Influence of Counterface Material on the Tribological and Thermal Response of Carbon-Graphite for Aerospace Seals
Influence of Counterface Material on the Tribological and Thermal Response of Carbon-Graphite for Aerospace Seals
Wednesday, September 30, 2026: 8:20 AM
302B (Québec City Convention Centre)
Reliable operation of carbon-graphite seals in aerospace gas turbines depends not only
on the intrinsic properties of the carbon material but also on the ability of the mating surface to
maintain a stable tribological interface under severe operating conditions. Although tungsten
carbide- and oxide-based coatings have been proposed as candidate counterfaces, their
influence on friction evolution, interface heating, and transfer layer stability has not been fully
established. This work compares the tribological performance of aerospace-grade carbongraphite against HVOF-sprayed WC-17Co and suspension plasma-sprayed (SPS) CoO
coatings under representative dry sliding conditions. Experiments were carried out using an
ASTM G77 block-on-ring tribometer, as a reference, at a constant sliding speed of 10 m/s under
normal loads of 14 N and 140 N for approximately 160,000 sliding cycles. Friction coefficient
and interface temperature were continuously recorded throughout the tests, while the coatings
were characterized before testing with respect to thickness, hardness, chemical composition,
and microstructure. Both counterfaces exhibited comparable tribological behavior at the lower
load, producing steady friction coefficients of approximately 0.40–0.45 and interface
temperatures below 120°C. A different response was observed at 140 N. The CoO coating
sustained stable sliding conditions, with the interface temperature near 210°C. In contrast, the
WC-17Co counterface underwent rapid thermal escalation, exceeding 420°C and causing
premature termination of the experiment. Post-test surface analyses confirmed material transfer
on both tribological pairs. However, Raman spectroscopy identified the formation of Co₃O₄ on
the CoO surface, indicating tribo-oxidation and the development of a protective tribological
layer that promoted thermal stability during high-load operation. The results demonstrate that
the thermal response of carbon-graphite sealing interfaces is strongly governed by counterface
selection. Compared with WC-17Co, the CoO coating provided a more stable tribological
interface under severe loading, effectively controlling friction and interface temperature. These
findings identify CoO as a promising counterface material for next-generation aerospace
sealing systems
on the intrinsic properties of the carbon material but also on the ability of the mating surface to
maintain a stable tribological interface under severe operating conditions. Although tungsten
carbide- and oxide-based coatings have been proposed as candidate counterfaces, their
influence on friction evolution, interface heating, and transfer layer stability has not been fully
established. This work compares the tribological performance of aerospace-grade carbongraphite against HVOF-sprayed WC-17Co and suspension plasma-sprayed (SPS) CoO
coatings under representative dry sliding conditions. Experiments were carried out using an
ASTM G77 block-on-ring tribometer, as a reference, at a constant sliding speed of 10 m/s under
normal loads of 14 N and 140 N for approximately 160,000 sliding cycles. Friction coefficient
and interface temperature were continuously recorded throughout the tests, while the coatings
were characterized before testing with respect to thickness, hardness, chemical composition,
and microstructure. Both counterfaces exhibited comparable tribological behavior at the lower
load, producing steady friction coefficients of approximately 0.40–0.45 and interface
temperatures below 120°C. A different response was observed at 140 N. The CoO coating
sustained stable sliding conditions, with the interface temperature near 210°C. In contrast, the
WC-17Co counterface underwent rapid thermal escalation, exceeding 420°C and causing
premature termination of the experiment. Post-test surface analyses confirmed material transfer
on both tribological pairs. However, Raman spectroscopy identified the formation of Co₃O₄ on
the CoO surface, indicating tribo-oxidation and the development of a protective tribological
layer that promoted thermal stability during high-load operation. The results demonstrate that
the thermal response of carbon-graphite sealing interfaces is strongly governed by counterface
selection. Compared with WC-17Co, the CoO coating provided a more stable tribological
interface under severe loading, effectively controlling friction and interface temperature. These
findings identify CoO as a promising counterface material for next-generation aerospace
sealing systems