The XRD analysis (Figure 2 ) explains the presence of
Cr3C2 [13, 15, 20, 27, 29], and
Cr7C3 in the micrometric powder. The
intensity of the peaks decreases, while they expand as a function of
milling time. The increase in the width of the XRD peaks with the
grinding time is attributed to the decrease in the carbide structure
that forms small grains. Moreover, the peaks of the
Cr3C2 persist after 12 hours of HEM,
indicating preservation of some extent of the crystalline structure. The
Cr7C3 content decreases with the HEM
time, which can be explained by the atom’s rearrangement due the high
strain energy. Furthermore, the Cr2O3peak emerges with the HEM time increase, which could be explained by the
increased amount of the Cr2O3 protective
film surrounding the increased amount of nanoparticle free surfaces, as
the particle’s diameter decrease. Ni XRD analysis was not performed
because the major concern was with carbide, as it is harder and has a
higher melting point, which makes it more difficult to deform when HEM
process is performed.