Akademik Veri Yönetim Sistemi
JOM, 2025 (SCI-Expanded, Scopus)
This study investigated the effect of powder mixture-driven aluminum activity on the microstructure of out-of-pack aluminide coatings applied to selective laser melting-fabricated Inconel 939 substrate. The samples were aluminized via a single-step process at 1100°C for 2.5 h using a 10 wt.% Al (99.99)-5 wt.% NH4Cl -balance Al2O3 high-activity pack. The combination of process temperature and aluminum concentration reflects high-temperature high-activity (HTHA) conditions, though its mechanism remains debated due to inconsistent findings in the literature. Formation mechanisms were analyzed using SEM, EDS, XRD, and microhardness (Vickers) test. These findings were also compared with reference aluminide coatings produced via high-temperature low-activity (HTLA). Utilizing HTHA conditions resulted in inward-grown coatings with a thick additive layer (470 ± 9 μm), including precipitates and intermetallics, and a thin internal diffusion zone (IDZ) (22 ± 3 μm). XRD and SEM-EDS analysis suggested that δNi2Al2 and β-NiAl phases were present in the additive layer. The average hardness level of the additive layer was 954 ± 96 HV; however, the hardness varied within additive layer due to possible phase transformations (from δ-Ni2Al3 to β-NiAl). Although HTHA coatings exhibit both beneficial and potentially undesirable characteristics, further high-temperature corrosion testing is required to assess their overall suitability for turbines.