Low-friction coatings based on lubricious vanadium oxides

Nazanin Fateh

Research output: ThesisDoctoral Thesis

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Abstract

The contribution of the present work is focused on the design of a new class of low-friction coatings based on lubricious vanadium oxides. The main approach is to fill the gap between room temperature low-friction coatings (e.g. DLC or MoS2) and high temperature low-friction coatings such as the previously developed TiAlVN or AlCrVN. Within this work, the beneficial effect of vanadium oxide formation on the tribological properties of V and VN coatings was reported. In this case a significant decrease of friction coefficient at temperatures above 400°C was observed due to the formation of easy-shearable V2O5. The lowest friction coefficient value of 0.25 at 700°Cis connected to the subsequent melting of V2O5 which has a low melting point of 680°C, resulting in liquid lubrication. In order to design well-defined coatings for potential applications, a detailed characterization on the structural and mechanical properties of V2O5 thin films deposited by reactive magnetron sputtering was conducted. Subsequently, the correlation of V2O5 film structure and properties with its tribological performance in the temperature range between 25-600°C was characterized by testing V2O5 as single-layer and bi-layer coatings. Here, the friction and wear performance of all investigated coatings was improved with increasing temperature, where thermally activated processes seem to be necessary to promote the low friction effect. Growth orientation and film structure seem to determine this onset temperature, and both together with the surface morphology determine the frictional behaviour. The investigations conducted in the present work have confirmed that V2O5 provides low friction and wear protection in the temperature range between 300 and 600°C due to its substantial beneficial lubricious effect.
Translated title of the contributionNiedrigreibschichten basierend auf schmierenden Vanadiumoxiden
Original languageEnglish
QualificationDr.mont.
Supervisors/Advisors
  • Dehm, Gerhard, Assessor B (internal)
  • Mitterer, Christian, Assessor A (internal)
Publication statusPublished - 2008

Bibliographical note

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Keywords

  • V2O5
  • PVD
  • magnetron sputtering
  • tribology
  • lubricious oxide
  • low-friction

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