RE: Metallography Evaluation
Hi Vcduramais,
Since the major failure is observed quite a distance from the substrate, you should not expect the preparation of your substrates to be the major source for this type of failure. I have seen similar failures, but slightly more homogenous, in water cooled kerosene guns when there has been small water leaks present. If there is oil or other hydrocarbons in the compressed air used for cooling the substrate you could expect failures similar to the image presented. However, It will highly depend on amount and consistency of the contaminants coming to your sample.
In addition, I will add that hot mounting of brittle coatings could cause mid layer failures due the the high pressure and temperature during the embedding. Hard to determine embedding technique from the image. If this is likely for you coating, I cannot tell.
I acknowledge that my input is a bit late. Therefore I ask, is the problem solved and root cause eliminated? Would be interesting to hear development moving to a new system.
|