Chromium-Aluminide Coatings via Pack Cementation Method on Inconel 718 Alloy and Fe-Cr-Ni SuperAlloy

In this study, it is invastigated the low-temperature formation of chromium aluminide coatings on a CrNiFe-base superalloy and Inconel 718 by pack cementation process. A novel pack-aluminizing diffusion coating was applied at 800°C during 4 and 6 hours.The chrom-aluminising powder packs were prepared using aluminium and chromium powders as a source for depositing aluminium and chrominium, Al2O3 powder as an inert filler and ammonium chloride NH4Cl as an activator. A scanning electron microscope (SEM) with energy dispersive X-ray spectrometer (EDS) and XRD were used to characterize the surface layers. SEM analysis revealed that coating layers were homogenous, compact and nonporous and there was a good bonding at the interface of the coating and matrix. Layer thickness variation was changed from 11,17 to 18,2 µm measured from the surface to the matrix. The hardness of the coating layer increased to 1000 HVN while the hardness of the matrix was 350 HVN with the increasing process time.