| In this paper, commonly use the 9Cr-1Mo tempered martensitic steel, which was commonly used by ultra-supercritical thermal power units , was a kind of typically P91 steel as the research object. Using optical microscopy, a method X-ray diffraction, scanning electron microscopy and energy spectrum to investigate and analysis steel microstructure evolution during creep different stages of the microstructure evolution behavior.Making the comparison and reached the following summary conclusions:1) High temperature uniaxial tensile and creep rupture test, measured at 620 ? P91 steel yield strength ?0.2as 215.08MPa, ultimate tensile strength ?0 is 306.95MPa, elastic modulus E is 107.54GPa. Then obtain a complete creep curves and creep life (110h) by creep experiments, and the experimental data under different stress temperature, etc. have been analyzed and the results between the loading stress fracture time quantitative relationship.2) Using a scanning electron microscope (SEM) and energy spectroscopy (EDS) to analysis and make a contradistinction between the 620? creep rupture specimens and the 600 ? laboratory of existing data macro and micro fracture morphology. The results show that the fracture belongs to ductile fracture, which dimple significantly, and see a small hole is dimple nucleation center. Spectrum scan results show that there is a second phase of carbide, thus indicating that under the experimental conditions here in P91 steel creep rupture empty formation and precipitate particle coarsening interaction.3) Intermittent creep experiments at 620?,145MPa condition after creep optical microscopy specimens basic organization is still tempered martensite, martensite block number has increased while the gradual emergence of small grains, recovery phenomenon occurs gradually and is also becoming increasingly apparent.A slight increase in their organization in the number of carbide particles M23C6 type was found in prior austenite grain boundaries, subgrain boundaries lath organizations, as well as its internal lath martensite dispersed carbide particles exist between the border and the matrix phase and the number of carbide particles increase during the creep..4) By scanning electron microscopy discontinuous microstructure on the creep specimens were examined. The results show lath martensite microstructure of the P91 steel structure. With the extension of the creep time, the lath martensite and austenite grain boundaries and the sub-region carbide precipitation, and its small size can play the role of pinning dislocations in the early precipitation.5) X- ray diffraction measurements show crystal face diffraction peaks almost the same location, the peak half width and height (Full width at half maximum-FWHM) with the creep process and change. Lattice strain fluctuate with the creep deformation, creep deformation of the grain size with increased and then decreased again after showing upward trends.As used here in, the use of metallographic observation and analysis, observation analysis X- ray diffraction analysis, scanning electron microscopy and energy spectrum analysis are able to achieve P91 steel creep microstructure analysis and research, reflect different creep times and status of the internal microstructure such as martensite lath structure, dislocation, and a second phase particle formation, movement and distribution. So as to further understanding of the profound influence of the creep process of the evolution of the microstructure on the creep properties of the organization has opened a new way, but also to provide a reliable theoretical basis creep life prediction for the working member, and doing an anti-creep steel properties field a useful exploration. |
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