Deformation Characteristics of a High Chromium, Power Plant Steel at Elevated Temperatures

Abstract

The changing face of power generation requires an improved understanding of the deformation and failure response of materials that are employed in power plants. Important insights can be obtained through microstructurally motivated modelling studies. With the drive for increased efficiency, there is a corresponding drive towards increasing operating temperatures in conventional power plant. With these increasing temperatures, and with the increased flexibility required of modern power plant working in a mixed energy economy, more robust material testing and modelling tools are required to accurately predict the response of power plant steels. This works deals with the development of a material model for a martensitic steel, P91, relevant to the range of temperatures typically seen in a modern power plant. High temperature (20, 400, 500, 600°C) tensile testing at various strain rates was carried out the steel. Tests were taken to failure and the stress strain response recorded. Electron backscatter diffraction (EBSD) is employed to determine the complex microstructure of the P91 material. This information is incorporated within a representative volume element (RVE) and a nonlinear, rate dependent, finite strain crystal plasticity model used to represent the deformation of the material. The material model was calibrated to each temperature and strain rate to give a robust physically based model that has been fully validated through experimental data.

A physically-based creep damage model for effects of different precipitate types

“…The nominal compositions of the various materials investigated in this study are presented inTable 1. The required material parameters are identified using a combination of creep and thermal aging data, in conjunction with the results of published microstructural data.The temperature-dependent Young's modulus is identified from the elastic region of monotonic tensile test data[30] and presented inTable 2. The magnitude of Burgers vector, b, and the Taylor factor, M, have values of 0.248 nm and 2.9 respectively for body centre cubic materials.…”

Cyclic plasticity of welded P91 material for simple and complex power plant connections

“…Thus, the average calculated triaxiality value is approximately 0.5672. The failure strain of a uniaxial P91 CW test specimen is approximately 13.5 %, based on a monotonic test at 500 °C [50]. Using Equations (14) and (15), this results in a predicted multiaxial failure strain for this T-joint of 7.35 % and a predicted number of cycles to failure of approximately 3500 cycles.…”

Microscale deformation of a tempered martensite ferritic steel: Modelling and experimental study of grain and sub-grain interactions

“…These data was generated from standard tensile tests carried out from room temperature up to 625 • C and at three different strain rates (0.1, 0.033 and 0.025%/s). More details on these experimental tests are provided in [52]. Data from a typical room temperature tensile test are shown in figure 5, taken from the same header [53] as the miniature three point bend specimen.…”