Many power plant facilities today are burning difficult to handle fuels such as high-sulfur coal and fuel oil.
Difficult to handle, in as much as process internals are too often subject to both reducing carburizing atmospheres and sulfidizing environments which lead to early failure. This can mean frequent replacement or maintenance for components such as burner buckets, grates, tube supports, rapper bars, soot blowers, and numerous other traditional boiler internals. And, in the never fluidized bed technology facilities, in-bed tubulars and support hardware require materials which can stand up to even harsher environments.
HAYNES® 556® alloy is one of few materials to combine excellent design strength with broad spectrum resistance to most key forms of high-temperature corrosion. This resistance includes carburizing atmospheres, sulfidizing environments, chlorine-contaminated process gases and several others, proven in such demanding uses as internals in municipal waste incinerators.
556 alloy is covered by ASME Boiler Code Case No. 2010 for use to 1200°F (650°C), with extension to 1650°F (900°C) coverage soon to be proposed. It is currently in service in several boiler and fluidized-bed facilities, and on test in many others.
HAYNES 556 alloy is an iron-nickel-chromium-cobalt alloy that combines effective resistance to sulfidizing, carburizing, and chlorine-bearing environments at high temperatures with good oxidation resistance, fabricability, and excellent high-temperature strength. It has also been found to resist corrosion by molten chloride salts and molten zinc.
HAYNES 556 alloy is highly useful for service at elevated temperature in moderately to severely corrosive environments. Applications include tubing and structural members in waste heat recuperators, super heaters, and internals in municipal and chemical waste incinerators; power plant burner buckets, cair nozzles, and fluidized bed combustor heat exchangers and internals; high-speed furnace fans, galvanizing bath hardware and brazing fixtures; and high-temperature rotary calciners and kilns. There are also additional uses in the chemical petrochemical process and pump and paper industries.
Oxidation in Air - Excellent at 2000°F (1095°C)
Sulfidation - Second only to Co-base alloys
Molten Chloride Salts - Equal to alloy X
Chlorination - Very good to 1650°F (900°C)
Carburization - Equal to alloy 800H