1. Tec Star S.r.l.
Viale Europa, 40 – 41011 Campogalliano (MO), Italy
Tel. +39059 526845 – Fax +39059 527000
Tribology: Case Histories
Dr. Alberto Borghi
Tec Star Srl - President | CEO
borghi@tec-star.it
www.tec-star.it

2. Tec Star S.r.l.
Viale Europa, 40 – 41011 Campogalliano (MO), Italy
Tel. +39059 526845 – Fax +39059 527000
Summary
Facilities
Short description of analytical equipment used for
problem solving.
Case Histories
Polymer choice for low coefficient of friction and
low wear rate applications;
Wear rate induced by different synthetic lubricants;
Polymer-steel coupling in alternate motion.

3. Tec Star S.r.l.
Viale Europa, 40 – 41011 Campogalliano (MO), Italy
Tel. +39059 526845 – Fax +39059 527000
FACILITIES
Tribometer
A tribometer is an instrument that measures tribological quantities, such as
coefficient of friction (COF), and wear rate (WR), between two surfaces in
contact.
Physical parameters which can be varied:
 contact geometry
 vertical load (from 100mN to 1000N)
 sliding velocity (from 0,1 mm/s to 5 m/s)
 temperature (from -10°C to 250°C)
 presence of lubricant or grease
 humidity
This instrument can provide measurements on a wide range of materials
(polymers, metals, thin coatings).
If particular requirements are necessary, the instrument can be customized in
order to change contact geometry, to use real samples and to create particular
environmental conditions.

4. Tec Star S.r.l.
Viale Europa, 40 – 41011 Campogalliano (MO), Italy
Tel. +39059 526845 – Fax +39059 527000
Ball-on-Disk / Pin-on-Disk
A ball or a cylindrical pin slides against a flat rotating sample; the instrument
measures the coefficient of friction during the whole duration of the tribo test.
After the test, a wear track usually appears on the sample surface: the volume
of the removed material is proportional to wear rate.
Due to its high degree of flexibility this technique allows comparison between
different materials (polymers, metals, coatings, glass, sintered materials)
under a wide range of testing parameters.

5. Tec Star S.r.l.
Viale Europa, 40 – 41011 Campogalliano (MO), Italy
Tel. +39059 526845 – Fax +39059 527000
Block-on-Ring
A flat block is in contact on the side of a rotating ring; while a vertical load is
applied on the block.
The coefficient of friction is measured during the whole test; at the
end a typical wear scar is made on the block side, allowing the
determination of wear rate.
A small liquid container at the bottom of the ring is used for test in
wet conditions. In this way the contact between block and ring is
kept in constant lubrication and it is possible to measure
performances of fluids lubricants or greases.

6. Tec Star S.r.l.
Viale Europa, 40 – 41011 Campogalliano (MO), Italy
Tel. +39059 526845 – Fax +39059 527000
Reciprocating Mode
A ball or a cylindrical pin slides over a flat sample, which moves alternatively on a
linear path.
The instrument can reach high frequencies (60Hz) of motion.
The coefficient of friction is measured during the test
and characteristic wear tracks are produced on the
sample.

7. Tec Star S.r.l.
Viale Europa, 40 – 41011 Campogalliano (MO), Italy
Tel. +39059 526845 – Fax +39059 527000
Case Histories
Polymer Coefficient of Friction
Issue The goal for this study is to measure static and dynamic coefficient of
friction of four different technical polymers (PTFE with different formulations)
for choosing the best material.
Analysis approach  In order to simulate real
conditions of work of these polymer items, a
tribometer was chosen to measure coefficient of
friction in pin-on-disk and ball-on-disk configuration.

8. Tec Star S.r.l.
Viale Europa, 40 – 41011 Campogalliano (MO), Italy
Tel. +39059 526845 – Fax +39059 527000
Procedures  The measurement of static and dynamic coefficient of
friction requires two different instrumental configurations.
The evaluation of wear track produced during dynamic measurements
allows the determination of wear rate.

9. Tec Star S.r.l.
Viale Europa, 40 – 41011 Campogalliano (MO), Italy
Tel. +39059 526845 – Fax +39059 527000
Results  The diagrams show friction and wear rate values obtained for the
four polymer samples.
The best material that combines low friction and high wear resistance is
Material B

10. Tec Star S.r.l.
Viale Europa, 40 – 41011 Campogalliano (MO), Italy
Tel. +39059 526845 – Fax +39059 527000
Wear Rate induced by different synthetic lubricants
Issue study of tribo performances of synthetic PAG lubricant for gear box.
Wear rate of metallic counterparts (bronze-steel coupling), using two
commercial lubricants and three pressure conditions, was recorded.
Analysis approach  tribometer in
Block-on-Ring configuration with the use
of a specific liquid container to maintain
the contact in lubrication.

11. Tec Star S.r.l.
Viale Europa, 40 – 41011 Campogalliano (MO), Italy
Tel. +39059 526845 – Fax +39059 527000
Results  Lubricant #2 showed a very low wear rate of Bronze surface, in
particular under 400 MPa of pressure.
At higher pressure the behavior of two lubricants is almost the same.
Coefficient of friction is similar for the two lubricants.
Wear Rate measured for two
lubricants as a function of
contact pressure.
Wear scar produced on
Bronze surface measured
by stylus profilometer.

12. Tec Star S.r.l.
Viale Europa, 40 – 41011 Campogalliano (MO), Italy
Tel. +39059 526845 – Fax +39059 527000
Polymer-Steel coupling in alternate motion
Issue study of tribo properties of technical polymers during alternate
sliding against a steel counterpart.
We needed to reproduce the contact geometry and environment
(temperature and relative humidity) of real working application.
Analysis approach  tribometer in reciprocating
configuration.
Custimozation of sample geometry in order to
simulate the real contact geometry.

13. Tec Star S.r.l.
Viale Europa, 40 – 41011 Campogalliano (MO), Italy
Tel. +39059 526845 – Fax +39059 527000
Results  Tests on materials were made by varying both linear sliding velocity
and environment temperature.
For each material there is the possibility of drawing a 2D map of coefficient of
friction and wear rate which shows its tribological behaviour in different test
conditions.

14. Tec Star S.r.l.
Viale Europa, 40 – 41011 Campogalliano (MO), Italy
Tel. +39059 526845 – Fax +39059 527000
Contacts
Dr. Alberto Borghi
borghi@tec-star.it
TEC STAR Srl
Viale Europa, 40
41011 Campogalliano (MO) - Italy
Tel (+39)059.526845
Fax (+39)059.527000