scholarly journals Mechanical Stability Diagrams for Thermal Barrier Coating Systems

2021 ◽  
Vol 30 (3) ◽  
pp. 694-707
Author(s):  
Mario Rudolphi ◽  
Mathias Christian Galetz ◽  
Michael Schütze
Keyword(s):  
Thermal Barrier Coating ◽  
Mechanical Stability ◽  
Yttria Stabilized Zirconia ◽  
Assessment Model ◽  
Thermal Barrier ◽  
Emission Measurement ◽  
Stabilized Zirconia ◽  
Gadolinium Zirconate ◽  
Stability Diagrams ◽  
Barrier Coating

AbstractLoss of mechanical integrity due to thermal aging and subsequent spallation of the ceramic top layer is one of the dominant failure mechanisms in thermal barrier coating systems. In order to predict and avoid such mechanical failure, a strain-based lifetime assessment model is presented for a novel double-layer thermal barrier system. The investigated ceramic system consists of a gadolinium zirconate layer on top of a layer of yttria-stabilized zirconia prepared by atmospheric plasma spraying. The mechanical stability diagrams generated by the model delineate areas of safe operation from areas where mechanical damage of the thermal barrier coating becomes imminent. Intensive ceramographic inspection is used to investigate the defect growth kinetics in the ceramic top coat after isothermal exposure. Four-point bending experiments with in situ acoustic emission measurement are utilized to determine the critical strain to failure. The results are then used to generate mechanical stability diagrams for the thermal barrier coatings. From these diagrams, it becomes evident that the gadolinium zirconate layer has significantly lower strain tolerance than the yttria-stabilized zirconia. However, the underlying yttria-stabilized zirconia layer will provide some thermal protection even when the gadolinium zirconate layer has failed.

Thermal Conductivity and Specific Heat Capacity of Different Compositions of Yttria Stabilized Zirconia-Nickel Mixtures

2015 ◽  
Vol 1119 ◽  
pp. 783-788 ◽  
Author(s):  
Muhammad Rabiu Abbas ◽  
Alias Mohd Noor ◽  
Srithar Rajoo ◽  
Norhayati Ahmad ◽  
Uday M. Basheer ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Specific Heat ◽  
Thermal Barrier Coating ◽  
Specific Heat Capacity ◽  
Yttria Stabilized Zirconia ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Percentage Composition ◽  
Barrier Coating

Ceramic-metal composites also known as functionally gradient materials (FGM) are composite materials which are fabricated in order to have a gradual variation of constituent materials’ thermal and mechanical properties so as to have a smooth variation of the material properties in order to improve the overall performance and reduce the thermal expansion mismatch between ceramic and metal. The objective of the study is to determine the thermal properties of various percentage composition of Yttria stabilized zirconia-Nickel mixtures for application as thermal barrier coating materials in automotive turbocharger turbine volute casing. Specific heat capacity of different percentage composition of ceramic-metal powder composite were determined using DSC822 differential scanning calorimeter (Mettle Tolodo, Switzerland) at temperature ranges between 303K to 873K. While the thermal conductivity of the different percentage composition of ceramic-metal composite structures were determined using P5687 Cussons thermal conductivity apparatus (Manchester, UK) which uses one-dimensional steady-state heat conduction principle. The results have indicated that the specific heat capacity of the FGM increases sharply with an increase in temperature while the thermal conductivity of the FGM decreases with an increase in temperature. These results strongly agree with the theoretical and experimental values as well as the rule of mixtures obtainable in literature, which indicated the suitability of these FGM materials for thermal barrier coating applications.

scholarly journals The Thermal Conductivity of 8 Yttria Stabilized Zirconia and Mullite Thermal Barrier Coating on Medium Carbon Steel Substrate

2019 ◽  
Vol 9 (1) ◽  
pp. 5886-5892
Keyword(s):  
Thermal Conductivity ◽  
Carbon Steel ◽  
Thermal Barrier Coating ◽  
Steel Substrate ◽  
Medium Carbon Steel ◽  
Yttria Stabilized Zirconia ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Medium Carbon ◽  
Barrier Coating

Thermal conductivity is one of the main features of a thermal barrier coating (TBC) that is important in making sure that the TBC gives its best functionality to the system. A good TBC has low thermal conductivity, so that the temperature can drop across the coating which allows the system to operate in extremely high temperatures. There are several factors that can influence the thermal conductivity of the TBC such as the type of ceramic material used, the deposition method and the physical features of the TBC itself. For this research, air plasma spray (APS) is used to deposit 8 wt% yttria stabilized zirconia (8YSZ) and mullite on medium carbon steel substrates to study their respective thermal conductivities. The aim here is to develop a heat shield using TBC to protect the electric motor in an electrical turbocompounding system. The characteristics of the deposited TBC such as microstructure, element composition, phases and thermal conductivity are studied. The thermal conductivity is reduced when medium carbon steel substrate deposited with TBC. The thermal conductivity of 8YSZ, mullite and uncoated sample at minute 60 is 0.868 W/mK, 0.903 W/mK and 1.057 W/mK, respectively. Therefore, the deposition of 8YSZ TBC can lower the thermal conductivity of the medium carbon steel heat shield.

scholarly journals OBSERVATIONAL ANALYSIS ON RESULT OF YSZ COATED PISTON CROWN ON THE BEHAVIOUR OF A PETROL ENGINE

2021 ◽  
pp. 153-160
Author(s):  
Muhammad Asad Riaz
Keyword(s):  
Thermal Barrier Coating ◽  
Thermal Efficiency ◽  
Mechanical Efficiency ◽  
Yttria Stabilized Zirconia ◽  
Petrol Engine ◽  
Thermal Barrier ◽  
Stabilized Zirconia ◽  
Piston Engine ◽  
Piston Crown ◽  
Barrier Coating

An observational study of thermal barrier coating (TBC) on the working of 4-stroke single cylinder petrol engine was studied. Yttria Stabilized Zirconia (YSZ) used as coating material. YSZ has less thermal conductivity, sustainability under high temperature and pressure. Main aim of TBC is to decrease heat losses to the cooling jacket of the engine. YSZ is coated on the piston crown by Plasma spray method. YSZ coating improves the performance of petrol engine. Experimental study was carried out on 4-stroke single cylinder OHV petrol engine 25‎°C inclined cylinder horizontal shaft engine on performance of ceramic coated engine and compared with baseline engine under different speed. Results show that ceramic coated engine is more effective than conventional engine as brake specific fuel consumption (BSFC) is reduced 2-4% than normal piston engine, brake thermal efficiency (BTE) of modified engine is expanded 4-8% than unmodified engine. Indicated thermal efficiency (ITE) of modified piston engine is increased 5-10% than normal engine. Mechanical efficiency (ME) of the TBC engine is increased 4-10% than standard engine. Volumetric efficiency (VE) of modified engine is decreased 3-9% when compared with standard engine and exhaust gas temperature (EGT) of ceramic coated engine is increased 1-3% than unmodified engine. KEYWORDS: Petrol Engine, Thermal barrier coating (TBC), Yttria Stabilized Zirconia (YSZ). Mechanical Efficiency

An Investigation of Phase Crystallinity in Laser Modified Yttria Stabilized Zirconia (YSZ) Thermal Barrier Coating

2014 ◽  
Vol 611-612 ◽  
pp. 1601-1607
Author(s):  
Mohamed Suffian Reza ◽  
Syarifah Nur Aqida ◽  
Mohd Radzi Mohd Toff
Keyword(s):  
Surface Roughness ◽  
Thermal Barrier Coating ◽  
Pulse Repetition Frequency ◽  
Sample Surface ◽  
Yttria Stabilized Zirconia ◽  
Thermal Barrier ◽  
X Ray Diffraction ◽  
Stabilized Zirconia ◽  
X Ray ◽  
Barrier Coating

This paper presents laser surface modification process of plasma sprayed yttria stabilized zirconia (YSZ) thermal barrier coating (TBC) for enhanced hardness properties and low surface roughness. A 300W JK300HPS Nd: YAG laser was used to process YSZ TBC sample surface. The parameters selected for examination were laser power, pulse repetition frequency (PRF) and residence time. Micrographs of the TBC system were captured using EVO 15 Scanning Electron Microscope (SEM). Surface roughness was measured using 2-dimensional stylus profilometer. X-ray diffraction analysis (XRD) was conducted to measure phase crystallinity of the laser-modified coating surface. X-ray diffraction patterns were recorded in the 2θ range of 10 to 80° using Bruker D8 Advance system with 0.7Å wavelength from a copper source (~1.5Å). The laser modified surface exhibited higher crystallinity compared to the as-sprayed samples. The presence of tetragonal phase was detected in the as-sprayed and laser processed samples. The hardness properties of laser modified TBC increased 15% of the as-sprayed sample. These finding are significant to development of thermal barrier coating design optimization for enhanced surface properties of semi-solid forming die.

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