Posted by Hong Wei Wang (193.116.28.254) on 17:23:02 13/12/05
In Reply to: Re: coating homoginization posted by Gordon England
MCrAlY is highly enriched with Cr and Al compared with typical
Ni- or Co-base superalloys. A drawback is the metallurgical
instability of these coatings in service condition such that there
would be service high temperature driven inwards diffusion of these
elements and outwards diffusion of base-alloy elements to create a
brittle interdiffuison zone (due to sigma, mu phases
formation). Post coating HT (1050 oC) for stabilisation
is a general requirement for LPPS MCrAlY. other reasons of PCHT is
to reduce the brittleness and close loose porosity
(sintering) of the as-sprayed coating by plasma spray.
As for the absence of need to HT HVOF MCrAlY, are you sure this is
true (certainly for the hi-temperature
applications)?
Regards,
Dr. Hong Wei Wang
ERA Technology Ltd
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