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© WZL/Fraunhofer IPT

Cutting materials, tools and coolants

for machining with geometrically

defined cutting edges – part 1

Manufacturing Technology I

Lecture 4

Laboratory for Machine Tools and Production Engineering

Chair of Manufacturing Technology

Prof. Dr.-Ing. Dr.-Ing. E.h. F. Klocke

1

Seite 1© WZL/Fraunhofer IPT

Contents of the lectures 4 and 5

� tool steels

� cemented carbides

� coatings

� ceramics

� tool design

� cooling lubricants

� Lecture 4

� Lecture 5

2


Structure

� Introduction

– classification according to hardness and toughness

– nomenclature and classification of cutting materials

Tool steels

Cemented carbides

Coatings

Summary

3


Main requirements on tool materials

� Hardness

– Abrasion

� Toughness

– Heavy cuts ( high feed values and depth of cut, high cutting forces)

– Interrupted cuts

– High dynamics

� Heat resistance

– Diffusion

– High cutting speed (heat generation)

– Heat shock resistance

4


Classification of cutting materials

toughness, flexural strength and feed

Cu

ttin

g s

pe

ed

,W

ea

r re

sis

tan

ce

, th

erm

al

resis

tan

ce

DP

optim

al cut

ting

mat

erial

1BN

1 in consideration of hardness2 in consideration of hardness

and temperature

DP:

2

fine and ultra fine grain

cementedcarbide

Al2O3 + TiC Cermet

coatedCermet

Coated cemented

carbide

Si3N4-ceramic

Al2O3 -

ceramic

cemented carbide basedon tungsten carbide

coated HSS

HSS

5


Classification of cutting materials

cold working steel

high speed steel

WC-Co

TiC/TiN - Co,Ni

WC-(Ti,Ta,Nb)C-Co

oxide ceramic

silicium-nitride ceramic

composite ceramics

boron nitride

diamond

tool steel

cemented carbides

ceramics

super hard cuttingmaterials

cutting materials for processing with geometrically defined cutting edge

6


Application Groups

P Group WC-(Ti,Ta,Nb)C-Co

high heat resistance, reduced toughness

M Group

K Group (WC, Co…)

high toughness, reduced heat resistance

7


cemented carbides

denotation cemented carbide group

HW uncoated cemented carbide, main content tungsten-carbide (WC) with grain size ≥ 1 µm

HT 1) uncoated cemented carbide, main content titanium carbide (TiC) or titanium nitride (TiN) or both

HC cemented carbide as above, coated

1) these cemented carbides are also called "Cermets"

HF uncoated cemented carbide, main content tungsten-carbide (WC) with grain size < 1 µm

Classification and application of hard cutting materials (DIN ISO 513)

8


Classification and application of hard cutting materials (DIN ISO 513)

ceramic

denotation group of ceramic

CAoxide ceramic,major content aluminum oxide (Al2O3)

CM

composite ceramic, major content oxide ceramic(Al2O3), also non-oxide ceramic

CN

nitride ceramic, major content silicon nitride (Si3N4)

CR

oxide ceramic,major content aluminum oxide (Al2O3)

reinforced

CC oxide ceramic as above, but coated

diamond

denotation diamond group

DPpoly-crystalline diamond

DMmono-crystalline diamond

boron nitride

denotation boron nitride group

BL

cubic-crystalline boron nitride with low content of boron nitride

BH

BC

cubic-crystalline boron nitride with high content of boron nitride

cubic-crystalline

boron nitride as

above, but coated

9


denotation color

P blue

M

K

hard cutting materials

application group

work piece material

yellow

red

P01P10P20P30P40P50

P05P15P25P35P45

M01M10M20M30M40

M05M15M25M35

K01K10K20K30K40

K05K15K25K35

a increasing wear resistance of the cutting material, increased cutting speeds possible

b increasing toughness of the cutting material, increased feed rates possible

a

a

a

b

b

b

machining main group (Source: DIN ISO 513)

steel:all kinds of steel and cast steel,except rustproof steel with austenitic microstructure

stainless steel:stainless austenitic and austenitic-ferriticsteel and cast steel

cast iron:cast iron with flake graphite, cast iron with spherical graphite, annealed cast iron

Application of cutting materials (DIN ISO 513)

10


Application of cutting materials (DIN ISO 513)

N

S

H

green

brown

grey

N01N10

N20N30

non-ferrous metal:

aluminum and other non-ferrous metals, non-metal work materials

N05

N15N25

S01S10S20S30

special alloys and titanium:high-temperature special alloys based upon iron, nickel and cobalt, titanium and titanium alloys

S05S15S25

H01H10H20H30

hard work materials:hardened steel, hardened cast iron materials, chilled cast iron

H05H15H25

denotation color hard cutting materialswork piece material

a

a

a

b

b

b

machining main group (Source: DIN ISO 513) application group

a increasing wear resistance of the cutting material, increased cutting speeds possible

b increasing toughness of the cutting material, increased feed rates possible

11


Structure

Introduction

� Tool steels

– unalloyed tool steels

– alloyed tool steels

– high speed steel (HS)

Cemented carbides

Coatings

Summary

12


Main design features of tool steels

Ordinary tool steels

Matrix: Martensite, primary carbides

High speed steel

Matrix: Martensite, primary carbides, secondary carbides

13


Examples of unalloyed cold working steels

unalloyed cold working steelcomposition [%] application

C Si Mn Cr Mo V W

hammer, axe, shear, screw driver, chisel

wood saw, hand saw, solid of composite saw blades

file, scraper, paper shear

all kind of chisels

file, scraper, paper shear

cutting tools, shear for steel cutting, broaching tools

0,80-

0,90

0,25-

0,40

0,50-

0,70

1,20-

1,35

0,10-

0,30

0,10-

0,35

-0,50

0,40-

0,40

0,15-

0,80

0,60

0,42-

0,47

0,20-

0,30

0,85-

1,0

1,7-

1,9

0,25-

0,30 0,05

1,10-

1,25

0,15-

0,30

0,20-

0,40

0,5-

0,8

-

-

0,07-

0,12

0,15-

0,45

2,0-

2,25

0,10-

0,40

11,0-

12,0

-

-

-

-

0,6-

0,8

C45W1.1730

C85W1.1830

C125W1.1563

45CrMoV71.2328

115CrV31.2210

X210CrW121.2436

alloyed cold working steel

denotationNr.

14


Variations and applications of high speed steels

cutting steel atmedium load maximum load

compo-sition

denotation

W - Mo - V - Co< 850 N/mm2 > 850 N/mm2 roughing finishing

18% WHS18-0-1

HS18-1-2- 5

+

-

-

-

-

+

-

-

12% WHS12-1- 4 - 5

HS10-4- 3 - 10

-

-

-

-

(+)

(+)

+

+

6% W + 5% Mo

HS6-5-2 - + - -

HS6-5- 3 - - (+) +

HS6-5-2- 5 - - + -

2% W + 9% Mo

HS2-9-1

HS2-9-2

HS2-10-1-8

+

-

-

-

+

-

-

-

+

-

-

-

I

II

III

IV

High-speed steels are notated with the letters “HS“ and the indication of the percental

amount of alloying additions in the sequence W-Mo-V-Co, e.g. HS10-4-3-10.

The classification of high-speed steels is raised by their W- and Mo-concentraion into

four alloy- and performance groups.

15


Main applications of the most important high speed steels

steel groupdenotation according to

DIN EN ISO 4957

HS6-5-2

HS6-5-3

HS6-5-2-5

HS10-4-3-10

HS2-9-2

HS2-9-1-8

mater-ialNr.

1.3343

1.3344

1.3243

1.3207

1.3348

1.3247

application

standard material for roughing and finishing, twist drills, tapping tools,

milling tools, broaching tools, reaming tools, countersinker, hobbing tools, saws, forming tools

high performance tapping and reaming tools, high performance millingtools, broaching tools, twist drills

high performance milling tools, turning and hobbing tools, high performancetwist drills and tapping tools, cold working tools, roughing tools with high tenacity

universal roughing and finishing tools, turning and high performance millingtools, free cutting steel, tools for wood machining

twist drill and tapping tools, milling tool, reaming tool, broaching tool

end milling tools, turning tools for free cutting operations, twist drills, tapping tools

16


Production of high speed steel by melting

0

200

400

600

800

1000

1200

1400

1600

meltin

g a

nd foundin

g

blo

ck turn

ing

block annealing forging rolling final annealing

tem

pera

ture

T / º

C

time t / h

denotation HS18-1-2-5 HS10-4-3-10 HS12-1-4-5 HS12-1-4 HS6-5-2

hardening temperature ºC 1280 1240 1240 1240 1230

annealing at 0,5 – 1 h3 ×

560 ºC2 × 570 ºC1 × 550 ºC

2 ×570 ºC

2 ×560 ºC

2 ×540 ºC

17


Heat treatement of high speed steel

1. a

nnea

ling

2. a

nnea

ling

oil / air

air air air airheating in vacuum furnace

annealing time in each case: 1 – 2 h

time t / h

slo

w f

urn

ace

dow

n c

oolin

g

tem

pera

ture

T / º

C

com

pensating tem

pera

ture

heat

ing

austen

ize

annealingstre

ss re

lief a

nnea

ling

pre

machin

ing

finis

hin

g

3. a

nnea

ling

A

B

C

D

E

F

G

A 600 - 650 °C

B 1. pre-heating stage ca. 400 °C (in salt bath)

C 2. pre-heating stage 850 ºC

D 3. pre-heating stage 1050 ºC

E hardening temperature ~1200 ºC

F salt bath 500 - 600 ºC

G 50-80ºC

To realize their endhardness HSS-Tools are preapared by a heattreatment. In a first step

they are hardend ( heated, held on austenite temperature and cooled down with high

speed), afterwards several times tempered.

18


Temperature dependent effects on the hardness in tempering HS

~ 600

A

S

M

A1

A2

M1

M2

~ 66

temper temperature T / ºC

ha

rdn

ess

/

HR

C

Tempering of high-speed-steel takes place bei temperatures between 540 – 580 °C and is

for this reason in the temperature range of secondary harndess. This pickup of hardness

leads under normal hardening- and temperconditons to hardness values, which can be

clearly higher then these after quenching.

The cutting material hardness resulting from the overlay of the different processes is

shown as a sum graph S depending on the tempering temperature.

19


Tools made of high speed steel - examples

source: Forst

source: Sandvik

source: PWS

tools for gear shaping

cylinder gearspline shaft chain wheelinternal gear

broaching tools for

internal broachingexternal broachinghard broaching

tools for

drillingmillingtapping thread millingthread forming

20


Structure

Introduction

Tool steel

� Cemented carbide

– WC-Co-based cemented carbide (HW)

– TiN/TiC-based cemented carbide „cermet“ (HT)

– fine grain cemented carbide

Coatings

Summary

21


Milestones in the development of cemented carbides

patent for manufacturing of WC.Co-HM,K. Schröter

Spring Fair Leipzig: 1. WC-Co-HMManufacturer Krupp, Denotation WIDIA

Carboloy (General Electric)

WC-TIC-Co cemented carbides

TiC-Mo2 C-Ni (1. cermet-generation )Manufacturer Plansee, denotation Titanit S

Titanit (Plansee), Böhlerit (Böhler)

Coromant (Sandvik)

presentation of coated cemented carbides

fine grain

Spinodal - Cermet ( 1. Cermet with TiN )

increased development of Cermets

ultrafine and nanocrystalline grain

hardness HV30

flexural strength N/mm2

mean grain diameter µm

standard (1,4 - 1,8)

fine grain (< 1)

ultra fine grain (< 0,5)

un

co

ate

d

mu

lti la

yer

0 1000 2000 3000 4000

tool life

1923

100%

360%

1927

1928

1931

1934

1937

1942

68/69

1970

1973

73/74

1993

( )

22


Production process of cemented carbide components

23


Influences on wear resistance and toughness of cemented carbides

With regard to the wear- and performance abillity of uncoated and coated cemented

carbides the features of cemented carbide substrates play a key role

24


Microstructure of conventional cemented carbide and cermet

In conventional cemented carbides based on WC the tungsten carbides mostly exist in

prism shape with a triangular base. The carbide skeleton is filled up with the binding

phase.

The structure of cermets is only made of chamfered mixed carbonitrides. Characteristicly

for their microstructure is the core-shell-structure of the hard material.

25


Composition and properties of conventional WC-Co cemented

carbides

cemented carbide classificationsource: DIN ISO 513

HW - K05 HW - K10 HW - K25 HW - K40

sort WC - 4Co WC - 6Co WC - 9Co WC - 12Co

15,1 14,9 14,6 14,2

1730 1580 1420 1290

5700 5400 5000 4500

1600 2000 2350 2450

650 630 590 580

6,9 9,6 12,3 12,7

0,21 0,22 0,22 0,22

80 80 70 65

5,0 5,5 5,6 5,9

source: ISO 3369

source: ISO 3878

source: ISO 4506

source: ISO 3327

source: ISO 3312

density / (g/cm-3)

hardness HV 30

compression strength

(cyl.-specimen) / (N/mm2)

flexural strength / (N/mm2)

Young‘s Modulus / (103⋅N/mm2)

fracture toughness / (N⋅m1/2/mm2)

Poisson ratio

thermal conductivity / (W⋅m-1⋅K-1)

thermal expansion coefficient

(293 K–1073 K) / (10-6⋅K-1)

Cemented carbides of this group exist almost completely out of hexagonal tungsten

monocarbide and the binding phase cobalt. They can contain up to 0,8 mass% VC and/or

CR3C2 and/or up to 2 mass% (TaNb)C as doping additives to controle the grain size and

constancy.

26


Microstructure of micro grain and sub micro grain cemented

carbides

turning of chilled cast iron( 80 shore )

0

2

4

6

8

10

14

min

too

l lif

e

standard micro grain sub micron

standard micro grain sub micronWC - 6-Co carbides

(H):

ha

rdn

ess H

V30

(B):

fle

xu

ral str

eng

th N

/mm

2

source: Krupp Widia

vc = 16 m/minf = 0,1 mmap = 1,0 mminsert:SPGN 120308sharp cornered,

κ = 75°

27


Dependency of grain size, hardness and toughness

source: Widia

� nano: < 200 nm

� fine: 0,8 - 1,3 µm

� super fine: 0,5 - 0,8 µm

� ultra fine: 0,2 - 0,5 µm

1000

1200

1400

1600

1800

2000

2400

hardnessHV30

500

1000

1500

2000

2500

3000

4000

flexural strengthN/mm²

4 6 8 10 12 16

cobalt content / %

14

28


Cutting edge after hard milling 55 HRC

conventional cemented carbide 9.5% Comilling time 90 min

ultra fine cemented carbide 7.5% Comilling time 175 min

29


Application of ultra fine grain cemented carbide - micro milling

work piece: X5CrNi18-10cutting speed: 6 m/minrevolutions: 8000 min-1

feed per tooth: 1 to 5 µmdepth of cut: 64 µmwidth of cut: 254 µm

1 mm

30


Composition and properties of WC-(Ti,Ta,Nb)C-Co cemented

carbides

cemented carbide classification source: DIN ISO 513

HW - P10 HW - P15 HW - P25 HW - P30 HW - M10 HW - M15

composition (mass-%)WC(Ti, Ta, Nb)CCo

31,0

60,0

9,0

25,5

64,5

10,0

17,3

72,7

10,0

10,0

78,5

11,5

9,5

84,5

6,0

11,0

82,5

6,5

10,6 11,7 12,6 13,0 13,1 13,3

1560 1500 1490 1380 1700 1550

4500 5200 4600 4450 5950 5500

1700 2000 2200 2250 1750 1900

520 500 550 560 580 570

8,1 9,5 10,0 10,9 9,0 10,5

0,22 0,23 0,22 0,23 0,22 0,22

25 20 45 60 83 90

7,2 7,9 6,7 6,4 6,0 6,0

source: ISO 3369

source: ISO 3878

source: ISO 4506

source: ISO 3327

source: ISO 3312

density / (g/cm-3)

hardness HV 30

compression strength(cyl.-specimen) / (N/mm2)




Poisson ratio


thermal expansion coefficient

(293 K–1073 K) / (10-6⋅K-1)

Cemented carbides of this group contain besides tungsten mixed carbides (MC) out of

titanium- tantalum- niobium- and/or zirconiumcarbide. Compared to the WC-Co-

cemented carbides they show improved high temperature abbilities.

31


source: Pulvermetallurgie der Hartmetalle

cermet group source: DIN ISO 513

HT – P05 HT – P10 HT – P20

composition (mass-%)carbon nitrideadditional carbidesCo/Ni

89,00,6

10,4

85,70,8

13,5

82,31,0

16,7

source: ISO 3369 6,1 7,0 7,0

source: ISO 3878 1650 1600 1450

source: ISO 45065000 4700 4600

source: ISO 3327 2000 2300 2500

source: ISO 3312 460 450 440

7,2 7,9 10,0

0,21 0,22 0,21

9,8 11,0 15,7

9,5 9,4 9,1

density / (g/cm-3)

hardness HV 30

compression strength(cyl.-specimen) / (N/mm2)




Poisson ratio


thermal expansion coefficient (293 K–1073 K) / (10-6⋅K-1)

Composition and properties of Cermets

In comparison with conventional cemented carbides cermets show a lower density.

Significant differences compared to WC-based cemented carbides are the clearly lower

heat conductivity and at the same time higher thermal extension.

32


Turning of steel using cermets

Due to the high edge strength, the high resistance against abrasive wear, and little

adhesive wear cermets are particularly suited for finishing steels.

33


Milling with Cermets

end mill,

carbide K25

P

end mill,

cutting speed vc

34


Application of different cemented carbide qualities

WC-Co-carbide: + high hardness and wear resistance because of tungsten carbide(K-group) + high edge toughness because of high solubility of WC in the

WC-Co binder- reduced heat resistance because of diffusion

WC-(Ti,Ta,Nb)C-Co: + high heat resistance, resistance against oxidation and (P-group) diffusion because of high content of TiC, TaC and NbC

- reduced edge toughness because of poor solubility of carbidesin the binder

cermet (TiC/TiN) : + high heat resistance, high resistance against oxidation and diffusion

+ high surface quality because of low adhesion - low toughness- low thermal shock resistance

35


Structure

Introduction

Tool steel

Cemented carbide

� Coatings

– Chemical vapour deposition (CVD)

– Physical vapour deposition (PVD)

Summary

36


Wear phenomena on coated cutting tools

diffusionoxidation

abrasiondelamination

adheasion

surface effects

volume effects

stresses

fracture formation

outbreak

break

Primary task of the hard material layer is to prevent the contact between work material

and tool during machining in order to reduce the tool wear caused by adhesion, abrasion,

diffusion and oxidation at the surface of the cutting material.

37


Design of a CVD coating installation

CH

H2

H2+TiCl4

liquidTiCl4

evaporatorgas exit

coating furnace

gas entrance

H2

To produce a TiC-layer for example Titantetrachlorid??? (TiCl4) is vaporized and let

together with methane to a reaction vessel which can hold a couple of thousands of

cutting inserts. Thereby the titaniumcarbide is produced in a chemical reaction at a

temperature between 900 °C and 1100 °C and a pressure below atmospheric pressure.

38


TTT-curve of a WC – Co alloy at coating temperatures

WC Eta Eta'

Co3W

200

400

600

800

1000

1200

0,01 0,1 1,0 10 100 1000

tem

pera

ture

T / º

C

time t / h

Co - 5 W - 0,23 C

HT-CVD

MT-CVD

P-CVD

PVD

Time-Temperature-Transformation chart of a cobalt aloy. Listed are typical coating

temperatures and –times for the processes HAT-CVD, MT-CVD, PA-CVD and PVD.

The figure shows that in the classical HT-CVD and middle temperature-CVD-process the

area of eta-phase-precipitation is run through respectively affected.

Compared to that in low temperature processes like PA-CVD- and PVD-processes no

changes of constitution is to be expected.

39


Coating process and flexural strength

14,5

2,6

F

PA-CVD

PVD

PVD

CVD

ch

an

ge

of

flexu

ralstr

en

gth

/ %

10

10

0

-10

-20

-30

-40

-50

-600 2 4 6 8

700°C

550°C

1000°C

400°C

coating thickness / µm

TiN

TiN/Ti(C,N)

PVD

CVD PVD

PVD

PA-CVD

The comparing examination of the bending strength of thin, differently coated WC-Co

cemented carbides shows which influence the coating temperature and layer thickness

have on this important paramater of toughness performance.

40


Coating method and cutting performance

100000

50000

10000

5000

1000

500

10060 80 100 200 400300

imp

ac

tsn

cutting speed vc / (m/min)

work mat.: 42CrMo4+QTRm= 980 N/mm2

substrate: P30/40SPUN 120312f = 0,2 mmap = 2,5 mm

MT-CVD

uncoated

Arc-PVD

The MT-CVD- as well as the PVD-coated cemented carbide are clearly superior in their

performance compard to the uncoated cemented carbide. Coming to lower cutting

speeds the PVD-layer shows advantages.

41


Commonly used layer structure

typical multi-layer with functional

Intermediate layers

multilayer (nano-structure)

graded layer

monolayer (thin hard layer)

t = 0.5 ... 50 µm

t = 0.5 ... 10 µm

t = few atomic cells ... 100 nm

hard and soft compounds

(MoS2 , WC/C, graphite etc..)

hard film + solid lubricant

film

(a-Me-C:H)

super hard coatings

(CVD-DP / BN)

42


Increased tool life using Middle-Temperature-CVD-coatings

43


Performance of Plasma-CVD coated cemented carbide

carbide P25 / TiN, PA-CVD - coated

disk milling

work material: 60WCrV8,220 HB

cutting material: HW-P25

vc= 80 m/min

fz = 0,08 mm

ae= 42 mm

ap= 6 mm

type of coating

wo

rktr

avell f

/ m

PA-CVDnone HT-CVD0

4

12

16

8

The attributes of PA-CVD-coated cemented carbides have a positive affect on their

performance in machining higher-strength steel workmaterials in interupted cut.

The sensitivity of the composite against Kammrissbildung ??? and failure through

decomposotion is much smaller compared to HAT-CVD-coated cutting materials.

44


Improved wear resistance and tenacity using multilayer coatings

0

10

20

30

40

60

70

80

%

100

1 µ

m /

9 µ

m

4 µ

m /

6 µ

m

6 µ

m /

4 µ

m

AlON

TiN

AlON

TiN

AlON

TiN

AlON

TiN3 µm

pro

ba

bili

ty o

f to

ol b

rea

ka

ge

single layer thickness Al2O3 / TiC

PVDCVD

PVDP-CVD

CVD

we

ar

resis

tan

ce

ten

acity

coating thickness

transientcoating

substrate

CVD -coatingAl2O3 / TiC

total coating thickness for all

tools 10 µm

source: Widia, Sumitomo

With rising coat thickness the wear resistance of CVD-coated cemented carbides

increases, at the same time however the bending strength and therewith the toughness

decreases.

45


Increased fracture resistance using graded subsurfaces

360%

P 251000 1200 1400 1600

hardness HV

multilayercoating on

gradedsubsurface

100%tool life

workpiece: C25vc = 200 m/minf = 0,15 - 0,3 mmap = 0,5 - 1,5 mm

gradedsubsurface

hardness 10 µm

multilayer coating

46


Improvement of edge stability using Ti(C,N)-transition layers

47


CVD multilayer-coatings with Zr

SEM-picture

carbide

calotte crater

48


C-based coatings

hydrogen-content

ha

rdn

ess

crystal latticeof graphite

crystal lattice of diamond

classification of C-based coatings basedon hydrogen-content and hardness

diamond

graphiteplasma-

poymer

amorphous carbon(DLC)

49


CVD-diamond thin-film coatings

micro-crystalline (standard) nano-crystalline (even) multi-layer (even)

micro-crystalline

nano-crystalline

source: CemeCon

50


Reduced adhesion and abrasion by smooth CVD-diamond coating

100 µm

5 µm

900 µm

900 µm

rake

fa

ce

900 µm 900 µm

severe adhesions

900 µm

severe adhesions

fla

nk fa

ce

PVD-TiB2CVD-diamond coated tool (coating thickness 4µm)

New lc = 40 m lc = 40 m

vc = 200 m/min fz = 0,15 mm dry

HC-K20 end mill with two teethd = 10 mm

ap = 3 mm

slot milling

51


Physical Vapour Deposition (PVD) coatings

� ~500°C instead of 1000°C (CVD)

� limited chemical bonding with substrate

� preservation of compressive stresses during the substrate grinding process

� sharp edges

� preservation of the toughness in the substrate material

� HS coatable

� lower layer thicknesses compared to CVD

52


PVD-process – vacuum plating

gas inletinert process gas

reaction gas

vacuum plating device- electrical heatingor

- electron beam (EB-PVD)

vacuum pump

energy supply

evaporator

specimen holder,

bias voltagewater cooled

recipient

electron beam (EB-PVD)

target material

metal ions

plasmaand

reaction gas ions

coating

Beim Vakuumverdampfen wird das Schichtmaterial in einem Tiegel im Hochvakuum

verdampft. Die Dampfatome weisen bei diesen Drücken mittlere freie Weglängen von

bis zu mehreren Metern auf. Sie treten deshalb i. Allg. nicht in Wechselwirkung

miteinander und gelangen geradlinig zum Substrat. Da dieses erheblich kälter ist als der

Dampf, kondensieren die Teilchen auf dem Substrat. Aufgrund des geradlinigen

Teilchenflugs muss der Substratwerkstoff in der Beschichtungskammer bewegt werden,

um Abschattungseffekte und ungleichmäßige Schichtdicken zu vermeiden.

53


PVD-process – sputtering

vacuum pump

additionalmagnet system

sputter device

- without additionalmagnetic field:diode-sputter-source

- with additionalmagnetic field:magnetron-sputter-source

1…-5 kV

electrode as additionalion source

-+


reaction gas

metal ions

plasmaand

reaction gas ions

coating

specimen holder,bias voltage

evaporator

target material

In einem Niederdruckplasma wird ein Inertgas (z.B. Argon) durch Anlegen einer

Hochspannung ionisiert. Die positiv geladenen Inertgasionen werden auf das als Kathode

geschaltete Target (Schichtwerkstoff) hin beschleunigt und schlagen dort durch

Impulsaustausch Atome, Atomgruppen und Moleküle des Beschichtungsmaterials

heraus.

54


PVD-process – Arc-ion plating


reaction gas

vacuum pump

magnets for arc stabilizingresp. steering

rotating arcplasma channel

10…5000 V- +

bias voltage

specimen holder

metal ions

plasmaand

reaction gas ions

coating

Beim Ionenplattieren wird das Substrat mit einer negativen Spannung, die sog.

Biasspannung, beaufschlagt. Der Metalldampf wird durch im Gasraum angeordnete

Elektroden und elektromagnetische Felder ionisiert. Ein Teil der ionisierten Teilchen

wird zum Substrat hin beschleunigt.

55


Example for a coating machine

56


Coating prevents built-up edges

0,2 mm

α0 λs ρ0γ0

5° 9° 0° 35µm

PVD - TiN - coated

vC = 63 m/min broaching oil vC = 63 m/min dry

vC = 63 m/min dry vC = 63 m/min dry

workpiece material: 17CrNiMo 6 BGtool material: WC 6 Corise per tooth: h - 0,1 mm

cutting tool geometrie:

Becaue of the use of PVD-TiN- coated instead of uncoated cemented carbides the built-

up-edge formation is supressed in the complete examined cutting speed area of vc = 10 –

63 m/min because of the decreased adhesion between the chip and cutting material.

57


Physical and chemical properties of coatings

*data for the cubic NaCl-structure at 50% TiC/TiN or TiN/AlN

verygood

verygood

meangoodmeanchemical resistance

8,0––9,47,7

coefficient of thermal exspansion

αααα25/1000 / 10-6/K

-1675,7-156,3*-260,0*-337,6-184,1enthalpy of formingΔΔΔΔH298K / kJ/mol

23002400 -3300

2600 -3400

23003100micro hardness/ HV 0,05

αααα-Al2O3(Ti,Al)NTi(C,N)TiNTiC

58


Notch Wear and Abrasion

HW-P10

HC-P10(TiAlN)

Dry Synthetic Ester

Substrate

Spalling

100µm

Notch

= 37 min

VB

N=

0,2

mm

Process:Turning (external)

Material:42CrMo4V

Inserts:HW-P10, HC-P10(SPUN 120304)

Cutting parameter:vc = 150 m/minf = 0,12 mmap = 1,0 mm

Abrasion

= 69 min

= 48 min = 23 min

59


Oxidation Resistant Coating Systems

ester with additives

overview

wear of minor cutting edge

600 µm

300 µm

VB

Nm

a

x

(Ti,Al)N/Al2O3

tc = 57 min

Process:Ext. cyl. turning

Material:X5CrNi18-10

Cutting material::HC-K20

(SPUN 120308)

Cooling lubricant::Ester without add.

Cutting parameters::vc = 150 m/min

f = 0,12 mmap = 2,5 mm

0

50

100

150

200

µmW

idth

of

wea

rla

nd

VB

Nm

ax

,

V

B N

n

(Ti,Hf,Cr)N (Ti,Al)N-Reference-

VB

Nn

tc = 40 min

tc = 57 min VB

Nm

ax

VB

Nn

VB

Nm

ax

60


Structure

Introduction

Tool steel

Cemented carbide

Coatings

� Summary

61


Questions

� Which are the main components in high speed steel (HS), WC-Co-based cemented carbides (HW) and cermets (HT)?

� Why are complex tools such as broaching and gear hobbing mills often made of high speed steel (HS)!

� Why do cermets (HT) have a higher thermal strength than WC-Co-based cemented carbides (HW)?

� A given finishing turning process does not deliver the required surface finish. The surface obtained is too rough. What measures can be taken to increase the surface finish.

� Cemented carbides from the P-group have high content of TiC, TaC and NbC carbides, low content of WC. What is the benefit of this composition, what are the disadvantages?

� What are the advantages of CVD-coatings compared to PVD-coatings?

� A high speed steel has to be coated. What type of process (CVD, PCD) do you consider.

� What wear effects can be influenced by a coating?

� What are main failure effects of coating?

62


Questions

� How does particle size in cemented carbides influence toughness

� What can be done to overcome build up edges

� What are the main conditions to promote adhesive wear

� What can be done to prevent adhesion

� Which material more sensitive to adhesion (compare against tool steel): Aluminum, carbon steel (0,6% C) or grey cast iron (GG 15)

� Show for K - grade carbides the dependence of grit size and cobalt contend on toughness

� Show for K - grade carbides the dependence of grit size and cobalt contend on hardness

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