Structural changes in a ferritic heat-resistant steel after long-term service

1984 ◽  
Vol 62 (1) ◽  
pp. 129-136 ◽  
Author(s):  
R.A. Varin ◽  
J. Haftek
Keyword(s):  
Structural Changes ◽  
Resistant Steel ◽  
Heat Resistant Steel ◽  
Heat Resistant

scholarly journals 3D Observation on Precipitates of a Ferritic Heat Resistant Steel after Long-term Creep

Materia Japan ◽  
2018 ◽  
Vol 57 (12) ◽  
pp. 619-619
Author(s):  
Tomoyuki Hatta ◽  
Nobuaki Sekido ◽  
Mitsuharu Yonemura ◽  
Kouichi Maruyama ◽  
Kyosuke Yoshimi
Keyword(s):  
Resistant Steel ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
Term Creep

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

2011 ◽  
Vol 1295 ◽  
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).

Effect of Long-Term Ageing at 600 °C on Microstructure of ZG1Cr10MoWVNbN Martensitic Heat-Resistant Steel

2018 ◽  
Vol 37 (6) ◽  
pp. 539-544
Author(s):  
Chengzhi Zhao ◽  
Ning Li ◽  
Yihan Zhao ◽  
Hexin Zhang
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
M23c6 Carbide ◽  
Resistant Steel ◽  
Steam Turbines ◽  
Heat Resistant Steel ◽  
Property Variation ◽  
Heat Resistant ◽  
Before And After

AbstractA new kind of martensitic ZG1Cr10MoWVNbN heat-resistant steel has been attracted more attentions in recent years, which is mainly applied in ultra-supercritical steam turbines. The ageing property for ZG1Cr10MoWVNbN heat-resistant steel is very important because it often serves for long-time at high-temperature environment. Herein, a long-term ageing heat treatment was conducted on ZG1Cr10MoWVNbN steel at 600 °C heat for 17,000 hours. The microstructure evolution and property variation of the ZG1Cr10MoWVNbN steel were analysed before and after ageing, and also the effect of the precipitates on the mechanical properties was studied. The result showed that strength, the plastic index and impact power of the ZG1Cr10MoWVNbN steel were gradually decreased after long-term and high-temperature ageing at 600 °C due to the changes of martensite morphology and the coarsening of M23C6 carbide precipitation phase. Furthermore, fine precipitation of matrix MX carbide can also attribute to the change of mechanical properties at high temperature.

Microstructure Evolution in a 3%Co Modified P911 Heat Resistant Steel under Creep Conditions

2010 ◽  
Vol 89-91 ◽  
pp. 295-300 ◽  
Author(s):  
Alla Kipelova ◽  
Rustam Kaibyshev ◽  
Andrey Belyakov ◽  
Izabella Schenkova ◽  
Vladimir Skorobogatykh
Keyword(s):  
Structural Changes ◽  
Elevated Temperatures ◽  
Second Phase ◽  
Resistant Steel ◽  
Creep Tests ◽  
Tempering Temperature ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
Static Annealing ◽  
Average Size

The microstructural changes in a 3%Co modified P911 heat resistant steel were examined under static annealing and creep at elevated temperatures. The quenched steel was tempered at temperatures ranging from 673 to 1073 K for 3 hours. The temperature dependence of hardness for the tempered samples exhibits the maximum at 723 – 823 K which is associated with the precipitations of fine carbides with an average size of about 20 nm. The transverse lath size of martensitic structure is  200 nm after air quenching and remains unchanged under tempering at temperatures below 800 K. An increase in tempering temperature to 1073 K resulted in hardness drop. Coagulation of carbides and growth of martensitic laths takes place at these temperatures. The creep tests were carried out at 873 and 923 K up to rupture, which occurred after about 4.5 × 103 hours. The structural changes in crept specimens were characterized by the development of coarse laths/subgrains. The mean transverse size of which was  0.67 and  1.3 m after the creep tests at 873 and 923 K, respectively. On the other hand, an average size of second phase particles of  165 nm was observed in the samples tested at both temperatures.

scholarly journals Low-Stress Creep Deformation in Long-Term Aged Ferritic Heat-Resistant Steel

2014 ◽  
Vol 55 (5) ◽  
pp. 842-849 ◽  
Author(s):  
Shigeto Yamasaki ◽  
Masatoshi Mitsuhara ◽  
Ken-ichi Ikeda ◽  
Satoshi Hata ◽  
Hideharu Nakashima
Keyword(s):  
Creep Deformation ◽  
Resistant Steel ◽  
Heat Resistant Steel ◽  
Heat Resistant

The Corrosion Behavior of 9Cr Ferritic–Martensitic Heat-Resistant Steel in Water and Chloride Environment

2015 ◽  
Vol 137 (3) ◽  
Author(s):  
Z. Zhang ◽  
P. M. Singh ◽  
Z. F. Hu
Keyword(s):  
Grain Boundaries ◽  
Corrosion Behavior ◽  
Electrochemical Impedance ◽  
Optical Microscope ◽  
Resistant Steel ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
Chloride Environment ◽  
Chloride Concentrations

The corrosion behavior of 9Cr ferritic–martensitic heat-resistant steel was investigated in water and chloride environment at room temperature (RT). The results of linear polarization, electrochemical impedance spectroscopy (EIS), and potentiodynamics (PD) polarization tests on long-term exposure show that 9Cr ferritic–martensitic steel has weaker corrosion resistance and greater pitting corrosion tendency in higher chloride concentrations. Corresponding scanning electron microscopy (SEM) observation displays that higher concentration chloride promotes the pitting initiation. During long-term exposure, pitting susceptibility decreases, the average pit size increases, and the density declines in higher chloride concentrations. Pits in the grains and along the grain boundaries are observed by optical microscope (OM), and it indicates that inclusions in grains and carbide particles at grain boundaries are the sites susceptible to pitting initiation.

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