The effect of dwell times on the thermomechanical fatigue life performance of grade P92 steel at intermediate and low strain amplitudes

MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING

卷:805

Article

Juergens, Maria¹  Sonntag, Nadja¹  Olbricht, Jurgen¹  Fedelich, Bernard¹  Skrotzki, Birgit¹ 

[1] Bundesanstalt Mat Forsch & Prufung BAM, Div Expt & Model Based Mech Behav Mat 5 2, D-12205 Berlin, Germany

关键词: 9-12%Cr steel;    Thermomechanical fatigue;    Symmetric dwell periods;    Low strain;    Parametric modeling;   

DOI  :  10.1016/j.msea.2020.140593

来源: Elsevier

【 摘 要 】

Results of an extended TMF test program on grade P92 steel in the temperature range of 620 degrees C-300 degrees C, comprising in-phase (IP) and out-of-phase (OP) tests, partly performed with symmetric dwells at Tmax/Tmin, are presented. In contrast to previous studies, the low-strain regime is also illuminated, which approaches flexible operation in a power plant with start/stop cycles. At all strain amplitudes, the material performance is characterized by continuous cyclic softening, which is retarded in tests at lower strains but reaches similar magnitudes in the course of testing. In the investigated temperature range, the phase angle does not affect fatigue life in continuous experiments, whereas the IP condition is more detrimental in tests with dwells. Fractographic analyses indicate creep-dominated and fatigue-dominated damage for IP and OP, respectively. Analyses of the (micro)hardness distribution in the tested specimens suggest an enhanced microstructural softening in tests with dwell times for the low- but not for the high-strain regime. To rationalize the obtained fatigue data, the fracturemechanics-based DTMF concept, which was developed for TMF life assessment of ductile alloys, was applied. It is found that the DTMF parameter correlates well with the measured fatigue lives, suggesting that subcritical growth of cracks (with sizes from a few microns to a few millimeters) governs failure in the investigated range of strain amplitudes.

【 授权许可】

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