[CR4102] Tribology Assignment-118CR0129
Tribological study of a ternary carbide namely Ti3SiC2, a thermodynamically stable laminates, exhibits both Metallic and Ceramic features.
Here we discussed about the properties, structure, R-curve, fretting and tribological behavior of Ti3SiC2 by taking references from various frontline researchers.
1. TRIBOLOGICAL STUDY OF TI3SIC2
N A M E - B I S W A J I T K A L O
R O L L N O - 1 1 8 C R 0 1 2 9
C O U R S E : [ C R 4 1 0 2 ] T R I B O L O G Y O F M A T E R I A L S
C O U R S E M E N T O R : P R O F . D E B A S I S H S A R K A R
D E P A R T M E N T O F C E R A M I C E N G I N E E R I N G ,
N A T I O N A L I N S T I T U T E O F T E C H N O L O G Y , R O U R K E L A
2. INTRODUCTION
It’s documented that a serious limitation of ceramics for
various applications is the brittleness or poor fracture
toughness.
This has motivated researches to develop toughened
ceramics either by composite/laminate approach or by
engineering the composition/microstructure of ceramic
monoliths.
Recently, the research on ternary carbides like TI3SiC2 is
triggered by many researchers.
Ti3SiC2 is a Ternary Carbide and a thermodynamically
stable laminates, exhibits both Metallic and Ceramic
features.
3. PROPERTIES
High Young’s modulus (325GPa)
Relatively low hardness (4-5GPa)
High fracture toughness (~9MPa m1/2)
High thermal shock resistance.
Good Machinability with conventional tools.
Excellent resistance to oxidation up to 1400°c.
4. STRUCTURE
•Graphite like structure ; has a
hexagonal crystal structure.
•The Ti3SiC2 is a planar stacking
sequence along the c-axis, consisting
of double layers of Ti-C edge sharing
octahedra, sandwiched between
sheets of square planar coordinated Si
atoms.
•It may be thought of as a layered
structure with a c-axis repeat distance
of 1.762 nm and a stacking sequence
consisting of alternating double Ti–C
blocks and Si layers.
5. TRIBOLOGICAL STUDY
Three major mechanism contributing to the process of
friction and wear of Ti3SiC2
a) Abrasion
b) Tribochemical layer formation
c) Plastic deformation
6. Contd..
Table: The summary of the Friction and wear data obtained
with Ti3SiC2 under varying test condition
D.Sarkar
and B.Basu
7. Contd..
Myhra et al. Measured a low kinetic friction coefficeint of
0.002 at 25 nN lateral force for the basal planes of Ti3SiC2
, using the LFM (Lateral Force Microscopy).
They also reported a steady state COF of ~0.12 for a
polycrystalline Ti3SiC2 rubbed against a lightly peened
stainless steel sheet at 0.25-0.9 N load.
Barsoum measured a steady state COF of around 0.8 in
case of Ti3SiC2/Steel tribocouple under 5N load and
Observed that frictional response is independent of grain
size(5-100um).
Zhang et al. reported that the friction of self mated Ti3SiC2
tribocouple is ~1.16-1.43 and that of Ti3SiC2/Diamond is
arounf 0.1 under varying loads of 0.98-9.8N.
8. THE FRETTING WEAR OF Ti3SiC2
The fretting is defined as small amplitude linear relative
tangential sliding at normal constant load.
An experiment was done by Debasis Sarkar, B.V.
Manojkumar, Bikramjit Basu using a ball on disk type
tribometer and commercial bearing SAE 52100 grade
steel balls (Hardness 63-65HRc) of 8 mm in diameter.
The fretting wear administrated with varying loads (1-10
N) with constant testing duration , at constant frequency
(8 Hz) and constant displacement stroke (100 μm) at
room temperature.
10. Contd..
Result:
•The evolution of frictional
behaviour was strongly
dependent on normal load as
well as fretting cycles.
•The increase in COF was
due to severe abrasive action
with increase load.
•But a decrease in COF from
0.62 to 0.5 was recorded
when the load was increased
from 6 to 8N and COF remains constant at 10N due to the formation of
tribochemical reaction product and wear debris takes place to a large
extent. These debris particles are entrapped in between the tribocouple
and tends to roll during sliding motion, thereby decrease the friction.
11. R-CURVE
One among the characteristic material properties for
several of the high toughness ceramics is the enhanced
resistance to crack growth during crack extension , a
phenomena known as ‘R-curve’ behaviour.
The crack resistance curve of ternary carbides has been
characterized by only Compact Tension (CT) method
(ASTM standard E647).
Usually in ternary carbides, unlike other ceramics , it is
difficult to introduce initial flaws by any conventional
indentation bridge technique, because of lower hardness
and layered structure. Therefore single edge pre-crack
beam (SEPB) technique is been used to introduce
controlled crack.
12. Contd..
•The fracture mechanism and
characteristic R-curve of
Ti3SiC2 can be explained as
follows;
•Ti3SiC2 is characterized by
relatively weak bonding
between the silicon layer and
the TiC octahedra along the
basal plane.
•The dislocation movement is
restricted to two orthogonal
directions: basal plane and
walls or kink boundaries.
•The delamination along the weaker basal planes results in the creation of
microlaminae contained within a grain and consequently, the deformation
and distortion of such laminae provides a potent contribution to toughening.