most resistant substrate layer to embed a specific wire
Electric oven elements are usually swaged metal tube over ceramic (mullite or
alumina) beads strung on NiCr wire.   The ceramic beads will crack, but once
the metal tube is drawn tight over the cracked parts, the whole assembly
remains intact through many temperature cycles.

The packed granules of temperature-stable ceramic are able to maintain
spacing of the heating wire from the external tube.   It isn't resistant to cracks, but remains functional despite them.