Sulfidation behavior of Al-modified MP35N alloys. [35Co-35Ni-20Cr-10Mo]

Journal Article · Mon Apr 01 04:00:00 EST 1991 · Oxidation of Metals; (United States)

DOI:https://doi.org/10.1007/BF00738291· OSTI ID:6074833

Shing, Chichang; Douglass, D L ^[1]; Gesmundo, F ^[2]

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1. Univ. of California, Los Angeles (United States)
2. Univ. di Genova (Italy)

A commercial superalloy, MP35N, which was modified by adding various amounts of Al up to 10 wt.%, has been studied over the temperature range of 600-900C in 0.01 atm sulfur vapor. The Al-modified alloys contained a second phase whose amount increased with increasing Al. The sulfidation rate followed the parabolic rate law and decreased with increasing Al content. An activation energy of 46 kcal/mol was obtained for MP35N, MP35N-5Al, and MP35N-7Al, while a value of 56 kcal/mol was found for MP35N-10Al at 700-800C. Triplex sulfide scales formed on MP35N, consisting of an outer layer of solid solution (Co, Ni){sub 3}S{sub 4}, an intermediate layer of Cr{sub 2}S{sub 3}, and a complex, heterophasic inner layer of mostly MoS{sub 2}. The Al-modified alloys also formed an outer scale of (Co, Ni){sub 3}S{sub 4}, and an inner layer containing a mixture of CoCr{sub 2}S{sub 4} and Al{sub 2}S{sub 3}. An internal-sulfidation zone containing an Al-rich sulfide was formed in the substrate. Only a moderate beneficial effect of Al additions to MP35N was observed at 600C. The observation of the location of platinum markers suggests that cobalt, nickel, chromium, and aluminum diffuse outward to form the major part of scale, and sulfur diffuses inward to produce an internal-sulfidation zone. Transport processes in the internal-sulfidation zone governed the sulfidation rate of the alloys.

• OSTI ID: 6074833
• Journal Information: Oxidation of Metals; (United States), Journal Name: Oxidation of Metals; (United States) Vol. 35:3-4; ISSN 0030-770X; ISSN OXMEA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
ACTIVATION ENERGY
ALLOYS
ALUMINIUM
ALUMINIUM ALLOYS
ALUMINIUM COMPOUNDS
ALUMINIUM SULFIDES
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHROMIUM ALLOYS
CHROMIUM COMPOUNDS
CHROMIUM SULFIDES
COBALT ALLOYS
COBALT COMPOUNDS
COBALT SULFIDES
CRYSTAL STRUCTURE
DIFFUSION
ELECTRON MICROSCOPY
ELEMENTS
ENERGY
EPRI
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
HIGH TEMPERATURE
KINETICS
LAYERS
MATERIALS
METALLURGICAL EFFECTS
METALS
MICROSCOPY
MICROSTRUCTURE
MOLYBDENUM ALLOYS
MOLYBDENUM COMPOUNDS
MOLYBDENUM SULFIDES
NICKEL ALLOYS
NICKEL COMPOUNDS
NICKEL SULFIDES
NONMETALS
REACTION KINETICS
REFRACTORY METAL COMPOUNDS
SCALING
SCANNING ELECTRON MICROSCOPY
SPECTROSCOPY
SULFIDATION
SULFIDES
SULFUR
SULFUR COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
X-RAY SPECTROSCOPY