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

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.

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Effect of aging temperature on the microstructures and mechanical properties of ZG12Cr9Mo1Co1NiVNbNB ferritic heat-resistant steel

International Journal of Minerals Metallurgy and Materials ◽

10.1007/s12613-016-1224-1 ◽

2016 ◽

Vol 23 (2) ◽

pp. 168-175 ◽

Cited By ~ 2

Author(s):

Xue Yang ◽

Lan Sun ◽

Ji Xiong ◽

Ping Zhou ◽

Hong-yuan Fan ◽

...

Keyword(s):

Mechanical Properties ◽

Aging Temperature ◽

Resistant Steel ◽

Heat Resistant Steel ◽

Heat Resistant ◽

Microstructures And Mechanical Properties

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A Review of Austenite Memory Effect in HAZ of B Containing 9% Cr Martensitic Heat Resistant Steel

Metals ◽

10.3390/met9111233 ◽

2019 ◽

Vol 9 (11) ◽

pp. 1233

Author(s):

Li ◽

Cai ◽

Pan

Keyword(s):

Memory Effect ◽

Prior Austenite ◽

Welding Process ◽

Peak Temperature ◽

Reverse Transformation ◽

Resistant Steel ◽

Heat Resistant Steel ◽

Heat Resistant ◽

Matrix Microstructure ◽

Austenite Grains

During the welding process of B containing 9% Cr martensitic heat resistant steel (9Cr-B steel), austenite memory effect (referred to that the prior austenite grains in the heat affected zone (HAZ) after welding inherit the shape and size of prior austenite grains before welding) occurs in its normalized sub-zone of HAZ and the grain refinement is suppressed, which can effectively prevent type IV crack, and improve the service life of the welded joint at high temperatures. In the present article, α/γ reverse transformation behavior in the normalized sub-zone of 9Cr-B steel HAZ is reviewed. Austenite memory effect of 9Cr-B steel is derived from B addition. The main mechanisms of austenite memory effect during α/γ reverse transformation are discussed. Various models of boron causing austenite memory effect are discussed in detail. Matrix microstructure also plays an important role in austenite memory effect. Effects of heating rate, peak temperature, and holding time at peak temperature on austenite memory effect are also discussed.

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High Temperature Fatigue Behavior of 23Cr26Ni Heat Resistant Steel

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.452-453.433 ◽

2010 ◽

Vol 452-453 ◽

pp. 433-436

Author(s):

Hee Woong Lee ◽

S.I. Kwun ◽

Woo Sang Jung

Keyword(s):

High Temperature ◽

Dislocation Density ◽

Low Cycle Fatigue ◽

Fatigue Behavior ◽

Solution Treatment ◽

Cyclic Hardening ◽

Resistant Steel ◽

Heat Resistant Steel ◽

High Temperature Fatigue ◽

Heat Resistant

The influence of the cooling condition after solution treatment on the high temperature fatigue resistance of 23Cr-26Ni heat resistant steel was investigated. Two different cooling conditions were applied to the steel after solution treatment at 1230oC for 3 hours. One specimen was water quenched immediately after the solution treatment. The other one was furnace cooled at a rate of 0.5oC/min down to 750oC after the solution treatment. Then, both specimens were aged at 750oC for 5 hours. The low cycle fatigue (LCF) test was conducted to investigate the influence of high temperature on the LCF behaviors of the heat-resistant 23Cr26Ni alloy. Under two different heat treatment conditions, the LCF test was performed at total strain amplitudes ranging from ±0.4~0.9% at room temperature (RT) and 600°C. During the test, initial cyclic hardening occurred at both experimental temperatures. This phenomenon was attributed to the increase in the dislocation density due to cyclic deformation, which resulted in the interaction between the newly created dislocations and precipitates. Cyclic softening was observed in the later stages of the LCF test at RT. The formation of precipitates and increase in the dislocation density were observed using TEM. Also, the XRD and EDS techniques were used to verify the type and composition of the precipitates.

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Effect of Al on the Microstructure and Mechanical Properties of HK40 Heat-Resistant Steel at High Temperature

Materials Science Forum ◽

10.4028/www.scientific.net/msf.849.542 ◽

2016 ◽

Vol 849 ◽

pp. 542-548

Author(s):

Yan Zhang ◽

Yu Fei Mei ◽

Ning Zhou ◽

Zheng Qin Liu ◽

Yu Fu Sun

Keyword(s):

Mechanical Properties ◽

Electron Microscope ◽

High Temperature ◽

Solution Treatment ◽

Resistant Steel ◽

Heat Resistant Steel ◽

Al Content ◽

Heat Resistant ◽

High Temperature Mechanical Properties ◽

Transmission Electron

The high-temperature mechanical properties and microstructure of HK40 heat-resistant steel with different content of Al were investigated. The results from scanning electron microscope and transmission electron microscope showed that a large amount of spheroidal and dispersed γ′ phase were observed HK40 steel with 4.72wt.% and 7.10wt.% Al. The diameter of γ′ phase decreases from about 1.5μm to 50nm after solution treatment of 1200°C for 5h. The results of short term tensile test showed that tensile strength at 900°C decreased and the elongation was improved with increasing Al content. The oxides in the alloy with 4.72wt.% and 7.10wt.% Al were more uniform and finer than that in the alloy with and without 1.68wt.% Al.

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The Effect of Long-Term Annealing at Elevated Temperature on Microstructure and Hardness of Heat-Resistant Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.782.209 ◽

2014 ◽

Vol 782 ◽

pp. 209-214

Author(s):

Ladislav Kosec ◽

Mirko Gojić ◽

Stjepan Kožuh ◽

Borut Kosec ◽

Goran Dražič ◽

...

Keyword(s):

Electron Microscopy ◽

Sigma Phase ◽

Surface Mode ◽

Resistant Steel ◽

Heat Resistant Steel ◽

X Ray ◽

Heat Resistant ◽

Transmission Electron ◽

Austenite Grains

The stainless steel group AISI 310 is very often used for application in high-temperature conditions. This study investigated the effect of long-term annealing on microstructure and hardness of AISI 310S (24.3% Cr-19.3% Ni 1.8% Mn 0.21% Mo 0.67% Si, wt.%) heat-resistant steel. Microstructural changes and hardness distribution were analyzed after isothermal annealing at 800 °C in long-term exposure (from 1 to 1740 hours). Microstructure and fracture surface mode were analyzed using scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). It was found that after annealing the sigma phase particles were precipitated at grain boundaries and within austenite grains. The chromium content in the sigma phase increased with the prolongation of annealing time. The morphology of sigma phase was changed from fine precipitates at lower annealing times to coarser particles at higher annealing times. Also, presence of sigma phase was confirmed by transmission electron microscopy (TEM). At annealing temperature of 800 °C the hardness began to increase after 16 hours. With longer times of annealing the fracture surfaces were changed. This change is associated with a change of content and the morphology of sigma phase.

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