scholarly journals Detection of segmentation cracks in top coat of thermal barrier coatings during plasma spraying by non-contact acoustic emission method

2014 ◽  
Vol 15 (3) ◽  
pp. 035007 ◽  
Author(s):  
Kaita Ito ◽  
Hitoshi Kuriki ◽  
Hiroshi Araki ◽  
Seiji Kuroda ◽  
Manabu Enoki
Keyword(s):  
Acoustic Emission ◽  
Plasma Spraying ◽  
Thermal Barrier Coatings ◽  
Thermal Barrier ◽  
Acoustic Emission Method ◽  
Emission Method ◽  
Barrier Coatings ◽  
Segmentation Cracks

Highly Porous Thick Thermal Barrier Coatings Produced by Air Plasma Spraying of a Plastic-Ceramic Mixed Powder

1997 ◽  
Author(s):  
G. Gualco ◽  
S. Corcoruto ◽  
A. Campora ◽  
R. Taylor ◽  
D. Schwingel ◽  
...  
Keyword(s):  
Thermal Shock ◽  
Plasma Spraying ◽  
Thermal Barrier Coatings ◽  
Gas Turbines ◽  
Thermal Barrier ◽  
High Porosity ◽  
Air Plasma ◽  
Air Plasma Spraying ◽  
Barrier Coatings ◽  
Segmentation Cracks

Abstract In order to increase the efficiency of heavy duty gas turbines for power generation and to reduce their emissions, higher combustion chamber temperature is required; a considerable improvement of the insulation properties of the thermal barrier coatings is therefore required. 1.5 mm thick thermal barrier coatings have been deposited by air plasma spraying a mixed polyester-zirconia powder; by this process high porosity, up to 22%, has been achieved together with a good deposition efficiency (about 50%); the coating microstructure has been thoroughly examined by quantitative image analysis, determining the pores size distribution and the vertical segmentation cracks density. Thermal shock tests showed a life improvement with respect to the state-of-art by a factor > 100; relationships among thermal shock life, deposition rate, segmentation cracks density and porosity were determined. Thermal expansion and thermal diffusivity were measured up to 1200 °C; failure strength, failure strain and Young's modulus were determined by a four-point bending technique.

scholarly journals Influence of SiC Addition on Mechanical Behavior of Thermal Barriers with the Aid of Acoustic Emission

2021 ◽  
Vol 5 (1) ◽  
pp. 16
Author(s):  
David Jeronimo Busquets ◽  
Carlos Bloem ◽  
Amparo Borrell ◽  
Maria Dolores Salvador
Keyword(s):  
Acoustic Emission ◽  
Mechanical Behavior ◽  
Thermal Barrier Coatings ◽  
Wavelet Transforms ◽  
Coefficient Of Thermal Expansion ◽  
Microstructural Analysis ◽  
Thermal Barrier ◽  
Transfer Coefficients ◽  
Barrier Coatings ◽  
Thermal Barriers

The improvement of high temperature materials with lower heat transfer coefficients lead to the development of thermal barrier coatings (TBCs). One of the most widely used materials for thermal barrier coatings is Y2O3 stabilized ZrO2 (Y-TZP) because of its excellent shock resistance, low thermal conductivity, and relatively high coefficient of thermal expansion. The aim of this work is to study the TBCs mechanical behavior with the addition of SiC into the suspension of Y-TZP/Al2O3 by acoustic emission (AE). Additionally, a microstructural analysis and a finite elements model were carried out in order to compare results. The coatings were made by suspension plasma spray (SPS) on metal plates of 70 × 12 × 2 mm3. An intermetallic was deposited as a bond coating, followed by a coating of Y-TZP/Al2O3 with and without 15 wt.% SiC, with thicknesses between 87 and 161 μm. The AE becomes a fundamental tool in the study of the mechanical behavior of thermal barriers. The use of wavelet transforms streamlines the study and analysis of recorded sound spectra. The crack generation arises at very low stress levels.

Thermal Cycling Behavior of Lanthanum-Cerium Oxide Thermal Barrier Coatings Prepared by Air Plasma Spraying

2007 ◽  
Vol 336-338 ◽  
pp. 1759-1761 ◽  
Author(s):  
Wen Ma ◽  
Yue Ma ◽  
Sheng Kai Gong ◽  
Hui Bin Xu ◽  
Xue Qiang Cao
Keyword(s):  
Cerium Oxide ◽  
Plasma Spraying ◽  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Room Temperature ◽  
Thermal Barrier ◽  
Air Plasma ◽  
Air Plasma Spraying ◽  
Cyclic Testing ◽  
Barrier Coatings

Lanthanum-cerium oxide (La2Ce2O7, LC) is considered as a new candidate material for thermal barrier coatings (TBCs) because of its low thermal conductivity and high phase stability between room temperature and 1673K. The LC coatings with different La2O3 contents were prepared by air plasma spraying (APS) and their lifetime was evaluated by thermal cyclic testing from room temperature to 1373 K. The structures of the coatings were characterized by XRD and SEM and the deviation of the composition from the powder was determined by EDS analysis. Long time annealing for the freestanding coating at 1673K reveals that the near stoichiometric LC coating is stable up to 240h, and the stability decreases with increasing the deviation from stoichiometric LC composition. During thermal cyclic testing, spallation was observed within the top coat near the bond coat. It is considered that the effect of intrinsic stress caused by the coefficient of thermal expansion (CTE) mismatch between top coat and bond coat is larger than that of thermally grown oxide (TGO) and the bond adherence of top coat with TGO.

Investigation about Thermal Shock Property of Plasma-Spraying Sm2Zr2O7 Thermal Barrier Coatings with Different Substrate Condictions

2011 ◽  
Vol 354-355 ◽  
pp. 145-148
Author(s):  
Hong Song Zhang ◽  
Hong Chan Sun
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Thermal Expansion ◽  
Residual Stresses ◽  
Plasma Spraying ◽  
Thermal Barrier Coatings ◽  
Thermal Barrier ◽  
Shear Stresses ◽  
Substrate Thickness ◽  
Barrier Coatings

Effect of substrate conditions, including material type, thickness and radius of substrate, on thermal-shocking stresses of plasma spraying Sm2Zr2O7/ NiCrCoAlY TBCs was analyzed through finite element method. Results show that radial stresses decrease with time increasing, and they decrease with the increasing of distance from center to edge along radius. However, axial residual stresses increse abruptly at the edge of specimen. All residual stresses increse with incresing of thermal expansion coefficient of substrate. Radial stresses increase with substrate thickness increasing, however, they are not effectd by substrate thickness if it is great than 20mm.and axial residual stresses and shear stresses are not effected by the substrate thickness. The maximum values of axial stresses and shear stresses were not effected by sustrate radius. and values of radial stresses remian invariable when substrate radius is over 18mm.

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