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Title: High temperature deformaton at dissimilar metal interfaces
Author: Chilton, I. J.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1982
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A study has been made of the relative importance of the many possible factors which could be determining failure of austenitic-ferritic dissimilar metal welds, during service within steam boilers in electricity generating plant. In service this type of localised intergranular failure occurs in the heat affected zone of the ferritic steel at a distance only around 100 um from the weld metal/ferritic steel fusion interface. The characteristic nature of the fracture mode appears similar to that typifying many intergranular creep failures. As a result a programme has been undertaken to assess whether service failures can be simulated in laboratory creep tests in order that the relevance of each variable which may affect plant failures can be examined individually. The experimental programme established that failures characteristic of those encountered in service, for austenitic 316/2}CrlMo ferritic steels with Armex T welds, can be reproduced in high temperature creep tests performed under specific experimental conditions. This has enabled the rate of accumulation of creep-strain as a function of distance from the weld/ferritic steel interface to be quantified, using high precision surface measurements. The critical nature of this pattern of strain accumulation typifying transition joint failures not only demonstrates why difficulties in simulating service intergranular failures can be encountered, when using relatively simple laboratory test procedures, but also enables the precise role of the microstructural features associated with welds in commercial ferritic steels to be clarified. In this way, the deformation and fracture properties of cross-weld test pieces can be correlated with those for the parent 2*CrlMo steel in both the initial normalised and tempered condition and for the various regions of the heat affected zone resulting from the welding procedure.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available