NDT method for surface cracks & voids
NDT method for surface cracks & voids
(OP)
I have a part produced from a CoNiCr alloy. I'm looking to identify a method to check for microscopic cracks and voids. I've looked at fluorescing dye penetrant testing to limited success (i.e., even on a surface where cracks were identifiable under a light microscope, the dye did not facilitate easy identification of cracks). The surface is about .06" wide. Any thoughts? Hopefully something that can be easily brought in house.





RE: NDT method for surface cracks & voids
Also, proper cleaning is of paramount importance for tiny indications. Try vapor-degreasing or a caustic soap wash. Both have worked will on 'tough' parts.
RE: NDT method for surface cracks & voids
Have you any experience with Eddy current testing? Besides the tedious (and expensive) task of using an SEM to go over a large population of parts, and assuming I can't find a suitable dye penetrant test option, I was considering this as an option. I used it in the past, but I'll need to freshen up on it.
RE: NDT method for surface cracks & voids
Easy-to-obtain caustic soap is dishwasher detergent. Electrasol, etc. Like anything else, wash HOT 110-140°F and use a low-mineral content rinse. Distilled/deionized water preferred. Keep an eye [and stopwatch] on the parts while drying, and when all visible water is gone, continue drying for at least double the time it toof for the water to 'flash' off.
Also, are you aware that you cannot follow red visible-dye with fluorescent? There is something in the red dye that 'quenches' the fluorescence. Is it possible that that is the reason you cannot get the cracks to show up during PT?
If this gives you good results [lots of 'rejects'], you might give me a star.
RE: NDT method for surface cracks & voids
RE: NDT method for surface cracks & voids
metengr: I was actually on the phone this morning with a supplier for Magnuflux who "reprimanded" me for even thinking about doing this in house. I think I'll follow your and his suggestion. The call actually worked to my benefit since he was able to refer me to a lab.