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HAYNES® Alloys

Sulfidation Resistance

HAYNES® 556® alloy is second in resistance only to HAYNES® HR-160® alloy to the types of sulfur-bearing environments that are present in many high-temperature industrial processes. This is due partly to its comparatively low nickel content coupled with the important addition of cobalt, the high chromium level, and the carefully balanced minor elements. For comparison, data illustrating the relative sulfidation resistance of INCONEL® alloy 601, HASTELLOY® X alloy, alloys 600 and 800H, and Type 310 stainless steel are shown in the accompanying photomicrographs. 556® alloy had little sulfide penetration or wastage after 215 hours of exposure in an Ar+5%H2+5%CO+1%CO2+ 0.15%H2S+0.1%H2O test gas at 1800°F (980°C). By contrast, alloys such as INCONEL® alloy 601 were completely destroyed, while other materials suffered severe wastage and sulfide penetration or pitting.

Comparative Sulfidation Resistance at 1800°F (980°C) for 215 Hours

(Width of Micros Indicates Original Sample Thickness)

556 - Comparative Sulfidation Resistance at 1800°F (980°C) for 215 Hours

HAYNES® 556® alloy

Average Metal Affected =
2.0 Mils (50 μm)/Side

Type 310 Stainless Steel - Comparative Sulfidation Resistance at 1800°F (980°C) for 215 Hours

Type 310 Stainless Steel

Average Metal Affected =
7.4 Mils (190μm)/Side

Alloy 800H - Comparative Sulfidation Resistance at 1800°F (980°C) for 215 Hours

Alloy 800H

Average Metal Affected =
23.2 Mils (590μm)/Side

HASTELLOY® X alloy - Comparative Sulfidation Resistance at 1800°F (980°C) for 215 Hours

HASTELLOY® X alloy

Average Metal Affected =
> 22 Mils (560 μm)/Side

INCONEL alloy 601 - Comparative Sulfidation Resistance at 1800°F (980°C) for 215 Hours

INCONEL alloy 601

Average Metal Affected =
> 22 Mils (560 μm)/Side

alloy 600 - Comparative Sulfidation Resistance at 1800°F (980°C) for 215 Hours

alloy 600

Average Metal Affected =
> 22 Mils (560 μm)/Side

Sulfidation Resistance at Other Temperatures

Alloy 1400°F (760°C) 1600°F (871°C)
Metal Loss Average Metal Affected** Metal Loss Average Metal Affected
- mils µm mils µm mils µm mils µm
HR-160® 0.2 5 1.1 30 0.1 3 3.8 95
556® 2.5 65 3.8 95 5.2 130 11.7 295
Type 310 6.2 155 9.2 230 9.5 240 13.5 345
800H 7.1 180 11.2 285 11.7 295 19.2 490
X >29.5 >750 Perforated >21.7 >550 Consumed
600 >21.7 >560 Perforated >21.7 >550 Consumed
601 >29.5 >750 Perforated >21.7 >550 Perforated

*215 Hour Exposure in Ar+5% H2 +5%CO+1% CO2 +0.15%H2 S+0.10%H2O **Metal Loss + Average Internal Penetration

Field Experience - Municipal Waste Incinerator

Samples were exposed for 950 hours in the superheater section of a municipal waste incinerator. Combustion gas temperatures were about 1475°F (800°C) with excursions to 1740°F (950°C). The mode of corrosion observed was oxidation/sulfidation, although alkali chloride compounds were known to be present. HAYNES 556 alloy was found to be one of the best alloys for resisting this highly corrosive environment.
556 - Max Metal Affected - Municipal Waste Incinerator

Field Experience - Aluminum Remelting Furnace

Samples of tubing were exposed for 1150 hours in the recuperator of an aluminum remelting furnace producing 1250°F (675°C) flue gases. The tube samples were internally cooled by combustion preheat air the same as the operating recuperator tubes. The mode of corrosion observed was combined attack by alkali sulfates and chlorides together with oxidation. HAYNES 556 alloy exhibited outstanding resistance to corrosion in this environment.

556 - Max Metal Affected - Aluminum Remelting Furnace


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