The effectiveness of aluminizing in protecting iron-base alloys in sulphidizing gases at high temperature
- 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), Vol. 36:3-4; ISSN 0030-770X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Diffusion Coatings for Corrosion Resistant Components in Coal Gasification Systems
The effect of preoxidation on the sulfidation of Ni-20Cr (2-5)Al alloys. 1. Effect of preoxidation on scale characteristics and sulfidation at 750C
Related Subjects
FERRITIC STEELS
PROTECTIVE COATINGS
SULFIDATION
STAINLESS STEEL-310
STAINLESS STEEL-321
STAINLESS STEELS
ALUMINIUM
ALUMINIUM OXIDES
BOILERS
CHEMICAL COMPOSITION
CHROMIUM OXIDES
CORROSION RESISTANCE
CORROSION RESISTANT ALLOYS
DECOMPOSITION
DIFFUSION
HEAT EXCHANGERS
HEAT RESISTING ALLOYS
HYDROGEN
HYDROGEN SULFIDES
MICROSTRUCTURE
OPTICAL MICROSCOPY
PERFORMANCE
TEMPERATURE RANGE 1000-4000 K
THERMAL CYCLING
WATER VAPOR
ALLOYS
ALUMINIUM COMPOUNDS
AUSTENITIC STEELS
CHALCOGENIDES
CHEMICAL REACTIONS
CHROMIUM ALLOYS
CHROMIUM COMPOUNDS
CHROMIUM-NICKEL STEELS
COATINGS
CRYSTAL STRUCTURE
ELEMENTS
FLUIDS
GASES
HEAT RESISTANT MATERIALS
HIGH ALLOY STEELS
HYDROGEN COMPOUNDS
IRON ALLOYS
IRON BASE ALLOYS
MATERIALS
METALS
MICROSCOPY
NICKEL ALLOYS
NONMETALS
OXIDES
OXYGEN COMPOUNDS
STEEL-CR18NI10TI
STEEL-CR25NI20
STEELS
SULFIDES
SULFUR COMPOUNDS
TEMPERATURE RANGE
TITANI
TRANSITION ELEMENT COMPOUNDS
VAPORS
360105* - Metals & Alloys- Corrosion & Erosion