Laves Phase Formation and Its Effect on Mechanical Properties in P91 Steel

• Published in: Acta metallurgica sinica : English letters 2015-10, Vol.28 (10), p.1238-1246
• Main Authors: Xia, Zhi-Xin, Wang, Chuan-Yang, Zhao, Yan-Fen, Zhang, Guo-Dong, Zhang, Lu, Meng, Xin-Ming
• Format: Article
• Language: English
• Subjects: Boundary conditions; Characterization and Evaluation of Materials; Chemistry and Materials Science; Chromium molybdenum steels; Corrosion and Coatings; Crack initiation; Ferritic stainless steels; Finite element analysis; Finite element method; Formations; Grain boundaries; Heat resistant steels; Impact tests; Laves phase; Laves相; Martensite; Materials Science; Mathematical analysis; Mechanical properties; Metallic Materials; Molybdenum; Nanotechnology; Organometallic Chemistry; P91钢管; Pipe; Service life; Solid solutions; Spectroscopy/Spectrometry; Steel pipes; Steels; Stress distribution; Stresses; Tensile properties; Tribology; Vapor pressure; 冲击能量; 力学性能; 平均尺寸; 应力分布; 热力学计算; 裂纹扩展
• ISSN: 1006-7191; 2194-1289
• DOI: 10.1007/s40195-015-0318-5

Effect of Laves phase formation on mechanical properties in a pressurized T-junction of P91 steel pipe at849 K for 58,000 h with 25.65 MPa vapor pressure was studied. Thermodynamic calculations had been performed by using the software Thermo-Calc to study the phase at equilibrium state. Counter plot of von Mises stress in the pipe during service life was calculated by finite element analysis to study the effect of the operated stress distribution on the evolution of Laves phase. The change in the microstructure and mechanical properties in the sites with different stress was also studied. The results indicated that the formation of Laves phase in P91 steel was a thermodynamically possible process due to enrichment of Mo and depletion of C adjacent to M23C6 particles or along martensite lath and packet boundaries. The formation of Laves phase had a detrimental influence on the mechanical properties in P91 steel. The mean size of Laves phase would be significantly increased with increasing operated stress, leading to a reduction in tensile properties and impact energy. In particular, crack initiation energy and crack growth energy during impact test rapidly decreased with increasing the mean size and volume fraction of Laves phase.