Ceramic cutting tools in manufacturing implementation

Material alat potong keramik

1. 1
Ceramic, Cermet,
PCBN, and PCD Cutting
Tools
Session 6

2. 2
Ceramic Cutting Tools
•First cutting-tool inserts on market in 1956
•Inconsistent: improper use and lack of knowledge
•Uniformity and quality greatly improved
•Widely accepted by industry
•Used in machining of hard ferrous materials and
cast iron
•Gain: lower costs, increased productivity
•Operate 3 to 4 times speed of carbide toolbits

3. 3
Manufacture of Ceramic Tools
•Primarily from aluminum oxide
•Bauxite chemically processed and converted into
denser, crystalline form (alpha alumina)
•Micro sized grains obtained from precipitation of
alumina or decomposed alumina compound
•Produced by either cold or hot pressing
•Finished with diamond-impregnated grinding
wheels

4. 4
Manufacturing Process
•Cold Pressing
•Fine alumina powder compressed into required form
•Sintered in furnace at 2912º F to 3092ºF
•Hot Pressing
•Combines forming and sintering with pressure and
heat being applied simultaneously
•Titanium oxide or magnesium oxide added for
certain types to aid in sintering and retard growth

5. 5
Ceramic Inserts
•Stronger inserts developed
•Aluminum oxide and zirconium oxide mixed in
powder form, cold-pressed into shape and sintered
•Highest hot-hardness strength and gives
excellent surface finish
•Used where no interrupted cuts and with
negative rakes
•No coolant required

6. 6
Indexable Insert
Copyright © The McGraw-Hill Companies, Inc.
Permission required for reproduction or display.
•Most common
•Fastened in mechanical holder
•Available in many styles: square, round,
triangular, rectangular
•When cutting edge
becomes dull, sharp
edge can be obtained by
indexing (turning) insert
in the holder

7. 7
Cemented Ceramic Tools
•Most economical
•Especially if tool shape must be altered from
standard shape
•Bonded to steel shank with epoxy glue
•Eliminates strains caused by clamping inserts in
mechanical holders

8. 8
Ceramic Tool Applications
•Intended to supplement rather than replace
carbide tools
•Extremely valuable for specific applications
•Must be carefully selected and used
•Can be used to replace carbide tools that wear
rapidly
•Never replace carbide tools that are breaking

9. 9
Ceramics Usage
1.High-speed, single-point turning, boring, and
facing operations with continuous cutting
2.Finishing operations on ferrous and
nonferrous materials
3.Light, interrupted finishing cuts on steel or
cast iron

10. 10
Ceramics Usage
4.Machining castings when other tools break
down because of abrasive action of sand,
inclusions or hard scale
5.Cutting hard steels up to hardness of
Rockwell c 66
6.Any operation in which size and finish of part
must be controlled and previous tools not
satisfactory

11. 11
Factors for Optimum Results
From Ceramic Cutting Tools
1.Accurate and rigid machine tools essential
2.Machine tool equipped with ample power and
capable of maintaining high speeds
3.Tool mounting and toolholder rigidity
important as machine rigidity
4.Overhand of toolholder kept to minimum: no
more than 1 ½ times shank thickness

12. 12
5.Negative rake inserts give best results
•Less force applied directly to ceramic tip
6.Large nose radius and large side cutting edge
angle on ceramic insert reduces its tendency to
chip
7.Cutting fluids generally not required, if
required, use continuous and copious flow
8.As cutting speed or hardness increases, check
ratio of feed to depth of cut
9.Best to use toolholders with fixed or adjustable
chipbreakers

13. 13
Advantages of Ceramic Tools
•Machining time reduced due to higher cutting
speeds
•Increased productivity because heavy depths of
cut can be made at high surface speeds
•Lasts from 3 to 10 times longer than plain carbide
tool and exceed the life of coated carbide tools
•More accurate size control of workpiece

14. 14
Advantages of Ceramic Tools
•Retain their strength and hardness at high
machining temperatures [in excess of 2000°F]
•Withstand abrasion of sand inclusions
•Better surface finish
•Heat-treated materials as hard as Rockwell c
66 can be readily machined

15. 15
Disadvantages of Ceramic Tools
•Brittle and therefore tend to chip easily
•Satisfactory for interrupted cuts only under ideal
conditions
•Initial cost of ceramics higher than carbides.
•Require more rigid machine than is necessary for
other cutting tools
•Considerably more power and higher cutting
speeds required for ceramics to cut efficiently

16. 16
Ceramic Tool Geometry
•Material to be machined
•Operation performed
•Condition of machine
•Rigidity of work setup
•Rigidity of toolholding device

17. 17
Cutting Speeds
•Use highest cutting speed possible that gives
reasonable tool life
•Two to ten times higher than other cutting
tools
•Less heat generated due to lower coefficient
of friction between chip, work, and tool surface
•Most of heat generated escapes with chip

18. 18
Ceramic Tool Problems
•Tool should be large enough for job
•Cannot be too large but easily be too small
•Style (tool geometry) should be right for type
of operation and material
•Table 32.4 in text lists tool problems and their
possible causes

19. 19
Grinding Ceramic Tools
•Grinding not recommended
•May be resharpened with proper care
•Resinoid-bonded, diamond-impregnated wheels
recommended
•Coarse-grit wheel for rough grinding
•220-grit for finish grinding
•Hone or lap cutting edge after grinding to
remove any notches

20. 20
Cermet Cutting Tools
•Developed about 1960
•Made of various ceramic and metallic
combinations
•Two types
•Titanium carbide (TiC)-based materials
•Titanium nitride (TiN)-based materials
•Cost-effective replacement for carbide and
ceramic toolbits
•Not used with hardened ferrous metals or nonferrous
metals

21. 21
Characteristics of Cermet Tools
•Great wear resistance (permit higher cutting
speeds than carbide tools)
•Edge buildup and cratering minimal
•High hot-hardness qualities
•Greater than carbide but less than ceramic
•Lower thermal conductivity than carbide because
heat goes into chip
•Fracture toughness greater for ceramic but less
for carbide tools

22. 22
Cermet Tool Advantages
•Surface finish better than carbides under same conditions –
often eliminates finish grinding
•High wear resistance permits close tolerances for extended
periods
•Cutting speeds higher than carbides (same tool life)
•Tool life longer than carbine tools (same cutting
speed)
•Cost per insert less than coated carbide inserts
and equal to plain carbide inserts

23. 23
Use of Cermet Tools
•Titanium carbide cermets hardest
•Used to fill gap between tough tungsten carbide
inserts and hard, brittle ceramic tools
•Used for machining steels and cast irons
•Titanium carbide-titanium nitride inserts used
for semifinish and finish machining of harder
cast irons and steels (less than 45 Rc)

24. 24
Manufacture of Polycrystalline
Cutting Tools
•Two distinct types
•Polycrystalline cubic boron nitride
•Polycrystalline diamond
•Manufacture of blanks basically same
•Layer of polycrystalline diamond or cubic
boron nitride (.020 in. thick) fused on cemented-
carbide substrate by high temperature (3275ºF), high
pressure (1 million psi)

25. 25
Polycrystalline Mass
•Created from substrate composed of tiny grains
of tungsten carbide cemented tightly together
•Cobalt binder
•High-heat, high-pressure conditions
•Cobalt liquefies, flows up and sweeps around
diamond or cubic boron nitride abrasive
•Serves as catalyst that promotes intergrowth

26. 26
High Pressure
High Temp

27. 27
Polycrystalline Cubic Boron
Nitride Tools
•Structure of cubic boron nitride feature
nondirectional, consistent properties
•Resist chipping and cracking
•Provide uniform hardness
•Abrasion resistance in all directions
•Qualities built into turning and milling butting-
tool blanks and inserts
•Can operate at higher cutting speeds, and take
deeper cuts

28. 28
Types and Sizes of PCBN Tool
Blank Insert Shapes Available
Copyright © The McGraw-Hill Companies, Inc.
Permission required for reproduction or display.

29. 29
Main Properties of PCBN
•Hardness
•Impact resistance, high strength, hardness in all
directions (random orientation of tiny CBN crystals)
•Highest Hot Hardness of all tools
•Abrasion Resistance
•Maintain sharp cutting edges much longer
•Second only to Diamond

30. 30
Main Properties of PCBN
•Compressive Strength
•Maximum stress in compression material will take
before ruptures
•Thermal Conductivity
•Allow greater heat dissipation or transfer

31. 31
Types of PCBN Tools
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
•Tipped inserts
•Available in most carbide insert shapes
•Usually most economical
•Only one cutting edge (can be reground)
•Full-faced inserts
•Layer of PCBN bonded to cemented-carbide
•Available as triangles, squares and rounds
•Can downsize repeatedly
•Brazed-shank tools
•Made by machining pocket in proper-style of
tool shank and brazing PCBN blank in place

32. 32
Four General Types of
Metal Cut
1.Hardened ferrous metals ( >45 Rc)
•Hardened steels
•Cast irons
2.Abrasive ferrous metals (180-240 Brinell)
•Pearlistic gray cast iron and Ni-Resist
3.Heat-resistant alloys
4.Superalloys (jet engine parts)

33. 33
Advantages of
PCBN Cutting Tools
•High Material-Removal Rates
•Cutting speeds (250 to 900 ft/min) and feed rates
(.010 to .020 in.) result in removal rates three time
carbide tools with less tool wear
•Cutting Hard, Tough Materials
•Capable of machining all ferrous materials with
Rockwell C hardness of 45 and above
•Also used to machine cobalt-base and nickel-base
high temperature alloys (Rockwell c 35)

34. 34
More Advantages
•High Quality Products
•Wear very slowly
•Uniform Surface finish
•Surface finishes in range of 20 to 30 µin. possible
during roughing operations
•Finishing surfaces in single-digit micro-inches
•Lower Cost per Piece
•Reduced Machine Downtime
•Increased Productivity

35. 35
Polycrystalline Diamond Tools
•Polycrystalline diamond (PCD) layer fused to
cemented-carbide substrate
•.020 in. thick
•Highly efficient cutting tool
•Increased production when machining abrasive
nonmetallic, nonferrous materials

36. 36
High Pressure
High Temp

37. 37
Types and Sizes of PCD Tool
Blank Insert Shapes Available

38. 38
Types and Sizes of PCD Tools
•Catalyst-bonded PCD available in three
microstructure series
•Coarse PCD blanks
•Medium-fine PCD blanks
•Fine PCD blanks
•Basic difference between types is size of
diamond particle used to manufacture blank

39. 39
Properties of PCD Tools
•Composite materials found in base provide
mechanical properties
•High thermal conductivity and low coefficient of
thermal expansion
•Diamond layer
•Hardness, abrasion resistance, compressive
strength, and thermal conductivity
•Compressive strength highest of any tool
•Thermal conductivity highest of any tool

40. 40
Advantages of PCD Tools
Offset their higher initial cost
1.Long tool life
2.Cuts tough, abrasive material
3.High quality parts
4.Fine surface finishes
5.Reduced machine downtime
6.Increased productivity

41. 41
Types of Material Cut
1.Nonferrous metals
•Typically soft but have hard particles dispersed
•Silicon-aluminum alloys
•Copper alloys
2.Tungsten carbide
3.Advanced composites
4.Ceramics
5.Wood composites

42. 42
Disadvantages of PCD Tools
1.Carbon Solubility Potential
2.Their higher initial cost
3.Their higher initial cost
4.Their higher initial cost
5.Their higher initial cost
6.Their higher initial cost

43. 43
Electro-Plated Diamond Tools
•Process
•Polycrystalline Diamond coated with copper or nickel
metal
•Copper or nickel mixture electroplated to a metallic
form
•Electroplated form then dressed to remove a small
amount of metal to expose PCD within
•Form tools can be de-plated and re-plated multiple
times

44. 44
Diamond-Coated Tools
•Early 1980s brought new process of chemical
vapor deposition (CVD)
•Produce diamond coating few microns thick
•Process
•Elemental hydrogen dissolved in hydrocarbon gas
around 1330º
•Mixture contacts cooler metal, carbon precipitates in
pure crystalline form and coats metal with diamond
film (slow 1-5 microns/hr)

45. 45
QQC
•Process developed by Pravin Mistry in mid
1990s
•Eliminated problems of adhesion, adjusting to
various substrates, coating thickness and cost
•Process creates diamond film through use of
laser energy and carbon dioxide as source of
carbon

46. 46
QQC Process
•Laser energy directed at substrate to mobilize, vaporize
and reate with primary element (carbone) to change
crystalline structure of substrate
•Conversion zone created
beneath substrate surface
•Changes metallurgically
to composition of
diamond coating on
surface
•Diffusion bonding of
diamond coating to substrate

47. 47
Major Advantage of the
QQC Process
•Superior bonding and reduced stress form
metallurgical bond between diamond and
substrate
•Diamond-coating process can be carried out
in atmosphere (no vacuum needed)
•Parts do not require pretreatment or
preheating to be coated

48. 48
More Advantages
•Only carbon dioxide primary or secondary source
for carbon; nitrogen acts as shield
•Diamond deposition rates exceed 1 micron per
second
•Process can be used for wide variety of materials
•Tool life up to 60 times better than tungsten
carbide and 240 times better than high-speed
steel