effect of multiaxiality on the stress rupture properties of p92 steel

High thermal conductivity, low coefficient of thermal expansion makes p92 a candidate material for ultra super critical (usc) power plant piping. microstructural features viz., high dislocation density, lath martensitic microstructure, fine precipitates of m23c6 and mx (x=c, n) contribute towards the high rupture strength. however, most components are typically subjected to multiaxial stress conditions; either metallurgical (weldments), or mechanical (change in the dimension). the present work involves stress rupture testing of circumferential 60° v- notch specimens in the range of 300 – 375 mpa at 650 °c. notch strengthening effect was observed; with rupture times ranging from 200 – 1300 h. scanning electron microscopy (sem) fractography revealed mixed mode of fracture with brittle fracture observed at notch root, while ductile fracture was seen at the centre of the specimen.