John A. Siefert
Electric Power Research Institute
Heat-affected zoneCreepBoiler (power generation)Composite materialMartensiteMetallurgyMaterials scienceWeldingStructural materialCorrosionSuperalloyPipingAlloyFracture processBase metalDuctilityStructural engineeringFossil fuelMicrostructureWeldabilityStress (mechanics)Austenite
54Publications
10H-index
319Citations
Publications 51
Newest
#1Jonathan Parker (EPRI: Electric Power Research Institute)H-Index: 8
#2John A. Siefert (EPRI: Electric Power Research Institute)H-Index: 10
Damage equivalent to that seen over very long times in Grade 91 steel welded components was successfully formed in laboratory, feature sized samples tested under controlled conditions. This paper ...
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#2John A. Siefert (EPRI: Electric Power Research Institute)H-Index: 10
#3Martin Strangwood (Warw.: University of Warwick)H-Index: 24
Last. Geoffrey D. West (Warw.: University of Warwick)
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The quantification of key microstructural parameters as a function of aging or creep exposure time is commonplace in the assessment of 9Cr Creep Strength Enhanced Ferritic (CSEF) power-plant steels. In these studies, the sample is either assumed chemically homogenous at the micro-scale or that a material average will be achieved by collecting enough images at random locations. In this paper, the micro-scale chemical homogeneity of two ex-service boiler components, a pipe and a forging, are quant...
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#1Xu Xu (Lboro: Loughborough University)H-Index: 4
#2John A. Siefert (EPRI: Electric Power Research Institute)H-Index: 10
Last. Rachel C. Thomson (Lboro: Loughborough University)H-Index: 25
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Abstract The microstructure in the heat affected zone of the multi-pass welds constructed by using the 9% Cr tempered martensitic steels is complex and susceptible to premature creep failure. In the present research, a systematic investigation has been conducted after long-term creep exposure in the heat affected zone of a multi-pass weld on the 9% Cr Grade 92 steel to identify the sub-optimal microstructures with a high susceptibility to creep cavitation. The characterisation techniques employe...
4 CitationsSource
#1Xu Xu (Lboro: Loughborough University)H-Index: 4
#2John A. Siefert (EPRI: Electric Power Research Institute)H-Index: 10
Last. Rachel C. Thomson (Lboro: Loughborough University)H-Index: 25
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Abstract An excessive concentration of boron in the 9% Cr tempered martensitic steels alloyed with nitrogen has a detrimental effect on creep performance, as the relatively large boron nitride phases are formed and act as the preferred sites for cavity nucleation. In the current research, a systematic investigation has been performed documenting details of creep damage in the heat affected zone of a weld joint constructed by using a 9% Cr Grade 92 steel. A combination of correlative characterisa...
4 CitationsSource
#1Jonathan Parker (EPRI: Electric Power Research Institute)H-Index: 8
#2John A. Siefert (EPRI: Electric Power Research Institute)H-Index: 10
This paper describes specific results from a unique study which involves design, manufacture and internal pressure testing of two Grade 91 steel vessels. The vessel results which are the focus of t...
2 CitationsSource
#1Sean Orzolek (Lehigh University)H-Index: 2
#2John N. DuPont (Lehigh University)H-Index: 27
Last. John A. Siefert (EPRI: Electric Power Research Institute)H-Index: 10
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Dissimilar metal weld failures between low alloy Cr-Mo ferritic steels and austenitic stainless steels made with Ni-base filler metals are typically observed along the fusion line. Such DMW failures often exhibit the onset of damage well before their expected service life. Failure is typically associated with a carbon-depleted region in the ferritic steel and formation of creep voids along a row of so-called Type I carbides. More recently, the formation of Type I carbides adjacent to a carbide-f...
2 CitationsSource
#1Fabian Dittrich (TUM: Technische Universität München)H-Index: 1
#2Peter Mayr (TUM: Technische Universität München)H-Index: 18
Last. John A. Siefert (EPRI: Electric Power Research Institute)H-Index: 10
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Modern computational calculation power enables scientists to accurately predict the microstructural evolution of complex metallurgical systems and, for example, their phase formation at elevated temperature for an extended amount of time. Valuable information can be derived from those calculations without the necessity of expensive and complicated experiments. Especially the field of power generation, where service parameters strongly influence the applied materials, can benefit from computation...
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#1Yukio Takahashi (CRIEPI: Central Research Institute of Electric Power Industry)H-Index: 18
#2Haruhisa Shigeyama (CRIEPI: Central Research Institute of Electric Power Industry)H-Index: 2
Last. John A. Siefert (EPRI: Electric Power Research Institute)H-Index: 10
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2 CitationsSource
#1John A. SiefertH-Index: 10
#2Jonathan ParkerH-Index: 8
Last. Rachel C. ThomsonH-Index: 25
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Damage in the grade 91 steel partially transformed zone has historically been associated with many different types of features in the microstructure. Susceptible features responsible for the nucleation of damage are frequently cited to include particles such as laves phase, coarse M23C6, inclusions, nitrides, or interactions between creep strong and creep week grains, grain boundaries and potentially other sources. Few studies have attempted to link these observations on a statistically relevant...
1 Citations
#1Jonathan Parker (EPRI: Electric Power Research Institute)H-Index: 8
#2John A. Siefert (EPRI: Electric Power Research Institute)H-Index: 10
Welding is a vital process required in the fabrication of ‘fracture critical’ components which operate under creep conditions. However, often the procedures used are based on ‘least initial cost’. Thus, it is not surprising that in many high energy applications, welds are the weakest link, i.e., damage is first found at welds. In the worst case, weld cracks reported have had catastrophic consequences. Comprehensive Electric Power Research Institute (EPRI) research has identified and quantified t...
3 CitationsSource