Inconel 690 Alloy
General Characteristics of Inconel 690 Alloy
Alloy 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.
| Chemical Analysis | |
|---|---|
| C | Carbon 0.05 max |
| Mn | Manganese 0.50 max |
| S | Sulfur 0.015 max |
| Fe | Iron 0.50 max |
| Si | Silicon 0.50 max |
| Ni(+Co) | Nickel Colbalt 0.80 – 1.10 |
| Cr | Chromium 27.0/31.0 |
| Cu | Copper 27.0/31.0 |
Applications
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.
Forging
The alloy may be forged between 2250/1900ºF (1230/1040ºC.) Light forging may be continued down to 1600ºF (870ºC.)
Heat treatment
Annealing
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.
Machinability
Inconel 690 may be machined using sharp tools and positive feeds, to minimize work hardening of the material.
Weldability
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.
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