Characterization of microstructure of HAZs in as-welded and service condition of P91 pipe weldments

• Published in: Metals and materials international Vol. 23; no. 1; pp. 148 - 162
• Main Authors: Pandey, C., Giri, A., Mahapatra, M. M., Kumar, P.
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Institute of Metals and Materials 2017; Springer Nature B.V; 대한금속·재료학회
• Subjects: Aging; Aging (metallurgy); Characterization and Evaluation of Materials; Chemistry and Materials Science; Creep rupture strength; Engineering Thermodynamics; Ferritic stainless steels; Grain size; Grain size distribution; Heat affected zone; Heat and Mass Transfer; Heat resistant steels; Heat treatment; High temperature; Impact strength; Iron; Machines; Magnetic Materials; Magnetism; Manufacturing; Materials Science; Mechanical properties; Metallic Materials; Microstructure; Pipe joints; Post-weld heat treatment; Power plants; Precipitates; Precipitation; Precipitation heat treatment; Processes; Solid Mechanics; Steel pipes; Stress corrosion cracking; Thermal power plants; Toughness; Welded joints; Weldments; 재료공학; tempering; microstructure; toughness; scanning electron microscopy (SEM); grain boundary
• ISSN: 1598-9623; 2005-4149
• DOI: 10.1007/s12540-017-6394-5

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 °C for time of 2 h and ageing at 760 °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 °C for 2 h. The main phase observed in weld fusion zone in as-welded, PWHT and ageing conditions were M 23 C 6 , MX, M 7 C 3 , Fe-rich M 3 C and M 2 C. The unwanted Z-phase (NbCrN) was also noticed in weld fusion zone after ageing of 1440 h.