Effect of matrix hardness on the creep properties of a 12CrMoVNb steel

Lee, Y. S.; Yu, Jin

doi:10.1007/s11661-999-0242-2

Cited by 17 publications

(10 citation statements)

References 21 publications

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“…Similar results were confirmed in the previous work. 12) As shown in Fig. 2 the initial creep rate of Z200 was comparable to that of ZRT, and therefore, while the microstructure of Z200 could be similar to that of ZRT, it should contain something to delay the onset of acceleration creep.…”

Section: Effect Of Martensitizing Temperaturementioning

confidence: 74%

Effect of Martensitizing Temperature on Creep Strength of Modified 9Cr Steel

et al. 2011

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A modified 9Cr-1Mo steel was cooled to a temperature between the M s point and room temperature from the normalizing temperature and then directly heated to the tempering temperature. It was found that the time to rupture at 650 and 700 C of the steel heat-treated by the new heat treatment increased 2-3 times longer than that of the steel conventionally normalized and tempered. The microstructure of the improved steel was tempered martensite and the size of martensite blocks was larger than for the conventional heat treatment. The hardness of the improved steel was fully recovered after tempering. This strengthening is not caused by fresh martensite, but caused by the refining of M 23 C 6 and V(C,N) particles in addition to the increase in the martesite block size, where M denotes metallic elements.

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Section: Effect Of Martensitizing Temperaturementioning

confidence: 74%

Effect of Martensitizing Temperature on Creep Strength of Modified 9Cr Steel

et al. 2011

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“…Therefore, the controlling factors of the creep rate are determined by Eq. [6]. In other words, if the MDDP increases, the creep rate increases and, when the activation energy, which is a measure of resistance to the dislocation motion (climb and back stress from the obstacles), [36] reduces, the creep rate increases.…”

Section: Analysis Methods Of Creep Curvementioning

confidence: 98%

“…Using a creep curve for each set of tests, we knew the value of the strain rate as a function of the strain and we could calculate Q, V, and C by the regression of a form of Eq. [6]. If we could assume that the creep time t for a given strain is inversely proportional to the strain rate at the time, we can easily obtain a following relation:…”

Section: Analysis Methods Of Creep Curvementioning

confidence: 99%

“…Similar trends of time to rupture were confirmed in the 9Cr [44] and 12Cr steels. [5,6] 2. Analysis of creep curves The creep curves were analyzed using Eq.…”

Section: Creep Deformation and Rupture Lifementioning

confidence: 99%

“…[4] Decreasing the tempering temperature increases the hardness, which causes an improvement in the low-temperature or short-term creep strength; in general, however, low-temperature tempering is not favorable to the heat-resistant steels for use in high temperatures, because rapid recovery could occur during service in low-temperature tempering materials, resulting in a large drop in creep strength. Concerning this problem, experimental results were reported in some 12Cr steels [5,6] and low-alloy steels. [7] In the case of modified 9Cr steel, the rupture strength of one heat in the NIMS data sheet was reported to drop unexpectedly after several tens of thousands of hours in rupture time.…”

Section: Introductionmentioning

confidence: 99%

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Recovery and Precipitate Analysis of 9 Pct Cr-1 Pct MoVNb Steel during Creep

Kabadwal

Tamura

Shinozuka

et al. 2009

Metall Mater Trans A

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The effect of tempering temperature and creep exposure on the microstructure of a modified 9Cr steel was investigated. Creep-interrupted specimens, including the grip portion, were investigated precisely using mainly X-ray and inductively coupled plasma (ICP) spectroscopy. After saturation of precipitation due to creep exposure, the amount of extracted residue decreased once and then increased within a short period (dip). Chemical analysis showed that during the dip, the precipitates temporarily dissolved into the matrix and precipitated again. The size of the Cr 23 C 6 increased gradually during creep, but the growth rate was relatively small, as compared to the Ostwald ripening. The size of the VN particles in the specimens tempered at 800°C in the early stage of creep was very fine, approximately 20 nm, and tended to decrease further with the progress of creep. The size variations of the precipitates and the dip were explained from the annihilation or migration of precipitation sites, i.e., dislocations and boundaries, during creep. Transient creep for the specimens tempered at 500°C was controlled by a reduction of the mobile dislocation density. On the other hand, transient creep for 800°C was due to precipitation hardening of fine VN particles with the progress of creep, which was supported by the increase in both the lattice strain and the activation energy with creep.

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