1. CUTTING TOOL MATERIALS
& CUTTING FLUIDS

2. TOPICS : Cubic Boron Nitride Introduction
Silicon Nitride based ceramics
Diamond
Whisker-reinforced tool materials
Cutting-Tool Reconditioning
Cutting fluids
Introduction
Carbon and medium alloy steels
High speed steels
Cast-cobalt alloys
Carbides
Coated tools
Alumna-based ceramics

3. Introduction: Characteristics of cutting tool :
Hardness (Elevated temperatures)
Toughness (Impact forces on tool in interrupted operations)
Wear resistance (tool life to be considered)
Chemical stability or inertness (to avoid adverse reactions)

4. Cutting tool materials
Carbon & medium alloy steels
High speed steels
Cast-cobalt alloys
Carbides
Coated tools
Alumina-based ceramics
Cubic boron nitride
Silicon-nitride-base ceramics
Diamond
Whisker-reinforced materials

5. Carbon and Medium alloy steels :
Oldest of tool materials
Used for drills taps,broaches ,reamers
Inexpensive ,easily shaped ,sharpened
No sufficient hardness and wear resistance
Limited to low cutting speed operation
High speed steels (HSS)
Hardened to various depths
Good wear resistance
Relatively
Suitable for high positive rake angle tools

6. Two basic types of HSS
Molybdenum ( M-series)
Tungsten ( T-series)
M-series - Contains 10% molybdenum, chromium, vanadium, tungsten, cobalt
Higher, abrasion resistance
H.S.S. are majorly made of M-series 
T-series - 12 % - 18 % tungsten, chromium, vanadium & cobalt
undergoes less distortion during heat treating

7. H.S.S. available in wrought ,cast & sintered (Powder metallurgy)
Coated for better performance
Subjected to surface treatments such as case-hardening for improved hardness and wear resistance or steam treatment at elevated temperatures
High speed steels account for largest tonnage

8. Cast-Cobalt alloys Commonly known as stellite tools
Composition ranges – 38% - 53 % cobalt
30%- 33% chromium
10%-20%tungsten
Good wear resistance ( higher hardness)
Less tough than high-speed steels and sensitive to impact forces
Less suitable than high-speed steels for interrupted cutting operations
Continuous roughing cuts – relatively high g=feeds & speeds
Finishing cuts are at lower feed and depth of cut

9. Carbides : 3-groups of materials
Alloy steels
High speed steels
Cast alloys
These carbides are also known as cemented or sintered carbides
High elastic modulus,thermal conductivity
Low thermal expansion
2-groups of carbides used for machining operations
tungsten carbide
titanium carbide

10. Tungsten Carbide
Composite material consisting of tungsten-carbide particles bonded together
Alternate name is cemented carbides
Manufactured with powder metallurgy techniques
Particles 1-5 Mum in size are pressed & sintered to desired shape
Amount of cobalt present affects properties of carbide tools
As cobalt content increases – strength hardness & wear resistance increases

11. Titanium carbide
Titanium carbide has higher wear resistance than tungsten carbide
Nickel-Molybdenum alloy as matrix – Tic suitable for machining hard materials
Steels & cast irons
Speeds higher than those for tungsten carbide

12. Inserts

13. Inserts Individual cutting tool with severed cutting points
Clamped on tool shanks with locking mechanisms
Inserts also brazed to the tools
Clamping is preferred method for securing an insert
Carbide Inserts available in various shapes-Square, Triangle, Diamond and round
Strength depends on the shape
Inserts honed, chamfered or produced with negative land to improve edge strength

14. Fig : Methods of attaching inserts to toolholders : (a) Clamping and (b) Wing lockpins. (c) Examples of inserts attached to toolholders with threadless lockpins, which are secured with side screws.
Insert Attachment

15. Fig : Relative edge strength and tendency for chipping and breaking of inserts with various shapes. Strength refers to the cutting edge shown by the included angles.
Edge Strength
Fig : edge preparation of inserts to improve edge strength.

16. Chip breakers: Purpose : Eliminating long chips
Controlling chip flow during machining
Reducing vibration & heat generated
Selection depends on feed and depth of cut
Work piece material,type of chip produced during cutting

17. Coated tools :
High strength and toughness but generally abrasive and chemically reactive with tool materials
Unique Properties :
Lower Friction
High resistance to cracks and wear
High Cutting speeds and low time & costs
Longer tool life

18. Coating materials Titanium nitride (TiN) Titanium carbide (Tic)
Titanium Carbonitride (TicN)
Aluminum oxide (Al2O3)thickness range – 2-15 µm (80-600Mu.in)
Techniques used :
Chemical –vapor deposition (CVD)
Plasma assisted CVD
Physical-vapor deposition(PVD)
Medium –temperature chemical- vapor deposition(MTCVD)

19. Properties for Group of Materials
Fig : Ranges of properties for various groups of tool materials.

20. Cutting tool Characteristics for coating :
High hardness
Chemical stability
Low thermal conductivity
Good bonding
Little or no Porosity
Titanium nitride (TiN) coating :
Low friction coefficients
Resistance to high temperatures
Good adhesion to substrate
High life of high speed-steel tools
Titanium carbide (TiC) coating:
Titanium carbide coatings on tungsten-carbide inserts have high flank wear resistance.

21. Ceramics : Low thermal conductivity ,resistance ,high temperature
Resistance to flank wear and crater wear
Ceramics are suitable materials for tools
Al2O3 (most commonly used)
Multi Phase Coatings :
First layer –Should bond well with substrate
Outer layer – Resist wear and have low thermal conductivity
Intermediate layer – Bond well & compatible with both layers
Coatings of alternating multipurpose layers are also formed.

22. Multiphase Coatings
Fig : Multiphase coatings on a tungsten-carbide substrate. Three alternating layers of aluminum oxide are separated by very thin layers of titanium nitride. Inserts with as many as thirteen layers of coatings have been made. Coating thick nesses are typically in the range of 2 to 10 µm.

23. Diamond Coated tools : Use of Polycrystalline diamond as a coating
Difficult to adhere diamond film to substrate
Thin-film diamond coated inserts now commercially available
Thin films deposited on substrate with PVD & CVD techniques
Thick films obtained by growing large sheet of pure diamond
Diamond coated tools particularly effective in machining non-ferrous and abrasive materials

24. New Coating materials :
Titanium carbo nitride (TiCN)
Titanium Aluminum Nitride(TiAlN)
Chromium Based coatings
Chromium carbide
Zirconium Nitride (ZrN)
Hafnium nitride (HfN)
Recent developments gives nano coating & composite coating
Ion Implementation :
Ions placed into the surface of cutting tool
No change in the dimensions of tool
Nitrogen-ion Implanted carbide tools used for alloy steels & stainless steels
Xeon – ion implantation of tools as under development

25. Alumina-Based ceramics:
Cold-Pressed Into insert shapes under high pressure and sintered at high temperature
High Abrasion resistance and hot hardness
Chemically stable than high speed steels & carbides
So less tendency to adhere to metals
Good surface finish obtained in cutting cast iron and steels
Negative rake-angle preferred to avoid chipping due to poor tensile strength
Cermets, Black or Hot- Pressed :
70% aluminum oxide & 30 % titanium carbide
cermets(ceramics & metal)
Cermets contain molybdenum carbide, niobium carbide and tantalum carbide.

26. Cubic boron Nitride ( CBN ) :
Made by bonding ( mm ( in)
Layer of poly crystalline cubic boron nitride to a carbide substrate by sintering under pressure
While carbide provides shock resistance CBN layer provides high resistance and cutting edge strength
Cubic boron nitride tools are made in small sizes without substrate
Fig : (a) Construction of a polycrystalline cubic boron nitride or a diamond layer on a tungsten-carbide insert. (b) Inserts with polycrystalline cubic boron nitride tips (top row) and solid polycrystalline CBN inserts (bottom row).

27. Silicon-Nitride based ceramics (SiN)
They consists various addition of Aluminum Oxide ythrium oxide, titanium carbide
SiN have toughness, hot hardened & good thermal – shock resistance
SiN base material is Silicon
High thermal & shock resistance
Recommended for machining cast iron and nickel based super alloys at intermediate cutting speeds

28. Diamond : Hardest known substance Low friction, high wear resistance
Ability to maintain sharp cutting edge
Single crystal diamond of various carats used for special applications
Machining copper—front precision optical mirrors for ( SDI)
Diamond is brittle , tool shape & sharpened is important
Low rake angle used for string cutting edge

29. Polycrystalline-Diamond ( PCD ) Tools:
Used for wire drawing of fine wires
Small synthesis crystal fused by high pressure and temperature
Bonded to a carbide substrate 
Diamond tools can be used fir any speed
Suitable for light un-interrupted finishing cuts
To avoid tool fracture single crystal diamond is to be re-sharpened as it becomes dull
Also used as an abrasive in grinding and polishing operations

30. Whisker –reinforced & Nanocrystalline tool materials
New tool materials with enhanced properties :
High fracture toughness
Resistance to thermal shock
Cutting –edge strength
Hot hardness

31. Whiskers used as reinforcing fibers :
Examples: Silicon-nitride base tools reinforced with silicon-carbide( Sic)
Aluminum oxide based tools reinforced with silicon-carbide with ferrous metals makes Sic-reinforced tools
Progress in nanomaterial has lead to the development of cutting tools
Made of fine grained structures as (micro grain) carbides

32. Cutting-Tool Reconditioning
When tools get worned, they are reconditioned for further use
Reconditioning also involves recoating used tools with titanium nitride
Cutting Fluids: (Lubricants + Coolants)
Used in machining as well as abrasive machining processes
Reduces friction wear
Reduce forces and energy consumption
Cools the cutting zone
Wash away the chips
Protect Machined surfaces from environmental corrosion

33. Application of Cutting Fluids
Fig : Schematic illustration of proper methods of applying cutting fluids in various machining operations: (a)turning, (b)milling, (c)thread grinding, and (d)drilling