HAYNES® 556™ alloy - Haynes International, Inc.

SULFIDATION RESISTANCEHAYNES ® 556 alloy is secondin resistance only to HAYNESHR-160 ® alloy to the types ofsulfur-bearing environments thatare present in many hightemperatureindustrial processes.This is due partly to itscomparatively low nickel contentcoupled with the importantaddition of cobalt, the highchromium level, and the carefullybalanced minor elements.For comparison, data illustratingthe relative sulfidation resistanceof INCONEL ® alloy 601,HASTELLOY ® X alloy, alloys600 and 800H, and Type 310stainless steel are shown in theaccompanying photomicrographs.556 alloy had littlesulfide penetration or wastageafter 215 hours of exposure inan Ar+5%H 2+5%CO+1%CO 2+0.15%H 2S+0.1%H 2O test gas at1800°F (980°C). By contrast,alloys such as INCONEL alloy601 were completely destroyed,while other materials sufferedsevere wastage and sulfidepenetration or pitting.Comparative Sulfidation Resistance at 1800°F (980°C) for 215 Hours(Width of Micros Indicates Original Sample Thickness)46983 4700647021HAYNES 556 alloyAverage Metal Affected =2.0 Mils (50 µm)/SideType 310 stainless steelAverage Metal Affected =7.4 Mils (190 µm)/SideAlloy 800HAverage Metal Affected =23.2 Mils (590 µm)/Side4717547031 47172HASTELLOY X alloyAverage Metal Affected =>22 Mils (560 µm)/SideINCONEL alloy 601Average Metal Affected =>22 Mils (560 µm)/SideAlloy 600Average Metal Affected =>22 Mils (560 µm)/SideSulfidation Resistance at Other TemperaturesMaterialHR-160 ® alloy556 alloyType 310alloy 800HX alloyalloy 600alloy 6011400°F (760°C)*Metal Loss Average Metal Affected**Mils µm Mils µm0.2 5 1.1 302.5 65 3.8 956.2 155 9.1 2307.1 180 11.2 285>29.5 >750 Perforated>21.7 >560 Perforated>29.5 >750 Perforated1600°F (871°C)*Metal Loss Average Metal AffectedMils µm Mils µm0.1 3 3.8 955.2 130 11.7 2959.5 240 13.5 34511.7 295 19.2 490>21.7 >550 Consumed>21.7 >550 Consumed>21.7 >550 Perforated*215 Hour Exposure in Ar+5% H 2+5%CO+1% CO 2+0.15%H 2S+0.10%H 2O**Metal Loss + Average Internal PenetrationHAYNES ® 556 TM alloy 4