Thermal Shock Induced Phases Transformation and Microstructural Changes in a Novel Hydrogen Transport Membrane

2015 ◽  
Vol 1810 ◽  
Author(s):  
Lily, Yongjun Zhang ◽  
Sukumar Bandopadhyay ◽  
U. (Balu) Balachandran ◽  
Nagendra Nag
Keyword(s):  
Thermal Cycling ◽  
Thermal Shock ◽  
Study Phase ◽  
Metal Composite ◽  
Hydrogen Transport ◽  
Electron Fractography ◽  
Microstructural Changes ◽  
Electron Probe Micro Analyzer ◽  
Micro Cracks ◽  
Crack Tips

ABSTRACTBulk samples of a novel cermet (ceramic/metal composite) hydrogen transport membrane (HTM) were subjected to thermal cycling in the temperature range between 25-850°C to study phase transformations and microstructural changes under thermal shock. Scanning electron microscopy (SEM) and electron probe micro analyzer (EPMA) with energy dispersive spectroscopy (EDS) were used to characterize the microstructural and chemical changes in the membrane upon thermal cycling. SEM & EPMA analyses indicated that the temperature gradient during thermal cycling produced more micro-cracks inside the HTM disc, whereas, the chemical reaction between Pd and oxygen to form PdO disturbed the continuity of the metal palladium (Pd) - Yttria Stabilized Zirconia (YSZ) dual phases interconnection system from surface down. The agglomerates of un-crystallized YSZ grains found to be the inherent in the cracks of the as-received HTM. A combination of trans-granular and inter-granular crack propagation results around the YSZ grains and the new precipitates. Based on the electron fractography analyses by both SEM and EPMA, the micro voids coalescence develops ahead of the crack tips in the cross-section of the HTM after 500 thermal cycles.

Thermal shock resistance of Ti3SiC2 ceramic under extremely rapid thermal cycling

2021 ◽  
Vol 866 ◽  
pp. 158985
Author(s):  
Xiaojia Su ◽  
Yiwang Bao ◽  
Detian Wan ◽  
Haibin Zhang ◽  
Ludi Xu ◽  
...  
Keyword(s):  
Thermal Cycling ◽  
Thermal Shock ◽  
Thermal Shock Resistance ◽  
Shock Resistance ◽  
Rapid Thermal Cycling

scholarly journals LC/8YSZ TBCs Thermal Cycling Life and Failure Mechanism under Extreme Temperature Gradients

Coatings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1051
Author(s):  
Kun Liu ◽  
Xi Chen ◽  
Kangping Du ◽  
Yu Wang ◽  
Jinguang Du ◽  
...  
Keyword(s):  
High Temperature ◽  
Surface Temperature ◽  
Thermal Cycling ◽  
Thermal Shock ◽  
Failure Mechanism ◽  
Extreme Temperature ◽  
Temperature Gradients ◽  
Accelerated Life Test ◽  
Ceramic Layer ◽  
Cycling Life

The purpose of this paper is to study the thermal shock resistance and failure mechanism of La2Ce2O7/8YSZ double-ceramic-layer thermal barrier coatings (LC/8YSZ DCL TBCs) under extreme temperature gradients. At high surface temperatures, thermal shock and infrared temperature measuring modules were used to determine the thermal cycling life and insulation temperature of LC/8YSZ DCL TBCs under extreme temperature gradients by an oxygen–acetylene gas flame testing machine. A viscoelastic model was used to obtain the stress and strain law of solid phase sintering of a coating system using the finite element method. Results and Conclusion: (1) Thermal cycling life was affected by the surface temperature of LC/8YSZ DCL TBCs and decreased sharply with the increase of surface temperature. (2) The LC ceramic surface of the failure coating was sintered, and the higher the temperature, the faster the sintering process. (3) Accelerated life test results showed that high temperature thermal cycling life is not only related to thermal fatigue of ceramic layer, but is also related to the sintering degree of the coating. (4) Although the high temperature thermal stress had great influence on the coating, great sintering stress was produced with sintering of the LC ceramic layer, which is the main cause of LC/8YSZ DCL TBC failure. The above results indicate that for new TBC ceramic materials, especially those for engines above class F, their sinterability should be fully considered. Sintering affects the thermal shock properties at high temperature. Our research results can provide reference for material selection and high temperature performance research.

Failure characteristics of zirconia-coated structural steel under thermal cycling and thermal shock

1990 ◽  
Vol 4 (6) ◽  
pp. 437-442
Author(s):  
Y Mutoh ◽  
I Sakamoto ◽  
T Nishimura ◽  
O Watanabe
Keyword(s):  
Thermal Cycling ◽  
Structural Steel ◽  
Thermal Shock ◽  
Failure Characteristics

Failure Analysis of Steel Superheater Tube Fractured in a Boiler of a Power Plant

2011 ◽  
Vol 462-463 ◽  
pp. 467-471
Author(s):  
Zainul Huda
Keyword(s):  
Power Plant ◽  
Steam Temperature ◽  
Hardness Testing ◽  
Visual Examination ◽  
Creep Failure ◽  
Electron Fractography ◽  
Superheater Tube ◽  
Micro Cracks ◽  
Long Time

This paper presents a case study of ASME SA213 type-T22 alloy steel superheater tube that failed in a boiler of a power plant. The failed superheater tube was investigated by visual examination, metallography, optical microscopy, electron fractography, and hardness testing. Microscopic examinations revealed inclusion, pre-existing micro-cracks and cementite precipitates at the grain boundaries in the microstructure; which were thought to be one of the major causes of failure of the superheater tube. Another major cause failure of boiler type T-22 was found to be creep failure because the boiler had been under use for a long time (36573 hours) at high steam temperature of around 420 °C with 130 bar pressure. Finally, recommendations have been suggested to improve the material characteristics and properties of the superheater tube for application in boiler of the power plant.

TEM Specimen Preparation from Micro-Areas of Metallurgical Interest

1977 ◽  
Vol 35 ◽  
pp. 318-319
Author(s):  
Edward F. Koch
Keyword(s):  
Base Material ◽  
Region Of Interest ◽  
Surface Oxidation ◽  
Specimen Preparation ◽  
Intergranular Stress Corrosion ◽  
Microstructural Changes ◽  
Single Region ◽  
Reaction Zones ◽  
Crack Tips ◽  
Intergranular Stress Corrosion Cracking

Most metallurgical phenomena of industrial interest can trace their origin to specific regions in operating components. Determining the microstructural changes that accompany the origins of these metallurgical phenomena helps considerably in their overall understanding. Examples include studies of microstructural changes at crack tips, surface oxidation effects on base material, and narrow reaction zones in suitably heat treated material. For such microareas, only a single region of interest is usually available for microstructural examination, making TEM specimen preparation procedures extremely critical.304 austenitic steel is susceptible to intergranular stress corrosion cracking when subjected to a corrosive environment in the presence of stress and a sensitized microstructure. The latter is characterized by chromium carbide, Cr23C6, at the grain boundaries. Confirmation of the presence of these carbides at the tip of an intergranular crack created in an environment can be provided by TEM examination. The microarea of interest can be pinpointed by using selective platinum washers during electropolishing, yielding electron-transparent regions of the type shown in figure 1.

High temperature Au-based solder reliability in electronic packages for harsh environments

2011 ◽  
Vol 2011 (1) ◽  
pp. 000438-000445
Author(s):  
M.F. Sousa ◽  
S. Riches ◽  
C. Johnston ◽  
P.S. Grant
Keyword(s):  
High Temperature ◽  
Thermal Cycling ◽  
Thermal Shock ◽  
Microstructural Analysis ◽  
Temperature Stability ◽  
Acoustic Microscopy ◽  
Harsh Environments ◽  
Electronic Packages ◽  
High Temperature Stability ◽  
Die Attach

The operation of electronic packages in high temperature environments is a significant challenge for the microelectronics industry, and poses a challenge to the traditional temperature limit of 125°C for high electronic systems, such as those used in down-hole, well-logging and aero-engine applications. The present work aims to develop understanding of how and why attach materials for Si dies degrade/fail under harsh environments by investigating high temperature Au based solders. Au-2wt%Si eutectic melts at < 400°C and offers high temperature stability but high temperature processing and complex manufacturing steps are the major drawbacks. Changes in the die attach material were investigated by isothermal ageing at 350°C, thermal shock and thermal cycling treatments. Die attach reliability investigated by thermal shock and thermal cycling showed that the bonded area degraded. Nevertheless, most of the samples tested had high bonded area ranging from 92.5 to 97.5%. The failure behaviour of the die attach materials included cracking of die and/or attach material, delamination and voiding. Scanning acoustic microscopy images provided a rapid assessment of delamination and other defects and their location within the package. Microstructural analysis and die shear testing were also carried out, along with the high temperature endurance of a SOI test chip for signal conditioning and processing applications at 250°C. All functions evaluated have shown stable performance at 250°C for up to 9000 hours.

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