The document discusses various coating processes for cutting tools, emphasizing the differences between coated and uncoated carbide inserts in terms of tool life and surface roughness during metal cutting. It highlights the impact of cutting speed, feed rate, and depth of cut on these factors, showcasing that coated tools generally outperform uncoated ones. The study also details the experimental setup, techniques, and significant findings related to tool performance and surface quality.

1. Coated and Uncoated
inserts

2. Thumbnail
■
Foreword
■
Coating Processes
■
Physical Vapour Deposition(PVD)
■
Chemical Vapour Deposition(CVD)
■
Chemical and Electrochemical Techniques
■
Spraying
■
Experimental Techniques
■
Experimental Data
■
Tool Life
■
Surface Roughness
■
Denouement

3. Foreword
■ Tool wear is one of the most important aspects in metal cutting, especially
when machining hardened steels.
■ The effect of cutting speed and feed rate on tool wear (tool life) and surface
roughness of the TiN coated carbide inserts was experimented.
■ The tool life is influenced principally by the depth of cut and on the other
hand, both feed rate and workpiece hardness have statistical significance on
surface roughness.

4. Coating Processes
A coating is a integument that is applied to the surface of an object,
usually referred to as substrate. The purpose of administer the coating
may be decorative, functional or both.
Categorizing of Coating Processes:
1. Vapour Deposition
a. Physical Vapour Deposition(PVD)
b. Chemical Vapour Deposition(CVD)
2. Chemical and Electro-Chemical Techniques
3. Spraying

5. Physical Vapour Deposition(PVD)
■
The PVD coating processes are evaporation and sputtering. All of these
processes occur in vacuum pressure and generally involve bombardment of
the substrate to be coated with energetic positively charged ions during the
coating process to promote high density
■
PVD process is the range of suitable materials for coating, relatively low-
operating temperatures, around 450° C, allowing for coating of sharp cutting
edges.
■
The Coefficient of Friction of our coatings is significantly lower than un-coated
tool substrates.

6. Chemical Vapour Deposition(CVD)
■ CVD is an atmosphere controlled process conducted at elevated
temperatures (~1925° F) in a CVD reactor.
■ During this process, thin-film coatings are formed as the result of reactions
between various gaseous phases and the heated surface of substrates within
the CVD reactor.
TiN is formed as a result TiCl4 + N2 + H2 1000° C → TiN + 4 HCl + H2.
■
In high stress metal-forming applications, where the tool's tolerances and
substrate permit, high temperature CVD coating processes will perform better
than "cold" processes like PVD.

7. Chemical and Electrochemical Depositions
■ Electrochemical deposition is a versatile technique by which a thin desired
metallic coating can be obtained on to the surface of another metal by
simple electrolysis of an aqueous solution containing the desired metal ion.
■ In the electrochemical method, reduction takes place by supplying current
externally and the sites for the anodic and cathodic reactions are separate.
■ For the chemical deposition method, electrons required for the reduction
are supplied by a reducing agent and the anodic/cathodic reactions are on
the inseparable workpiece.

8. Thermal Spray Deposition
■ The processes in which metallic and some materials in the form of powder,
wire, or rod are fed to a torch or gun with which they are heated to near or
somewhat above their melting point.
■ Molten droplets of material are accelerated in a gas stream and projected
against the surface to be coated (i.e., the substrate).
■ The droplets flow into thin lamellar particles adhering to the surface,
overlapping and interlocking as they solidify.

9. Experimental Details
Workpiece:
The workpiece used in this study was
thoroughly hardened AISI 4140 steel, which
typically has a chemical composition of;
- 0.4% Carbon,
- 1.85% Nickel,

10. Experimental Details(Cont.)
Cutting Inserts
The inserts used were 432, 55o
Diamond With chip breaker coated
carbide inserts and 431 uncoated
inserts. The inserts were rigidly
mounted on a tool holder with an ISO
designation.

11. Experimental Details(Cont.)
Experimental Techniques
■
Cutting tests were carried out on a CNC flexturn or flexmill under dry
conditions. The turning experiments were carried out at different cutting
speeds.
■
The coated and uncoated carbide tools performance were on both tool life
and surface finish

12. Experimental Data
The coated carbide tool and the uncoated carbide tool will be tested at following;
Cutting speed (v) : 120, 160 m/min
Spindle speed : 1200, 1600 RPM
Feed (f) : 0.01, 0.05 & 0.1 mm/rev
Depth of cuts (d) : 0.5, 1 & 1.5 mm

13. Tool life
Tool life generally indicates, the amount of satisfactory performance
or service rendered by a fresh tool or a cutting point till it is declared
failed.
Taylor’s tool life equation
Tool life of any tool for any work
material is governed mainly by
the level of the machining
Parameters I.e., cutting velocity, (VC),
feed, (SO) and depth of cut (t).
cutting velocity affects maximum
and depth of cut minimum.

14. Tool life(Cont.)
Taylor derived the simple equation as VTn=C
where, n is called, Taylor’s tool life exponent. The values of both ‘n’ and ‘c’
depend mainly upon the tool-work materials and the cutting environment
Modified Taylor’s Tool Life equation
practically, the variation in feed (so) and depth of cut (t) also play role on tool life
to some extent.
TL = tool life in min
CT = a constant depending mainly upon the tool – work materials
x, y and z exponents so called tool life exponents depending upon the tool –⎯
work materials and the machining environment.

15. Surface Roughness
■ Surface roughness plays an important role as it influences the fatigue
strength, wear rate, coefficient of friction, and corrosion resistance of the
machined components.
■ Surface roughness increases with increasing the feed rate but decreased
with increasing the cutting speed and the depth of cut, respectively.
■ There are various simple surface roughness amplitude parameters used in
industries, such as roughness average (Ra), root-mean-square (rms)
roughness (Rq), and maximum peak-to-valley roughness (Ry or Rmax), etc.

16. Surface Roughness(Cont.)
The parameter Ra was used in this study. The average roughness (Ra) is the
area between the roughness profile and its mean line, or the integral of the
absolute value of the roughness profile height over the evaluation length
Therefore, the Ra is specified by the following equation;
where Ra is the arithmetic average
deviation from the mean line, L is
the sampling length and Y the
ordinate of the profile curve.

17. Denouement
■ Coated carbide tools perform better than uncoated carbide tools as far as
tool life is concerned. Tool life obtained with coated carbide tool was higher
than those obtained with uncoated carbide tools under experimental
conditions.
■ The forces over coated inserts are less than the uncoated inserts which
results in less amount of stress over coated inserts than uncoated inserts.
■ The feed rate has highest influence on surface roughness, cutting speed
and followed by depth of cut. The surface finish was improved as cutting
speed was increased and deteriorated with feed rate.

18. Advertence
1. Comparative performance of coated and uncoated inserts during
intermittent cut milling of AISI 4340 steel - Journal of Engineering Science
and Technology Vol. 10, No. 5 (2015) 606 - 616 School of Engineering,
Taylor’s University
2. Evalution of Surface Finish on Machining Of Mild Steel Using High Speed
Steel Tool in Lathe with Normal Coolant (Or) Nano Material Added Coolant -
IOSR Journal of Mechanical and Civil Engineering (IOSR-JMCE) e-ISSN: 2278-
1684,p-ISSN: 2320-334X, Volume 11, Issue 3 Ver. V (May- Jun. 2014), PP
01-09
3. Performance evaluation of tin coated carbide insert for optimum surface
roughness in turning of AISI 1045 steel - International Journal of Research in
Engineering and Technology eISSN: 2319-1163 pISSN: 2321-7308

19. Q&A

20. Thank you