Microstructural and topographical characterization of the pack cemented aluminide coating applied on Inconel-600

چکیده مقاله

In this research, the pack cementation method was employed to apply a uniform aluminide coating on
asubstrate of nickel-based superalloy. The obtained intermetallic coating was synthesized using a pack
containing 18Al–80Al2O3–2NH4Cl (wt.%) as the main deposition source, an inert filler, and an
activator, respectively. The surface morphology and topography, cross-sectional microstructure, the
elemental and phase composition, microhardness of the synthesized aluminide coating were studied
using atomic force microscopy (AFM), optical microscopy (OM), scanning electron microscopy
(SEM), energy-dispersive spectroscopy (EDS), x-ray diffraction (XRD), and Vickers microhardness
indenter as the characterization techniques. According to the 3D topography results, the average
surface roughness of the Inconel-600 substrate was about 2.446±0.239 nm compared to
43.558±3.876 nm measured for the produced aluminide coating. Additionally, the synthesized
coating consisted of NiAl and Ni2Al3 as major phases considering the XRD spectrum. It is also
observed that the deposited aluminide coating had a three-layer structure including an outer layer, an
inner layer, and a diffusion zone. The Vickers microhardness measurements indicated a significant
increase in the microhardness of the substrate (from 185.6±15.8 Hv to 1130.4±42.5 Hv) after
applying the aluminide coating. Moreover, the microstructural variations across the deposited
aluminide coating led to different microhardness values obtained for each layer. The highest
microhardness was observed in the coating diffusion zone, whereas the lowest value belonged to the
outer layer.