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Alloy 625 (Inconel 625)

Alloy 625 (Inconel 625)


ALLOY625 is a low-carbon Ni-Cr-Mo-Nb alloy which shows excellent resistance to a

variety of corrosive media.

outstanding resistance to pitting, crevice corrosion, erosion and intergranular attack

almost complete freedom from chloride-induced stress-corrosion cracking

good resistance to mineral acids, such as nitric, phosphoric, sulphuric and hydrochloric acids

good resistance to alkalis and organic acids

good mechanical properties

Corrosion resistance

For optimal corrosion resistance the material must be in a clean condition and free from all kinds of contaminants before any fabricated component is placed into service. Under these conditions ALLOY625 exhibits excellent corrosion resistance in a wide variety of media:

excellent resistance to pitting and crevice corrosion in chloride-bearing media
essentially resistant to chloride-induced stress-corrosion cracking
high resistance against impingement and erosion corrosion
high resistance to corrosive attack by mineral acids, such as nitric, phosphoric, sulphuric and hydrochloric acids, as well as to alkalis and organic acids in both oxidizing and reducing conditions
practically no corrosive attack in marine and industrial atmosphrers. High resistance to seawater and brackish water, even at higher temperatures
high resistance against intergranular corrosion following thermal treatment and welding

The solution-annealed version (grade 2) shows good resistance to many corrosive gas atmospheres:

good resistance to carburization and to oxidation under
resistance to nitridation
good resistance to halogen containing gases and to hydrogen chloride


The soft-annealed version of Nicrofer 6020 hMo (grade 1) is preferred for applications in the chemical process industry, in marine engineering and in pollution control equipment for environmental protection.

Typical applications are:

superphosphoric acid production equipment

nuclear waste reprocessing equipment
sour gas production tubes
piping systems and sheathing of risers in oil exploration
offshore industry and marine equipment
flue gas scrubber and damper components
chimney linings

For high-temperature applications, up to approximately 1000 ‹C (1830 ‹F), the solution-annealed version of alloy 625 (grade 2) can be used in accordance to the ASME code for pressure vessels. For design calculations for equipment for use within the temperature range of approximately 500 ?1000 ‹C (930 ? 1830 ‹F) the loss in ductility resulting from prolonged exposure within that temperature range must be kept in mind

components in waste gas systems and waste gas cleaning plants exposed to higher temperatures
flare stacks in refineries and offshore platforms
recuperators and compensators
submarine diesel engine exhaust systems
superheater tubes in waste incineration plants
cladding of waterwall sections and superheater tubes in waste incineration plants by overlay welding