High Temperature Tribology and Wear

Jens HardellAssociate Professor

Head of DivisionDivision of Machine Elements

Division of Machine Elements

Tribo-materials

15 senior researchers20 PhD students

TribologyFrictionWear

Lubrication

Modelling and simulation

Lubrication and lubricants

Biotribology

Tribo-condition monitoring and control

Vehicles and machine components

HT Research Resources and InfrastructureReciprocating friction and wear up to 900 °C

Pin-on-disc up to 700 °C

Nanoindentation up to 750 °C

HT Research Resources and InfrastructureHot strip tribometer

StripTool pins

Test parameters ValueLoad 5000 NTemperature strip 1000 °CTemperature tool 700 °CSliding velocity 250 mm/sSliding distance 500 mm/strip

BackgroundHigh temperature tribology – a complex process

FN

vslideHeat

conduction

Oxidation

Diffusion

Thermal fatigue

Thermal softening

Microstructural changes

Abrasion

Adhesion

Tribology in hot stamping

vslide F N

Fμ (T)=?

Wear behaviour?

Process economy

Quality

Reduce galling

Minimise wear

Friction control

Surface engineering

Surface quality of component

Tribology in hot forming

Aim and objectivesAims

– Enhanced understanding of the effect of temperature on friction and wear processes

– Efficient friction control and minimised wear at high temperatures

Objectives– To experimentally characterise and understand the tribological

behaviour of hot forming tool steels and ultra high strength boron steel both room and elevated temperatures

– To investigate and understand the mechanisms governing friction and wear at different temperatures

– To explore the potential of certain surface modification technologies

Results – analysis of real tools

• Forming of Al-Si coated steel severely affected by galling – Tool surface altered by transferred material– Negative effect on formed components– Increased maintenance costs and downtime

Results – analysis of real tools

Forming tool*Pin specimen

Galling on actual forming tool

Galling on pin specimen

*Image from: http://help.solidworks.com/2013/English/SolidWorks/sldworks/HIDD_DVE_FORM_TOOL.htm

Results – effect of contact pressure and surface roughness on galling

Results – effect of contact pressure and surface roughness on galling

Results – effect of contact pressure and surface roughness on galling

• Sliding parallel to surface lay significantly reduces galling

• Debris pushed out of the contact– Observed accumulation of debris at the edge

Perpendicular sliding Parallel sliding

10 MPa

0

10

20

30

40

50

60

Perpendicular tosurface lay

Parallel tosurface lay

Cov

ered

are

a (%

)

Future research needs

• Tribological performance of “new” workpiece materials and sheet coatings

• Development and characterization of surface engineering for hot forming tools

• High temperature lubrication – understanding mechanisms and formulating customized products