Heat Treatment of Inconel 825 Material

[jerin james]

Hello Sirs,


We have got below feedback from a Reputed Cladding mill regarding Inconel 825 being subject to PWHT. You might wonder why PWHT is required for Inconel 825, the base material is CS , Inconel 825 is the cladding material .

quote

The PWHT is limited through sensitization. A PWHT of 630°C for the requested holding time (up to 9h) would be ok for the base material but the corrosion resistance properties of the clad material would be strongly deteriorated. In case the PWHT will be carried out at 630° & holding time up to 9h, there is no chance to meet the corrosion resistance requirements as per ASTM G-28 practice A.
Acceptance criteria of 0,457mm/y could be confirmed for a PWHT of 575°C for 9 hours in total when using alloy 825 as cladding material. In figure below the max. possible PWHT is pictured:

Unquote

Above reference from Fig 1 of ASTM G-28 (check attached) is theoretical we understand.

However, another Reputed mill has confirmed to guarantee corrosion resistance after PWHT , we are actually confused.

Experts can we have your advise.

Thanks

 

[SJones]

Will you be demanding the G28 A test for either plate acceptance, or welding procedure qualification, after PWHT? If not, you should be, and then it comes down to how lucky do you feel with the manufacturer that reckons their alloy will pass.

The figure is NOT from ASTM G28 - it is from some other publication, possibly a TTT diagram from steeldata.info

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/in/drstevejones

All answers are personal opinions only and are in no way connected with any employer.

 

[EdStainless]

The clip is from the VDM literature.
Sensitization is not the formation of carbides.
It is the Cr depletion around the carbides that leads to corrosion susceptibility.
I don't know, but one vendor may have found that 630C x 9hr is enough to get Cr diffusion back into those areas.
The result would be no localized corrosion.
Or they may be working with a slightly different composition of alloy.
Or ?

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[jerin james]

@EdStainless ,

you must be correct the clip is from VDM ,because we got this graph from mill who uses VDM material for 825.

The other vendor who confirmed corrosion resistance is manufacturing the 825 plates themselves so may be they have the knowhow to get through this.

My doubt is will this material be actually able to show corrosion resistance properties , how can we conclude on this ?

Thanks