T23 T11 DMW Failure

[purduemateng]

I'm new to this site, so hopefully I'm posting in the correct area.

I have an issue with a failed tube that we received in our lab. It is a T23 to T11 DMW with an 80S-B2 filler metal. At the moment I can say that, in the two sections we’ve examined, that the crack is filled with oxide and mostly appears to follow a transgranular path with little branching (more like a fatigue crack), propagating through both weld metal and T23 HAZ without regard for microstructural features. No cavitation or other indication of creep damage. No large weld defects. There are a few curious features, though – in some areas the crack seems to locally follow an intergranular path, with nearby short, intergranular cracks adjacent and parallel to the primary crack (reheat cracks?). I've attached a micrograph detailing what I'm explaining.

Thoughts?

 

[purduemateng]

additional micrograph...

 

[purduemateng]

one more!

 

[metengr]

Yes, these appear to be intergranular fissures. My comment is that Grade T23 has had issues in the Power generation industry with intergranular cracking in the heat affected zone of welded water wall panels, with similar appearance as what you have produced. There was minimal preheat and no PWHT and so the cracks were more hydrogen cracking related.

T23 has been reported to have issues with stress relief cracking. It would not surprise me this could be stress relief cracking, as well, given the T23 weld heat affected zone microstructure susceptiblity, thermal stresses associated with a DMW joint and service temperature.

Here is a paper for your review regarding stress relief cracking;

http://www.jwri.osaka-u.ac.jp/publication/trans-jwri/pdf/WSE2011-M2.pdf

 

[pandithan]

It appears to be Reheat crack
pandithan

 

[davefitz]

Refer to the following on similar reheat cracking of T23/T24:

“Influence of post weld heat on secondary hardening of CrMoV welded joints “, P Mohla et al, Metal science and heat treatment. 2011, vol. 53, no. 7-8, p. 374-378

“Quality management at RWE using T24 boiler material as an example”, R Nowack et al, VGB PowerTech(eng) 11/2011

“Hot Cracking of welded joints of the CrMoVTiBo 10-10(T/P24) steel”, J Adamiec, IOP conf series: Material science and engineering 22(2011).

And other references therein cited.


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