NbSi 2 coatings were deposited on pure niobium by halide-activated pack cementation method. The effect of copper addition in pack mixture on the siliconizing process was investigated. After siliconizing on niobium at 1050 C for 2 h using a pack mixture composed of Si, NaF and SiC, a single phase of hexagonal NbSi 2 coating was formed. The addition of copper in pack mixture not only increased the growth rate of the coatings, but also led to form a very thin interlayer between the NbSi 2 coating and the niobium substrate.