Re: adhesion of coatings

Posted by Hong Wang ( on 19:52:34 17/01/06

In Reply to: Re: adhesion of coatings posted by Gordon England

I need suggestions to solve the coating seperation. Part is ring shape(Ni base superalloy) with dia 12'', thickness 1/8''. APS Co based alloy coating on ID. Coating thickness was 0.06'' but bond coat was not allowed. Coatings (with or without front air cooled)detached after sample cutting from the ring. Used preheat on I.D. and cool air blowing on back of ring during spray. Cutting followed the Standard.
Although normally heat is remaved by cool air blowing on back of substrate, I am suspecting it (plus the preheat on ID) built up extra compressive stress due to the long spray time. If back air blow is not used, torch dewell has to be used but it will reduce productivity. Will preheat on O.D. help?
Thank you in advance
Hong Wang

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