Abstract
Abstract The effect of hold time with 0, 20, and 40 s on in-phase thermomechanical fatigue (TMF) behavior and life of P92 steel is investigated in this study. TMF tests are carried out under mechanical strain control with strain amplitudes of 0.4 0.4 , 0.6 0.6 , and 0.8 % 0.8\text{\%} , and temperature range of 550–650°C which is closely relevant to the operating condition in power plant. TMF tests are performed in a mechanical strain ratio of R = − 1 R=-1 and cycle time of 120 s. The fatigue life variation follows the sequence of N f 0 s < N f 20 s < N f 40 s {N}_{\text{f}}^{0\hspace{.1em}\text{s}}\lt {N}_{\text{f}}^{20\hspace{.1em}\text{s}}\lt {N}_{\text{f}}^{40\hspace{.1em}\text{s}} for the same mechanical strain amplitude. In addition, the influence of hold time on fatigue life decreases with the increasing strain amplitude. A continuous softening can be observed from the cyclic stress response under all test conditions. Fractographic and microstructural tests indicate that the fracture surfaces are characterized by a multi-source cracking initiation and an oxidation phenomenon. Furthermore, a modified Ostergren model is used to predict the fatigue life and achieves a good predicted result.
Highlights
IntroductionIn the process of thermal power generation, with the continuous addition of temperature and pressure, a new type of heat-resistant material with high performance is one of the key points to assure the safety and stable working of the unit
In the process of frequent startup and shutdown in power plant, the unit components are subjected to temperature change and mechanical load at the same time, which is a typical condition
The present paper aims at understanding the influence of hold time varying from 0, 20 and 40 s on in-phase (IP) thermomechanical fatigue (TMF) behavior and life of P92 power station steel with strain amplitudes of 0.4, 0.6, and 0.8%, and temperature range of 550–650°C
Summary
In the process of thermal power generation, with the continuous addition of temperature and pressure, a new type of heat-resistant material with high performance is one of the key points to assure the safety and stable working of the unit. Effects of various temperatures on the low cycle fatigue behavior of P92 steel have been compared, which reported that the cyclic softening of materials is more obvious, and the crack propagation rate is faster along with the increase of temperature [8]. The study of creep–fatigue interaction of high-temperature materials is achieved by adding hold time in continuous low cycle fatigue tests [13]. The addition of tensile hold in low cycle fatigue tests at elevated temperature results in lower fatigue life of the material, which is even less than that with the compressive hold under the same conditions. The present paper aims at understanding the influence of hold time varying from 0, 20 and 40 s on in-phase (IP) TMF behavior and life of P92 power station steel with strain amplitudes of 0.4, 0.6, and 0.8%, and temperature range of 550–650°C. The material behavior under different hold time is compared by fractographic and microstructural tests
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