Wear simulation and evaluation of

heavy duty exhaust valve systems

in a test rig

P. Forsberg, P. Hollman and S. Jacobson

Exhaust valve?

10-20 Hz

Mechanical movement

200 Bar

Up to 10 Rpm

5 µm

~75%

Cooling

channels

Heat transfer

Parameters affecting the valve system

Wear problem

ΔVCombustion

Wear

Change of emission rates

Recession

Leakage Excessive

temperature Failure Sacramento skyranch inc.

Z.W. Yu, X.L. Xu

Current trends changing the valve

system parameters

Reduced amount of combustion residues

increased metal/metal contact

0

8

Euro III

0 0.36 0.15 0.10 0.02

PM [g/kWh]

NO

x [g

/kW

h]

7

5

4

3

2

1

6

Euro I

Euro II

Euro IV

Euro V

Euro VI US - EPA

•Temp

•Pressure

Increased

Performance and

Lifetime

Tougher demands on emission

Japan

Low wear High wear

Difference in recession

900 µm

Low wear High wear

2 µm

1 µm 10 µm

Ca, S, P, Zn, C and O

Test rig

Evaluation method

Reference Valve Reference Valve seat insert

1 000 8 000

30 000 100 000

1 000 8 000

30 000 100 000

Example of result in dry air

Evaluation of coated valves in dry

atmosphere

Reference

Polished reference

Nitrided

Polished Nitrided

Nitrided Eatonite

CrN

AlCrN

TiAlN

TiAlCrN

Stellite F: Co, Cr, Ni, W

Coated on polished

Stellite F

Crutonite: Fe, Ni, Cr

All tested against Winsert VSI: Fe, Cr, Mo, V

Test Parameters: 20kN, 7Hz, Heater ~750C

Hot air ~500C

Ts = ~200C, Tv ~420C

Eatonite: Fe, Cr, Ni

0

1

2

1 10 100

TiAlNTiAlCrNAlCrN

RefCrNNE

Pol NpolNitrided

Wea

r sca

r wid

th [m

m]

Cycles x1000

Coated Valve results

TiAlN

CrN

Conclusions from the coated

valve tests

• Stellite F too weak to support the thin

hard PVD coatings at these parameters

• Before failure the PVD coatings show

potential

0

8

Euro III

0 0.36 0.15 0.10 0.02

PM [g/kWh]

NO

x [g

/kW

h]

7

5

4

3

2

1

6

Euro I

Euro II

Euro IV

Euro V

Euro VI

“From the literature it is clear that the main

contributor to ash emissions from diesel engines

is the lubrication oil” – P.Tornehed Thesis 2010

Different compositions found in exhaust particles

CaSO4

Zn2P2O7

ZnMg(PO4)2

Zn3(PO4)2

MnO

Oil inlet

Hot air

First test with oil inlet

0,35 ml / min

20 kN, 7 Hz,

500 000 cycles

100 µm

C

2 µm

Ca, P, S, Zn, O

Comparison between the two

tribofilms

2 µm

1 µm

• The test rig works very well!

• The oil particles/mist builds up a protective tribofilm

on the valve surface that protects the surfaces and

reduces the wear to a minimum in the test rig in a

similar way that we can see from real engine

specimens

• The high friction forces is the major contributor to

wear of the valve sealing interface

Conclusions from the first oil test

Future work

0

8

Euro III

0 0.36 0.15 0.10 0.02

PM [g/kWh]

NO

x [g

/kW

h]

7

5

4

3

2

1

6

Euro I

Euro II

Euro IV

Euro V

Euro VI

•Build up of tribo film for different parameters

•Tear down of the tribo film?