I am looking for assistance on an unusual topic - Viking Age staffs (not necessarily used as weapons, maybe as ritual implements and sometimes interpreted as roasting spits) made of iron that commonly had basket handles and cast-on bronze parts for decoration. The image is a close-up of the end of a staff from a double grave (male and female) of Viking Age, Klinta, Köping parish, Öland, Sweden. The image shows an additional decoration of a 3D representation of a longhouse of Trelleborg-type. Unfortunately, I do not have a good image of the bronze details. Other staffs come from Birka and Fyrkat. Similar basket handles with bronze details are found in keys from Gotland (t.ex. Mästermyr tool chest).

The technical issues may include these:
1. casting-on bronze onto iron done simply could cause failure of the iron due to embrittlement by high levels of copper in iron depending on levels of carbon
2. problems with wetting
3. problems with differences in thermal expansion upon cooling.

I may be off-base on some of these, since my metallurgy is a little 'rusty' (pun intended).

Many of these staffs ended up in cremations and are often found broken at the point of casting. The heat of the cremation pyre would allow the migration of copper atoms into the iron and time for carbides to form.

I have not been able to examine the staffs directly yet, but my first guess about the casting process are that possibly an interlayer of tin or silver was used to address failure issues?

Anyone have other ideas? Maybe some experience from similar designs in weapons?

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Close-up of top of Klinta staff