Heat Damaged Inconel 600

[pdiculous963]

Upon recent inspection of a process vessel a heat damaged area was found, see the attached picture. The vessel is made from Inconel 600 (all plate was supplied in the hot rolled and annealed conditon) and has some purple and brownish discoloration. Before it is put back in service I plan to check vessel dimensions for distortions, examine the welds for defects, and likely have in situ metallography performed. If all of the mentioned tests results are acceptable, I plan to put the vessel back into service. I have time to perform any necessary evaluation as there was a ready spare for this vessel. My copy of API 579 lists stress relieving as possible degradation in Nickle alloys, but what are other possible consequences or degradation due to heat damage on inconel 600 or other nickle chromium alloys?

Thanks for the help.

 

[mrfailure]

You may also want to perform a portable hardness check to make sure there has been no degradation in mechanical properties.

Aaron Tanzer

http://www.lehightesting.com

 

[stanweld]

The heat tints shown are not indicative of temperature exposures that would adversely affect the microstructure and mechanical properties of annealed Alloy 600. What is the design, operating temp?

 

[mrfailure]

I once performed controlled heat tint tests for 304 which allowed me a quick-and-dirty method to estamate maximum temperature exposure for austenitic SS. However, I would not try to estimate temperature for Inconel 600 unless I had some sort of reference point as heat tint colors as a function of temperature will vary between alloys (and that is a little oversimplification too - tint colors vary even at the same temperature until the thickness of oxide film stabilizes - i.e. short exposures may alter color).

Aaron Tanzer

http://www.lehightesting.com

 

[pdiculous963]

Process gases can reach 2800°F in the inner chamber of this vessel, but a nitrogen pad is used to keep the inconel cool. In the section where it is discolored normal process temperature is about 850°F, and there is refractory lining in the nozzle shown. Design temperature is 900°F.

It seems there was at least one upset event that could have led to the 2800°F process gasses backing up that nozzle.

 

[metengr]

I think based on your list of in-situ examinations, I think this covers it. Hardness testing in-situ can be problematic. I think the field metallograpy (using a portable field microscope to view the microstructure) in addition to thickness and surface NDT (Liquid PT) will be the critical examination methods.

If the above examination results yield comparable results with unaffected regions of the vessel, document the results and place it back into service. Frankly, based on your picture the material if the material was indeed exposed to higher than design service temperatures (above 1600 deg F or higher) and no local warping or distortion is apparent, you may have dodged a bullet. The real concern for Inconel 600 is exposure at 1000 to 1800 deg F, where sensitization can occur, which may affect corrosion resistance.

 

[EdStainless]

For the field metallography you may want to polish and take replicas, then take them back to the lab to coat and put into the SEM. Sensitization is the biggest risk.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube