Comparative Study of Cutting Tool Materials

1. CUTTING TOOL MATERIAL
MANUFACTURING TECHNOLOGY

2. PROPERTIES OF CUTTING TOOL MATERIAL
 Performance of a cutting tool material in a given machining
application is mainly determined by three important properties:
 WEAR RESISTANCE: Wear Hardness is necessary to enable the
cutting tool to retain its shape and cutting efficiency.
 HOT HARDNESS: Hot Hardness is necessary to enable the cutting
 HOT HARDNESS: Hot Hardness is necessary to enable the cutting
tool to retain its cutting ability and hardness at the high
temperatures developed at the TOOL – CHIP interface.
 TOUGHNESS: Toughness is necessary to enable the TOOL to
withstand the forces, to absorb shocks associated with interrupted
cuts and to prevent the chipping of the fine cutting edge.
Whereas HIGH – SPEED steel starts to rapidly lose its hardness at temperature above
540°C, CARBIDES, CERAMICS and DIAMOND retain their hardness at very high
temperatures.

3. COMMON CUTTING TOOL MATERIAL
 CARBON TOOL STEEL
 HIGH SPEED STEELS
 CAST COBALT BASE ALLOYS
 CEMENTED CARBIDES
 TITANUIUM CARBIDES AND TITANIUM NITRIDES
 TITANUIUM CARBIDES AND TITANIUM NITRIDES
 COATED CARBIDES
 MICRO GRAIN CARBIDE
 CAST CARBIDES
 CEMENTED OXIDES (CERAMICS)
 DIAMOND TOLLS
 UCON
 CUBIC BORON NITRIDE

4. CARBON TOOL STEEL
 CARBON TOOL STEEL are PLAIN CARBON TOOL STEELS to which
no appreciable amount of alloying elements have been added.
 Very small quantities of silicon, manganese, chromium or
vanadium are included for increasing the hardness and to refine
the grain size.
the grain size.
 The carbon content in CARBON TOOL STEEL generally varies
from 0.6 to 1.5 %.
 The properties of the CARBON TOOL STEEL vary with the
percentage of CARBON.
 Low CARBON STEELS are tough and Shock resistant.
 High CARBON STEELS are Abrasion resistant with a ability to maintain a keen cutting
edge.

5. CARBON TOOL STEEL
 CARBON TOOL STEEL are broadly classified into two categories: Low
carbon Steel and High Carbon Steel.
 CARBON TOOL STEEL has a low Hot Hardness.
 At temperatures above 200°C, CARBON – TOOL –STEEL, loose their
hardness rapidly.
hardness rapidly.
 CARBON TOOL STEEL posses Wear Resistance and Toughness.
 CARBON STEEL are employed in the manufacture of MILLING
CUTTERS, TWIST DRILS, TURNING TOOLS and FORM TOOLS.
 CARBON STEEL TOOLS are used in cutting materials like WOOD,
MAGNESIUM, BRASS and aluminium.

6. HIGH SPEED STEELS
 HIGH SPEED STEELS are basically developed by adding
alloying elements to HIGH CARBON STEELS. Alloying
elements like Tungsten, Modybdenum, Chromium, Vanadium
and Cobalt are added to improve their Hardness,
and Cobalt are added to improve their Hardness,
Toughness and Wear Resistance properties.
 HIGH SPEED STEELS can retain their cutting edge hardness
at temperatures up to 600°C.
 A typical HIGH SPEED STEEL contains 18% W (Tungsten),
5.5% Cr (chromium) and 0.7% C (carbon) plus small amount
of Magnesium, V (vanadium) and Si (silicon).

7. Surface Treatment of Tools
 The surface Treatment is done on Tools to:
 Remove burrs,
 Improve surface finish on the cutting edge.
 To resist corrosion.
 To resist corrosion.
 To obtain surface hardness on the skin of the Tool.
 SURFACE FINISHING PROCESS includes fine grinding, honning,
polishing, blasting and electroplating.
 SURFACE TREATMENTS include oxidizing, sulfudizing and
phosphating. These treatments provide solid lubrication and decrease
heat flow from the Chip to the Tool.
 Gas Nitriding, Cyaniding, Carbo Nitriding and Bluing are some of the
surface hardness processes for getting a Hard Skin on the Tools.

8. CAST COBALT BASE ALLOY
 CAST COBALT BASE ALLOY are combination of
Tungsten, Chromium and Cobalt formed an Alloy having
extremely High Red Hardness, Wear Resistance and
Toughness.
Toughness.
 CAST ALLOY are used for machining cast and maleable iron, alloy
steels, stainless steels, non-ferrous metals, inconel-x , nitroloy, bronze,
monel, graphite and plastics.
 The Shock and Impact resistance of CAST COBALT BASE ALLOYS
allow them to perform better than carbides on interrupted cuts.

9. CEMENTED CARBIDE
 Refining the ORE and reducing in hydrogen atmosphere to get a powder of Tungsten,
Titanium, Tatalum, Niobium, etc.
 Milling and blending of the individual powders with lamp black under carefully controlled
conditions to ensure opinion dispersion of Carbon in the individual powders.
 Carburising in a reducing atmosphere to form carbides of the individual elements.
MANUFACTURE OF CEMENTED CARBIDE
 Carburising in a reducing atmosphere to form carbides of the individual elements.
 Binding of the individual CARBIDE and COBALT in proper proportion after thorough
mixing.
 Addition of paraffin followed by drying, pressing, granulating or pelletizing and
screening.
 Pressing of blanks to desired shapes and size with shrinkage allowance.
 Pre-sentering to remove the lubricant and to give sufficient strength for carrying out
operations before final sintering.
 Sintering in Hydrogen and Vacuum furnace.
 Grinding and Lapping depending on requirements.
 CARBIDES can be graded into two classes
depending on the mechanical properties and
chemical composition. They are straight tungsten
carbides and alloyed tungsten carbides.
GRADES OF CEMENTED CARBIDE

10. TITANIUM CARBIDES AND TITANIUM NITRATE
 Shortage of tungsten has led to the development of many
non-tungsten cutting tool material. Among them, the most
promising are the Titanium Carbide and Titanium Nitride
tool materials.
tool materials.
 The bonding materials used are nickel and molybdenum.
 Titanium Carbides and Titanium Nitrate have high strength
of the material, good resistance of chip-tool welding and
reduced friction between chip and tool.
 These tools are used to machine Annealed Carbon and
Low –Alloy Steels.

11. COATED CARBIDES
 The emphasis in the development of Cemented Carbide is on improving
the wear resistance, while retaining adequate toughness.
 This led to the development of Coated Carbides in which a microscopic
layer of wear resistant material (Titanium Carbide, Titanium Nitride) is
chemically coated over a tough carbide substrate to attain a single
grade of Carbide having the property of both high wear resistance and
grade of Carbide having the property of both high wear resistance and
toughness.
 TITANIUM CARBIDE COATING: The Titanium carbide is coated over a Tungsten carbide
substrate by the vapour deposition technique, without the need for a Cobalt binder.
Hydrogen and Titanium Tetrachloride vapours are passed over the hot carbide insert at the
surface of which carbon diffusing from the substrate reacts with Titanium Carbide.
 TITANIUM NITRIDE COATING: This is similar in concept to Titanium Carbide coating. A layer of
about 7 to 8 µm pure Titanium nitride without binder, which is very fine grain size, is
chemically bonded to a tough carbide base.
Titanium nitride, because of its lower coefficient of friction, has far greater resistance to
crater wear than Titanium Carbide coating.

12. MICR0 – GRAIN CARBIDE
 In micro-grain Carbides, the particles size of Carbides is reduced to
the submicro level. It is found that micro grain carbides exhibit
significantly higher transverse rupture strength at any given hardness
level than convensional carbides. They are used for severe metal
cutting operations which require a higher strength than those of
convensional grades of Carbide.
convensional grades of Carbide.
 They are recommended by applications where high-speed steel or cast
alloy tools wear too fast, or where cutting speeds are too slow for
carbides, or where cutting fail by chipping. Because of their high
strength, they can be used in positive rake angles in machining high
nickel-base alloys (super alloys). They are also recommended for cut-
off tools since the slow speed encountered towards the center of the
bar does not affect these tool materials. They are also recommended
for form tools.

13. CAST CARBIDES
 As opposed to the powder metallurgy technique, this Cast
Carbide consists in dispersing a hard Carbide alloy in a high-
strength refractory binder.
 Cast Carbide tool materials are fabricated by consumable and
 Cast Carbide tool materials are fabricated by consumable and
non-consumable electrode arc melting and by spin casting of the
metal into graphite moulds.
 A typical composition of Cast Carbide is 20% atomic Titanium,
22% atomic Carbon and 58% atomic Tungsten.
 Cast carbides are particularly resistant to Crater formation and
plastic flow at high operating temperatures.

14. CEMENTED OXIDES (CERAMICS)
 Among the numerous tool materials available, the best results have been
obtained with aluminium oxide or aluminium oxide combined with small
quantity of various other oxides.
 Ceramics are hard and have a high degree of compressive strength
even at elevated temperature.
even at elevated temperature.
 Cemented Carbide (Ceramics) tool material have good abrasive
resistance, resistance to cratering, low frictional coefficient and they are
not sensitive to the higher range of temperatures encountered during
metal cutting operation.
 Ceramic Tools can retain cutting edge hardness upto about 1400°C and
exhibit uniform strength upto 1200°C.
 CEMENTED CARBIDE (CERAMIC) tools can be used at higher cutting
speeds and at higher temperatures as compared to other Tool materials.

15. DIAMOND TOOLS
 DIAMOND is the hardest substance known.
 Diamond, because of its high modulus of elasticity, chemical inertness and
exceptionally high hardness, is ideal for obtaining fine surface finish and accuracy
when used as a Tool material.
 Though the initial cost of DIMOND is high, when compared with High Speed Steel or
Carbide Tools, the cost per piece of workpiece, machined with Diamond Tools are
Carbide Tools, the cost per piece of workpiece, machined with Diamond Tools are
invariably lower.
 DIAMOND has the highest thermal conductivity among the cutting tool materials i.e.
about two to three times that of Carbide, this results in lower temperature in cutting.
 DIAMOND as a tool material is chemically inert and takes high polish while
machining.
 DIAMOND has high hot hardness.
 DIAMOND as a tool material is extremely brittle and its chips or fractures if it is not
handled properly.
 DIAMOND tools are used in various industrial applications such as in Grinding wheels,
dressing tools, drawing dies, hones, lapping compounds, core drills, ets.
As a cutting tool, DIAMOND is mainly used for machinng non –ferrous metals like
aluminium, brass, copper, bronze,. It is also used for machining other non-metallic materials
like plastic, epoxy resins, hard rubber, glass, gold, silver, platinium.

16. UCON
 UCON is a nitrided refractory alloy developed in Union
Carbide, USA.
 UCAN has a composition of 50% columbium, 30% titanium
and 20% tungsten and contains no carbide.
and 20% tungsten and contains no carbide.
 UCON has excellent thermal shock resistance, high
hardness and toughness.
 It also exhibits excellent resistance to diffusion and
adhesion wear.

17. CUBIC BORON NITRIDE
 Next to diamond Cubic Boron nitride (CBN) is the hardest
substance known.
 It consists of atoms of nitrogen and boron, with a special
structural configuration similar to diamond.
Cubic Boron Nitride has high hardness and thermal
 Cubic Boron Nitride has high hardness and thermal
conductivity.
 Cubic Boron Nitride is used in grinding wheel on high speed
steel tools, providing good surface finish, precision and high
output products.
 CBN tools are used for grinding of hardened steel.
 CBN tools are also used for the grinding slideways of Cast Iron
beds.

18. GENRAL GUIDELINES FOR SELECTION OF
TOOL MATERIALS
 Each CUTTING TOOL has a unique combination of properties
that are important to its performance.
 PLAIN CARBON TOOL STEELS are still in use, having survived
competition from HIGH – SPEED STEELS, CARBIDES, and
competition from HIGH – SPEED STEELS, CARBIDES, and
CERAMICS.
 Traditional tool materials like HIGH – SPEED STEEL continue to
undergo substantial improvements in their properties through
suitable modifications in their composition by optimizing the
processing techniques.
 A wide variety of cutting tool materials are still in use and
guidelines for their selection for specific applications are given
below.

19. PLAIN CARBON STEELS
 For cutting tools such as hand taps, threading dies,
saws , etc.
 Machining of non-ferrous materials.
 Machining of non-ferrous materials.
 Intricate form tools for low volume production.
 Handtools, like chiesel, hammers, files, shears, etc.
 Applications where keeness of edges is important
like razor blades, knives, engraving tools, reamers,
etc.

20. HIGH – SPEED STEELS
 HIGH – volume low cutting speed operations.
 General purpose tools like drills, milling cutters,
broaches, etc.
 Form tools, parting off and recessing tools.
 On machine tools or set – ups lacking rigidly and
power.
 Machining of heat resistant steels and tough alloys.

21. CAST ALLOY
 For the range of applications intermediate between
high – speed steel and carbides.
 In multiple tooling set-ups.
 In multiple tooling set-ups.
 Form tools, and parting – off tools.
 On machines lacking rigidity.

22. CARBIDES
 Carbides are used for applications employing
higher cutting speeds on machine tools having
sufficient power. However the rigidity of the
machine tool, tooling and worpiece is to be
machine tool, tooling and worpiece is to be
ensured.

23. CERAMICS
 For application where the rigidity of the machine
tool, tooling and workpiece is extremely high and
the workpiece configuration does not cause
interrupted cutting.
interrupted cutting.
 For maching operations permitting higher cutting
speeds compared to carbides.
 For applications where good surface finish is
demanded on the workpiece.

24. DIAMIOND TOOLS
 High-volume production of precession components.
 Machining non-metallic and non-ferrous materials,
bearing elements, and precious metals.
bearing elements, and precious metals.
 For application where the demand for surface finish
geometrical and dimensional accuracies is very high.
 In applications where machine rigidity is extremely
high.