Relation between Creep Rupture Strength and Substructure of Heat Resistant Steel.

The microstructure and creep strength of 403Nb martensitic heat-resistant steel after tempering at 650°C, 680°C and 730°C were analyzed by SEM and TEM. Microstructural observation shows that 403Nb steel tempered at 650°C provides a finer lath structure and a smaller size of precipitates than that tempered at 680°C or 730°C. The dislocation density is also higher in 403Nb steel tempered at 650°C. The creep rupture strength of 403Nb steel tempered at 650°C is the highest among those tempered. The main creep strengthening mechanisms in 403Nb steel usually include precipitates hardening, dislocation hardening and sub-grain boundary hardening.

Download Full-text

Novel Concept of Creep Strengthening Mechanism using Grain Boundary Fe2Nb Laves Phase in Austenitic Heat Resistant Steel

MRS Proceedings ◽

10.1557/opl.2011.558 ◽

2011 ◽

Vol 1295 ◽

Cited By ~ 20

Author(s):

Imanuel Tarigan ◽

Keiichi Kurata ◽

Naoki Takata ◽

Takashi Matsuo ◽

Masao Takeyama

Keyword(s):

Grain Boundary ◽

Strengthening Mechanism ◽

Local Deformation ◽

Creep Rupture ◽

Laves Phase ◽

Resistant Steel ◽

Heat Resistant Steel ◽

Heat Resistant ◽

Term Creep

ABSTRACTThe creep behavior of a new type of austenitic heat-resistant steel Fe-20Cr-30Ni-2Nb (at.%), strengthened by intermetallic Fe2Nb Laves phase, has been examined. Particular attention has been given to the role of grain boundary Laves phase in the strengthening mechanism during long-term creep. The creep resistance increases with increasing area fraction (ρ) of grain boundary Laves phase according to equation ε/ε = (1−ρ), where ε0 is the creep rate at ρ = 0. In addition, the creep rupture life is also extended with increasing ρ without ductility loss, which can yield up to 77% of elongation even at ρ = 89%. Microstructure analysis revealed local deformation and well-developed subgrains formation near the grain boundary free from precipitates, while dislocation pile-ups were observed near the grain boundary Laves phase. Thus, the grain boundary Laves phase is effective in suppressing the local deformation by preventing dislocation motion, and thereby increases the long-term creep rupture strength. This novel creep strengthening mechanism was proposed as “grain boundary precipitation strengthening mechanism” (GBPS).

Download Full-text

Relationship between loss of creep rupture strength and microstructure in the heat affected zone of heat-resistant ferritic steel

Welding International ◽

10.1533/wint.2005.3377 ◽

2005 ◽

Vol 19 (2) ◽

pp. 109-117 ◽

Cited By ~ 8

Author(s):

H Hirata ◽

K Ogawa

Keyword(s):

Heat Affected Zone ◽

Ferritic Steel ◽

Rupture Strength ◽

Creep Rupture ◽

Creep Rupture Strength ◽

Heat Resistant

Download Full-text

Growth Kinetics of Laves Phase and Its Effect on Creep Rupture Behavior in 9Cr Heat Resistant Steel

Journal of Iron and Steel Research International ◽

10.1016/s1006-706x(16)30106-6 ◽

2016 ◽

Vol 23 (7) ◽

pp. 685-691 ◽

Cited By ~ 10

Author(s):

Zhi-xin Xia ◽

Chuan-yang Wang ◽

Chen Lei ◽

Yun-ting Lai ◽

Yan-fen Zhao ◽

...

Keyword(s):

Growth Kinetics ◽

Creep Rupture ◽

Laves Phase ◽

Resistant Steel ◽

Heat Resistant Steel ◽

Heat Resistant ◽

Kinetics Of ◽

Rupture Behavior

Download Full-text

Creep Rupture Behavior in Dissimilar Weldment between FB2 and 30Cr1Mo1V Heat-Resistant Steel

International Journal of Photoenergy ◽

10.1155/2021/1143989 ◽

2021 ◽

Vol 2021 ◽

pp. 1-11

Author(s):

Jiankun Xiong ◽

Jianping Yang ◽

Haiyan Zhao ◽

Lin Yang ◽

Yang Guo ◽

...

Keyword(s):

Subgrain Size ◽

Fracture Initiation ◽

Creep Rupture ◽

Transgranular Fracture ◽

Resistant Steel ◽

Laves Phases ◽

Heat Resistant Steel ◽

Heat Resistant ◽

Fracture Character ◽

Rupture Behavior

Creep rupture behavior of dissimilar weldments between FB2 and 30Cr1Mo1V heat-resistant steel by multipass welding at 783 K (510°C) under different stresses (260 to 420 MPa) was researched. The fitted creep rupture exponent is 14.53, and the 10,000 h extrapolating strength values predicted by the power law and Larson-Miller parameter show good agreement with experimental data. The samples exhibit a ductile fracture character and fracture in the weld fusion zone, which has a highly heterogeneous microstructure and grains with different morphologies and sizes and an obvious softening. There exist a decrease in the dislocation and precipitate density and an increase in the subgrain size in the weld metal after creep. The rupture is a transgranular fracture characterized by dimples as a result of microvoid coalescence. Laves phases along with copper-rich precipitates are observed in the vicinity of fracture surface, which creates a stress concentration that can cause transgranular fracture initiation.

Download Full-text