Hi

a.luemkemann@platit.com / martin.beutner@ovgu.de ICMCTF 2016, April 25 - 29, San Diego

Dedicated PVD Coating Development for High-Performance Gear Hobbing A. LÜMKEMANN1, M. BEUTNER2, M. MORSTEIN1, T. CSELLE1, B. KARPUSCHEWSKI2

1 PLATIT AG, Switzerland 2 UNIVERSITY OF MAGDEBURG, Germany

Motivation o Increasing global gear production

(approx. 90 million units in 2014)

o Gear hobbing is the commonest

green manufacturing process

o Specific characteristic of hobbing are

continously changing chip thicknesses

o Sophistcated demands for the coated cutting edge

Multilayer with Nanolayered Substructure

Coating Thickness & EdgePrep o Edge rounding by wet blasting

o Increased surface roughness for

higher radii

o High tool life time possible for

wide radius range

Coating of Fly-Hobbing Teeth

Multilayer Structure:

o Alternating hard & tough

AlCr based layers

o Composition by

ARC control

o Alternating Al and

Si or Ti content

o Periode: 50 – 100 nm

Test Setup and Conditions

workpiece

rotation

Hobbing Fly-Hobbing Test

workpiece

rotation

axial

feed

o To investigate wear behaviour in gear hobbing an analogy test is used

o Wear behaviour of a full hob can be reproduced using only a single tooth

gear type Europe Japan

module mn 2.7 mm 2,31 mm

pressure angle α 22.5 ° 14,5°

tool diameter da0 100 mm 90 mm

number of starts z0 2 5

number of gashes i 19 14

substrate PM-HSS

helix angle β 24.5 °

number of teeth z2 41 48

face width b 25 mm 29 mm

gear material AISI 5120

tensile strength Rm 590 N/mm²

lubrication none

LF TF

500 µm

rake face LFC = 10,4 m/tooth

-120 -60 -40 -20 -0 [µm]

Maximum Load of all GP‘s

GP‘s

in

tra

ns

ve

rse

se

cti

on

o Tests were conducted on a

Liebherr LC180 hobbing

machine using a manual

transmission gear geometry

o A gap of a gear is generated

via multiple generating

positions (GP‘s)

o The wear of a tooth is

caused by superpositioning

of all GP‘s

AlCr

Al Ti Cr

Nanolayered Substructure by:

o Deposition rate

o Carousel rotation speed

o Ratio rpm tree : rpm carousel

o NL in the range of d = 5-15 nm

o AlCrN based Multi- / Nanolayer prevents crack propagation

Analogy test Japan: mn = 2.31 mm, vc = 150 m/min, fa = 1.69 mm/rev, zo = 5, dry

Analogy test Europe: mn = 2.7 mm, vc = 220 m/min, fa = 3.6 mm/rev, zo = 2, dry

AlCrN-ML 27 m/tooth Opt. AlCrN-ML 32 m/tooth

Optimized

ML / NL

o Base coating: CrN, columnar

o All4 = AlCrN+AlCrTiN: Fine columnar

o nACRo4 = AlCrN+AlCrN/SiNx: Very fine structure

o All4 with Ti doped top layer inhibits crater wear best,

shows lowest flank wear and highest tool life!

Testing Nanostructured QuadCoatings4

HR-TEM: nACRo (AlCrN/SiNx)

Nanolayer + Nanocomposite

0

25

50

75

100

4,5 5,4 6,3

coating thickness [µm]

life time

Roughness Rpk

[A.U

.]

0

25

50

75

100

14 19 24

edge radius [µm]

life time Roughness Rpk

[A.U

.]

ground

0

40

80

120

160

0 10 20 30 40 50

flan

k w

ear

[µm

]

tool life [m/tooth]

Market JP: AlCr(Si)N

AlCrN-ML

opt. AlCrN-ML

AlCrN + AlCrN/SiN

AlCrN + AlCrTiN

shadowing hob

tooth

decreasing

coating thickness

mounting device for

blasting & coating

coating

unit

o Edge prep & Coating of fly-hobbing teeth like a real hob

o Realistic shadowing during micro blasting & PVD process

o Very high coating thickness

induce drops in life time due to

cracks inside the coating

0

2

4

6

8

10

12

14

13

,0

12

,4

10

,5

13

,6

too

l lif

e [

m/t

oo

th]

AlCr based

Benchmark

AlCrN

high Bias

AlCrN+ AlCrTiN AlCrN+ AlCrTiN

high Bias

Bias + 70 %

100 µm

+Ti

+Si

opt. NL

High Bias Voltage

blasted

o All tested coatings with 4 µm coating thickness

o High Bias: Top layer with +70% increased Bias voltage

50 nm

1 µm

AlC

r-b

ased

A

lCrN

-ML

“ML“

APT analysis

Cr

Al

Sou

rce:

J.M

. Sch

nei

der

, O. H

un

old

, K.G

. Pra

dee

p, M

Ch

RW

TH A

ach

en

GP-11

Al

Cr

2,3 m/tooth 6,5 m/tooth

Calotest

13,6 m/tooth 12,4 m/tooth 13,0 m/tooth

100 µm 6,5 m/tooth 2,3 m/tooth

10,5 m/tooth

30 µm 20 µm