Analysis of the Fracture Morphology of FB2 under Low-cycle Fatigue

doi:10.11930/j.issn.1004-9649.201801009

Abstract

Abstract: Low-cycle fatigue properties of FB2 steel under room temperature and 620℃ are analyzed by axialload constant-amplitude method. The fracture morphology and microstructure of the low-cycle fatigue specimen are observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). Results illustrate that the FB2 is cyclic softening material. Its cyclic life under high temperature is far shorter than that under room temperature. The relationship between the cyclic strain and its life satisfies the Manson-Coffin model. SEM analysis shows that the fatigue cracks usually initiate from the surface defects or BN inclusions. The fatigue striations as well as the intact BN inclusions can be clearly distinguished. TEM analysis shows that the cyclic softening of FB2 steel is the consequence of the reduced density of dislocation, the transform of martensite laths together with the form and coarsening of sub-grain.

Key words: steam turbine, FB2, low-cycle fatigue, fracture morphology, microstructure, 620 ℃, fatigue life

CLC Number:

YANG Baixun, DING Lingling, TIAN Xiao, XU Hui, LI Yimin. Analysis of the Fracture Morphology of FB2 under Low-cycle Fatigue[J]. Electric Power, 2018, 51(11): 20-25.

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URL: https://www.electricpower.com.cn/EN/10.11930/j.issn.1004-9649.201801009

https://www.electricpower.com.cn/EN/Y2018/V51/I11/20

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