Effect of Multiaxiality on the Stress Rupture Properties of P۹۲ Steel

High thermal conductivity, low coefficient of thermal expansion makes P۹۲ a candidate material for Ultra Super Critical (USC) power plant piping. Microstructural features viz., high dislocation density, lath martensitic microstructure, fine precipitates of M۲۳C۶ 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 ۶۰° V- notch specimens in the range of ۳۰۰ – ۳۷۵ MPa at ۶۵۰ °C. Notch strengthening effect was observed; with rupture times ranging from ۲۰۰ – ۱۳۰۰ 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.

کلیدواژه ها:

Multiaxiality ، notched specimen ، stress rupture ، transient creep