William,
well at least we are in agreement over the terminology (sugaring).

I would say yes to contamination and/or oxidation of Ti could be visible on film. You also mentioned the overall quality of the shot was "excellent" and "chalky white" in the area of interest. I also agree that shielding (or lack thereof) could very possibly be the source of the problem. Shielding can be problems in the shop, and even more so in the field. [What about joint and filler metal cleanliness?]

Very fine porosity is typically not hard to distinguish in many materials (IMHO). The presence of oxides within a weld have been noted by a few VERY sharp technicians I have worked with in the aerospace industry. In fact this conversation has come up more than once.

More problamatic were technicians that would reject their own artifacts! In another post I noted small dia. Inconel tubing with "dummy" welds (they were placed to justify manufacturing costs). There was no weld joint whatsoever and some of the welds were rejected for incomplete joint penetration - go figure. I adamantly countered the techs. call, but ultimately lost to my supervisor who instructed me to throw in the towel, which I did.

I have seen my own Ti welds with a similar indication (density variations) on several welds back when I myself was the welder, not the interpreter. The companys' RT technician typically would let us review the film so when a "fix" was required, we could do the repair with some knowledge of the location and type of discontinuity present. Back then, I usually just noted the location because I had no knowledge of how to interprete radiographs, but some indications were obvious. After all, we all have a bad day now and then. Contaminated multi-pass welds were a bit more easily noted by a welder. That is why I asked about the number of passes. Single pass welds were another story. I had trouble back then discerning what the radiographer was calling. So, I (or my fitter) would just grind the rejected area.

Years later and several RT and RT Interpretation courses, years of looking at radiographs and the advantage of being under the hood I have seen contaminated Ti welds that were not obvious by visual methods. It really does take a trained eye and the knowledge gained repairing my own welds. Weld geometry (bead profile) can play tricks on the eye, I don't think there is a tech. out there that would argue that fact. I am assuming the technician has performed RT on numerous Ti welds or he/she would not be there to begin with.

Let me know how things turn out. I have not made any technical replies in this forum for a while, just general stuff, but this was a very interesting topic. Sorry I could not provide more definitive info.

Hi guys,

This is a very interesting and informative post. Please allow me to expand it a little by mentioning hardness testing (HT).
I have also been warned about over relying on RT to inspect Ti welds.
Perhaps that is because of the fact, as DGXL has clearly explained, that it takes a real RT tech to detect the slightest of density variances that indicate contamination, which many would not detect.
As an additional contamination detection method, Hardness Testing of Ti welds and haz has shown to be a cut and dry indicator of contamination.
Granted that in this case porosity was the overriding defect indication and negated the need for further NDE.
My point is that if a weld RT did not exhibit porosity or other obvious defects, but was rejected or questioned concerning contamination due to on an indication of density variations, the contamination could be verified or ruled out by HT.
In the case of a repair, HT could be also be used as part of the fit-up inspection to ensure the complete removal of contaminated material.

I'm curious about the cause of the porosity and contamination in this particular weld. As it has been explained that the work area, consumables and atmosphere were extremely clean. I wonder if the defects were caused by moisture in the shielding gas. Couldn't this be a probable cause for the extremely fine porosity?

Thanks for hearing me out. Please let me know if I am mistaken.

Tim Gary

William:
Your post has without a doubt received some of the best responses I have seen in a long time (not my own). I learned something from the comments by Tim Gary (Good reply Tim.) A very good lesson in physics was also posted by Lawrence.


Another post in the other forum by Alan Riddle was also pertinent and I am posting the thread below:

Well, if you have been following this subject, it has been a long time coming but we do now have a final report. The false indications created on RT film are commonly called "ghost lines" or "density lines." I like the ghost line one myself, because they aren't really there! Anyway, on Inconel materials, less than .060" thick, a condition called epitaxial grain growth occurs in the center of the weld. Enlarged grain size, dendrite formations running in a totally different plane and the presence of Ti and Al migration all contribute to "beam diffraction" during the RT exposure. This creates the false images commonly interpreted as lack of fusion in the weld. I want to thank everyone who assisted me in finding the answer to this issue. Special Metals and CBI especially. If you ever have a job like this one, tell the RT evaluators before hand that they will see centerline indications which look like lack of fusion. Then when they do read the film, they will take you seriously and think you are very very good and wonder "How'd he/she know that?"

Thanks again,

Alan


All that has been noted are appropriate and may be of some use to us all. A local aerospace company has had similar problems and had contacted me. It had come down to a question of the interpreters ability to read film. I think you may have a good interpreter, just more info on the indication and the sources of this type of indication are needed by everyone involved. Subtle variations in densities can be interpreted in many ways by different people. This is one very good example.

I noted above I have had to cut up welds to confirm my calls many times. We had the luxury of multiple parts which permitted destructive testing. This really puts the technician on the spot when they found there calls were incorrect - which is not the intent. The intent is to make accurate radiographic interpretations. Some of these radiographers do not want to touch my parts anymore because they say my projects are too difficult to interprete. Keep in mind I have knowledge of the joint configuration, process, WPS parameters, etc. The more you know increases the accuracy of the interpretation.

Originally William noted the presence of small pores and contamination were confirmed. I like the idea of the hardness testing to confirm the presence of undesirable oxides, but destructive testing would still be required to evaluated various regions of the weld and HAZ.

It has always been my understaning contamination of welds on these materials are due to:
A.) Foreign materials or substances on the base or filler metal. (The source may come from gloves, bench tops, dirty rags, etc.)
B.) Loss of or inadequate shielding. (If moisture was present in the gas, the entire weld would divulge this. I have had my purge dams come loose during welding but was not aware because my hood was down. Lots of sources for this problem as well.)
FYI: A bulk tank at an aerospace comany had been charged with poor quality gas resulting in a major lawsuit for numerous manhours and parts that were rejected. Very expensive mistake by the gas supplier.

Not only did the forum enjoy a very good technical problem, some excellent replys were posted. Hope we hear the final determination of the source of the problem, but also the disposition of the radiograph(s) in question.

I'll have to agree, this has been very interesting reading. I hope to get more exposure to the RT method of testing in the future. I'm more familiar with other testing methods due to the nature of work I'm envolved in, but that may change and the need for RT will certainly arise. I look forward to learning more of this fasinating method to further my knowledge of NDE. Keep the info coming, I'm trying to absorb this and keep up with all that is being discussed.
John Wright