tribology in cutting process and comparison between pin-on ... · university of west bohemia in...

University of West Bohemia in Pilsen

Tribology in cutting processand comparison between

"PIN-on-DISC" and cutting test

Jiří Hájek, Antonín Kříž

WBU Plzeň, Univerzitní 22, 306 14 Plzeň, ČR, [email protected] Plzeň, Univerzitní 22, 306 14 Plzeň, ČR, [email protected]


Goal of the experiment

Problem at present is in cutting of aluminium alloys.This area is marginal question for company which produces thin

layer.But for users this problem is in centre of their interest.During cutting process there is a strong creation of build up

edge.1/27


Most of companies which produce thin layers use DLC and equivalent layers. It is due to prevent of build up edge creation.

IS IT BEST SOLUTION??

Goal of the experiment

Cutting tip Structure of aluminium alloyAlSi1Mg0,5Mn 2/27


Experimental materialExperimental material - thin layer substrate system.Substrate - TH10 (SC)

Operative marking

specifications Composition Total layer thickness[µm]

Thickness of low-friction layer [µm]

4 Monolayer CrN 3,8 –

Carbon based layer+TiAlSiN 0,3

2,4

0,2

3,3

3Low-friction layer+Nano-

composite layer2,3

1 Special low-friction layer

2Carbon low-

friction layer+adhesion

1,8WC/C+TiAlN

DLC+WC/Cr

3/27


Experimental material

Low frictionlayer

Co

W

Cr

C

Composition of the thin layer DLC+WC/Cr – operative marking no. 2

4/27Low frictionlayer


EXPERIMENTS1.CONVENTIONAL TRIBOLOGICAL

„PIN-ON-DISC“ TEST

2.MODIFIED TRIBOLOGICAL TEST vs. REAL CUTTING

5/27


Tribological analysis „PIN-on-DISC“

„PIN-on-DISC“ test is provided on CSEM Instruments tribometer. During the test tightly griped „PIN“ (shape of ball) is loaded onto the test sample („DISC“) with a constant force (chosen radius). The sample rotates with a constant speed.

Equipment parameters:Maximum load 20NRotation speed from 10 to 500 revolutions/min.Temperature range 20°C –1000°C.Data processing with the use of PC

6/27


Tribological analysis „PIN-on-DISC“- frictioncoefficient

0,00

0,10

0,20

0,30

0,40

0,50

0,60

0,70

0,80

0,90

1,00

0,00 0,02 0,04 0,06 0,08 0,10 0,12

TRACK [km]

Frictio

n co

ef.

Layer no. 1 Layer no.2 Layer no.4 Layer no.3

r=4,5mm; F=2N; BALL=Si3N4; n=500 cycles; v=2cms

Carbon basedlayer+TiAlN

WC/C+TiAlN

CrN

DLC+WC/Cr

7/27


Tribological analysis „PIN-on-DISC“- Wear track

r=3mm; F=10N; BALL=Si3N4; n=5000 cycles; v=8,25cms

Carbon based layer+TiAlSiN

Carbon based layer + TiAlSiN - was the worst.Thin layer was damaged at once.

8/27


Tribological analysis „PIN-on-DISC“- Wear track

WC/C+TiAlN layerWear of the thin layer was mild.Wear was realized by combination of adhesion and abrasion.

r=4,5mm; F=2N; BALL=Si3N4; n=500 cycles; v=2cms

WC/C+TiAlN

9/27


Tribological analysis „PIN-on-DISC“- Weartrack

Wear of thin layer was very mild during the experiment

DLC+WC/Cr

10/27


The goal of our simulation is description of tribological behaviour and wear mechanism during the turning process.

In the experiment was used modified "PIN-on-DISC" test.

Principle of this test consist in the change of "PIN".

The ball is substituted by a rolling pin. This "PIN" has a special shape and is fixed below definedangle.

This Rolling - PIN takes over the function of the tool.

PIN is fixed stationary. Disc revolves - analogy with turning.

„PIN-on-DISC“ modified test

Testingsystem

WorkpieceAlSi1Mg0,5Mn

11/27


Detail nárůstku u systému s vrstvou č. 3

In this case is along whole cutting edge most extensive "built-up edge“.The shape of the chip is slightly acicular.

“Rolling – PIN” without thin layer

„Cutting edge “ (Rolling – Pin) without layer– model test

Detail of the „Cutting edge “ (Rolling –Pin) without layer- model test

12/27


Mechanism of "built-up edge" creation is different."Built-up edge" is much thinner, but "built-up edge" area is larger.The shape of the chip is slightly acicular as in previous caseCoefficient of friction was stable during whole test (0,75 it is same as in other case).

„Cutting edge “ (Rolling – Pin)- model test

Detail of the „Cutting edge “ (Rolling –Pin ) - model test

„Rolling – PIN“ with WC/C+TiAlN layer

13/27


Scratches on workpiece due to the "built-up edge" are very imperceptible.

Detail of the scratch on workpiece after model test

„Rolling – PIN“ with WC/C+TiAlN layer

14/27


“Built-up edge” is also created during this test.In comparison to other cases it didn’t cover the cutting edge.Its range is about three time lower compared to other systems.Due to the cutting edge preservation, there was significant punning of machined

material (deep “kerf” of cutting edge in short distance).

„Built-up edge“ covers face ot the tool

”Cutting edge “ (Rolling– Pin)- model test


„Rolling – PIN“ with DLC+WC/Cr layer

15/27


No unevenness caused by “built-up edge” were observed during the whole experiment.

The shape of the chip has a specific character.

Specific shape of thechip after model test

„Rolling – PIN“ with DLC+WC/Cr layer

Details of the workpiece after model test

16/27


Mechanism of "built-up edge" creation is similar to the test without thin layer.But in this case the "built-up edge" area is a lower.The shape of the chip is slightly acicular.

Detail of the „ built-up edge“ (Rolling –Pin ) - model test

„Rolling – PIN“ with Carbon based layer+TiAlSiN layer


17/27


Details of the workpiece after model test

Scratches on the workpiece are due to the " built-up edge" very significant.

„Rolling – PIN“ with Carbon based layer+TiAlSiN layer

18/27


Conclusions of the tribological tests

System with WC/C+TiAlN layer (no. 1)

This system has low friction coefficient (0.18 ball Si3N4), but the wear resistance is not so high.

In one of tested specimens the wear appeared very early. It can be caused by unregarded layer preparation.

In all the others tested specimens behaviour was very positive. “Built-up edge" was not so compact, cutting edge was very sharp, quality of machined surface was very high.

System with DLC+WC/Cr layer (no. 2)

This system showed the best tribological behaviour (combination of wear resistance and low friction coefficient 0.15 ball Si3N4).

In developed model test this system had specific properties (good cutting power, specific shape of the chip, long time to “built-up edge” formation.

19/27


System with Carbon based layer+TiAlSiN (no. 3)

This system has the lowest wear resistance.After delamination of thin low-friction layer, the friction coefficient increased (0.31). Easy creation of "built-up edge" is the another disadvantage of this system."Built-up edge" markedly influenced machined surface in model test.

System with CrN monolayer (no 4)

This system has the highest wear resistance. Disadvantage of this system is friction coefficient (0,55).

Sintered carbide K20 without thin layerThese samples were used as etalon materials.

Conclusions of the tribological tests

20/27


Real cutting with WC/C+TiAlN layer

Time[min]

Wea

r vb

[µm

]

First value from tested edge 1-1 is higher than in other measurement.It is typical problem for cutting of aluminium alloys.

21/27


Real cutting with WC/C+TiAlN layer

Tool after 10 minutes of real cutting Tool after 20 minutes of real cutting

22/27


Real cutting with DLC+WC/Cr layer

Time[min]

Wea

r vb

[µm

]

As in previous system, there were same problems with acurate measure of the wear.

23/27


Real cutting with DLC+WC/Cr layer


24/27


Real cutting with with Carbon based layer+TiAlSiN layer

Time[min]

Wea

r vb

[µm

]

Amount of heat rised during this test (top of all system)

Build up edge was very large in this case. It is due to higher heat concentration on theedge and on the workpiece

25/27


Real cutting with with Carbon based layer+TiAlSiN layer


26/27


ConclusionsRank according to build up edge. 1. layer DLC+WC/Cr

2. layer WC/C+TiAlN

3. layer CrN

4. layer Carbon based layer+TiAlSiN

All tested systems are suitable for cutting of aluminium alloys.

Important requierement is layer with good adhesion to substrate.

When the thin layer is damaged, creation of build up edge increases and after thisthe scratches on the surface of workpiece are significant.

Friction coefficient and heat concentration increased due to build up edge.The shape of the chips show this change. The chips became from short to long.The results from cutting are in correlation with tribological analyses. And that anables

prediction of real cutting conditions.

27/27


THANK YOU FOR ATTENTION

Text of this contribution and the presentation will be available at website http://www.ateam.zcu.cz

This contribution was solved under the support of WBU in Pilsen

tribology in cutting process and comparison between pin-on ... · university of west bohemia in...

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