Abstract High total strain-controlled creep-fatigue tests of 1.8% were performed for a directionally-solidified Ni-based superalloy, DZ445, at 900 °C in air. Dwell times of 0, 2, and 5 min. were introduced at the tensile peak strain for each cycle. Experimental results show a decrease in fatigue life with increasing dwell time. The significant cyclic softening is observed after the application of the dwell time. The mean compressive stress and large plastic-strain accumulation are produced due to the stress relaxation in the tensile-dwell period, resulting in the increase of the hysteresis loop area. The typical single-source crack-initiation and transgranular crack-propagation are transformed into multi-source crack-initiation and mixed transgranular and intergranular crack-propagation mode by these characteristics. Dislocation features are transformed from cutting of γ' precipitates by multiple stacking faults to the mixed mode of dislocation climbing and slipping. The reduction in the fatigue life with increasing the dwell time is well explained on the basis of the mechanical response and damage mechanism. The fatigue life is also predicted by the energy-based life-prediction model.
Last. Zhifang Gao(Tianjin University of Technology)H-Index: 4
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Abstract The low cycle fatigue and low cycle fatigue-creep behaviours of P92 steel with strain-control mode and fully inverse loading waveforms at the temperature of 630 °C were investigated. A typical cyclic softening behaviour of P92 steel was observed. As the hold time was introduced at the tensile peak and compressive valley strains, the failure cycle was reduced and the stress reduction became more obvious with the increasing hold time because of the improvement in creep deformation. Moreov...
#1Run-Zi Wang(ECUST: East China University of Science and Technology)H-Index: 10
#2Shun-Peng Zhu(University of Electronic Science and Technology of China)H-Index: 34
Last. Cheng-Cheng Zhang(Arkansas Electric Cooperative Corporation)H-Index: 11
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Abstract The low cycle fatigue (LCF) and creep-fatigue behaviors of Ni-based GH4169 superalloy are investigated by uniaxial strain-controlled fully-reversed testing at 650 °C. Compared with LCF tests, the effects of tensile and compressive strain hold times on creep-fatigue lifetimes are experimentally explored with varying total strain ranges in the present work. In order to elucidate the damage mechanisms under complex loading waveforms, an additional series of tests with both tensile and comp...
Abstract Austenitic stainless Sanicro 25 steel has been subjected to high temperature elasto-plastic cyclic straining at 700 °C. The isothermal cyclic tests without and with a dwell in the loading cycle were implemented. Several strain amplitudes and optional dwells of 10 min in tensile part of the loading cycle were applied to the specimens. Cyclic stress-strain response was recorded, cyclic hardening/softening curves and fatigue life curves were obtained. Scanning electron microscopy combined ...
#1Ankur Chauhan(KIT: Karlsruhe Institute of Technology)H-Index: 9
#2Jan Hoffmann(KIT: Karlsruhe Institute of Technology)H-Index: 19
Last. Jarir Aktaa(KIT: Karlsruhe Institute of Technology)H-Index: 25
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Abstract Creep-fatigue (CF) interaction in a tempered martensitic Fe-9%Cr-based oxide dispersion strengthened (ODS) steel was studied at 650 °C by introducing hold-time of up to 30 min at peak tensile strain of 0.7%. The symmetrical loops under pure fatigue/continuous cycling (PF/CC) became asymmetrical due to stress relaxation during hold-time. Moreover, this also resulted in a reduction of cyclic life. For the investigated hold-time durations, the increase in tensile hold (TH) period had a neg...
#1Sunil Goyal(RRC: Indira Gandhi Centre for Atomic Research)H-Index: 15
#2K. Mariappan(RRC: Indira Gandhi Centre for Atomic Research)H-Index: 11
Last. A.K. Bhaduri(RRC: Indira Gandhi Centre for Atomic Research)H-Index: 33
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Abstract In this investigation, response of Alloy 617 M to creep-fatigue interaction loading has been studied. The creep-fatigue interaction tests were conducted in air environment at a constant strain rate of 3 × 10−3 s−1 and strain amplitude of ± 0.4% with hold periods of 1 min, 10 min and 30 min at peak tension or compression at 973 K. The material showed initial hardening to a saturation followed by reduction in stress initiated by crack nucleation, propagation and final failure. The fatigue...
#1Jinghao Xu(CSU: Central South University)H-Index: 3
#1Jinghao Xu(CSU: Central South University)H-Index: 6
Last. Liang Jiang(CSU: Central South University)H-Index: 13
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Abstract Low cycle fatigue (LCF) performance of a novel high Co nickel-base polycrystalline superalloy was investigated at 750 °C under the strain ranges from 0.6 to 1.0%. The objective is to focus on fatigue life, cyclic deformation behavior, deformation substructure, fracture mode, crack propagation pathway as well as oxidation attack at the crack tip. The fatigue life decreases with strain range increasing and follow the Coffin-Manson power law with plastic strain. The experimental results sh...
Last. Jianbo Yu(SHU: Shanghai University)H-Index: 11
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Abstract Total strain-controlled creep-fatigue tests were performed for a directionally solidified Ni-based superalloy at 850 °C in air. Dwell times of 0, 1, 2, 3, 5, and 8 min were introduced at the tensile peak for each cycle. The results demonstrated that the fatigue life firstly decreased and then slightly increased with increasing dwell time. The fatigue life showed a minimum at a dwell time of 3 min. The initial softening rate was faster than the subsequent softening rate when dwell times ...
#1Ivo Šulák(CAS: Academy of Sciences of the Czech Republic)H-Index: 5
#2Karel Obrtlík(CAS: Academy of Sciences of the Czech Republic)H-Index: 20
Abstract Hot isostatically-pressed, nickel-based superalloy MAR-M247 was tested under fatigue and creep-fatigue conditions. Continuous cycling and cycling with 10 min tensile dwells in each cycle were applied in symmetrical strain control cycle with constant total strain amplitude at 900 °C in air. Cyclic hardening/softening curves, cyclic stress-strain curves and fatigue life curves were obtained. The introduction of tensile dwells resulted in lower fatigue life in total strain representation. ...
#1Ankur Chauhan(KIT: Karlsruhe Institute of Technology)H-Index: 9
#2Luis Straßberger(KIT: Karlsruhe Institute of Technology)H-Index: 4
Last. Jarir Aktaa(KIT: Karlsruhe Institute of Technology)H-Index: 25
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Abstract The present study reports on the creep-fatigue (CF) behavior of a ferritic bimodal 12Cr-ODS steel. The tests were performed in air at 550 °C and 650 °C by introducing hold-time at peak tensile, peak compressive and both peak tensile as well as compressive strains of ±0.5%. The symmetrical loops under pure fatigue/continuous cycling (CC) became asymmetrical upon introducing hold-time at either peak tensile or peak compressive strain. On the contrary, hold-time on both sides had no influe...