Corrosion behavior of coated 2 1/4 Cr-1Mo and mild steel substrates in a simulated waste heat recovery system environment of a coal gasifier. [FeCrAl or CoCrAl alloys and pack-diffusion aluminizing or chromizing]

Technical Report · Mon Jul 01 04:00:00 EDT 1985

OSTI ID:5435853

Baxter, D J

Cossosion tests have been conducted on coated 2 1/4Cr-1Mo and A106 mild steel in a gaseous environment typical of that expected in a downstream waste-heat recovery system of a coal gasifier. The environment contained controlled oxygen and sulfur levels, and the tests were run in a rig designed to expose specimens under simulated heat-exchanger conditions. Uncoated steel substrates exhibited breakaway corrosion behavior. Furnace-fused coatings of FeCrAl or CoCrAl alloys contained numerous defects, such as voids and cracks, and subsequently underwent substantial degradation during exposure. Coatings containing the stable oxide-forming elements Al and Cr were also applied by pack diffusion processes. Sequential chromizing of the A106 mild steel could not be achieved due to massive Cr carbide formation in the initial chromizing stage. Sequential chromizing/aluminizing of the 2 1/4Cr-1Mo steel was successful, but the coating contained numerous defects, which permitted considerable attack of the coated substrate. Simultaneous aluminizing/chromizing produced mixed results, depending upon the particular process used in applying the coating. Coatings exhibited behavior ranging from protective to complete breakdown. A solid FeCrAlY alloy exhibited protective oxidation behavior. With respect to joining or repair methods for coated steels, four different weld metals were used to simulate joining or repair operations of prior aluminized steel substrates. The Ni-base Inconel 625 weld showed good corrosion resistance with Inconel 72 sustaining minor internal attack. The Co-base L605 and Fe-base 309 SS weld metals exhibited breakaway corrosion characterized by the formation of thick scales and deep internal attack. 19 refs., 21 figs., 3 tabs.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 5435853
• Report Number(s): ANL/FE-85-5; ON: DE85017665
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010404* -- Coal
Lignite
& Peat-- Gasification
36 MATERIALS SCIENCE
360105 -- Metals & Alloys-- Corrosion & Erosion
ALLOYS
CARBON STEELS
CHEMICAL REACTIONS
CHROMIUM ALLOYS
CHROMIUM STEELS
CHROMIUM-MOLYBDENUM STEELS
CHROMIUM-NICKEL STEELS
COAL GASIFICATION PLANTS
COMPARATIVE EVALUATIONS
CORROSION
CORROSION RESISTANT ALLOYS
DATA
DEPOSITION
ELEMENTS
EXPERIMENTAL DATA
FABRICATION
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
INCONEL 625
INCONEL ALLOYS
INDUSTRIAL PLANTS
INFORMATION
IRON ALLOYS
IRON BASE ALLOYS
JOINING
MATERIALS
MATERIALS TESTING
MOLYBDENUM ALLOYS
NICKEL ALLOYS
NICKEL BASE ALLOYS
NIOBIUM ALLOYS
NONMETALS
NUMERICAL DATA
OXYGEN
REPAIR
SIMULATION
STAINLESS STEEL-309
STAINLESS STEELS
STEEL-ASTM-A106
STEELS
SULFUR
SURFACE COATING
TANTALUM ALLOYS
TESTING
WELDING