Microstructural change and stress rupture property of Nimonic 105 superalloy for advanced ultra-supercritical power plan
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ORIGINAL PAPER
Microstructural change and stress rupture property of Nimonic 105 superalloy for advanced ultra-supercritical power plants Tao Peng1,2 • Bin Yang1,3 • Gang Yang2 • Lu Wang4 • Zhi-hua Gong2 Received: 14 April 2020 / Revised: 2 June 2020 / Accepted: 9 June 2020 China Iron and Steel Research Institute Group 2020
Abstract Microstructural change, stress rupture property, deformation and fracture mechanisms of Nimonic 105 superalloy at 750 C have been studied. Experimental results showed that the stress rupture strength of the alloy at 750 C for 105 h is about 200 MPa. c0 precipitates and M23C6 carbides grew gradually with prolonging the rupture time, while no significant change was observed in MC carbide morphology. After stress rupture test at 750 C and 250 MPa for 23,341 h, a transition from spherical to cuboidal morphology of c0 precipitates was found, and nearly continuous chains of M23C6 carbides formed on the grain boundary. Orowan looping and strongly coupled dislocation pairs cutting and microtwinning were the dominant deformation mechanisms at 750 C and 350–450 MPa, while the main deformation mode was Orowan looping at 750 C and 250 MPa. The failure of the alloy was mainly attributed to the nucleation, growth and interlinkage of voids. Keywords Nimonic 105 superalloy Ni-based superalloy Microstructural change Stress rupture property Deformation mechanism
1 Introduction Advanced ultra-supercritical (A-USC) power plants are under development in the world to enhance the thermal efficiency and reduce energy consumption and SOx, NOx and CO2 emissions of coal-fired power plants. It is expected that A-USC power plants, operated at 700–750 C with pressures up to 37.5 MPa, will achieve 50% thermal efficiency. This is more than 10%
& Bin Yang [email protected] & Gang Yang [email protected] 1
Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083, China
2
Institute for Special Steels, Central Iron and Steel Research Institute, Beijing 100081, China
3
State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China
4
Huadian Electric Power Research Institute Co., Ltd, Hangzhou 310030, Zhejiang, China
improvement than present 600 C class ultra-supercritical (USC) power plants while decreasing CO2 emissions by as much as 17%–22% [1, 2]. However, the increased operating parameters in A-USC power plants disqualify conventional ferritic and austenitic heat-resistant steels from use as turbine blades because they cannot meet the demands of creep rupture strength of at least 100 MPa at 750 C for 105 h and corrosion resistance [3, 4]. As a consequence, c0 -strengthened Ni-based superalloys have been proposed for use as A-USC steam turbine blades since they have higher creep rupture strength than traditional steels. Nimonic 105 alloy is a wrought Ni-based superalloy that has excellent high-temperature strength and stress rupt
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