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G. M. Michal X. Gu W. D. Jennings H. Kahn F. Ernst A. H. Heuer 《Metallurgical and Materials Transactions A》2009,40(8):1781-1790
AISI 301 and E-BRITE stainless steels were subjected to low-temperature (743 K) carburization experiments using a commercial
technology developed for carburization of 316 austenitic stainless steels. The AISI 301 steel contained ~40 vol pct ferrite
before carburization but had a fully austenitic hardened case, ~20-μm thick, and a surface carbon concentration of ~8 at. pct after treatment; this “colossal” paraequilibrium carbon supersaturation
caused an increase in lattice parameter of ~3 pct. The E-BRITE also developed a hardened case, 12- to 18-μm thick, but underwent a more modest (~0.3 pct) increase in lattice parameter; the surface carbon concentration was ~10 at. pct.
While the hardened case on the AISI 301 stainless steel appeared to be single-phase austenite, evidence for carbide formation
was apparent in X-ray diffractometer (XRD) scans of the E-BRITE. Paraequilibrium phase diagrams were calculated for both AISI
301 and E-BRITE stainless steels using a CALPHAD compound energy-based interstitial solid solution model. In the low-temperature
regime of interest, and based upon measured paraequilibrium carbon solubilities, more negative Cr-carbon interaction parameters
for austenite than those in the current CALPHAD data base may be appropriate. A sensitivity analysis involving Cr-carbon interaction
parameters for ferrite found a strong dependence of carbon solubility on relatively small changes in the magnitude of these
parameters.
This article is based on a presentation given at the “International Conference on Surface Hardening of Stainless Steels,”
which occurred October 22–23, 2007 during the ASM Heat Treating Society Meeting in Cleveland, OH under the auspices of the
ASM Heat Treating Society and TMS.
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A. H. Heuer (Professor)Email: |
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