Role of alloying additions in the oxidation-sulfidation of Fe-base alloys

Conference · Wed Mar 01 04:00:00 EST 1989

OSTI ID:6434967

Natesan, K; Park, J H

Thermogravimetric studies have been conducted on Fe-25 wt % Cr and Fe-25 wt % Cr-20 wt % Ni model alloys with and without additions of refractory metals such as Nb and Zr. In addition to bulk alloying, specimens of both alloys were prepared with surface implantation of Nb. The alloys with bulk additions of Nb and Zr exhibited Cr/sub 2/O/sub 3/ surface scales upon exposure to air and low partial pressure O/sub 2/ environments. The oxide grain size was much larger than that observed in the absence of Nb/Zr addition. In the oxygen-sulfur mixed-gas environments, the Nb- and Zr-modified alloys exhibited a barrier layer of an oxide of Nb or Zr at the Cr/sub 2/O/sub 3//substrate interface; this layer minimizes the outward transport of base-metal elements, thereby extending the time for initiation of breakaway corrosion. Experiments conducted with Nb-implanted binary and ternary alloys showed no effect on the oxidation rate in air and low partial pressure O/sub 2/ environments; however, the oxide grain size was substantially larger compared to that observed in the absence of implant. The Nb implant resulted in a substantial reduction in the oxidation rate of both alloys when exposed in low- and high-sulfur mixed-gas atmospheres. Information on the morphological features of the scales in these specimens as well as possible reasons for the implant benefit is presented. 6 refs., 16 figs.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 6434967
• Report Number(s): CONF-890294-1; ON: DE89009825
• Country of Publication: United States
• Language: English

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36 MATERIALS SCIENCE
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ALLOYS
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
CHROMIUM ALLOYS
CORROSION
CRYSTAL STRUCTURE
FLUIDS
GASES
GRAIN SIZE
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ION IMPLANTATION
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METALLURGICAL EFFECTS
MICROSTRUCTURE
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NIOBIUM ADDITIONS
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OXIDATION
QUANTITATIVE CHEMICAL ANALYSIS
SCALING
SIZE
SULFIDATION
THERMAL ANALYSIS
THERMAL GRAVIMETRIC ANALYSIS
ZIRCONIUM ADDITIONS
ZIRCONIUM ALLOYS