Posted by Gordon England (62.252.0.12) on 19:51:18 04/09/05
In Reply to:Embedded Aluminum oxide grit posted by Dennis A. Pearson
: I am having a problem with embedded aluminum oxide
: grit prior to coating Inconel 718. We think it is
: coming from a tumble finishing operation prior to
: sending out for coating. The grit is added to a
: burnishing media (ceramic)each time the barrel is
: filled. Could adding too much grit cause a build-up
: that could cause this problem? Would the tumble process have enough energy to cause the embedded grit?
: What would you use as an inspection method to insure
: grit is not embedded? Is there a good way to remove
: the embedded grit on affected parts? Appreciate any help since this has become a very big problem.
:
: Thanks
:
Hi Dennis
Are you sure the problem is not from the grit blast surface preparation prior to coating?
Some grit contamination at the substrate/coating interface is inevitable. Many aerospace specifications quote limits around 20% max grit contamination measured on cross-section through interface.
Air blast or ultrasonic cleaning may remove some retained grit but not all.
Magnified visual inspection or possibly seeing what adhesive tapes will lift off.
Regards Gordon
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