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Title: Low-cost, high-strength Fe--Ni--Cr alloys for high temperature exhaust valve application

Abstract

An Fe--Ni--Cr alloy is composed essentially of, in terms of wt. %: 2.4 to 3.7 Al, up to 1.05 Co, 14.8 to 15.9 Cr, 25 to 36 Fe, up to 1.2 Hf, up to 4 Mn, up to 0.6 Mo, up to 2.2 Nb, up to 1.05 Ta, 1.9 to 3.6 Ti, up to 0.08 W, up to 0.03 Zr, 0.18 to 0.27 C, up to 0.0015 N, balance Ni, wherein, in terms of atomic percent: 8.5.ltoreq.Al+Ti+Zr+Hf+Ta.ltoreq.11.5, 0.53.ltoreq.Al/(Al+Ti+Zr+Hf+Ta).ltoreq.0.65, and 0.16.ltoreq.Cr/(Fe+Ni+Cr+Mn).ltoreq.0.21, the alloy being essentially free of Cu, Si, and V.

Inventors:
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1379209
Patent Number(s):
9,752,468
Application Number:
14/497,550
Assignee:
UT-Battelle, LLC ORNL
DOE Contract Number:
AC05-00OR22725
Resource Type:
Patent
Resource Relation:
Patent File Date: 2014 Sep 26
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Muralidharan, Govindarajan. Low-cost, high-strength Fe--Ni--Cr alloys for high temperature exhaust valve application. United States: N. p., 2017. Web.
Muralidharan, Govindarajan. Low-cost, high-strength Fe--Ni--Cr alloys for high temperature exhaust valve application. United States.
Muralidharan, Govindarajan. Tue . "Low-cost, high-strength Fe--Ni--Cr alloys for high temperature exhaust valve application". United States. doi:. https://www.osti.gov/servlets/purl/1379209.
@article{osti_1379209,
title = {Low-cost, high-strength Fe--Ni--Cr alloys for high temperature exhaust valve application},
author = {Muralidharan, Govindarajan},
abstractNote = {An Fe--Ni--Cr alloy is composed essentially of, in terms of wt. %: 2.4 to 3.7 Al, up to 1.05 Co, 14.8 to 15.9 Cr, 25 to 36 Fe, up to 1.2 Hf, up to 4 Mn, up to 0.6 Mo, up to 2.2 Nb, up to 1.05 Ta, 1.9 to 3.6 Ti, up to 0.08 W, up to 0.03 Zr, 0.18 to 0.27 C, up to 0.0015 N, balance Ni, wherein, in terms of atomic percent: 8.5.ltoreq.Al+Ti+Zr+Hf+Ta.ltoreq.11.5, 0.53.ltoreq.Al/(Al+Ti+Zr+Hf+Ta).ltoreq.0.65, and 0.16.ltoreq.Cr/(Fe+Ni+Cr+Mn).ltoreq.0.21, the alloy being essentially free of Cu, Si, and V.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Sep 05 00:00:00 EDT 2017},
month = {Tue Sep 05 00:00:00 EDT 2017}
}

Patent:

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  • An Fe--Ni--Cr alloy is composed essentially of, in terms of weight percent: 1 to 3.5 Al, up to 2 Co, 15 to 19.5 Cr, up to 2 Cu, 23 to 40 Fe, up to 0.3 Hf, up to 4 Mn, 0.15 to 2 Mo, up to 0.15 Si, up to 1.05 Ta, 2.8 to 4.3 Ti, up to 0.5 W, up to 0.06 Zr, 0.02 to 0.15 C, 0.0001 to 0.007 N, balance Ni, wherein, in terms of atomic percent: 6.5.ltoreq.Al+Ti+Zr+Hf+Ta.ltoreq.10, 0.33.ltoreq.Al/(Al+Ti+Zr+Hf+Ta).ltoreq.0.065, 4.ltoreq.(Fe+Cr)/(Al+Ti+Zr+Hf+Ta).ltoreq.10, the alloy being essentially free of Nb and V.
  • The processes of nucleation and growth of metal carbides on the surfaces of Fe-Cr-Ni (25 Cr/20 Ni steel and 25 Cr/33 Ni steel) and Cr-Ni (50/50) alloys in presence of H2/CH4 mixture at 1098 K were investigated. All alloys were studied with surfaces in both cold-worked (CW) and electropolished (EP) conditions. The XPS spectra and the SEM and TEM micrographs revealed formation of transient alpha-Cr2O3 layers on all alloy surfaces during the heat-up period. On the CW surfaces chromium oxide formed homogeneous, compact, fine grained layers whereas on the EP surfaces, the oxide layers developed nonuniformly, with grain and phasemore » boundaries and scratches. Following an incubation period, M7C3 carbides were detected on the surfaces; they grew by replacing the Cr2O3 and through diffusion of metal from the alloy. The mode of nucleation of the M7C3 carbides and their rate of growth depend on the character of the alpha-Cr2O3 transient layers. After removal of Cr2O3 by replacement with M7C3, carbon ingresses into the alloy metal substrate, where M23C6 forms internally. These results are in line with the thermodynamic stability predictions. 29 references.« less
  • Highlights: • Effects of four different preparation processes were studied at 20/60 °C. • All NS + HT, RS and RS + HT processes can optimize the thermodynamic performance. • The HT process can provoke the precipitation of A{sub 2}B{sub 7} and leads to a poor cycling life. • Al exhibits the most remarkable dissolution for all the alloys, especially at 60 °C. - Abstract: In order to optimize the microstructure and high temperature electrochemical performances of low-cost AB{sub 5}-type Ml(NiMnAl){sub 4.2}Co{sub 0.3}Fe{sub 0.5} hydrogen storage electrode alloys, four different preparation methods including normal solidification (NS), normal solidification and 900more » °C heat treatment (NS + HT), rapid solidification (RS), rapid solidification and 900 °C heat treatment (RS + HT) were adopted in this work. All alloys exhibit CaCu{sub 5} type hexagonal structure and there is a small amount of A{sub 2}B{sub 7} phase in NS + HT and RS + HT alloys. It is found the using of HT process can decrease the hydrogen equilibrium plateau pressure, the plateau slope and hysteresis at 40, 60 and 80 °C. The NS + HT and RS + HT alloys also possess better activation, high rate discharge performance, larger discharge capacity, but poor cycling performance due to the existence of A{sub 2}B{sub 7} phase which can accelerate dissolution of Ni, Mn and Fe elements in KOH alkaline electrolyte. The RS process can make alloy exhibit the best cycling performance especially at 60 °C.« less