Effect of microstructural evolution on high-temperature strength of 9Cr–3W–3Co martensitic heat resistant steel under different aging conditions

Published on Dec 20, 2013in Materials Science and Engineering A-structural Materials Properties Microstructure and Processing5.234
· DOI :10.1016/J.MSEA.2013.09.033
Peng Yan5
Estimated H-index: 5
(THU: Tsinghua University),
Zhengdong Liu5
Estimated H-index: 5
+ 2 AuthorsWei Liu26
Estimated H-index: 26
(THU: Tsinghua University)
Sources
Abstract
Abstract Evolution of microstructures and high-temperature strength at 650 °C of 9Cr–3W–3Co martensitic heat resistant steel after aging at 650 °C and 700 °C for different time durations have been experimentally investigated using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), field emission transmission electron microscopy (FETEM) and post-aged tensile tests. The results show that after aging at 650 °C, the high-temperature strength and the microstructures of 9Cr–3W–3Co steel keep almost stable with increasing aging time from 300 h to 3000 h. In comparison, after aging at 700 °C, there are obvious changes in the high-temperature strength and the microstructures. The strengthening mechanisms of the 9Cr–3W–3Co steel were also discussed and the athermal yield stresses were calculated. The change of the high-temperature strength is mainly affected by the evolution of dislocations and laths. The precipitates mainly act as obstacles against motion of dislocations and lath boundaries.
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References26
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Abstract Boundary and sub-boundary hardening are shown to be the most important strengthening mechanism in creep of 9%Cr steel. Soluble boron reduces the coarsening rate of M23C6 carbides near prior austenite grain boundaries during creep, enhancing the boundary and sub-boundary hardening for long times at 650°C. The enhancement of boundary and sub-boundary hardening retards the onset of acceleration creep, which decreases the minimum creep rate and improves the creep life. Excess addition of bo...
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#1Fujio Abe (National Institute for Materials Science)H-Index: 52
AbstractIt is crucial for the carbon concentration of 9% Cr steel to be reduced to a very low level, so as to promote the formation of MX nitrides rich in vanadium as very fine and thermally stable particles to enable prolonged periods of exposure at elevated temperatures and also to eliminate Cr-rich carbides M23C6. Sub-boundary hardening, which is inversely proportional to the width of laths and blocks, is shown to be the most important strengthening mechanism for creep and is enhanced by the ...
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