The effectiveness of aluminizing in protecting iron-base alloys in sulphidizing gases at high temperature

Journal Article · Tue Oct 01 04:00:00 EDT 1991 · Oxidation of Metals; (United States)

DOI:https://doi.org/10.1007/BF00662964· OSTI ID:5477221

Green, S W; Stott, F H ^[1]

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1. Univ. of Manchester (United Kingdom)

Following earlier research which has shown that Al{sub 2}O{sub 3} scales are more effective than Cr{sub 2}O{sub 3} scales in protecting iron-nickel-base alloys against sulfur-containing gases, several commercial steels, 310 stainless, 314 stainless, and 321 stainless, and an experimental ferritic steel, FeCrAlHf, have been pack aluminized to develop aluminide coatings for applications in mixed-gas environments of high sulfur and low oxygen potential. Results are presented for long-term exposures to H{sub 2}/1.6% H{sub 2}O/1.1% H{sub 2}S at 750C and 1,000C under thermal-cycling conditions. Short-term tests in this environment at 750C led to considerable sulfidation of the uncoated, Cr{sub 2}O{sub 3}-forming alloys. The aluminized alloys were much more resistant to sulfidation than the uncoated materials, with relatively little degradation being observed after 200 hr at 750C. Even at 1,000C, with the exception of the ferritic steel, the coated systems showed reasonable degradation resistance for 500 hr. Eventual sulfidation resulted from the back diffusion of aluminum into the substrate and dilution of the coating surface in this element until an Al{sub 2}O{sub 3} scale was unable to reform and base metal sulfides could develop. The composition of the substrate was important in determining the rate of aluminum depletion from the coating, with interdiffusion being faster in ferrite-rich matrices than the austenite matrices. The structures of the various aluminized systems are presented and their mechanisms of protection and breakdown are discussed and correlated with their performances under these high-temperature conditions.

• OSTI ID: 5477221
• Journal Information: Oxidation of Metals; (United States), Journal Name: Oxidation of Metals; (United States) Vol. 36:3-4; ISSN 0030-770X; ISSN OXMEA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
ALLOYS
ALUMINIUM
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
AUSTENITIC STEELS
BOILERS
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHROMIUM ALLOYS
CHROMIUM COMPOUNDS
CHROMIUM OXIDES
CHROMIUM-NICKEL STEELS
COATINGS
CORROSION RESISTANCE
CORROSION RESISTANT ALLOYS
CRYSTAL STRUCTURE
DECOMPOSITION
DIFFUSION
ELEMENTS
FERRITIC STEELS
FLUIDS
GASES
HEAT EXCHANGERS
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
HIGH ALLOY STEELS
HYDROGEN
HYDROGEN COMPOUNDS
HYDROGEN SULFIDES
IRON ALLOYS
IRON BASE ALLOYS
MATERIALS
METALS
MICROSCOPY
MICROSTRUCTURE
NICKEL ALLOYS
NONMETALS
OPTICAL MICROSCOPY
OXIDES
OXYGEN COMPOUNDS
PERFORMANCE
PROTECTIVE COATINGS
STAINLESS STEEL-310
STAINLESS STEEL-321
STAINLESS STEELS
STEEL-CR18NI10TI
STEEL-CR25NI20
STEELS
SULFIDATION
SULFIDES
SULFUR COMPOUNDS
TEMPERATURE RANGE
TEMPERATURE RANGE 1000-4000 K
THERMAL CYCLING
TITANI
TRANSITION ELEMENT COMPOUNDS
VAPORS
WATER VAPOR