Process of Strengthening Titanium
Aluminum Carbide
The common problems that arise
during processing of these ternary carbides are inadequate densification and
presence of impurities. To improve the density and purity of the max phases,
now a day’s many methods have come which incorporate the use of external
pressure during sintering of the powder particles.
There are various process that are commonly employed for ceramic production.
Few of them are mentioned below:
Hot Pressing Method - Powder is placed in a graphite die inside a vacuum chamber, and
simultaneously uniaxial pressure, and high temperature either by direct heating
or induction heating, are used to compact and sinter the powder at once
Advantages of hot pressing method:
High sintering density, high bonding strength, compaction and
sintering steps are combined, production rate less than 15 minutes, low
pressure (around 20-30Mpa)
Limitations of hot pressing method:
High temperatures (around 14000C) are involved,
expensive, uneven heating that can result in development of thermal stresses
Spark Plasma Sintering - This is a modification of hot pressing (HP) process in that pulsed
DC electric field is used to heat the powder particles rather than direct
heating or induction heating in the hot pressing process.
The advantages of SPS process:
Fast sintering, uniform sintering, low grain growth, compaction
and sintering stages are combined, Better purification, low pressure
Limitations of SPS process:
Only simple symmetrical shapes can be prepared, Expensive.
There various
techniques that are used to strengthen the tertiary carbide ceramic, couple of
them are mentioned below
Multiphase strengthening
Along with the efforts to synthesize these carbides, many
researchers have attempted to reinforce these compounds with other ceramic
materials to improve its high temperature mechanical properties have been
reported. Among reinforcing ceramic materials, Aluminum Oxide has been
chosen frequently to enhance the properties due to the high hardness, modulus
and excellent chemical stability of Aluminum Oxide.
Solid solution strengthening
Solid
solution is another method to strengthen carbides by substituting Titanium
with Vanadium to form their relative compounds [Meng, F.L.,
Y.C. Zhou, and J.Y. Wang, Strengthening of Ti2AlC by substituting Ti with V.
Scripta Materialia, 2005. 53(12): p. 1369-1372.]. The properties
are improved by strengthening the chemical bonds and electronic structure
using the above mentioned elements. Solid solution is one of the effective
methods to adjust the bonds and structure.
Hydraulic pilot valve
The objective of this project is to develop a small micro solenoid pilot valve of a 1 inch in length and 1/4 inch is diameter that would have be 3 Way and 2-position valve to prevent contamination and leak. There were 5 design that broached into suffice the criterion.
The above image shows a cross sectional view of one of the designs that fitted the requirements. The current design handles the leak rate excellently with the usage of O-ring for dynamic sealing whereas elastomer on the edges for static sealing.
FEM was sued for the evaluation of the critical region that may yield on application of 5 kpsi. The image below gives one the regions that is a high stress region, but are still under the yield stress.
