delamination in the coating

[codep]

We have a general delamination problem in the coatings. We have observed this problem with Ni-Graphite (flame spray), Ni-Al (flame and plasma spray) , Al-Si (plasma spray) powders. During evaluation of the microstructures we found delamination more than 0,010" close to substrate or between substrate and coating or between bond coat and top coat. All the delaminations are close to substrate, we have not found any delamination in the upper layers of coating. For abradable coatings the thickness is about 0,040-0,060 inches, for the others generally 0,020-0,035 inches.
The humidity or oil in the cooling air may cause this problem.
Does grit size effect delamination?
Does anybody have any experience with this type of problem?

[Gordon]

Hi Codep

Before you blame your coatings, check your metallographic preparation procedures. Poor cutting-off and mounting methods in particular often cause these artifacts.

[codep]

Hi Codep

Before you blame your coatings, check your metallographic preparation procedures. Poor cutting-off and mounting methods in particular often cause these artifacts.

Dear Gordon;
Our laboratory technicians are good at preparation and inspection and they have 15 years experience. The delamination problem is just for two months. Before two months there was no any delamination problem. I am attaching some micrographs of coatings.

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The first four micrograph belongs to Ni-Al wire combustion spray with 14E gun, the other three belongs to Ni-%40 graphite powder combustion spray with 6P-II gun.
   
   
   
   
   
   
   

[Gordon]

Hi Codep

Dear Gordon;
Our laboratory technicians are good at preparation and inspection and they have 15 years experience. The delamination problem is just for two months. Before two months there was no any delamination problem. I am attaching some micrographs of coatings.

Look for any changes in equipment/process/procedures that may have occurred 2 months ago.

The humidity or oil in the cooling air may cause this problem.

Yes

Does grit size effect delamination?

It shouldn't. Quality and cleanliness of the blasted surface will though, but mainly effecting the coating/substrate interface.