NACE MR0175 Duplex CRO question

[MrGezus]

Good afternoon, everyone. I have a question regarding NACE MR0175 Part 3 A7.3

"A cross-section of the weld metal, HAZ and base metal shall be examined as part of the welding procedure qualification. The microstructure shall be suitably etched and examined at x400 magnification.... The ferrite content in the weld metal root and unreheated weld cap shall ve determined in accordance with ASTM E562 and shall be in the range of 30% to 70% volume fraction."

Does this apply to a 625 Ni alloy on a 2205 duplex base material? I am trying to get this passed through DNV and they are requesting me to include this in the testing. I don't see the purpose of looking for the ferrite in a 625 ni filler metal overlay.

What is your take?
Is there a code paragraph that I can give him to change his mind?

 

[SJones]

Your only way out is to get the end user to invoke the demonstration noted in paragraph 2 of Part 3, A.13.1.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

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

 

[MrGezus]

Your only way out is to get the end user to invoke the demonstration noted in paragraph 2 of Part 3, A.13.1.

Thank you for that. Have you ever had to do this? How would you go about that?

 

[SJones]

I am an end user, so I haven't had to do it. I wouldn't normally be considering putting 625 on duplex stainless steel either. What's it for, valve seal areas?

The first thing would be to check with DNV as to whether such an end user's statement would get them off your back. If yes, start the email with 'Dear Mr/Mrs End User Sir/Madam.....'

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

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

 

[MrGezus]

I was able to get DNV to concede. I'm actually unsure what this company wants it for.

This is what I told DNV

"Would you explain how anyone could get a ferrite content of a Nickel based overlay between 30%-70% volume fraction. The only possible way that I can see to do that is to have horrible dilution of the first layer of overlay which would be terrible for any application.

Is there anyone you can check with? I believe that A.7.3 is applicable only to using duplex as a filler metal in a groove type weld. Otherwise there is no root. First layer overlay is not considered a root. You mentioned it could be taken on the first layer, however nowhere that I can find would allow for that in NACE. How far above the fusion line?

Basically if you used a filler metal with 0% Fe and did this test on an overlay, no matter what it would not have the requirements 30%-70%. "

DNV now only wants me to do the 400x magnification.

 

[SJones]

That solves the A.7.3 (non)issue, but it doesn't solve the A.13.1 issue.

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

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

 

[Guest102023]

MrGezus,
You have to allow for the possiblity that the specification writer was clueless and may just have cut-and-pasted stuff he/she found on the internet. I've experienced that on a duplex SS spec prepared by a major EPC. Ferrite in 625 just ain't gonna happen.

"If you don't have time to do the job right the first time, when are you going to find time to repair it?"

 

[SJones]

Indeed, but what about the duplex SS substrate?

Steve Jones
Corrosion Management Consultant

http://www.linkedin.com/pub/8/83b/b04

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