scholarly journals Effect of Long-Term Creep on Microstructure of a 9% Cr Heat Resistant Steel

2014 ◽  
Vol 783-786 ◽  
pp. 1839-1844
Author(s):  
Valeriy Dudko ◽  
Alexandra Fedoseeva ◽  
Pavel Kozlov ◽  
Vladimir Skorobogatykh ◽  
Izabella Schenkova ◽  
...  
Keyword(s):  
Prior Austenite ◽  
Average Thickness ◽  
Resistant Steel ◽  
Secondary Phases ◽  
Heat Resistant Steel ◽  
Gauge Section ◽  
The Mean ◽  
Average Size ◽  
Term Creep

The effect of long-term creep at 600°C under 137 MPa on the microstructure of a P92-type steel was investigated. The microstructure after tempering consisted of laths with an average thickness of 400 nm. Dispersion of secondary phases consists of M23C6carbides with an average size of 85 nm located mainly on lath, block and prior austenite boundaries and MX carbonitrides with average size of 31 nm homogeniously distributed throughout. Creep with duration of 40738 hours led to coarsening of M23C6carbides up to 182 nm. Precipitation of Laves phase with an average size of 290 nm took place in both grip and gauge portions of ruptured specimen. Vanadium-rich MX particles were replaced by particles of Z-phase with sizes of 97 and 48 nm after long-term creep and aging, respectively. The average misorientation of the lath boundaries was approximately 2° and scarcely varied during creep, while the mean lath thickness increased to 890 nm in gauge section of ruptured specimen and remained essentially unchanged in the grip section. Dislocation density decreased slightly under long-range aging and creep.

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).

scholarly journals Creep behavior and cavitation evolution of 15CrMoG steel at high temperatures

2019 ◽  
Vol 11 (8) ◽  
pp. 168781401986566
Author(s):  
Jingping Pan ◽  
Shuheng Tu ◽  
Xinwei Zhu ◽  
Lianjiang Tan
Keyword(s):  
High Temperatures ◽  
Creep Behavior ◽  
Creep Rupture ◽  
Resistant Steel ◽  
Creep Data ◽  
Creep Tests ◽  
Rupture Stress ◽  
Heat Resistant Steel ◽  
Term Creep

15CrMoG steel is a type of heat-resistant steel frequently used in boiler and piping systems. Creep properties of the 15CrMoG steel at service temperatures are not much documented due to the difficulties in obtaining long-term creep data. Herein, the creep behavior and the cavity evolution of 15CrMoG steel were investigated based on 20,000 h of creep tests at varied temperatures. Creep curves were analyzed to elucidate the creep behavior and creep rupture mechanism of the 15CrMoG steel. A continuum damage model was adopted to fit the rupture stress versus creep time data, and the results showed the reliability of this model in describing the creep behavior and predicting the creep life. The creep rupture stress at 20,000 h decreased significantly with the increase in the temperature in the tested temperature range. The cavitation in the 15CrMoG steel samples occurring during the creep tests was also examined by microscopic analysis, the results of which confirmed that the cavitation evolution is responsible for the reduced mechanical performance and finally creep rupture of the steel. This work provides valuable high-temperature creep data of the 15CrMoG heat-resistant steel and insights into evaluation and prediction of long-term creep behavior at high temperatures.

Quantitative Evaluation of Secondary Phases in a Weld Joint Made of COST F and FB2 Creep Resistant Steels

2017 ◽  
Vol 270 ◽  
pp. 183-188
Author(s):  
Dagmar Jandová
Keyword(s):  
Quantitative Evaluation ◽  
Creep Strength ◽  
Weld Joint ◽  
Precipitate Size ◽  
Secondary Phases ◽  
Creep Tests ◽  
Transmission Electron ◽  
Creep Resistant Steels ◽  
Term Creep

Conventional (CCT) and accelerated (ACT) creep tests of a weld joint made of COST F and COST FB2 steels were carried out over a temperature range from 550 °C to 650 °C. Fracturing of the crept specimens was located in the heat affected zone (HAZ) of the F steel. Two specimens were selected after CCT and ACT for quantitative evaluation of the precipitates and compared to the weld joint in as-received conditions. Scanning and transmission electron micrographs were used to measure the precipitate size. Both methods were compared and the accuracy of the results was discussed. It was concluded that ACT can simulate the precipitation of chromium carbides and structure recovery during long term creep exposures. However, precipitation of Laves phase during CCT was not recorded after ACT. Therefore, it is difficult to use ACT in this experiment for estimating the long term creep strength.

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.

Influence of Microstructural Changes in Creep Resistant Steel after Long-Term Creep Tests on the Shape of the Polarization Curves

2015 ◽  
Vol 647 ◽  
pp. 153-161
Author(s):  
Jana Sladká ◽  
Dagmar Jandová ◽  
Eva Chvostová
Keyword(s):  
Martensitic Steel ◽  
Light And Electron Microscopy ◽  
Polarization Curves ◽  
Resistant Steel ◽  
Creep Tests ◽  
Microstructural Changes ◽  
Additional Peak ◽  
Term Creep ◽  
Non Destructive

Creep resistance of the steel depends on chemical and structural composition and structural stability. Therefore it is necessary to check microstructural changes in material during the long-term service, however the necessary material analyses are generally destructive. The submitted contribution describes non-destructive electrochemical method for detection of some microstructural changes taking place during creep exposures. The shape of polarization curves are correlated to the microstructure of CB2 steel, the most promissing (9-12) %Cr martensitic steel for the cast components. The dynamic polarization curves were measured using samples in as received conditions and after long-term creep tests at 650°C. Microstructure was analysed using light and electron microscopy. The microstructure of the CB2 steel changed during creep exposures. In polarization curves additional peak appeared in the main passivation region and the curve shape changed also in the secondary passivation region. The curve changed in dependence on precipitation and growth of Laves phase particles.

Precipitation of Nano-Sized Z-Phase in HR3C Austenitic Heat Resistant Steel

2013 ◽  
Author(s):  
Fengshi Yin ◽  
Zhen Xu ◽  
Bing Xue ◽  
Li Zhou ◽  
Xuebo Jiang
Keyword(s):  
Aging Temperature ◽  
Solution Treatment ◽  
Aging Treatment ◽  
Resistant Steel ◽  
Secondary Phases ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
M23c6 Type ◽  
Type Carbide ◽  
Austenite Grains

Effect of heat treatment on the precipitation behavior of secondary phases in a HR3C austenitic heat resistant steel was investigated. The microstructure of the steel in solution-treated state consists of austenitic matrix and coarse Z-phase particles. After aging treatment at 650–950°C for 1h, M23C6-type carbide precipitates along random grain boundaries. Dense and homogeneous nanosized Z-phase precipitates within austenite grains are obtained by an aging treatment at a temperature between 800 and 900°C for 1h. The high density of dislocation walls produced during the water-cooling process after solution treatment facilitate the precipitation of the nanosized Z-phase. With increasing the aging temperature, the hardness initially drops, then increases and reaches a peak when the aging temperature is at 850°C due to the precipitation of the nanosized Z-phase.

Sign in / Sign up

Export Citation Format

Share Document