Kinetics and mechanism of the sulfidation of Fe-Mo alloys

Journal Article · Thu Jun 01 04:00:00 EDT 1989 · Oxidation of Metals; (USA)

DOI:https://doi.org/10.1007/BF00666462· OSTI ID:6986505

Carter, R V; Douglass, D L ^[1]; Gesmundo, F ^[2]

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1. Univ. of California, Los Angeles (USA)
2. Universita di Genova (Italy)

Iron-molybdenum alloys containing up to 40 wt.% molybdenum were exposed to sulfur vapor at a partial pressure of 0.01 atm at temperatures of 600-900{degree}C. Sulfidation kinetics were measured over periods of up to 8 hr using a quartz-spring thermogravimetric method. The sulfidation kinetics of all alloys studied obeyed the parabolic rate law. The sulfidation rate of iron was found to be reduced by factors of 60 at 900{degree}C and 120 at 600{degree}C by the addition of 40 wt.% molybdenum. Duplex sulfide scales formed on all alloys at all temperatures, the scales consisting of an inner layer of mostly MoS{sub 2} and an outer layer of FeS. Platinum markers were located at the interface between the outer and inner scales, showing that outward iron diffusion and inward sulfur diffusion through the inner layer occurred. The improved sulfidation resistance was attributed to the formation of the MoS{sub 2}, which acted as a partially protective barrier to the diffusion of the reacting species. Sulfidation activation energies were found to range from 24.3 to 28.5 kcal mole for the alloys compared to 20.6 kcal/mole, for pure iron. The rate-controlling step was outward iron diffusion through the outer iron sulfide layer.

• OSTI ID: 6986505
• Journal Information: Oxidation of Metals; (USA), Journal Name: Oxidation of Metals; (USA) Vol. 31:5-6; ISSN 0030-770X; ISSN OXMEA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360105* -- Metals & Alloys-- Corrosion & Erosion
ACTIVATION ENERGY
ALLOY SYSTEMS
ALLOYS
BINARY ALLOY SYSTEMS
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COHERENT SCATTERING
CORROSION RESISTANCE
CORROSIVE EFFECTS
DIFFRACTION
DIFFUSION
ELECTRON MICROPROBE ANALYSIS
ELEMENTS
ENERGY
GRAVIMETRIC ANALYSIS
IRON
IRON ALLOYS
IRON BASE ALLOYS
IRON COMPOUNDS
IRON SULFIDES
KINETICS
METALLURGICAL EFFECTS
METALS
MICROANALYSIS
MOLYBDENUM
MOLYBDENUM ALLOYS
MOLYBDENUM COMPOUNDS
MOLYBDENUM SULFIDES
NONMETALS
QUANTITATIVE CHEMICAL ANALYSIS
REACTION KINETICS
REFRACTORY METAL COMPOUNDS
SCALING
SCATTERING
SULFIDATION
SULFIDES
SULFUR
SULFUR COMPOUNDS
THERMAL ANALYSIS
THERMAL GRAVIMETRIC ANALYSIS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
X-RAY DIFFRACTION