The influence of Cu content on transverse rupture strength of
the samples for each sintering temperature is depicted in Fig. 9.
It can be seen that the transverse rupture strength increases until
the appearance of the maximum values, and then followed a
decreasing trend with the Cu content. The sintering temperature
also has an influence on the transverse rupture strength. However,
the strength changes little as the temperature increasing from
1250 to 1350 C. This means that Cu content have more influence
on the transverse rupture strength than sintering temperature.
The maximum transverse rupture strength value is achieved by
the sample containing 1.5 wt.% Cu and sintered at 1300 C.
In the WC–Fe–Cu hard alloys, Cu dissolved in Fe and formed
Fe–Cu alloy. The solid solution of WC in Fe–Cu alloy is lower as
compared with in Fe. After sintering, the WC concentration of
in Fe–Cu alloy is lower than in Fe. The low concentration of WC
in Fe–Cu alloy can improve the ductility of Fe–Cu binder phase
and thus the transverse rupture strength of the hard alloy is
enhanced [24]. A further factor improving the transverse rupture
strength is the samples with Cu exhibited a higher relative
density. It is well known that pores are the primary fracture
sources of the hard alloys which can cause the intense build-up
of the internal stress, and nucleate cracks during deformation
[25]. When Cu was added into the hard alloys, the relative
density increases, and less pores will result in higher strength.