selection of materials for cutting tools
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8/9/2019 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
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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
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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
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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
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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.
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SOME APPLICATIONS
Turning with CBNMachining Case Hardened SteelGear
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Rough and semi-finish turning,milling, Grooving and boring
Machining White Iron Roll withCBN
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SPLINTER SIZE
OF THREE REPRESENTATIVE CBN GRADESAT HEATED AND UNHEATED CONDITIONS
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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
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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.
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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.
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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
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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.
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MANUFACTURING DIFFERENT SHAPES
OF PCD
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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.
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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.
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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.
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PHYSICAL PROPERTIES OF SOME PCD PRODUCTS
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COMPARISONS OF SOME CBN PRODUCTS
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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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