6
A. Patil et al.
of the composite as smaller grain size acts as a pinning point and hinders the dislocation movement [21]. Thus, the nanosized grain refinement of material improves
the mechanical properties such as strength and hardness of the composite material,
while retaining ductility of the base metal matrix.
Spark plasma sintering (SPS) is a rapid heating consolidation technique suitable
to sinter metal, alloys, and composite material at shorter holding time and relatively
low sintering temperatures below their melting point compared to the conventional
techniques. The ability to reach high processing temperature in a short duration of
time due to a high heating rate, the SPS process retards the grain growth retaining
refined microstructure and increases the microhardness and other mechanical properties of the composites [22, 23]. In the SPS process, the microstructure of the material can be controlled by changing the processing parameters such as applied load,
heating rate, holding time, and processing temperature [25]. The SPS technique
possesses numerous other advantages. Primarily, in SPS, sintering takes place in
shorter duration, thus, restraining grain growth and avoiding undesired phase transformation during processing, which makes the SPS process preferable over other
conventional techniques of sintering and help in achieving improved characteristic
properties [24, 25]. Also, previous research work has demonstrated that a wide variety
of both conducting and non-conducting materials such as metals, ceramics, and nonmetallic materials can be processed using the SPS technique [26–29]. Previously,
several researches are conducted to investigate the formation, stability, and strengthening effects of titanium carbide reinforcement as well as CNT as a reinforcing agent
and its effects on the mechanical properties of the metal matrix composites [30–32].
Results indicated improved microhardness and enhanced mechanical properties. In
the present research, efforts have been made to sinter in situ Ni-Ti-C composites using
MA followed by SPS at relatively low temperature with varying the carbon to titanium
ratio to alter the formation and distribution of titanium carbide and graphite phases
within the nickel matrix and to study its effect on phase formation, microstructure,
microhardness, mechanical properties, and tribological behavior of these composites.
The Ni-Ti-C composites are characterized to understand the tribological behavior and
to study the effect of the presence of the graphite phase along with hard titanium
carbide precipitates on the wear behavior under friction. To better understand the
wear mechanism and investigate the formation of the tribological layer and wear
debris, the wear tracks were analyzed using scanning electron microscope.
Experiment Methods
Materials
Elemental powder of Nickel (3–7 µm), Titanium (−325 mesh), and Graphite (−325
mesh) was used as a precursor. The powder was mixed in several different batches
with varying atomic weight percentages of the nickel, titanium, and carbon and milled
A. Patil et al.
of the composite as smaller grain size acts as a pinning point and hinders the dislocation movement [21]. Thus, the nanosized grain refinement of material improves
the mechanical properties such as strength and hardness of the composite material,
while retaining ductility of the base metal matrix.
Spark plasma sintering (SPS) is a rapid heating consolidation technique suitable
to sinter metal, alloys, and composite material at shorter holding time and relatively
low sintering temperatures below their melting point compared to the conventional
techniques. The ability to reach high processing temperature in a short duration of
time due to a high heating rate, the SPS process retards the grain growth retaining
refined microstructure and increases the microhardness and other mechanical properties of the composites [22, 23]. In the SPS process, the microstructure of the material can be controlled by changing the processing parameters such as applied load,
heating rate, holding time, and processing temperature [25]. The SPS technique
possesses numerous other advantages. Primarily, in SPS, sintering takes place in
shorter duration, thus, restraining grain growth and avoiding undesired phase transformation during processing, which makes the SPS process preferable over other
conventional techniques of sintering and help in achieving improved characteristic
properties [24, 25]. Also, previous research work has demonstrated that a wide variety
of both conducting and non-conducting materials such as metals, ceramics, and nonmetallic materials can be processed using the SPS technique [26–29]. Previously,
several researches are conducted to investigate the formation, stability, and strengthening effects of titanium carbide reinforcement as well as CNT as a reinforcing agent
and its effects on the mechanical properties of the metal matrix composites [30–32].
Results indicated improved microhardness and enhanced mechanical properties. In
the present research, efforts have been made to sinter in situ Ni-Ti-C composites using
MA followed by SPS at relatively low temperature with varying the carbon to titanium
ratio to alter the formation and distribution of titanium carbide and graphite phases
within the nickel matrix and to study its effect on phase formation, microstructure,
microhardness, mechanical properties, and tribological behavior of these composites.
The Ni-Ti-C composites are characterized to understand the tribological behavior and
to study the effect of the presence of the graphite phase along with hard titanium
carbide precipitates on the wear behavior under friction. To better understand the
wear mechanism and investigate the formation of the tribological layer and wear
debris, the wear tracks were analyzed using scanning electron microscope.
Experiment Methods
Materials
Elemental powder of Nickel (3–7 µm), Titanium (−325 mesh), and Graphite (−325
mesh) was used as a precursor. The powder was mixed in several different batches
with varying atomic weight percentages of the nickel, titanium, and carbon and milled