6% brown weldments in CA6NM 4

[BurningFuel]

We just pulled a small ca6nm case and there are some small weld repair areas in the volute discolored, Any way chrome content is 6% in those spots. We are told repairs were completed with 410nimo and that their engineer believes chrome content can weaken in slurry conditions. I have never heard of this... I'm thinking 6% chrome 8018 series.... any thoughts?

It will be repaired the correct way.

 

[metengr]

No such thing. The discolored regions were caused by surface oxidation in relation to the lower chromium containing weld repaired regions containing 6% mass content versus 12% mass content. I have seen weld repairs performed by shops for similar CA-15 or CA6NM castings using lower matching filler metal thinking it will be more forgiving and does not require PWHT.

 

[stanweld]

Obviously the weld repairs were not made with E/ER410NiMo weld filler metal, either deliberately or accidentally due to lack of appropriate filler metal issuance controls. I have audited a number of fabricators/manufacturers where mixes were found due to poor QA/QC.

 

[Guest102023]

Sounds like a mess, but agree the discolouration is oxidation, consistent with lower chromium content, I presume measured by PMI. 11%Cr mixed with 0%Cr could produce 6%Cr.

CA-6NM is not all that difficult when you understand it, and that starts with recognizing it cannot be classified together with any other martensitic SS. It is an alloy that amateurs (including many shop foremen) should resist playing with. (So contact me, its my signature dish.)

 

[arunmrao]

CA6NM castings are routinely upgraded by welding using standard welding rods and procedures. Perhaps the shop used a lower grade welding rod to avoid any cracking and prevent early detection by the user. Agree,you can redo the repair well.

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