Material Characterization of Power Plant Steel in the Virgin and Artificially-Aged Conditions

Abstract

In the present study the microstructural and mechanical properties including high-temperature tensile test of martensitic-ferritic steel 9–12% Cr were assessed. This steel, which is usually used in gas turbine power plants serving as shroud, was tested in the as-received (virgin) and artificially-aged condition for 1344hrs (8 weeks) at 700 °C and the results were compared and analyzed. The high-temperature service of this steel suggested investigating the high temperature tensile behavior and the deformation mechanism occurring at different testing temperature and strain rates which were 540, 580 and 620 °C and 10⁻³, 10⁻⁴ and 10⁻⁵ s⁻¹, respectively. The results showed that the microstructural features such as phases and carbides are factors which influence the high temperature mechanical properties. The stress- strain rate curves showed a large stress exponent of ≈ 15, indicating that the materials behavior lie in the power law breakdown regime. Based on stress vs. the reciprocal of temperature, the apparent activation energy was calculated as 443 kJ/ Mole. Plotting Zener Holloman parameter versus true stress made it possible to mathematically model all test results into a unified model.