| Due to the increasingly prominent energy shortage and serious environmental problems, the operation condition of coal-fired power plants was forced to tend to a development directi on with high temperature and pressure. Service components in the unit tend to creep unavoida bly when they are in the high temperature and pressure, and the performance of component d egrade gradually. Therefore, it becomes extremely important to evaluate the creep behavior rapidly and accurately and predict the remaining life quantitatively of the high temperature component.In this paper, P91 steel was used as the research object. The method of internal friction, X-ray diffraction and hardness measurement were used to characterize the creep behavior of the steel under the condition of 600℃ and 165 Mpa. First the elevated temperature mechanical behavior of P91 steel was studied by uniaxial tensile experiments. Then the complete creep curve and fracture time were obtained by the creep test under the given conditions. Based on the comprehensive analysis of creep curve, the different creep sample was prepared according to the interrupted tests. Finally combining with the method of internal friction, X-ray diffraction and hardness measurement, the different creep behavior of samples were characterized by their parameters respectively, the main research contents and conclusions are as follows:(1) The yield strength σ0.2 for 237.66 MPa, ultimate tensile strength Gb for 320.96MPa, elastic modulus E for 120.884GPa of P91 steel at 600℃ was measured by uniaxial tension and elevated temperature creep rupture test. Also the complete creep curves and creep lifetime (219h) was obtained under the conditions 600℃/165MPa which was about two-thirds σ00.2-(2)Creep fracture surface by SEM fine analysis showed that there were not only very dense dimple, but also many cavities, which show that the creep rupture of P91 steel mainly caused by voids grow up. In addition, the double-θ continuity equation was used to nonlinear fit the experiment creep curves, so as to provide the basis for calculating the remaining life quantitatively under given conditions.(3)The internal friction measurements of P91 steel with different creep statuses showed that the elevated temperature internal friction not only related with the temperature and frequency, but also depending on its creep state. Based on quantitative models between elevated-temperature friction and material internal dislocations, it showed a correlation dislocation parameters and creep state had a certain relevance.(4)X-ray diffraction measurements show, there were no new phase formation with creep process under the given conditions, but its half-width of the peak height (Full width at half maximum-FWHM) change over the course of creep, which mainly related to its sub-structure evolution.(5)Vickers hardness measurements show that with the increase of the life fraction, hardness showed "up-down-up-down" trend, which was mainly attributed to the dislocation movement, sub-structure reply and precipitate coarsening of P91 matrix.In summary, internal friction method, X-ray diffraction and hardness measurement methods used in this paper can achieve characterization of the different creep state of P91 steel, especially internal friction method could directly reflect the state of dislocation motion under different creep state, which provides a new way for further study of internal microstructure evolution and parametric characterization during creep.
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