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Harendra Kumar - An Integrated Approach for Evaluation of Microstructure and Mechanical Properties Degradation in Steels at...
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An Integrated Approach for Evaluation of Microstructure and Mechanical Properties Degradation in Steels used at Elevated Temperatures

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Name:
Harendra Kumar
University:
Brunel University London
Research Title:
An Integrated Approach for Evaluation of Microstructure and Mechanical Properties Degradation in Steels use at Elevated Temperatures
Abstract:

Ever increasing demand for power and environmental protection regulations together have stimulated the engineering world to achieve improved efficiency target of 50%. In order to realize this objective the increase in steam temperature and pressure in power plant have been proposed for advance ultra-super critical applications. In the process a number of advanced alloys have been developed and some are under test to ensure that proposed materials can sustain such extreme operating environment over extended periods of time. However the performance of such alloys depends on creation of precise microstructure and maintaining it over various stages of component life, e.g. fabrication, installation & in-service operation. A number of premature failures of components fabricated from ferritic/martensitic steels have been reported and post failure analysis indicates Type IV creep to be dominant failure mechanism in many cases. Type IV creep damage progresses in the form of creep voids for a significant portion of the creep life of a component and result in sudden catastrophic failure with no detectable warning sign on the surface. At present there is no field deployable technique for assessment of such degradation at early stage reliably so as to allow precautionary measures to be taken.  

 

Research will focus on developing a highly sensitivity integrated approach utilizing advanced ultrasonic and electromagnetic techniques for assessing the microstructure and mechanical properties degradation and to detect type IV creep at early stage. Although there are techniques being used to detect such degradation e.g. replication, positron annihilation etc., but these are limited in some sense for detection of type IV creep at early stage which has been reported to initiate at subsurface location. Also there are ultrasonic velocity and attenuation based approaches being practiced in the industry but their reliability has been questioned and these at times suffers from limited capability of defining the level of degradation. Using this realisation, an attempt will be made to perform a systematic study to establish empirical correlations between mechanical/microstructural properties and NDT parameters. Selected parameters describing a definite, repeatable pattern and discernible variation will be further integrated to provide a reliable evaluation of the state of material under test.

Publications: