Inconel 600 and 690

[sydneyjongleur]

Hi,

I am looking at the effects of corrosion resistance of Inconel 600 and 690 and I was wondering if someone could answer a question for me.

Most material specs states that the material is not heat treatable and that it gets supplied in the annealed or cold woked condition but I have then looked at literature which is subjecting the materials to thermal treatments to obtain different stress corrosion cracking properties etc. due to precipitatiing chromium carbides, grain growth etc.

I would just like to clarify and piece together the missing links. Is the thermal treatments carried out on an experimantal basis or can the material be supplied after being subjected to the treatments, or is there something else that I am missing.

 

[EdStainless]

The alloys cannot be strengthened by heat treatment.
The thermal stabilization treatment is just that. It slows long term aging of the alloy which would lead to increased sensitivity to SCC.
These are nuclear steam generator alloys. While 600 has many other applications I don't know of any other use for 690.
There are other similar alloys in Europe and Japan that are designed to do the same thing.
This stabilization treatment is why you can only get steam generator tubing from a few sources, there are only 3 vacuum furnaces in the world that can heat treat these long u-bends.

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Plymouth Tube

 

[Guest102023]

As EdStainless said, these are very much nuclear alloys. 690 has improved SCC resistance in steam generator tubes.

 

[metengr]

Your missing the most important fact, which is cold-worked Ni-base alloys should not be used in steam or water-wetted service because of reduced creep and corrosion resistance. Cold-working will indeed strengthen these alloys but it results in poor service performance mentioned above. Solution treatment is done for a reason - to obtain maximum creep and corrosion resistance.

 

[sydneyjongleur]

thanks guys, that provides me with the answers that I was looking for