Effect of Impurity Tin on the Creep Properties of a P91 Heat-Resistant Steel

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2014-09, Vol.45 (10), p.4361-4370
• Main Authors: Song, S.-H., Xu, Y.-W., Yang, H.-F.
• Format: Article
• Language: English
• Subjects: Applied sciences; Characterization and Evaluation of Materials; Chemistry and Materials Science; Creep; Creep (materials); Creep tests; Deterioration; Exact sciences and technology; Ferritic stainless steels; Heat resistant steels; Heat resisting alloys; Materials Science; Mathematical analysis; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Metallic Materials; Metals. Metallurgy; Nanotechnology; Power law; Steel; Steels; Stresses; Structural Materials; Surfaces and Interfaces; Thin Films; Tin
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-014-2400-4

The creep properties of P91 steel specimens undoped and doped with 0.058 wt pct tin, which was normalized from 1328 K (1055 °C) and tempered at 1033 K (760 °C), were examined under different engineering stresses (150 to 210 MPa) and temperatures [873 K to 923 K (600 °C to 650 °C)]. The creep behavior followed the temperature-compensated power law and Monkman–Grant equations. In the temperature-compensated power law equation, the apparent activation energy and stress exponent for creep were approximately 541 kJ/mol and 12 for the undoped steel and 527 kJ/mol and 11 for the Sn-doped one, respectively. In the Monkman–Grant relation, the values of constants m and C were around 1.062 and 0.0672 for the undoped steel, and 1.012 and 0.0650 for the Sn-doped one, respectively. The 100 MPa stress creep lifetime at 873 K (600 °C) was estimated as 100641 hours for the undoped steel and 35290 hours for the Sn-doped steel, respectively. These indicated that Sn substantially deteriorated the creep properties of the steel. It was found that grain or subgrain boundary segregation of Sn could promote the nucleation of cavities or microcracks, thereby leading to the deterioration of the steel creep properties.