Process for densifying and promoting inter-particle bonding of a

Details Process for densifying and promoting inter-particle bonding of a Process for densifying and promoting inter-particle bonding of a

1997-10-27

2000-08-01

Bareford, Katherine A.

Coating processes

Spray coating utilizing flame or plasma heat

Metal oxide containing coating

427455, 427456, C23C 406, C23C 418

Patent

active

060963816

ABSTRACT:
A method of depositing a bond coat (16) of a thermal barrier coating (TBC) system (14) for a component (10) designed for use in a hostile thermal environment. The method yields a bond coat (16) having an adequate surface roughness for adhering a plasma-sprayed ceramic layer (18), while also exhibiting high density and low oxide content. The method generally entails forming the bond coat (16) by depositing a metal powder on the substrate (12) using a plasma spray or high velocity oxy-fuel (HVOF) technique. The metal powder contains particles that are sufficiently large to incompletely melt during deposition, yielding a surface roughness of at least about 350 microinches Ra. The large particles cause the bond coat (16) to have relatively low density and a propensity to oxidize, both at the surface of the bond coat (16) and internally due to the porosity of the bond coat (16). The propensity for internal oxidation is considerably reduced by heat treating the bond coat (16) in a vacuum or inert atmosphere after deposition and before exposure to a high temperature oxidizing environment, such that interparticle diffusion bonding and densification of the bond coat (16) are promoted without oxidizing the bond coat (16). Thereafter, a ceramic layer (18) is plasma sprayed on the bond coat (16) without forming an oxide scale on the particle surfaces, which if formed would prevent subsequent interparticle diffusion bonding, leaving unclosed porosity that reduces the oxidation life of the bond coat (16).

REFERENCES:
patent: 4095003 (1978-06-01), Weatherly et al.
patent: 4275124 (1981-06-01), McComas et al.
patent: 5236745 (1993-08-01), Gupta et al.
patent: 5817372 (1998-10-01), Zheng

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