Abstract:Aluminized coatings on Ni based alloys greatly contribute to achieve process efficiency at higher operating temperatures. The present study characterized Pd-modified and unmodified aluminized coatings and compared with those of Pt-modified coatings regarding the mechanisms of formation and oxidation performance. The results show that Pd reduces the driving force for diffusion of Al during coating formation, increases outward diffusion of Ni and reduces diffusion of alloying elements (Cr and Ti) into the interm… Show more
The Pd+Rh modified aluminide coating were deposited on nickel and CMSX-4
nickel superalloy. The Pd layer (2.5 ?m thick) with next Rh layer (0.5 ?m
thick) were electroplated on both nickel and CMSX-4. The aluminizing of the
substrates with Pd+Rh layers were performed by the CVD method. Two zones
(outer and interdiffusion) were observed on both coatings. The palladium
doped ?-NiAl phase formed in the outer zones and palladium and rhodium doped
?-NiAl phase was formed at the outer/interdiffusion zone border of both
coatings. The ??-Ni3Al phase and ?-Co7Mo6 precipitates in the ?-NiAl matrix
were found in the interdiffusion zone on nickel and CMSX-4 superalloy
respectively. The simultaneous usage of Pd and Rh in the aluminide coating
slowed their oxidation rate, moreover the Pd+Rh co-doping is more efficient
than Pd+Hf in reducing the oxidation rate of aluminide coating on CMSX-4
superalloy.
The Pd+Rh modified aluminide coating were deposited on nickel and CMSX-4
nickel superalloy. The Pd layer (2.5 ?m thick) with next Rh layer (0.5 ?m
thick) were electroplated on both nickel and CMSX-4. The aluminizing of the
substrates with Pd+Rh layers were performed by the CVD method. Two zones
(outer and interdiffusion) were observed on both coatings. The palladium
doped ?-NiAl phase formed in the outer zones and palladium and rhodium doped
?-NiAl phase was formed at the outer/interdiffusion zone border of both
coatings. The ??-Ni3Al phase and ?-Co7Mo6 precipitates in the ?-NiAl matrix
were found in the interdiffusion zone on nickel and CMSX-4 superalloy
respectively. The simultaneous usage of Pd and Rh in the aluminide coating
slowed their oxidation rate, moreover the Pd+Rh co-doping is more efficient
than Pd+Hf in reducing the oxidation rate of aluminide coating on CMSX-4
superalloy.
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