The present study focused on the
development of NiMoAl-based self-lubricating
composites using solid lubricants as the second phase by powder metallurgy.
For this, Cr2AlC MAX phase, Cr2AlC–Ag,
and MoS2 powders were mixed with the NiMoAl-based matrix
and subsequently hot pressed to produce bulk composite samples. The
average hardness and wear resistance of the matrix were found to be
increased with the addition of MoS2, Cr2AlC
MAX phase, and Cr2AlC–Ag powder to the NiMoAl matrix.
The addition of Cr2AlC to NiMoAl was more effective in
improving the wear resistance than MoS2. The addition of
Cr2AlC and Cr2AlC–Ag has increased the
hardness by about 75% than that with the addition of NiMoAl alloy.
A scanning Kelvin probe system was used to study the surface properties
of the tribofilm in detail through work function mapping from the
edge area to the wear area (groove). Among all the samples, the one
with the addition of Cr2AlC–Ag powder to the NiMoAl
matrix possesses the best tribo-mechanical properties. Cr2AlC–Ag composite addition to NiMoAl was found to decrease
the wear rate by one-third and to reduce the coefficient of friction
by one-fourth, compared to the base NiMoAl alloy. This was attributed
to the high-sintered density and formation of strong tribofilms consisting
of mixed oxides such as Ag2MoO4 and Al2O3, as confirmed by micro Raman spectra.