Effect of aging on the impact toughness of 25Cr–20Ni–Nb–N steel

Peng, Bowen; Zhang, Hongxiang; Hong, Jie; Gao, Jianbao; Wang, Qijiang; Zhang, Hanqian

doi:10.1016/j.msea.2009.12.039

Cited by 55 publications

(19 citation statements)

References 13 publications

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“…19(b)). The fractographic features were observed in the other type of austenitic heat-resistant steel [30]. These results indicate that transgranular fracture occurred in the specimen with = 36%, as well as the specimen with > 80%.…”

Section: Charpy Impact Testmentioning

confidence: 62%

Mechanical properties of austenitic heat-resistant Fe–20Cr–30Ni–2Nb steel at ambient temperature

Kanno

Yoshimura

Takata

et al. 2016

Materials Science and Engineering: A

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The mechanical properties of Fe-20Cr-30Ni-2Nb (at.%) steels with controlled microstructures were examined by conducting tensile tests and Charpy impact tests at room temperature. The solution-treated specimen (-Fe single-phase) exhibited a yield strength (y) of 210 MPa and a maximum tensile strength (UTS) of 850 MPa. Its rupture strain (r) was more than 40%. The specimen with high area fraction of the Fe 2 Nb Laves phase on the grain boundaries () exhibited a higher y of 276 MPa and adequate tensile ductility (r = 29%). The specimen with high-density precipitates of the Ni 3 Nb phase in the grain interior exhibited a much higher y. The value of y of Fe-20Cr-30Ni-2Nb steel can be controlled by changing the precipitation morphology in the grain interior. Fractographic observations demonstrate that ductile intragranular fracture occurred in all of the tested specimens. The absorption energy measured by the Charpy impact test decreased from 211 to 31 J/cm 2 as was increased from 0 to 89%. The fracture mode appeared to vary from ductile transgranular fracture to cleavage transgranular fracture with increasing. There was no indication of crack propagation within the precipitates of the Laves phase covering the grain boundaries or along the interface between-Fe and the Laves phase. Therefore, the Laves phase that precipitated on the grain boundaries would not have a negative effect on the room-temperature ductility.

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Section: Charpy Impact Testmentioning

confidence: 62%

Mechanical properties of austenitic heat-resistant Fe–20Cr–30Ni–2Nb steel at ambient temperature

Kanno

Yoshimura

Takata

et al. 2016

Materials Science and Engineering: A

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“…In the as-received condition, HR3C steel is characterised by austenitic microstructure with precipitates of primary NbC carbides [7,9]. The research [20] shows that in the microstructure of HR3C steel in the as-received condition, apart from large primary NbC carbides, also the finedispersion precipitates of Z phase -NbCrN can be observed.…”

Section: Fig 4 Lost Austenite Grains In the Examined Steelmentioning

confidence: 84%

“…Similar effects will occur under the notch and in the hinge area. The foregoing results in overestimation of the obtained value of crack resistance for the examined steel, the more so that it was demonstrated in [3,7,20] that the impact strength of this type of steel decreases rapidly to ~20J after a short time of ageing. The researchers associate this effect with the precipitation processes of M 23 C 6 carbides and sigma phase at the grain and twin boundaries and the coarse-grain structure with grain size of 3-4 according to the ASTM scale.…”

Section: Properties Of Hr3c Steel After Servicementioning

confidence: 94%

“…Single M 23 C 6 carbides can also be observed inside the grains. The ratio of carbides precipitated inside the grains to those precipitated at the grain boundaries is 7:93 [20]. Due to their low thermodynamic stability, the M 23 C 6 carbides tend to coagulate during service and form the so-called continuous network at the grain boundaries.…”

Section: Fig 3 Diffractogram Of Isolates Extracted From Hr3c Steelmentioning

confidence: 99%

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Microstructure and mechanical properties of HR3C austenitic steel after service

Golański

Kolan

Zieliński

et al. 2016

Archives of Materials Science and Engineering

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Purpose: The purpose of the investigations was to determine changes in the microstructureand mechanical properties of HR3C creep resisting austenitic steel after service.Design/methodology/approach: The investigations were performed on test specimens takenfrom a part of the steam superheater tube. The range of the investigations included: microstructuralinvestigations - light and SEM microscope; analysis of precipitates - carbide isolates; investigationsof mechanical properties - hardness measurement, static tensile test, impact test.Findings: The precipitation processes at the grain boundaries lead to increase inintergranular corrosion of the HR3C steel resulting in loss of grains in the structure. Theimpact strength testing on test specimens with reduced width may result in overestimationof crack resistance of the material after service.Research limitations/implications: The comprehensive analysis of precipitationprocesses requires TEM examinations. Finding the correlation between the impact strengthdetermined on standard vs. non-standard test specimens with reduced width.Practical implications: The obtained results of investigations are used in industrialpractice for diagnosis of pressure parts of power boilers. Test procedures developed based oncomprehensive materials testing conducted under laboratory conditions are used in upgradingand design of pressure parts of steam boilers. The results of investigations are also the elementof database of the materials characteristics of steels and alloys as well as welded joints made ofthem working under creep conditions developed by the Institute for Ferrous Metallurgy.Originality/value: The results and analysis of the investigations of microstructure andmechanical properties of HR3C steel after service under actual boiler conditions are presented.

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“…The evolution of mechanical properties and microstructure of the HR3C steel after high-temperature aging has been widely reported by others. Iseda et al (2007) concluded that the sufficient toughness and microstructural stability can be maintained after the long term aging of HR3C steel at 500-750 • C. Peng et al (2010) found out that the M 23 C 6 precipitating on grain boundaries can result in the reduction of the impact toughness after aging for various time at 700 • C. The reasonable hot working process can be controlled to obtain high product rate and desired microstructures. Yin et al (2012) revealed a distinctive phenomenon that the recrystallization would occur during the annealing treatment after HR3C steel was solution-treated at 1150 • C. The dislocation of high density remained in the matrix of the steel is responsible for the driving force of recrystallization.…”

Section: Introductionmentioning

confidence: 99%