The abrasive wear behaviour of commercially available
Fe-Cr-C hardfacing alloys, a hypereutectic type (A1) and a
hypoeutectic type (A2), that are commonly used in the sugar
industry has been studied. Although there was significant difference
in their hardnesses, there was no clear superiority in
wear resistance under the conditions examined. The mass loss
of the hardfacings increased linearly with sliding distance in
both dry and slurry conditions. However, the wear rate was not
always directly proportional to load; the hypereutectic coating
(A1) exhibited a transition from low to high wear coefficientwhen the higher loads were applied, which was due to severe
fracturing of the primary carbides.
The abrasion resistance of the hardfacings is determined
primarily by the microstructure. On the one hand, the hypoeutectic
material attained its wear resistance through the dispersion
of the carbides within the matrix and its capacity to undergo
strain hardening, with subsequent enhancement in its resistance
to microploughing and microcutting. On the other hand, the
hypereutectic resisted wear by virtue of its primary and eutectic
carbides. However, the electrode coating was too enriched with
carbon and chromium, producing a weld with excess carbide
volume that eventually reduced wear resistance.
The contribution of corrosion to the wear of the hypereutectic
coating was significant at low load but of less importance at the
higher loads with the onset of severe fracturing of the carbides.
The abrasive wear mechanisms were found to be predominantly
microcracking and microploughing in A1 and A2,
respectively. Both coatings also exhibited microcutting. The
M7C3 carbides in A1 provided an effective barrier to ploughing
and cutting of the abrasive particles but under stress the carbides
were extensively fractured, and spallation occurred after
repeated rotations of the disc. In contrast, A2 underwent plastic
deformation creating long furrows in the matrix.