Failure has occurred due to plastic deformation of the
nickel interlayer between Stellite 4B and H13 material; this
caused tearing of the nickel interlayer, as shown inFig. 8b
and local distortions, which promoted the initiation of
cracks in stellite. The fracture of stellite has proceeded from
the back to the front face of the die, as shown by river patterns in Fig. 8c. It is clear that the die failed because of
absence of support from the backer (supporting piece
assembled in the back of the die during extrusion). Since
the backer is a piece that is used for several die shapes, it
was difficult to change its design for the particular case
and the idea of a full length insert was abandoned for the
time being.