Halide activators suitable for low temperature pack aluminisation of electroplated nickel on creep resistant ferritic steels

摘要

This study aims to identify suitable activators for pack aluminising electroplated Ni in order to provide processing flexibility for forming Ni-aluminide/Ni hybrid coatings on creep resistant ferritic steels at temperatures below 700 °C. Experiments are made using NH_4Cl, AlCl_3 (anhydrous), NaCl and NH_4F activated packs prepared from Al and Al_2O_3 powders. Both NH_4Cl and AlCl_3 (anhydrous) are found to be suitable activators. NaCl may be used as an activator if the amount of Al added is sufficiently high. But, the fluoride salts cannot be used as activators in the low temperature range concerned here due to their strong tendency to deposit AlF_3.