Role of Microstructure on the Potential of MAX and MAB Phases …
23
role in these composites. More particularly, they act as an anti-friction coating which
protects the underlying substrate from wear. It is vital to note that 15 weight %
Ti 3 SiC 2 in TiAl matrix can form anti-friction coating.
Sun and co-workers [69] designed Ti 2 AlN/TiAl composite by incorporating 30%
Ti 2 AlN in TiAl matrix by pressure casting. During sliding against GCr15 bearing
steel, they observed that the wear was negligible on the Ti 2 AlN/TiAl surface as
compared to oxidation wear on GCr15 surface under mild conditions of 0.5 m/s
and 1 N load. Deng and co-workers [70] observed low wear rates (1.78–3.14 ×
10
−6 mm
3 N
−1 m
−1 ) at 25–450 °C in M-50 steel matrix reinforced with 10 wt%
Ti 3 SiC 2 during sliding against Si 3 N 4 . This group also reported that the formation of
O-rich tribofilm was responsible for this behavior. Yu and co-workers [76] fabricated
composites of Ti 2 AlC and AZ91D magnesium alloy by stir casting technology. They
observed optimized strength at 10 vol% Ti 2 AlC (Fig. 2a). They did not observe any
interfacial reaction between Ti 2 AlC and AZ91D. This group also showed that Hall–
Petch strengthening and Forest strengthening are the main mechanism of strengthening in these composites. The group did not observe Orowan strengthening in these
micro-composites due to the coarse particle size and wider distance between particles.
A detailed review of type-I composites showed that they have the strong technological readiness level to be potential commercialized in tribology-based demanding
applications. These types of composites are especially important as low dosage of
MAX phases are used to reinforce the composites which can potentially lower the
cost of these composites. A detailed cost-analysis study vis-à-vis current state of
the art is highly recommended. In addition, more fundamental studies are needed
where the particle size of these phases is further tailored, for example, design and
manufacturing of nanocomposites is recommended. In the later part of this paper, I
will report a methodology by using which we engineer the surface morphology of
these particles by etching.
Type-I Composites with Complete Decomposition of MAX Phases
in Metal Matrix
Hu and co-workers [64] used reaction between Ti 3 AlC 2 and Ni to design TiC x -
Ni 3 (Al,Ti)/Ni alloy composite. They observed 50%, 50%, and 70% enhancement in
hardness, flexural strength, and fracture toughness, respectively, after the addition of
20 vol% Ti 3 AlC 2 as compared to Ni-alloy. More particularly, this composition had
a hardness and fracture toughness of 9.26 ± 0.17 GPa and 13.87 ± 0.32 MPa M
1/2 ,
respectively. This group also presented evidence that in situ precipitated TiC x can be
effective additives for deflective and bridging cracks.
Wang and co-workers [65] also designed in situ TiC x reinforced Ni (Si, Ti) alloy
composites by reacting Ti 3 SiC 2 (10 and 20 vol%) with Ni. These composites showed
enhanced mechanical properties, for example, 20.6 vol% TiC x –Ni(Si, Ti) had the
yield stress and ultimate compressive strength (UCS) of 466.8 ± 55.8 MPa and 733.3
± 78.4 MPa, respectively. These composites showed similar yield strength as NiTi 3 SiC 2 composite designed by Dey et al. [63] although the UCS of these composites
23
role in these composites. More particularly, they act as an anti-friction coating which
protects the underlying substrate from wear. It is vital to note that 15 weight %
Ti 3 SiC 2 in TiAl matrix can form anti-friction coating.
Sun and co-workers [69] designed Ti 2 AlN/TiAl composite by incorporating 30%
Ti 2 AlN in TiAl matrix by pressure casting. During sliding against GCr15 bearing
steel, they observed that the wear was negligible on the Ti 2 AlN/TiAl surface as
compared to oxidation wear on GCr15 surface under mild conditions of 0.5 m/s
and 1 N load. Deng and co-workers [70] observed low wear rates (1.78–3.14 ×
10
−6 mm
3 N
−1 m
−1 ) at 25–450 °C in M-50 steel matrix reinforced with 10 wt%
Ti 3 SiC 2 during sliding against Si 3 N 4 . This group also reported that the formation of
O-rich tribofilm was responsible for this behavior. Yu and co-workers [76] fabricated
composites of Ti 2 AlC and AZ91D magnesium alloy by stir casting technology. They
observed optimized strength at 10 vol% Ti 2 AlC (Fig. 2a). They did not observe any
interfacial reaction between Ti 2 AlC and AZ91D. This group also showed that Hall–
Petch strengthening and Forest strengthening are the main mechanism of strengthening in these composites. The group did not observe Orowan strengthening in these
micro-composites due to the coarse particle size and wider distance between particles.
A detailed review of type-I composites showed that they have the strong technological readiness level to be potential commercialized in tribology-based demanding
applications. These types of composites are especially important as low dosage of
MAX phases are used to reinforce the composites which can potentially lower the
cost of these composites. A detailed cost-analysis study vis-à-vis current state of
the art is highly recommended. In addition, more fundamental studies are needed
where the particle size of these phases is further tailored, for example, design and
manufacturing of nanocomposites is recommended. In the later part of this paper, I
will report a methodology by using which we engineer the surface morphology of
these particles by etching.
Type-I Composites with Complete Decomposition of MAX Phases
in Metal Matrix
Hu and co-workers [64] used reaction between Ti 3 AlC 2 and Ni to design TiC x -
Ni 3 (Al,Ti)/Ni alloy composite. They observed 50%, 50%, and 70% enhancement in
hardness, flexural strength, and fracture toughness, respectively, after the addition of
20 vol% Ti 3 AlC 2 as compared to Ni-alloy. More particularly, this composition had
a hardness and fracture toughness of 9.26 ± 0.17 GPa and 13.87 ± 0.32 MPa M
1/2 ,
respectively. This group also presented evidence that in situ precipitated TiC x can be
effective additives for deflective and bridging cracks.
Wang and co-workers [65] also designed in situ TiC x reinforced Ni (Si, Ti) alloy
composites by reacting Ti 3 SiC 2 (10 and 20 vol%) with Ni. These composites showed
enhanced mechanical properties, for example, 20.6 vol% TiC x –Ni(Si, Ti) had the
yield stress and ultimate compressive strength (UCS) of 466.8 ± 55.8 MPa and 733.3
± 78.4 MPa, respectively. These composites showed similar yield strength as NiTi 3 SiC 2 composite designed by Dey et al. [63] although the UCS of these composites