Presentation on Tribological study of WC-Co

1. Tribological study of WC-Co
Assignment by:
PANKAJ AGARWAL(118CR0124)
B. Tech. (8th semester)
Course instructor
Prof. Debashish Sarkar
NATIONAL INSTITUTE OF TECHNOLOGY ROURKELA
Department of Ceramic Engineering
CR-4102 : Tribology Of Materials

2. MOTIVATION
WC-CO are among the most critical engineering applications. Apart from wear-resistant
structural parts, they offer the majority of turning tools, milling cutters, and mining tools. This
hard metal is very successful in cutting cast iron, Al, Cu, Ni and Ti based alloy. Study of
tribology of this material can prove to be beneficial as these tools can be proved as a
replacement for costly cutting tools.

3. Contents
• Introduction
• Effect of Co content and grain size on abrasion resistance
• Effect of titanium carbide and tantalum carbide additions on
abrasion resistance
• Effect of grain size and hardness on flank wear rate
• Erosion of WC-Co as a function of Co(binder) content
• Comparison of conventional and micro grained cemented
carbides.
• Synthesis of WC-Co composites
• Functionally graded WC-Co
• Future scopes

4. INTRODUCTION
Tribology is a science and technology of interfacing surfaces in relative
motion. It is a system dependent property. Tribology is a broad term
that encompasses the ideas of friction, wear, and lubrication.
WC is most widely used industrial tool such as cutting tools
applications and rock drilling where high hardness, strength, and
excellent wear resistance will be required. Cobalt is generally used as
binder to prepare WC because of its good wettability in WC.
The major problem with WC-Co system is that the abrasion resistance
and fracture toughness of WC-Co are inversely related to each other

5. Effect of Co content and grain size on
abrasion resistance
The mechanical properties of WC-Co are principally
determined by the amount of Co and the size of the WC
grain. WC-Co has a higher abrasion resistance if Co
concentration is low and WC grains are finer.
The number of hard abrasive particles of a size capable of
directly contacting the binder regions grows as the mean
free path increases, and the effective hardness of the
binder decreases. Both of these factors contribute to
abrasive wear.

6. Effect of titanium carbide and tantalum carbide
additions on abrasion resistance
Tantalum carbide inhibits the grain growth that provides
improved abrasion resistance, within limits.
TaC also has the effect of enhancing deformation
resistance at high temperatures and lowering the
coefficient of friction between the tool and the work piece.
Although TiC reduces abrasion resistance, it is used in
steel cutting grades to improve cratering resistance.

7. Effect of grain size and hardness on
flank wear rate
Diffusion wear is a wear mechanism in which the tool form
is modified by atom diffusion into the work material, which
is equal to the chip material dissolving the tool surface.
overflowing
This type of wear is exceptionally severe with WC-Co hard
metals when cutting steels
Cutting speed is proportional to interface temperature, and
with carbide base cutting tools, diffusion wear is a primary
factor limiting cutting rates.

8. Erosion of WC-Co as a function of
Co(binder) content
Hard metal errosion research is important because these materials are employed in crucial
components such valves, dies, pump impellors, and cutting and drilling instruments.
Over a wide range of velocities, it was discovered that WC-Co cemented carbides with a low
binder exhibited greater erosion resistance to those with a high binder.

9. Effect of binder content and WC grain size on Vickers
hardness of WC-Co cemented carbides.
A comparison of conventional and micrograined cemented
carbides.

10. Synthesis of WC-Co composites

11. FUNCTIONALLY GRADED WC-Co
For specific engineering applications, composition gradient cemented carbide tools are
predicted to provide a variety of benefits.
Typically, cemented tungsten carbide is sintered in vacuum using a liquid phase sintering
technique. When WC-Co with an initial cobalt gradient is subjected to liquid phase sintering,
the liquid phase migrates quickly, eliminating any cobalt content gradient.
Pressure aided sintering techniques such as Hot Isostatic Pressing (HIP) and spark plasma
sintering can help solve this problem by consolidating the graded WC-Co compact at solid
state.

12. Processes for making functionally graded WC-Co
• Metal Melt Imbibition
process
• Processes based on
graded powder compact
• Denitriding processes
• DP carbide process
Direction of Co migration dependent on the gradients of liquid-Co volume, WC grain
size and C content in liquid Co phase.
The driving force of liquid phase migration is the liquid migration
pressure, and Co distribution during liquid phase sintering will fluctuate
until the liquid migration pressure is uniform throughout the specimen.

13. FUTURE SCOPES
The unique set of properties of fine grained WC-Co alloy draws attention of
many researchers. However many questions are still unanswered, for example
there is more work required in the field of manufacturing of functional graded
WC-Co to make this pocket friendly for industries. Also the effect of constraint,
composition, structure, and physical size on the flow stress of Co-W-C alloys
needs future evaluation.

14. THANK YOU
“CERAMICS ARE INCONSISTENT, FUNCTIONAL AND IMPERECT BUT
THESE ARE THE THINGS THAT MAKES LIFE BEAUTIFUL”