Inconel 625, Heat Treatment and Hardness 1

[lukerobert]

I have many projects that require Inconel 625 to be weld inlayed into various oilfield equipment (valves, etc). The Inconel is inlayed into 4130 steel and then put through a stress relief cycle of 1175 deg F for 3 hrs. Can anyone tell me the relationship between the said stress relief cycle and the hardness of the Inconel 625? I have read several articles that say that Inconel 625 will precipitate harden during said stress relief cycle.

 

[EdStainless]

It will depend on the weld dilution (contamination).
You really need to limit the Fe and C in the weld overlay.
While it might make it harder it will lower the corrosion resistance a lot.

You can look in 625 data sheets and see if the 1175 x 3hr should have any effect at all.

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Plymouth Tube

 

[OGMetEngr]

A PWHT of 625 at this temperature for this amount of time will not increase hardness to a level of concern. You will be looking at less than 30HRC. 625 will not be appreciably precipitation hardened (even at higher temps and/or longer times) as it is essentially a solid-solution nickel alloy. You will get some increase in strength/hardness from aging, but not enough to make it non NACE-compliant. The base material will be the limiting factor in this case.

 

[jbeckhou]

API-6A addresses UNS NO6625, see table 15. Also see Addendum 2 (API-6A-20th ed) API changed the whole section,"full overlay equipment" and "partial overlay equipment".

Petrotrim Services

http://www.petrotrim.com

 

[metengr]

jbeckhou is correct.

 

[BG169]

The main concern with hardness in this situation should be the hardness of the HAZ, not the 625 overlay. NACE MR-0175 has a maximum hardness of the HAZ, in this situation the max hardness should be 22 HRC.