  The purpose of this study is to investigate the mechanisms involved in the
wear of cobalt-based interfaces at high temperature. The studied contact is a
cobalt-based alloy subjected to fretting against an alumina sample. At high
temperature, a protective third body is spontaneously created at the interface
and presents excellent tribological properties. The formation of the so-called
''glaze layer'' leads to an absence of wear. The investigation presents on
complete description of the hightemperature tribolayer with microstructural,
chemical and mechanical characterizations. The glaze layer regime is mainly
related to a threshold temperature above which a thin cobalt-rich layer is
formed by a tribo-sintering process. A formalization of the tribo-sintering
process is proposed to predict the necessary number of fretting cycles N GL to
form the glaze layer. The tribo-sintering process prevents wear debris ejection
by continuously re-incorporating the wear debris particles in the glaze layer.
The re-incorporation of the wear debris may be the reason for the absence of
wear of the fretted interface from a macroscopic point of view. Finally, the
paper presents an extended friction energy wear approach taking into account
tribo-oxidation and tribo-sintering considerations. The formulation is able to
predict wear for a large range of tribological parameters (temperature,
frequency, sliding amplitude, number of cycles), when applied to the
Co-based/alumina contact.
