Journal
METALS
Volume 9, Issue 7, Pages -Publisher
MDPI
DOI: 10.3390/met9070782
Keywords
aluminide coating; chemical vapor deposition; surface roughness; oxidation resistance; thermal shock test
Funding
- Marie Curie COFUND scheme
- POLONEZ program from the National Science Centre, Poland [2015/19/P/ST8/03995]
- European Union [665778]
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In the present work, it is shown that the surface preparation method used on two Ni-based superalloys prior to aluminizing chemical vapor deposition (CVD) is one of the most important factors determining the oxidation resistance of aluminized Ni-based superalloys. It was found that grit-blasting the substrate surface negatively affects the oxidation resistance of the aluminized coatings. For grit-blasted and aluminized IN 625, a thicker outer NiAl coating was formed compared to that of IN 738. In contrast, no effect on NiAl coating thickness was found for grit-blasted and aluminized IN 738. However, a thicker interdiffusion zone (IDZ) was observed. It was shown that the systems with grit-blasted surfaces reveal worse oxidation resistance during thermal shock tests-namely, a higher mass loss was observed for both grit-blasted and aluminized alloys, as compared to ground and aluminized alloys. A possible reason for this effect of remaining alumina particles originating from surface grit-blasting on the diffusion processes and stress distribution at the coating / substrate is proposed.
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