High Temp Alloy 2

[chemgrl]

I am making a high temperature furnace liner that will house fused silica tubes. This is necessary as the glass tubes can sometimes blow up. The furnace will operate at a maximum of 1000 deg C and be slow cooled (1-5 deg C/hr) to room temperature. We are going to flow an argon atmosphere over the metal liner to minimize oxidation.

We are currently looking at Inconel alloy 601 and 617 as well as Udimet alloy L-605. From what I understand these Cr containing alloys have a tendency to sensitize in the temperature range we operate. Will sensitization significantly alter the integrity and mechanical properties of the alloy?

If so are there any other suggestions for the liner material?

 

[EdStainless]

Oxidation resistance is the key property. 601 is a valid options, as is Alloy X.
If I understand your operation this will be a near static temperature, no cycling. This is important. 601 has better resistance in cyclic conditions, 600 is just as good in static.
If you want a top end alloy to look at consider 214. Though I doubt that you need it.

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Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[metengr]

The attached web site lists various high temperature alloys by Special Metals;

http://www.specialmetals.com/products/

The Technical Bulletins are very comprehensive and will provide you the necessary information for optimizing your alloy selection. The Inconel 601 in the solution treated condition sounds like your best bet.

The Haynes International web site below has other high temperature alloys for consideration;

http://www.haynesintl.com/

 

[chemgrl]

We are going to cycle between room temp and 1000 deg C. I am not very worried about oxidation because there will be an inert argon atmosphere. What worries me about the integrity of the alloy is sensitization as they will be cooled at 1-5 deg C per hour in the key temperature range 500-800 deg C where sensitization occurs.

 

[metengr]

The Inconel 601 should be acceptable for use as a furnace liner. The solution-treated condition will assure best performance with minimal degradation of mechanical properties.

 

[EdStainless]

The slow cooling will not be hard on the alloy. Rapid coolong causes flaking of the oxide skin and accelerated metal loss.
If you have a pure argon atmosphere on one side of the metal, what is on the other side?
These alloys don't sensitize in the way common stainless does, they don't form CrC in the grain boundaries. They form all sorts of complex mixed metal carbides and intermetallic phases. It isn't a big deal with these alloys. This is what they are designed to do.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[btrueblood]

Also, Ed is right to caution you about oxidation damage. Most commercial argon contains residual oxygen (it has a b.p. very near argon's), and you are going to flow that residual oxygen over your metal liner. Spec. a chemically pure argon if you're concerned, or use a different inert gas.

 

[EdStainless]

Even impure argon will be better than air.
The ultimate failure of this liner will be from grain growth and creap.
You really want it as light weight as possible. It may distort a lot, but the stresses will be much lower. Let it warp and don't straighten it out.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[chemgrl]

Thanks for all of your help. I think we settled on 601 or 230, whichever price/availability work out for.

Just for your knowledge, Ar will be inside the container too. The only other substances the metal will come in contact with are silica tubes on the inside and alumina tube on the outside.

 

[MOB1]

I would add to the info already given that a cheap alternative in this application would be 310 austenitic stainless steel. This steel will probably precipitate embrittling sigma and chi phases but the emnbrittlement is only at low temperature(less than 260C). As long as there is no stress at low temperature it will be OK.

 

[rolledalloy]

601 is a good option. Another lower cost option at 1000C would be to use an alloy like RA 253 MA or RA 353 MA these are lower nickel, but have excellent oxidation resistance at 1000C due to their cerium additions.

Alloy 602 CA is a step up from 601 due to its higher chromium and aluminum and would be comparable to Haynes 230 at 1000C.

Oxidation testing can be found in the high temperature alloy brochure in the technical resource center of Rolled Alloys. It covers oxidation testing for alloys ranging from 309 to high nickel alloys at temperatures from 1600F to 2200F.

http://www.rolledalloys.com