A STUDY ON THE ALUMINIZING OF ELECTRODEPOSITED NICKELAT ۵۰۰ oC

Abstract: nanocrystalline nickel samples with the grain size of ~۲۵ nm were prepared via direct current electrodeposition andaluminized for different durations by pack cementation method at ۵۰۰ means of SEM, EDS and XRD techniques. According to results, short time aluminizing resulted in the formation of asingle aluminide layer whereas at long duration two distinct aluminide layers were formed. The growth kinetics of thecoating was non-parabolic at short times while it obeyed the parabolic law at long duration. The parabolic growthrate constant of single phase coating formed on electrodeposited samples was about ۳۰ ìm / h۱/۲ approximately ۳ timesgreater than the data reported for coarse grained nickel (۸.۴ ìm / h۱/۲). Meanwhile, the overall growth rate constantwas decreased to ۱۱.۷ ìm / h۱/۲, when double aluminide layers formed on nanocrystalline nickel.In this research, aluminizing behavior of ultra fine-grained nickel was investigated. For this purpose,oC. The aluminide layers were examined by

Keywords:

Aluminide , Coatings , Kinetics , Nanocrystalline , Nickel.