Prospects for Martensitic 12 % Cr Steels for Advanced Steam Power Plants

Published on Jan 5, 2016in Transactions of The Indian Institute of Metals1.499
· DOI :10.1007/S12666-015-0793-4
John Hald23
Estimated H-index: 23
Sources
Abstract
Creep strength improvements of martensitic 9 % Cr steels have been obtained by controlled additions of V, Nb, N and B to the steels, which resulted in precipitation hardening by fine stable nitrides based on V and Nb as well as in stabilization of Cr carbides against coarsening. The best steels P92 and FB2 are now used in power plants up to 600–620 °C steam temperature. For higher steam temperatures up to 650 °C steels with 11–12 % Cr are needed for better resistance against steam oxidation. However, fine V and Nb based nitrides may transform to coarse Z-phase [Cr(V,Nb)N] nitrides in steels with such Cr contents, leading to a strength loss in long-term creep. The paper presents the status of development of new stable 12 Cr steels based on the concepts of either strengthening by fine Z-phase nitrides or on elimination of nitrides from the steels.
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References20
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#1Kentaro Asakura (UTokyo: University of Tokyo)H-Index: 14
#2Toshihiko Koseki (UTokyo: University of Tokyo)H-Index: 28
Last. Toshio Fujita (UTokyo: University of Tokyo)H-Index: 11
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Source
#2John HaldH-Index: 23
Last. Marcel A. J. SomersH-Index: 43
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In 9–12% Cr creep-resistant steels Cr(V,Nb,Ta)N Z-phase is known to replace metastable (V,Nb,Ta)N MN precipitates at high temperatures. The precipitation process of Z-phase does not follow the classical nucleation theory, where dissolving MN particles provide constituents for Z-phase nucleation in the matrix. Using atomic resolution transmission electron microscopy, the current work demonstrates that metastable cubic TaN precipitates in a complex steel gradually transform compositionally and cry...
Source
#1Nadezhda Dudova (Belgorod State University)H-Index: 13
#2R. Mishnev (Belgorod State University)H-Index: 9
Last. Rustam Kaibyshev (Belgorod State University)H-Index: 60
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The effect of heat treatment on the microstructure and the mechanical properties of a 10%Cr steel with 0.008% boron was examined. The microstructure and the mechanical properties of this steel subjected to the normalizing were studied after tempering under different conditions. The layers of retained austenite are located along the lath boundaries. The formation of M23(B·C)6 phase having film-like shape takes place on interface boundaries of retained austenite/martensite during tempering at 525°...
Source
#1Nadezhda Dudova (Belgorod State University)H-Index: 13
#2Rustam Kaibyshev (Belgorod State University)H-Index: 60
Precipitation sequence under tempering in a 10%Cr steel has been considered in details. Two different precipitation processes have been identified, concurrently. First, at 350°C, a dispersion of M2C phase with orthorhombic lattice appears. At 525°C, the M2C phase is displaced by the formation of M23C6 carbide. However, this process remains uncompleted. Dissolution of M2C phase occurs completely due to the formation and growth of more stable M6C phase as a result of tempering in the range of 650 ...
Source
AbstractThe creep strength of martensitic 9% chromium steels is strongly coupled with the formation and interaction of different precipitate populations like MX (Nb,V)(C,N), M23C6, laves phase and modified Z-phase. Changes in microstructure can be correlated to a change in creep strength. Within this work, a boron-nitrogen balanced 9Cr3W3CoVNb steel is investigated in normalised and tempered (as-received), creep exposed and welded condition. Microstructural characterisation of as-received and cr...
Source
#1L. Cipolla (DTU: Technical University of Denmark)H-Index: 6
#2Hilmar Kjartansson Danielsen (DTU: Technical University of Denmark)H-Index: 18
Last. Marcel A. J. Somers (DTU: Technical University of Denmark)H-Index: 43
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Abstract A 12% Cr model steel was designed with the purpose of studying the nucleation and growth of modified Z -phase, Cr(V,Nb)N. The model alloy develops Z -phase after relatively short ageing times and contains only nitrides of Cr, V and Nb. Interferences from the presence of carbides and the development of Laves phase were avoided by keeping the C, W and Mo contents as low as possible. Transmission electron microscopy and X-ray diffraction analysis of extracted particles were used to follow ...
Source
#1Hilmar Kjartansson Danielsen (DTU: Technical University of Denmark)H-Index: 18
#2John Hald (DTU: Technical University of Denmark)H-Index: 23
Z-phases in tantalum-containing 12%Cr steels have been investigated. In 12%Cr steel without any Nb or V, the formation of CrTaN Z-phases was observed. In 12%Cr steel which also contained V, the Ta entered Z-phase as a minor element, Cr(V,Ta)N. The crystal structure of Cr(V,Ta)N seems to be identical to CrVN Z-phase, while CrTaN is similar to CrNbN Z-phase but with a different lattice parameter.
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#1Hilmar Kjartansson Danielsen (DTU: Technical University of Denmark)H-Index: 18
#2John Hald (DTU: Technical University of Denmark)H-Index: 23
Abstract Precipitation of large Z-phase particles, Cr(V,Nb)N, replacing fine MX nitrides, (V,Nb)N, has recently been identified as a major cause of premature breakdown in long-term creep strength of a number of new 9–12%Cr martensitic steels. The Z-phase precipitates slowly during long-term exposure at around 650 °C accelerated by high Cr content in the steels. It appears that the nucleation process controls the precipitation rate of Z-phase. A 12%Cr steel, which had precipitated Z-phase during ...
Source
Abstract The effect of boron on creep deformation behavior and microstructure evolution during creep has been investigated for a tempered martensitic 9Cr-3W-3Co-VNb steel containing boron up to 140 ppm at 650°C (923 K) with the emphasis on long term behavior. Creep tests were carried out at 650°C for up to about 70 000 h. The base steel without boron exhibits degradation in creep rupture strength after times above about 1000 h. The addition of boron retards the onset of tertiary or acceleration ...
Source
Abstract Advanced microstructure characterisation and microstructure modelling has demonstrated that long-term microstructure stability in 9–12% Cr steels under technical loading conditions is equivalent to precipitate stability. Mo and W can have a positive influence on long-term creep strength of 9–12% Cr steels by Laves phase precipitation hardening. Unexpected breakdown of long-term creep stability of a number of alloys is caused by precipitation of the complex Z-phase nitride, which may com...
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