Phase evolution of surface-modified Incoloy 825 superalloy using pack aluminization

Abstract

The objective of the study is to investigate the phase evolution of the aluminized surface of iron-concentrated nickel-based superalloys. Aluminization is carried out via pack cementation at constant temperature of 900 °C at three processing times of 1, 2.25 and 4 h. Backscattered images and X-ray diffractions are used for phase identification. Small incident angle X-ray diffraction applied on the surface and subjected to repetitive polishing elucidate a formation sequence of iron aluminides. The overall thickness of the aluminized layers is proportional to the processing time squared. The samples are composed of 4 zones, identified by elemental concentration profiles. Only iron aluminides are observed which is in agreement with thermodynamic- and atomic diffusion. The results conclude that aluminization on alloys is similar to oxidation and that nickel aluminide forms with great difficulty on the surface of an aluminized Incoloy 825 alloy.

Recent Advances in the Deposition of Aluminide Coatings on Nickel-Based Superalloys: A Synthetic Review (2019–2023)

“…It was found that the simultaneous addition of 1% cerium and 6% silicon led to the formation of Ce 1 Si 6 , which limits the oxygen diffusion, promotes the growth of the continuous Al 2 O 3 layer, and further enhances the hot-oxidation resistance of the coating. A similar improvement in the hot-temperature corrosion resistance was reported for aluminized Incoloy 825 [12], Inconel 625 [13], and Inconel 600 [14]. One should mention that PC could also significantly improve the mechanical behavior of the protected substrate.…”

“…Although all of them were used to deposit NiAl coatings to improve some functional properties of the base materials, one can expose different approaches leading to the same findings. It could be noticed that PC methods are mainly used to deposit pure NiAl or β-NiAl coatings [6,7,[12][13][14][15][16][17]23,24]. Some reports analyze the addition of different oxides [8,9] and Zr [18][19][20].…”

“…A summary of the pack cementation-related research[6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24].…”