Effects of W on creep behaviors of novel Nb-bearing high nitrogen austenitic heat-resistant cast steels at 1000 °C
- State Key Laboratory of Advanced Special Steel, School of Materials Science and Engineering, Shanghai University, Shanghai 200072 (China)
- Ford Research and Advanced Engineering Laboratory, Ford Motor Company, Dearborn, MI 48124-4356 (United States)
- State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)
Highlights: • The synergistic CALPHAD and experimental approaches are adopted. • Creep behaviors of high nitrogen austenitic alloys are investigated at 1000 °C. • Creep properties are improved through the W solid solution strengthening. • W additions promote the formation of (Cr,Fe,W){sub 23}C{sub 6} instead of (Cr,Fe,W){sub 7}C{sub 3}. • (Cr, W)-rich precipitates severely degrade the creep properties. - Abstract: Recently, there is an urgent demand from automotive industries to develop new austenitic heat-resistant cast steels that withstand exhaust gas temperatures as high as 1000 °C. In this study, the effect of W additions on the creep behavior of a series of Nb-bearing high nitrogen austenitic heat-resistant cast steels was investigated at 1000 °C and 50 MPa. Microstructures before and after creep rupture tests were carefully characterized to illustrate the microstructural evolution during creep deformation. Microstructural analyses revealed that the W addition did not affect the formation of primary Nb(C,N), whereas significantly promoted the precipitation of primary (Cr, W)-rich phases, particularly those cellular structures along grain boundaries. The W solid solution strengthening and the secondary precipitation strengthening of submicron-scale (Cr, W)-rich phase improved the creep resistance of the alloys through increasing the hardness of γ-austenite and pinning the dislocations. However, the primary cellular (Cr, W)-rich structures significantly accelerated the nucleation and propagation of creep cracks along grain boundaries, thereby increasing the creep rate and decreasing the creep life.
- OSTI ID:
- 22804962
- Journal Information:
- Materials Characterization, Vol. 139; Other Information: Copyright (c) 2017 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 1044-5803
- Country of Publication:
- United States
- Language:
- English
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