The Mechanical Performance of In Situ Processed …
11
precipitates is observed in Ni-10Ti-10C, Ni-5Ti-10C, and Ni-5Ti-20C, respectively.
Calculated values are in line with the expected amount of titanium carbide formation
according to the nominal composition of the sample, indicating the in situ formation
and homogeneous dispersion of titanium carbide precipitates in the composites.
Microhardness Analysis
Vickers microhardness of pure nickel and Ni-Ti-C composites is shown in Fig. 4.
Pure nickel exhibited a microhardness value of around 150 HV, whereas Ni-10Ti10C composites exhibited the highest hardness value of approximately 475 HV. It
is primarily attributed to the homogeneous dispersion of a high-volume fraction of
nanoscopic in situ titanium carbide reinforcement within the nickel matrix, which is
also observed in the micrographs. From Fig. 4, it is apparent that the microhardness
of Ni-Ti-C composites decreases as carbon to titanium ratio increases, primarily due
to a reduction in the volume fraction of hard titanium carbide precipitates in the
composites. Also, a decrease in microhardness with increasing graphite agglomeration has been reported by a few researchers in the past [6, 7, 34, 35]. The Ni-Ti-C
composites exhibited higher microhardness values in comparison with pure nickel.
Also, the standard deviation represented in the error bar shows that the values were
consistent throughout, indicating the homogeneous dispersion of titanium carbide
and graphite precipitates in the nickel matrix, as seen from the micrographs. An
increased microhardness indicated an improvement in the mechanical and tribological performance of these composites. Dispersion strengthening, smaller grain sizes,
and grain boundary strengthening effects attributes to such improvements in the
properties [10, 16].
0
100
200
300
400
500
600
Pure Ni
Ni-10Ti-10C
Ni-5Ti-10C
Ni-5Ti-20C
Microhardness (HV 0.5)
Fig. 4 Vickers microhardness of pure nickel and Ni-Ti-C composites. (Color figure online)
11
precipitates is observed in Ni-10Ti-10C, Ni-5Ti-10C, and Ni-5Ti-20C, respectively.
Calculated values are in line with the expected amount of titanium carbide formation
according to the nominal composition of the sample, indicating the in situ formation
and homogeneous dispersion of titanium carbide precipitates in the composites.
Microhardness Analysis
Vickers microhardness of pure nickel and Ni-Ti-C composites is shown in Fig. 4.
Pure nickel exhibited a microhardness value of around 150 HV, whereas Ni-10Ti10C composites exhibited the highest hardness value of approximately 475 HV. It
is primarily attributed to the homogeneous dispersion of a high-volume fraction of
nanoscopic in situ titanium carbide reinforcement within the nickel matrix, which is
also observed in the micrographs. From Fig. 4, it is apparent that the microhardness
of Ni-Ti-C composites decreases as carbon to titanium ratio increases, primarily due
to a reduction in the volume fraction of hard titanium carbide precipitates in the
composites. Also, a decrease in microhardness with increasing graphite agglomeration has been reported by a few researchers in the past [6, 7, 34, 35]. The Ni-Ti-C
composites exhibited higher microhardness values in comparison with pure nickel.
Also, the standard deviation represented in the error bar shows that the values were
consistent throughout, indicating the homogeneous dispersion of titanium carbide
and graphite precipitates in the nickel matrix, as seen from the micrographs. An
increased microhardness indicated an improvement in the mechanical and tribological performance of these composites. Dispersion strengthening, smaller grain sizes,
and grain boundary strengthening effects attributes to such improvements in the
properties [10, 16].
0
100
200
300
400
500
600
Pure Ni
Ni-10Ti-10C
Ni-5Ti-10C
Ni-5Ti-20C
Microhardness (HV 0.5)
Fig. 4 Vickers microhardness of pure nickel and Ni-Ti-C composites. (Color figure online)