scholarly journals Understanding the Failure Mechanism of Thermal Barrier Coatings Considering the Local Bulge at the Interface between YSZ Ceramic and Bond Layer

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 275
Author(s):  
Zhi-Yuan Wei ◽  
Hong-Neng Cai
Keyword(s):  
Crack Propagation ◽  
Thermal Barrier Coatings ◽  
Local Stress ◽  
Ceramic Layer ◽  
Thermal Barrier ◽  
Interface Morphology ◽  
Barrier Coatings ◽  
Coating Failure ◽  
Bond Layer ◽  
Tgo Growth

The TC/BC interface morphology in APS TBC is one of the important factors leading to crack propagation and coating failure. Long cracks are found near the bulge on the TC/BC interface. In this study, the TBC model with the bulge on the interface is developed to explore the influence of the bulge on the coating failure. Dynamic TGO growth and crack propagation are considered in the model. The effects of the bulge on the stress state and crack propagation in the ceramic layer are examined. Moreover, the effects of the distribution and number of bulges are also investigated. The results show that the bulge on the interface results in the redistribution of local stress. The early cracking of the ceramic layer occurs near the top of the bulge. One bulge near the peak or valley of the interface leads to a coating life reduction of about 75% compared with that without a bulge. The increase in the number of bulges further decreases the coating life, which is independent of the bulge location. The results in this work indicate that a smooth TC/BC interface obtained by some possible surface treatments may be an optional scenario for improving coating life.

Preparation and Distribution Analysis of Thermal Barrier Coatings Deposited on Multiple Vanes by Plasma Spray-Physical Vapor Deposition Technology

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
J. Mao ◽  
M. Liu ◽  
C. G. Deng ◽  
C. M. Deng ◽  
K. S. Zhou ◽  
...  
Keyword(s):  
Thermal Barrier Coatings ◽  
Plasma Spray ◽  
Vapor Deposition ◽  
Gas Turbines ◽  
Physical Vapor Deposition ◽  
Ceramic Layer ◽  
Thermal Barrier ◽  
Distribution Analysis ◽  
Barrier Coatings ◽  
Bond Layer

The multicomponent NiCoCrAlTaY coating as bond layer as well as the zirconia stabilized by yttrium oxide (YSZ) coating as top ceramic layer was deposited on duplex vane surface by plasma spray-physical vapor deposition (PS-PVD) system. The thickness and microstructure of thermal barrier coatings (TBCs) under the influence of duplex vane geometry were presented in this article. It has been proven that the entire surface of duplex vane was covered by NiCoCrAlTaY and YSZ coatings. The position with thickest coating was found close to the leading edge and trailing edge of the vane. In those places, the coating was approximately 80–100% thicker than in the other areas on duplex vane. The obtained results indicate that it is possible to manufacture the TBCs including metallic bond layer and top ceramic layer by PS-PVD process on multiple vanes for gas turbines.

Microstructure and Oxidation Resistance of Thermal Barrier Coatings with Different Ceramic Layer

2021 ◽  
Vol 320 ◽  
pp. 31-36
Author(s):  
Marek Góral ◽  
Tadeusz Kubaszek ◽  
Barbara Kościelniak ◽  
Marcin Drajewicz ◽  
Mateusz Gajewski
Keyword(s):  
Thermal Barrier Coatings ◽  
Bond Coat ◽  
Ceramic Layer ◽  
Thermal Barrier ◽  
Elemental Mapping ◽  
Stabilized Zirconia ◽  
Barrier Coatings ◽  
Bond Coats ◽  
All Ceramic ◽  
Zirconia Oxide

Thermal barrier coatings are widely used for protection of gas turbine parts against high temperature oxidation and hot corrosion. In present work the microstructural assessment of TBCs produced by atmospheric plasma spray (APS) method was conducted. Three types of ceramic powders were used: magnesia- stabilized zirconia oxide (Metco 210), yttria stabilized zirconia oxide (YSZ -Metco 204) and fine-grained YSZ – Metco 6700. As a base material the Inconel 713 was used as well and CoNiCrAlY was plasma sprayed (APS) as a bond coat. The thickness of all ceramic layers was in range 80 – 110 μm. The elemental mapping of cross-section of magnesia-stabilized zirconia showed the presence of Mg, Zr and O in outer layer. In the YSZ ceramic layer the Y, Zr and O were observed during elemental mapping. The isothermal oxidation test was conducted at 1100 °C for 500 h in static laboratory air. On all samples the delamination and spallation of ceramic layers was observed. Chemical composition analysis of coatings showed the presence of two areas: the first one contained elements from bond coats: Ni, Cr, Al, Co and second area contained O, Cr Co and O that suggest the scale formation. The obtained results showed the total degradation of all ceramic layers as a result of internal stresses in bond-coat. Microscopic analysis showed the areas with complete degradation of bond coats and formation of thick oxides layer.

A LIFE PREDICTION MODEL OF THERMAL BARRIER COATINGS

2010 ◽  
Vol 24 (15n16) ◽  
pp. 3161-3166 ◽  
Author(s):  
LIYONG NI ◽  
CHAO LIU ◽  
CHUNGEN ZHOU
Keyword(s):  
Crack Propagation ◽  
Prediction Model ◽  
Thermal Barrier Coatings ◽  
Life Prediction ◽  
Crack Propagation Rate ◽  
Thermal Barrier ◽  
Critical Crack ◽  
Critical Crack Length ◽  
Barrier Coatings ◽  
Life Prediction Model

The durability and reliability of thermal barrier coatings(TBCs) have become a major concern of hot-section components due to lack of a reliable life prediction model. In this paper, it is found that the failure location of TBCs is at the TBC/TGO interface by a sequence of crack propagation and coalescence process. The critical crack length of failure samples is 8.8mm. The crack propagation rate is 3-10µm/cycle at the beginning and increases largely to 40µm/cycle near coating failure. A life prediction model based a simple fracture mechanics approach is proposed.

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