Is there an alternative wet chemical method or electrochemical method to obtain precipitation of iron, nickel and silicon powder?
Both metal powders can be preapred electrochemically.

Iron dust is prepared using solution containing $\ce{FeCl3}$ with addition of $\ce{AlCl3}$ to make the solution more conductive. The process occurs at elevated temperature 60°C. Unfortunately exact process parameters are hard to find.  But following graph could help.



Nickel could be prepared electrochemically too and can be prepared by dissolving of Ni-Al alloy in hydroxide -Raney_nickel. The description of patent is here.

This is link to a study book PRÁŠKOVÁ METALURGIE, K. Skotnicová, M. Kursa
, unfortunately only in czech.