24
S. Gupta
were higher. By comparing the both results, we can reason that the decomposition
of Ti 3 SiC 2 can cause the formation of reaction products which can strengthen the
matrix although the property addition like machinability which is inherent to MAX
phase will be compromised during the process due to formation of binary carbides.
These types of composites present a novel design tool for manufacturing engineers
as we do not have to worry about preventing reaction between MAX phases and
metal matrix, thus offering a wider temperature range and flexibility in designing
these composites.
Type-I Composites of MAX Phases in Ceramics Matrix
Qi and co-workers [80] designed Al 2 O 3 matrix by reinforcing it with Ti and SiC
particulates which produced in situ phases like Ti 3 SiC 2 , TiC, Ti 5 Si 3 by reaction
process. These composites showed enhanced flexural strength and toughness as the
presence of these phases restricted grain growth and movement of grain boundaries
which resulted in finer and uniform grain size.
By analyzing these results, we can summarize that MAX phase can be successful
reinforcing agent in different types of matrices. In addition, MAX phases can also
undergo decomposition to form carbides during manufacturing with metals, and
these carbides can also act as reinforcement. Detailed machinability studies of these
different types of composites are needed for better comparative analysis.
Use of Metallic Phase as a Binder for Fabricating Cemented
MAX-Based Composites with 3-0 Connectivity (Type-II
Composites)
In these composites, the role of the metal is to bond the MAX phase particles by
percolating the metallic structure around MAX phase particulates by liquid phase
sintering, hot-pressing, or related processes (Fig. 1b). Gupta and co-workers [55, 56]
have manufactured Cr 2 AlC/Ag and Ta 2 AlC/Ag composites by using 20 vol% Ag
as a bonding phase to sinter Cr 2 AlC and Ta 2 AlC particles. These materials showed
good promise as solid lubricant material due to formation of oxidized tribofilms.
The authors also reported the successful testing of these composites in a foil bearing
rig [55, 56]. For example, composite of Cr 2 AlC and Ag were tested against Inconelbased superalloys for a cumulative cycle time of 5000 cycles in the temperature range
of RT to 550 °C. The surface of these composites was micro-smooth which further
indicates the self-lubricating nature of these composites [55]. Figure 3 shows the
pictures of rig used during foil bearing tests [56]. More studies are needed in these
composites to understand the property envelop of these composites. These industrial
tests further strengthen the case for large scale manufacturing and commercialization
of MAX phase-based composites.
S. Gupta
were higher. By comparing the both results, we can reason that the decomposition
of Ti 3 SiC 2 can cause the formation of reaction products which can strengthen the
matrix although the property addition like machinability which is inherent to MAX
phase will be compromised during the process due to formation of binary carbides.
These types of composites present a novel design tool for manufacturing engineers
as we do not have to worry about preventing reaction between MAX phases and
metal matrix, thus offering a wider temperature range and flexibility in designing
these composites.
Type-I Composites of MAX Phases in Ceramics Matrix
Qi and co-workers [80] designed Al 2 O 3 matrix by reinforcing it with Ti and SiC
particulates which produced in situ phases like Ti 3 SiC 2 , TiC, Ti 5 Si 3 by reaction
process. These composites showed enhanced flexural strength and toughness as the
presence of these phases restricted grain growth and movement of grain boundaries
which resulted in finer and uniform grain size.
By analyzing these results, we can summarize that MAX phase can be successful
reinforcing agent in different types of matrices. In addition, MAX phases can also
undergo decomposition to form carbides during manufacturing with metals, and
these carbides can also act as reinforcement. Detailed machinability studies of these
different types of composites are needed for better comparative analysis.
Use of Metallic Phase as a Binder for Fabricating Cemented
MAX-Based Composites with 3-0 Connectivity (Type-II
Composites)
In these composites, the role of the metal is to bond the MAX phase particles by
percolating the metallic structure around MAX phase particulates by liquid phase
sintering, hot-pressing, or related processes (Fig. 1b). Gupta and co-workers [55, 56]
have manufactured Cr 2 AlC/Ag and Ta 2 AlC/Ag composites by using 20 vol% Ag
as a bonding phase to sinter Cr 2 AlC and Ta 2 AlC particles. These materials showed
good promise as solid lubricant material due to formation of oxidized tribofilms.
The authors also reported the successful testing of these composites in a foil bearing
rig [55, 56]. For example, composite of Cr 2 AlC and Ag were tested against Inconelbased superalloys for a cumulative cycle time of 5000 cycles in the temperature range
of RT to 550 °C. The surface of these composites was micro-smooth which further
indicates the self-lubricating nature of these composites [55]. Figure 3 shows the
pictures of rig used during foil bearing tests [56]. More studies are needed in these
composites to understand the property envelop of these composites. These industrial
tests further strengthen the case for large scale manufacturing and commercialization
of MAX phase-based composites.