Re: Embedded Aluminum oxide grit

Posted by Gordon England ( 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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