Elevated-Temperature Ferritic and Martensitic Steels and Their Application to Future Nuclear Reactors

Abstract:The effect of increasing tungsten content from 2 to 3 wt % on the creep rupture strength of a 3 wt % Co-modified P92-type steel was studied. Creep tests were carried out at a temperature of 650 • C under applied stresses ranging from 100 to 220 MPa with a step of 20 MPa. It was found that an increase in W content from 2 to 3 wt % resulted in a +15% and +14% increase in the creep rupture strength in the short-term region (up to 10 3 h) and long-term one (up to 10 4 h), respectively. On the other hand, in the long-term creep region, the effect of W on creep strength diminished with increasing rupture time, up to complete disappearance at 10 5 h, because of depletion of excess W from the solid solution in the form of precipitation of the Laves phase particles. An increase in W content led to the increased amount of Laves phase and rapid coarsening of these particles under long-term creep. The contribution of W to the enhancement of creep resistance has short-term character.

Section: Crept Microstructuresmentioning

confidence: 85%

Effect of Tungsten on Creep Behavior of 9%Cr–3%Co Martensitic Steels

Fedoseeva

Dudova

Kaibyshev

et al. 2017

“…Quantitative metallography studies revealed an average lath size ranging from 0.25 to 0.5 µm [20]. Examination of this microstructure at higher magnifications with a TEM reveals the presence of MX precipitates, distributed in the matrix within the lath, in addition to M 23 C 6 , distributed only on boundaries.…”

Section: Microstructural Characterizationmentioning

confidence: 93%

Effect of Ausforming Temperature on the Microstructure of G91 Steel

Vivas

Capdevila

Jiménez

et al. 2017

Abstract:The development of thermomechanical treatments (TMT) has a high potential for improving creep-strength in 9Cr-1Mo ferritic/martensitic steel (ASTM T/P91) to operate at temperatures beyond 600 • C. To maximize the number of nanoscale MX precipitates, an ausforming procedure has been used to increase the number of nucleation sites for precipitation inside the martensite lath. Relative to standard heat treatments (consisting of austenitization at about 1040 • C followed by tempering at about 730 • C) this processing concept has enabled achieving a microstructure containing approximately three orders of magnitude higher number density of MX precipitates having a size around four times smaller in ASTM T/P91 steel. On the other hand; this TMT has little effect on the size and number density of M 23 C 6 particles. The optimized microstructure produced by this TMT route proposed is expected to improve the creep strength of this steel.

“…The modified 9Cr-1Mo ferritic heat-resistant steel, i.e., P91 steel, is extensively employed in the power generation and nuclear energy industries owing to its outstanding high temperature mechanical properties that enable higher operating temperatures and pressures to enhance the thermal efficiency [1][2][3]. Consequently, it is of great significance to explore the creep properties of this steel.…”

Section: Introductionmentioning

confidence: 99%

Impurity Antimony-Induced Creep Property Deterioration and Its Suppression by Rare Earth Ceriumfor a 9Cr-1Mo Ferritic Heat-Resistant Steel

Song

2016

Abstract:The high temperature creep properties of three groups of modified 9Cr-1Mo steel samples, undoped, doped with Sb, and doped with Sb and Ce, are evaluated under the applied stresses from 150 MPa to 210 MPa and at the temperatures from 873-923 K. The creep behavior follows the temperature-compensated power law as well as the Monkman-Grant relation. The creep activation energy for the Sb-doped steel (519 kJ/mol) is apparently lower than that for the undoped one (541 kJ/mol), but it is considerably higher for the Sb+Ce-doped steel (621 kJ/mol). Based on the obtained relations, both the creep lifetimes under 50 MPa, 80 MPa, and 100 MPa in the range 853-923 K and the 10 5 h creep rupture strengths at 853 K, 873 K, and 893 K are predicted. It is demonstrated that the creep properties of the Sb-doped steel are considerably deteriorated but those of the Sb+Ce-doped steel are significantly improved as compared with the undoped steel. Microstructural and microchemical characterizations indicate that the minor addition of Ce can stabilize the microstructure of the steel by segregating to grain boundaries and dislocations, thereby offsetting the deleterious effect of Sb by coarsening the microstructure and weakening the grain boundary.