Many Viking Swords had iron cores with the outer layers welded over them. It is hard to address your issues with out more detail.
Using general terms is hard to understand, If the tool steel could be A2, its not gonna work, where as if the tool steel is W-2 it should be fine.
Welding the sandwich should pose no troubles, IF you are experienced with forge welding, You didn't state if you have tried others welds or if this is your first time. IF first. did you clean it well enough? flux? correct temp?
If you need a primer to help you get started, I have one I wrote at
How to make Damascus Blades which explains forge welding and steel types.