. We investigate the possibility of replacing the traditional materials used as BC, with Ru-based alloys. They are important candidats because RuAl has the same structure as NiAl, has properties superior to those of NiAl at high temperatures and last but not least, Ru is much cheaper than Pt.We have prepared a RuAl 50/50 at% alloy in an induction furnace which was subsequently subjected to oxidation in an electric furnace, in air, at 1100°C, for 10h.The alloy was analysed before and after oxidation using advanced microscopy techniques (SEM, TEM).The challenge of this research is to obtain an adherent and uniform layer of alumina after oxidation. The results so far suggest encouraging results.

Fracture Behavior of Plasma-Sprayed Thermal Barrier Coatings with Different Bond Coats upon Cyclic Thermal Exposure

2009 ◽  
Vol 620-622 ◽  
pp. 343-346
Author(s):  
Young Seok Sim ◽  
Sung Il Jung ◽  
Jae Young Kwon ◽  
Je Hyun Lee ◽  
Yeon Gil Jung ◽  
...  
Keyword(s):  
Bond Coat ◽  
Fracture Behavior ◽  
Thermal Exposure ◽  
Thermally Grown Oxide ◽  
Fatigue Tests ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Bond Coats ◽  
Barrier Coating ◽  
Tbc Systems

The effects of bond coat nature in thermal barrier coating (TBC) systems on the delamination or fracture behavior of the TBCs with different bond coats prepared using two different processes—air plasma spray (APS) and high velocity oxyfuel (HVOF)—were investigated by cyclic thermal fatigue tests. The TBCs with the HVOF bond coat were delaminated or fractured after 3–6 cycles, whereas those with the APS bond coat were delaminated after 10 cycles or show a sound condition. These results indicate that the TBC system with the APS bond coat has better thermal durability than the system with the HVOF bond coat under long-term cyclic thermal exposure. The hardness values of the TBCs (top coats) in both systems are dependent on applied loads, irrespective of the hardness of the bond coats and the substrate. The values are not responded to the bond coat nature or the exposure time. Thermally grown oxide (TGO) layers in both cases consist of two regions with the inner TGO layer containing only Al2O3 and the outer TGO layer of mixed-oxide zone containing Ni, Co, Cr, Al in Al2O3 matrix. The outer TGO layer has a more irregular shape than the inner TGO layer, and there are many pores within the outer layer. At failure, the TGO thickness of the TBC system with the HVOF bond coat is 9–13 m, depending on the total exposed time, and that of the TBC system with the APS bond coat is about 20 m. The both TBC systems show the diffusion layer on the side of substrate in the interface between the bond coat and the substrate. The relationship between the delamination or fracture behavior and the bond coat nature has been discussed, based on the elemental analysis and microstructural evaluation.

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