Growth behavior and strengthening mechanism of Cu-rich particles in sanicro 25 austenitic heat-resistant steel after aging at 973 K

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).

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Effect of Ausforming on Creep Strength of G91 Heat-Resistant Steel

Materials Science Forum ◽

10.4028/www.scientific.net/msf.941.400 ◽

2018 ◽

Vol 941 ◽

pp. 400-406 ◽

Cited By ~ 1

Author(s):

Javier Vivas ◽

Rosalia Rementeria ◽

Marta Serrano ◽

Eberhard Altstadt ◽

David San Martín ◽

...

Keyword(s):

Heat Treatment ◽

Creep Strength ◽

Operating Temperature ◽

Strengthening Mechanism ◽

Processing Route ◽

Resistant Steel ◽

Creep Tests ◽

Heat Resistant Steel ◽

Heat Resistant ◽

Conventional Heat Treatment

The major challenge in a heat-resistant steel is to generate thermally stable microstructures that allow increasing the operating temperature, which will improve the thermal efficiency of the power plant without diminishing strength or time to rupture. The strengthening mechanism in tempered martensitic 9Cr steels comes mainly from the combination of solid solution effect and of precipitation hardening by fine MX carbo-nitrides, which enhance the sub-boundary hardening. This work is focused on the effect of ausforming processing on MX nanoprecipitation, on both their distribution and number density, during the subsequent tempering heat treatment. The creep strength at 700 oC was evaluated by small punch creep tests. The creep results after ausforming were compared to those obtained after conventional heat treatment concluding, in general, that ausforming boosts the creep strength of the steel at 700 oC. Therefore, conventional ausforming thermomechanical treatment is a promising processing route to raise the operating temperature of 9Cr heat-resistant steels.

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G030022 Creep Crack Initiation and Growth Behavior in Weldments of W-Added 9Cr Ferritic Heat-Resistant Steel

The Proceedings of Mechanical Engineering Congress Japan ◽

10.1299/jsmemecj.2011._g030022-1 ◽

2011 ◽

Vol 2011 (0) ◽

pp. _G030022-1-_G030022-5

Author(s):

Kazuto SATO ◽

Ryuji SUGIURA ◽

Toshimitsu YOKOBORI ◽

Masaaki TABUCHI ◽

Kenichi KOBAYASHI ◽

...

Keyword(s):

Crack Initiation ◽

Growth Behavior ◽

Resistant Steel ◽

Heat Resistant Steel ◽

Creep Crack ◽

Heat Resistant

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Strengthening Mechanism of S30432 Austenitic Heat-resistant Steel

High Temperature Materials and Processes ◽

10.1515/htmp.2010.29.4.215 ◽

2010 ◽

Vol 29 (4) ◽

pp. 215-224 ◽

Cited By ~ 1

Author(s):

Lihui Zhu, ◽

Yujie Zhang, ◽

Songqian Xu, ◽

Qijiang Wang, ◽

Zhengran Lu, ◽

...

Keyword(s):

Strengthening Mechanism ◽

Resistant Steel ◽

Heat Resistant Steel ◽

Heat Resistant

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Creep Stability of High Strength 9% Cr-W Ferritic Heat Resistant Tube Gr.92 After 15 Years in Service

Experience With Creep-Strength Enhanced Ferritic Steels and New and Emerging Computational Methods ◽

10.1115/pvp2004-2569 ◽

2004 ◽

Author(s):

Taro Muraki ◽

Masahiro Oghami ◽

Nobuyoshi Komai ◽

Kosei Matsufuji ◽

Masaaki Katata ◽

...

Keyword(s):

Thermal Power ◽

Creep Property ◽

High Strength ◽

Strengthening Mechanism ◽

Resistant Steel ◽

High Temperature Application ◽

Heat Resistant Steel ◽

Heat Resistant ◽

Super Heater ◽

Temperature Application

High strength 9%Cr-W ferritic heat resistant steel (ASME SA213 T92, KA-STABA29) was developed as the materials for high temperature application in USC plant with a temperature at 600°C and higher pressure than 25 MPa in steam conditions. The Gr.92 contains much W, and therefore, its creep property is attained by solute dragging of W on the dislocation gliding motion and also Nb and V forms concerning MX the precipitation strengthening mechanism. This material was installed as tertiary super heater of Tobata Co-operative Thermal Power Plant, and the plant had been operated about 15 years without any trouble. In this report, stability of several properties of ex-serviced Gr.92 steel was evaluated [1,2].

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Correlation between Microstructure and Nanohardness in Advanced Heat-Resistant Steel

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.326-328.277 ◽

2006 ◽

Vol 326-328 ◽

pp. 277-280

Author(s):

Jae Il Jang ◽

Sang Hoon Shim ◽

Shinichi Komazaki ◽

Takayuki Sugimoto

Keyword(s):

Prior Austenite ◽

Complex Structure ◽

Strengthening Mechanism ◽

Resistant Steel ◽

Heat Resistant Steel ◽

Heat Resistant ◽

Austenite Grain ◽

Heat Resistant Steels ◽

Prior Austenite Grain

As advanced ferritic/martensitic heat-resistant steels generally have a complex structure consisting of several microstructural units (lath, block, packet, and prior austenite grain), it is very hard to separate the contribution of each microstructural unit (or its each boundary) to the strengthening mechanism in such steels. Here we explore the role of each microstructural unit in strengthening of advanced high Cr steel through nanoindentation experiments performed at different load levels. Nanoindentation results are analyzed by comparing with microstructural observations and discussed in terms of prevailing descriptions of strengthening mechanism.

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Study on Strengthening Mechanism of 9Cr-1.5Mo-1Co and 9Cr-3W-3Co Heat Resistant Steels

Materials ◽

10.3390/ma13194340 ◽

2020 ◽

Vol 13 (19) ◽

pp. 4340 ◽

Cited By ~ 1

Author(s):

Long Zhao ◽

Xiangru Chen ◽

Tieming Wu ◽

Qijie Zhai

Keyword(s):

Strengthening Mechanism ◽

Microstructure Analysis ◽

Resistant Steel ◽

Heat Resistant Steel ◽

Steel Microstructure ◽

Heat Resistant ◽

High Temperature Mechanical Properties ◽

The Matrix ◽

Solution Strengthening ◽

Heat Resistant Steels

The strengthening mechanism of 9Cr–1.5Mo–1Co and 9Cr–3W–3Co heat resistant steel was studied by tensile test and microstructure analysis. At the same temperature, the yield strength of 9Cr–3W–3Co heat-resistant steel is higher than that of 9Cr–1.5Mo–1Co heat-resistant steel. Microstructure analysis proved that the strength of 9Cr–1.5Mo–1Co and 9Cr–3W–3Co heat-resistant steel is affected by grain boundary, dislocation, precipitation, and solid solution atoms. The excellent high temperature mechanical properties of 9Cr–3W–3Co heat-resistant steel are mainly due to the solution strengthening caused by Co and W atoms and the high-density dislocations distributed in the matrix; however, 9Cr–1.5Mo–1Co heat-resistant steel is mainly due to the martensitic lath and precipitation strengthening.

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