Inconel 690 Description

Inconel 690 is a kind of alloy mainly used in pressurized water reactor nuclear power plant steam generator heat transfer tube material, is the core technology of steam generator.

Grade: Inconel 690

Nominal composition: 62Ni-28Cr-10Fe

The main characteristics: It has excellent corrosion resistance and thermal stability.


Steam generator for pressurized water reactor.

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INCONEL 690 is a high-chromium-nickel alloy with excellent resistance to many corrosive aqueous media and high-temperature atmospheres. It has high strength and good fabrication characteristics. The high chromium content imparts a resistance to oxidizing chemicals and high-temperature oxidizing gases. The high nickel gives resistance to stress corrosion cracking in chloride-containing environments and to sodium hydroxide solutions.


CCarbon 0.05 max
MnManganese 0.50 max
SSulfur 0.015 max
FeIron 0.50 max
SiSilicon 0.50 max
Ni(+Co)Nickel Colbalt 0.80 – 1.10
CrChromium 27.0/31.0
CuCopper 27.0/31.0


The alloy finds applications involving processing of nitric acid and nitric/hydrofluoric acid solutions. As such it is used in tail-gas reheaters in nitric acid production and in heating coils and tanks for nitric/hydrofluoric acid solutions used to pickle stainless steels, and for the reprocessing of nuclear fuels.
The alloy’s resistance to sulfur-containing gases makes it suitable for use in coal gasification units, burners and ducts for processing sulfuric acid.
The alloy is further used for steam generator tubes, baffles and tube sheets as well as for hardware in nuclear power generation.


The alloy may be forged between 2250/1900ºF (1230/1040ºC.) Light forging may be continued down to 1600ºF (870ºC.)



The alloy might be annealed, following forging, at a temperature in the region 1700/1900ºF (925/1040ºC) followed by air cool or water quench, depending upon the part’s size and complexity.


Inconel 690 may be machined using sharp tools and positive feeds, to minimize work hardening of the material.


The alloy shows excellent weldability, and may be joined to other dissimilar metals and alloys using the appropriate filler metals. For extreme corrosive conditions, advice should be taken regarding the appropriate filler metal to be used.