The role of microstructural instability on creep behavior of a martensitic 9Cr-2W steel

Abe, Fujio; Nakazawa, Shizuo; Araki, Hiroshi; Noda, Tetsuji

doi:10.1007/bf02801164

Cited by 117 publications

(85 citation statements)

References 12 publications

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“…It is reported that lath width of high chromium martensite steel continuously increases from 0.5 to about 1 mm with increasing creep strain, [13][14][15][16][17] though the lath width of the previous works is rather small as compared with F82HD and, moreover, lath width in transition creep has been hardly reported.…”

Section: Change In Grain Size During Creep Deformationmentioning

confidence: 90%

“…These observations qualitatively coincide with the changes in TEM microstructures of the high Cr tempered martensitic steels. [13][14][15][16][17] 3.3.3 Particle size measured by X-ray X-ray diffraction peaks are broadened by many kinds of defects. Both elastic strain distributed locally in a specimen including elastic strain due to dislocations and grain size are the major causes of the line broadening.…”

Section: Creep Interruption Test For F82hd 331 Hardnessmentioning

confidence: 99%

“…Generally it is accepted that transition creep of martensitic steel is explained by the decrease in excess dislocation density, which is introduced by normalizing. 13) In this sense the creep behavior of F82HS is standard one.…”

Section: )mentioning

confidence: 99%

“…That is, dynamic recovery may occur during transition creep of F82HS, which is the origin of the decrease in creep rate during transition creep. Abe et al 13) observed the creep behavior of a martensitic 9Cr-2W steel and concluded that the transition creep was a consequence of the movement and annihilation of excess dislocations. The observed results and interpretation on the 9Cr-2W steel can be used to the explanation of the transition creep behavior of F82HS.…”

Section: Relation Between Eos and Mddpmentioning

confidence: 99%

“…The substructures of creep-interrupted specimens have been studied in detail only for F82HD, because the metallurgical changes in the usually normalized and tempered martensitic steel, like F82HS, are reported in the literatures. [13][14][15][16][17] 2. Experimental Procedure A 15 mm mill production plate of F82H 18) was used.…”

Section: Introductionmentioning

confidence: 99%

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Creep Behavior of Double Tempered 8%Cr-2%WVTa Martensitic Steel

Tamura

Nowell²,

Shinozuka

et al. 2006

Mater. Trans.

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Creep testing was carried out at around 650 C for a martensitic 8Cr-2WVTa steel (F82H), which is a candidate alloy for the first wall of the fusion reactors of the Tokamak type. Rupture strength of the double tempered steel (F82HD) is lightly higher than that of simply tempered steel (F82HS). On the other hand, creep rate of F82HD is obviously smaller than that of F82HS in acceleration creep, though creep strain of F82HD in transition creep, where creep rate decreases with increasing strain, is larger than that of F82HS. Hardness of the crept F82HD decreases with increasing creep strain, which corresponded with the transmission electron microscopy (TEM) observation. On the contrary, X-ray diffraction and electron back-scattered diffraction pattern measurements show that fine sub-grains are created during transition creep. The creep curves were analyzed using an exponential type creep equation and the apparent activation energy, the activation volume and the pre-exponential factor were calculated as a function of creep strain. Then, these parameters were converted into two parameters, i.e. equivalent obstacle spacing (EOS) and mobile dislocation density parameter (MDDP). While EOS decreases with increasing creep strain, MDDP increases with increasing strain during transition creep. The decrease in EOS and the increase in either EOS or MDDP are rate-controlling factors in transition and acceleration creep, respectively. On the other hand, in case of F82HS, EOS increases and MDDP decreases during transition creep. In this case, the decrease in MDDP controls the creep rate during transition creep of F82HS. It is concluded that both EOS and MDDP are representative parameters of the change in substructure during creep.

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