Journal
METALS AND MATERIALS INTERNATIONAL
Volume 23, Issue 1, Pages 148-162Publisher
KOREAN INST METALS MATERIALS
DOI: 10.1007/s12540-017-6394-5
Keywords
tempering; grain boundary; toughness; microstructure; scanning electron microscopy (SEM)
Funding
- Department of Science and Technology (DST) Govt. of India
- Indian Institute of Technology Roorkee
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Steels 9-12% Cr, having the high creep rupture strength are advocated for the modern low polluting thermal power plants. In the present investigation, the P91 pipe weldments have been characterized for microstructural responses in as-welded, post-weld heat treatment (PWHT) and ageing conditions. The PWHT of welded samples were carried out at 760 degrees C for time of 2 h and ageing at 760 degrees C for 720 h and 1440 h, respectively. The effect of time has been studied on precipitates size, distribution of precipitates and grain sizes present in various zones of P91 steel weldments. The impact toughness and hardness variation of heat affected zone (HAZ) have also been studied in as-welded condition as well as at different heat treatment condition. A significant change was observed in grain size and precipitates size after each heat treatment condition. The maximum impact toughness of HAZ was obtained after PWHT at 760 degrees C for 2 h. The main phase observed in weld fusion zone in as-welded, PWHT and ageing conditions were M23C6, MX, M7C3, Fe-rich M3C and M2C. The unwanted Z-phase (NbCrN) was also noticed in weld fusion zone after ageing of 1440 h.
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