Modern demands in power generation call for higher efficiencies from every area of the power plant. One aspect of this is a drive to increase plant operating temperatures placing higher demand on structural materials. P91 and P92 are two steels commonly used in steam pipes. In order to accurately predict the service lifetime of components, mechanical properties at operating temperatures are critical. In particular properties of material around weld fusion joints are of interest as it is in these regions where failures occur. Conventional techniques such as Vicker’s hardness testing and uniaxial tensile testing are used to characterise the mechanical properties and creep behaviour of bulk materials. These techniques are often used to determine the properties of P91 and P92 parent and weld materials, the limitation of these techniques is that they require large volumes of material. They are therefore unable to determine differences in properties through the heat affected zone of the parent material which is typically only a few millimetres across. Nanoindentation is a technique which offers a potential solution to this problem. It was developed in order to examine the properties of thin films and small material volumes. In recent years several approaches have been developed to perform nanoindentation experiments at elevated temperature. These approaches have been examined in order to establish which provides the best thermal stability for high temperature nanoindentation measurements. This technique has then been used to perform high temperature nanoindentation experiments to determine the mechanical properties and creep behaviour of P91 and P92 steel. The correlation between nanoindentation measurements on bulk materials and those obtained using conventional methods is examined. In particular the significance of creep stress exponents calculated from nanoindentation dwell data is discussed. Nanoindentation is then used to characterise the heat affected zone of a weld, giving clear indications of the effects of microstructural differences on the material properties.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:580225 |
| Date | January 2013 |
| Creators | Davies, Michael I. |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://eprints.nottingham.ac.uk/13233/ |
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