Selection of Materials for Cutting Tools

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SELECTION OF MATERIALS FOR CUTTING TOOLS

CUBIC BORON NITRIDE &

POLY CRYSTALLINE DIAMOND

PREPARED BY

N.KARTHICK

2009606001

¼ M.E.MANUFACTURING ENGG

ANNA UNIVERSITY MIT



INTRODUCTIONCUBIC BORON NITRIDE

Second hardest material

In 1957, by R.H.Wentorf Jr. of the General Electric

Company, USA Artificially manufactured

Cost-effective rapid stock removal

Finishing of hardened steels & Certain softer

ferrous materials

Replaces Al2O3 wheels



PROPERTIES Generally yellow, orange

Crystal system Cubic

Hardness ~ 4500 HK

KHN = F/A = P/CL2

(C = 0.07028 = Constant of indenter )

Specific heat [J/(mol K)]

12.55 at 300 K

25.1 at 600 K Melting point at triple point

~ 3500 K



APPLICATIONS

Typically they are used for hard ferrous materials

(RC 45 or harder) that are difficult to machine with

carbide or ceramic or that require time consuming

grinding operations.

Automotive engine blocks - Cylinder Boring

Brake rotors - O.D. Facing and Chamfer

Transmission gears - I.D. Boring

Steel mill rolls - O.D. Turning

Cylinder head - Milling



ADVANTAGES

ROUGHING :

Efficient machining of pearlitic gray cast iron

Turning hard facing alloys

Machining of powder metal alloys Turning of superalloys

FINISHING :

High speed finish machining of hardened steel

(>45 RC)

Suitable for continuous machining of

hardened steels

Replace grinding operations.



SOME APPLICATIONS

Turning with CBNMachining Case Hardened SteelGear



Rough and semi-finish turning,milling, Grooving and boring

Machining White Iron Roll withCBN



SPLINTER SIZE

OF THREE REPRESENTATIVE CBN GRADESAT HEATED AND UNHEATED CONDITIONS



POLY-CRYSTALLINE DIAMONDS

Diamond is the hardest, most abrasive-

resistant which makes diamond an ideal

cutting tool

Polycrystalline Diamond blanks producedunder conditions of high pressure (1 million

PSI) and temperature (1700 Degrees C),

similar to those of diamond synthesis



THREE MAIN REASONS FOR USING PCD TOOLS:-

Increased tool life results in reduced tool cost

per component and less idle machine time.

Increasing cutting speed improves productivity

through reduced cycle times.

Grinding and other less productive machining

methods can be replaced by PCD milling andturning.



POLY CRYSTALLINE DIAMONDS EXIST BOTH IN

NATURE AND ARTIFICIAL.

NATURAL PCD Carbonado, commonly known as the "Black

Diamond", is a natural polycrystalline diamondfound in alluvial deposits in the Central African

Republic and Brazil. Its natural colour is blackor dark grey, and it is more porous than otherdiamonds

ARTIFICIAL PCD

In 1976, the Baker Hughes Inc. companyintroduced bits with synthetic diamond cutterscalled polycrystalline diamond compact (PDC)bits.



PROPERTIES OF PCD

Vickers Micro hardness 25.0 - 98.0 Gpa

Modulus of Elasticity 749 953 Gpa

Poissons Ratio 0.0700 - 0.200

Density 3.00 - 4.00 g/cc

Colour - Clear

Crystal Structure - Cubic



APPLICATIONS

Can be inserted into PCD cutting tools, PCD drilling

bits/core bits, PCD wire drawing dies, reamers andother wear resistant components.

Well suited to high speed cutting of aluminium,particularly when good surface finishes are

mandatory. Recommended for cutting high content silicon

aluminium alloys.

Used on brass, copper, carbide and bronze in

applications including turning, boring, profiling,grooving, milling and hole making.

Used for oil field drilling and coal mining.



MANUFACTURING DIFFERENT SHAPES

OF PCD



ADVANTAGES

The results obtained in drilling medium to hard rocks andnon uniform abrasive formations are much better thanthose obtained with drill bits impregnated or surface-setwith single natural diamond crystals.

A factor that improves the toughness of poly-crystallinediamond is the presence of cobalt in the microstructurealong with the random orientation of the diamondparticles.

The tungsten carbide substrate also provides mechanicalsupport for the diamond abrasive layer, increasing impactresistance and making it easier for braze attachment intool fabrication.



Another benefit of poly-crystalline diamond bits is the

range of diamond grades available to fit any nonferrousapplication.

Typically, fine-grain diamond is used for less abrasive

applications requiring an excellent surface finish.Medium-grain diamond is considered a general-

purpose machining grade. Coarse-grain diamond is

used in rough machining and in extremely abrasive

materials where surface finish may not be as important.

It also excels in machining highly abrasive work pieces.



DISADVANTAGES

Because of a chemical interaction

between diamond and iron, poly-crystalline

diamond bits are not typically used to cut

ferrous materials. However, diamond bits canbe used to tackle bimetal applications

involving aluminium and cast iron.



PHYSICAL PROPERTIES OF SOME PCD PRODUCTS



COMPARISONS OF SOME CBN PRODUCTS



REFERENCES

http://www.springerlink.com/content/x584423376016731/f

ulltext.pdf

http://www.cutting-

tool.americanmachinist.com/guiEdits/Content/bdeee15/bde

ee15_1.aspx



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Selection of Materials for Cutting Tools