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Up Topic Welding Industry / Inspection & Qualification / What Defines a Crack?
- - By MRWeldSoCal (***) Date 01-09-2014 19:09
So I am working on a boriscope at work, checking 1" tubes that are connecting Inconel and 304 Stainless.  The company is using an ERNiCrMo-3 Filler metal.  My problem is that i am getting what appears to be maybe a scale or and odd pulling of the surface on the inside of the tube.  The purging they used appears to be successful but not perfect. It looks like the grand canyon or even the Nile delta again in a figurative sense.

So what defines a crack?  Is the grand canyon a crack in the earth? Or because its wide and has a difinitive bottom its just a gorge?

I hate to say I cant get a photo of what I am talking about because my scope doesnt take photos. I attached some photos of places on earth that look just like what I am seeing.  So this may turn into an interesting convo.

It seems to me that when these two metals come together maybe one is solidifying quicker than the other.  There are "cracks" on these but they are not deep, or they have a bottom.  It is hard to describe so maybe see the photos and try and throw in some info.

Thanks
Attachment: CRandcrackyoon.jpg (6k)
Attachment: GRANDCRADCK.jpg (262k)
Parent - By SCOTTN (***) Date 01-09-2014 21:31
Jefferson's Welding Encyclopedia, an AWS publication, defines crack as a fracture type of discontinuity characterized by a sharp tip and high ratio of length and width to opening displacement.
- - By 803056 (*****) Date 01-09-2014 22:19
When in doubt, confirm with an alternate test method.

Al
Parent - - By MRWeldSoCal (***) Date 01-09-2014 22:46
They passed PT, and are on their way to RT now.  When I am doing the VT though why is that still acceptable if it appears the be a great start for crack propagation?

thanks
J
Parent - - By 803056 (*****) Date 01-09-2014 23:56 Edited 01-10-2014 04:39
What has your employer done to determine what is being seen? Have samples been sectioned, polished, and examined to see what the cause of the visual indications are?

Are the tube assemblies properly purged while welding? If you are seeing oxides the answer is "No."

Are the indications caused by low melting point eutectics backfilling between the solidified grains?  This is a question that need to be answered by a metallurgist, not a visual inspector.

Was the welding procedure qualified by testing? What was the visual appearance of the weld assuming the mechanical properties and customer requirements were met? Did the tested weld have the same appearance as the welds you are looking at?

Then for the 10 thousand dollar question: what has the employer provided in the way of training for their inspection personnel to perform remote visual inspection? The CWI program does not require nor does it include remote viewing as part of the CWI examination.

I hate to say it, but it sounds like the employer isn't providing the proper training needed to inspect these welds. It appears the employer has no standards to compare these welds to. It all goes back to what I say when someone asks me, "are these welds are any good?"

My response is, "compared to what?"

The engineer might ask for the inspector's opinion, but the CWI's responsibility does not extend to developing acceptance criteria.  Developing the inspection plan and establishing criteria should be an engineering function.

Al
Parent - - By fschweighardt (***) Date 01-10-2014 12:40 Edited 01-10-2014 12:43
What kind of Inconel?  There are a bunch of different flavors, 600, 625 (pretty common), 617, 690, etc.  It looks like you are using 625 filler, which may or may not be suitable.  In your post, you mention 304, is it 304L, H or something else.
Parent - By MRWeldSoCal (***) Date 01-10-2014 19:35
stainless 304 to 625 Inco yea

Jordan
Parent - By MRWeldSoCal (***) Date 01-10-2014 19:31
Al-

The parts right now are going through RT.  The company I am working for now is a testing facility, and Im here to do the VT, ME, and destructive testing.  There are Oxides on some of the parts, there is definitely places where you can see differnt solidification rates.  There are welds that are clean as a whistle and gold or silver with no discoloration and some that are darker and occasional oxidation on the surface.  As for having a WPS for it, I dont not have one nor do they give us one.  We are just doing the testing.  Even though my inner self wants to see all the paper work for it, for this particular job that doesnt fit my description.

   Now the parts pass the standard that I am to perfrom the VT, there is nothing in it for oxidation of welds, and from what I am told the company will likely be blending the welds down when they get them back.  My concern is in crack propogation from the use of two metals with different cooling rates. There were no cracking that was sub surface but there we cracks on the "skin" of the weld. It had the look as does a sandy river bed with no water.  We work with many many different standards here and this isnt to anything AWS.  I guess i tend to be in more moral obligations to myself about quality, and the future of where this weld is going.

Jordan
Parent - - By Lawrence (*****) Date 01-10-2014 13:29 Edited 01-10-2014 13:34
Without a pic it is impossible to tell.

Al makes great points about training and especilly about comparative samples of common defects related to the work being done.  A super good thing that everybody doing high level work should have.

Having welded miles of backpurged superalloys, your verbal description reminds me of what is pretty common in poorly purged superalloys... Or hot section parts that are improperly prepped.

An "other side" or back side that has a dull *wrinkled* appearence is typically as sign of bad back purge.  The oxides on many of the Inco, Hastelloy, Waspelloy, Renee and Haynes alloys will form a sort of "skin" atop the molten back puddle if the purge is not adequate Or.. or   or... this same phenomina can occur if the normally formed oxides have not been properly removed from the backside of the weld zone and HAZ prior to joining... Surface prep on both sides here is more critical than other alloys.

(This means that the purge can be perfect, but oxides can cause problems, including defects, if the surface prep is not adequate on both sides)

Similar mechinisim to "sugaring" on stainless... But different appearence.

My money is on the solution being process control related.
Parent - - By ssbn727 (*****) Date 01-10-2014 18:37
I agree Larry, and just to answer SoCal's question regarding what kind of crack he's seeing... I would "guesstimate" that he's describing what can be interpreted as what started out as micro fissures that have opened up even more because of the metallurgical differences in the two metal alloy compositions, heat input, differing cooling rates, etc.

But the bottom line is that in the process control strategy, some of the many factors to be considered were not taken into account and/or ill prepared prior to striking an arc.

!!!!!hhhhhhhhhhuuuuuD:twisted::wink::roll::cool: It's just my own obtuse sense of humor Lar... No more - no less:smile:.

Respectfully,
Henry
Parent - By MRWeldSoCal (***) Date 01-10-2014 21:31
My biggest frustration has been knowing where the line in the sand is regarding what I am capable of doing.  For example I had to ride along for a MT testing gig and we were sent for only MT and just to check for cracks.  When we got there it passed but the welding work was total garbage.  The part was supposed to be D1.1 compliant but it would have been painted red with marks had i been asked to do VT on it.  I mean they had GMAW-S on 3" thick steel where they has screwed up with the ARC welding.  I wanted to ask for their WPS for the short circut cause I know its not pre qualified.  But again I am reminded by my coworker that we came to do the MT and thats all we are doing.  

I asked my MT guy if i could build his house on these parts and put his family inside the house... HELL NO! he said.   Then he saw my point.

Again, we were not called to do the VT, I was there to ride along.

Jordan
Parent - - By MRWeldSoCal (***) Date 01-10-2014 19:50
Lawrence,

Bingo, nailed it on the head. It is a "skin" esque on it.  The purging is certainly an issue after reading your help.  Now when you see the skin for tiny cracks that do not go any further than the skin is it still a crack? or indication?  this isnt to an AWS standard. Its from a standard made by the company, and the company is very well known.  Glad to know you have seen what I am seeing.  The closest thing I can find to flag these would be cracking since they meet the criteria.  They passed flourecent PT also. 

Thanks
Jordan
Parent - - By Lawrence (*****) Date 01-10-2014 20:50
I'm curious how they do a quality FPI on the inside diameter of a tube that is too small to get a boroscope camera into.

If you emulsify a penetrant long enough, anything will pass.   I would think that rough interior surface oxide would hold penetrant to such an extent that the whole zone would glow green.....  How do you get a black light into that zone anyhow?

So many questions.

Is it a crack?    You are the only guy at this party that has a copy of the standard in his hands. :)

Pratt, Rolls, GE, Allison, all have standard practice manuals for welding and inspection...  You might find some help there, especially when it comes to workmanship standards and maybe even the quality comparison issues Al brought up earlier.

OEM doccuments should be available to you....
Parent - By MRWeldSoCal (***) Date 01-10-2014 21:10
We dont have a camera in the sense of making a digital image, but for the florecent PT I use the same borescope but disconnect the fiberoptic lighting and go into a dark room with a black light from the bottom.  I get what you are saying though about a said amount of rinsing can clean off any surface.

Would I call it a crack. No.  But when is there a flag for propogation?  we are already informing the company that their purge is sub par.  Some of the welds are flawless, some the backing gas was lacking but no porosity just odd solidification.  I attached one last pic of what I am seeing. please refrain from laughter since I cant find an actualy weld photo to show you.  This pic is what I see through the scope.  The lines have endings, but they flow like the photo with abrupt edges much like a dried up river bed.  Seems to me like definite stress risers. again they are all within spec dimensionally.

Thanks again
Jordan
Attachment: 1698285_450_450_1_0_fit_6_7a9e6ff9558ff7.jpg (85k)
Parent - By MRWeldSoCal (***) Date 01-10-2014 19:55
Also I cant get a photo because we dont have a camera that small, to fit in the bore. Thats why I had to match what I saw to places on earth :wink:
Up Topic Welding Industry / Inspection & Qualification / What Defines a Crack?

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