Wüest M. 51 Wykes M. 82 Yamaguchi M. 17 Ybarra G. 129 Yubero F ...

JUNE 28 WEDNESDAY MORNING
JS2-WeM-OR.3 TRIBOLOGICAL CHARACTERIZATION OF TUNGSTEN NITRIDE
COATING AT ELEVATED TEMPERATURE. T. Polcar, N.M.G. Parreira and A. Cavaleiro a *.
ICEMS – Grupo de Materiais e Engenharia de Superfícies, Faculdade de Ciências e Tecnologia da
Universidade de Coimbra – Pólo II, 3030-201 Coimbra, Portugal. * To whom all correspondence
should be addressed (albano.cavaleiro@dem.uc.pt)
Transition metal nitrides are known for the unique combination of excellent mechanical properties
(hardness and Young’s modulus), high melting point, good chemical stability and high electrical
conductivity. However, tungsten nitrides still stand aside of the main attention, particularly compared
to titanium or chromium nitrides. The first studies of tungsten nitrides thin films were performed, basically,
for electronic applications such as, semiconductors or diffusion barriers. In the 90´s, W-N
coatings were started to be studied for mechanical applications and further studies were performed
on the addition of different elements (e.g. W-Ti-N and W-Si-N) in order to improve their mechanical
properties. There are only few studies dealing with tribological properties of tungsten nitrides and
showing their good wear resistance. In our previous study, tungsten nitride coatings with different nitrogen
content showed excellent wear resistance in case of sliding against ceramic Al 2 O 3 and Si 3 N 4
balls. However, many engineering applications require good tribological properties, particularly wear
resistance, at elevated temperature. Thus, the present study is focused on the tribological behaviour
(friction coefficient and wear rate) of tungsten nitride coating at temperature in the range 20 - 600°C.
The structure, hardness, friction and wear of tungsten nitride coating prepared by dc reactive magnetron
sputtering were investigated. The tribological tests were performed on a pin-on-disc tribometer
in terrestrial atmosphere with Al 2 O 3 balls as sliding partner. The wear tracks and the ball wear scars
were investigated by scanning electron microscopy in order to characterize the dominant wear
mechanisms. The coating wear rate was negligible up to 200°C exhibiting a decreasing tendency;
however, the wear dramatically increased at higher temperatures. The coating peeled off after the test
at 600°C.
102