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High temperature tribology up to 7.5 m/s of thermally sprayed coatings of the TiO2-Cr2O3 system and (Ti,Mo)(C,N)-Ni(Co)

: Berger, L.-M.; Stahr, C.C.; Saaro, S.; Thiele, S.; Woydt, M.; Kelling, N.

Gesellschaft für Tribologie, Moers:
Reibung, Schmierung und Verschleiß. Forschung und praktische Anwendungen. Bd.1: Werkstoffe und Werkstofftechnologien, Dünne Schichten und Oberflächentechnologien, Schmierstoffe und Schmierungstechnik : 49. Tribologie-Fachtagung, 22. bis 24. September 2008 in Göttingen
Aachen: GfT, 2008
ISBN: 978-3-00-025676-9
15 S.
Tribologie-Fachtagung <49, 2008, Göttingen>
Fraunhofer IWS ()
Fraunhofer IKTS ()
Verschleißschutzschicht; beschichteter Werkstoff; Aufdampfen; Titanoxid; Chromoxid; Cermet; Hartmetall; Gleitschicht; Oxidation; Reibungskoeffizient; Trockenreibung; Mikrogefüge; Kristallographie; Scherzone; Zustandsdiagramm

Since the term lubricious oxides was introduced to tribology in order to describe expected low coefficients of friction (COF) and wear rates in unlubricated dry sliding conditions numerous studies have been carried out on bulk materials and thermal spray coatings. Many studies have been conducted with bulk materials and coatings of the Ti-O system, of the binary TiO2-Cr2O3 system, as well as with (Ti,Mo)(C,N)-NiMo cermets or TiC-based thermally sprayed hardmetal coatings, which might form titanium suboxides as a result of tribo-oxidative and/or high-temperature reactions. In this paper, we shortly summarize the characteristics and dry sliding wear resistance of thermally sprayed oxide coatings of the Ti-O and TiO2-Cr2O3 systems, as well as of (Ti,Mo)(C,N)-Ni(Co) cermet coatings. The prediction of solid lubrication properties of titanium suboxides was based on the ability of the defects in the oxygen sublattice to form so-called crystallographic shear planes. While such structures with some limitations can be realised in coatings, the significant disadvantage is that TiOx tends to re-oxidize in air above 380 deg C. The isostructural phases in the TiO2-Cr2O3 phase diagram can be prepared in air and have a stable oxygen content. However, as can be concluded from the phase diagram, during thermal spraying phase transformations occur as well. In this paper, the dry sliding wear resistance of APS-sprayed coatings against alumina of three compositions in the TiO2-Cr2O3 systems (compositions in mass.-% 75Cr2O3/25TiO2, 27Cr2O3/73TiO2 and 23.5Cr2O3/76.5TiO2) is studied from room temperature up to 800 deg C and sliding speeds in the range of 0.1-7.5 m/s. The results are compared with those of chromia coatings, as well as with (Ti,Mo)(C,N)-Ni(Co) coatings and bulk (Ti,Mo)(C,N)-NiMo hardmetals in self-mated pairs.