Siliconizing Formation Mechanism and Its Property by Slurry Pack Cementation on Electro-deposited Nickel Layer into Copper Matrix

Silicide coating was prepared on electro-deposited nickel layer by the slurry pack cementation process on copper matrix at 1173 K for 12 h using SiO2 as Si source, pure Al powder as reducer, a dual activator of NaF+NH4Cl and albumen (egg white) as cohesive agent. Microstructure, properties and siliconizing mechanism of silicide coating were discussed. The experimental results show that the silicide coating with 220 μm thickness is mainly composed of a Ni2Si phase and a small amount of Ni31Si12 phase. Its mean microhardness (HV 790) is ten times than that of copper substrate (HV 70). The coefficient of friction decreases from 0.8 of pure copper to about 0.3 of the siliconzed sample. SiF2, SiCl2 and SiCl3 are responsible for the transportation and deposition of Si during the slurry pack cementation process.