Linear indications on 625 Inconel welds (from an earlier posting) I believe have been solved. We have .040" wall tubing, single pass full pen. GTAW welds. Always get a linear indication but don't know what it is. We have tensile tested, macro examined, micro hardness tested, you name it, we've done it and can't find anything suggesting a rejectable weld. Recently took a sample to my old employer who has a Scanning Electron Microscope. Did Electron Dispersion Scan on sample and the only positive evidence came when the elements of Aluminum and Titanium were found in the weld center, and not anywhere else in the weld area. We think this migration of Al and Ti is causing a density change in the weld metal creating these indications. Would like to try qualifying a new PQR for 625 base metal. Any suggestions on an alternate filler metal??? These are aerospace ducting systems, class A per AMS std 2219 specs. Everything I got only recommends ER625 fillers. Oh yeah, we thought about a post weld heat treat, but can't do that as the welded components have bellows/ball joints etc with carbons, so heat treatment is out. Appreciate any thoughts you may have. Feel free to email direct.
alan.riddle@perkinelmer.com
I also can't believe we are the "first" business to have these indications on 625 base metal. Anyone else ever see this, how did you fix?
You need to talk to a fine gentleman at Special Metals named Sam Kiser. Sam is very familiar with these indications and gave a great presentation on them last June at the EPRI Powerplant Maintenance Welding Conference in Point Clear, AL. They are known as "ductility dip cracking" and occur on a microscopic scale in Alloy 625 and 690 welds. They are caused by trace elements, such as aluminum, titanium, phosphorus and sulfur. Sam has been working on a new INCONEL 52M filler metal to help resolve the problem. It will have AWS classification ERNiCrFe-7A in the next edition of A5.14. I have Sam's e-mail address at work and can send it to you tomorrow, or you can go to the Special Metals website to get their phone number and give him a call directly. Here's a link to some info on the Alloy 52M filler metal:
http://www.specialmetalswelding.com/whatsnew/inconel52mnew.htm
Hope this helps,
Marty
Thanks Marty, this is the first solid lead I have gotten on this problem. You did use that ugly word "crack" though????? I just recieved the tensile test results yesterday from Sherry Labs in Indiana. I had them do four tensile pulls on areas that I specified for them. These areas had those linear indications running completely through them. All four pulls went above min. requirements and 3 out of four failed in HAZ, one failed in the weld. I don't have the remnants back yet to examine the fractured area on that one. I will get in touch with Sam today if he is available. Appreciate the info.
Thanks,
Alan
While I did use the "c" word, they would be characterized as microfissures. As I recall, they are on the order of 1 or 2 grain diameters. Not sufficient size to affect mechanical properties, but they do sometimes show up on eddy current and ultrasonic exams. Here's a link to Sam's phone number and e-mail address:
http://www.specialmetalswelding.com/contacts/contacts/newtoncontacts.htm
Just scroll down to the listing for Technology.
Marty
MB:
You have provided some of the best technical advice on this subject. I have been following this with interest.
I had noted in a previous post last year (or the year before), a company I used to work for that welded lots of tubing (ducting) for Boeing. We had this problem a number of times. Sometimes "dummy" welds were applied where there was not a joint so the part appeared to be fabricated per plan. The radiographers would reject these welds regularly as they asssumed there to be IF or IJP (a linear indication on the RT report).
Very good replies there MB.
ALAN,
I think the DDC comments may be leading you down the wrong path. The linear indication may be caused by X-ray diffraction. THe elemental segregation of Al and Ti may also be a good assumption. 52 and 52M have very long highly directional grains. it is hypothesized that these grains can cause x-ray diffraction. One way to prove this is if you change the angular orientation of your x-ray source and the indication goes away. We have seen some Phantom linear indications on 52M weldments.
Jeff
I think he already figured that out:
http://www.aws.org/cgi-bin/mwf/topic_show.pl?id=3927#15934
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