AlCrVN - Design of high-temperature low-friction coatings

Robert Franz

Research output: ThesisDoctoral Thesis

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Abstract

Within this work, V was incorporated into AlCrN coatings in order to design a hard coating that offers lubricious effects at elevated temperatures. AlCrN hard coatings are characterised by high hardness, good thermal stability and oxidation resistance, but reveal a high coefficient of friction at high-temperatures commonly encountered in metal cutting applications. On the contrary, the V oxide V2O5 has been found to act as solid and liquid lubricant in a temperature range from 500 to 700°C. The new AlxCryVzN coatings were synthesised by means of physical vapour deposition using an industrial-scale arc-evaporation system while the desired face-centered cubic (fcc) crystal structure was stabilised even at an Al concentration of x=0.7 by using higher energetic growth conditions. Due to this structural evolution hardness and residual stress values comparable to fcc-AlCrN were retained. The beneficial influence of the V incorporation on the tribological behaviour was shown in ball-on-disc tests at 700°C. Here, the coefficient of friction drops from 0.7 to 0.2 due to the formation of lubricious tribolayer containing V2O5. Annealing experiments in ambient air in this temperature range revealed the formation of a V-rich oxide scale on the top due to the immiscibility of V2O5 with the other oxides formed (Al2O3 and Cr2O3). Finally, in milling tests under dry conditions the AlCrVN coatings exhibited a competitive performance demonstrating its potential as wear resistant coating.
Translated title of the contributionAlCrVN - Design von selbstschmierenden Hartstoffschichten für Hochtemperaturanwendungen
Original languageEnglish
QualificationDr.mont.
Awarding Institution
  • Montanuniversität
Supervisors/Advisors
  • Dehm, Gerhard, Assessor B (internal)
  • Mitterer, Christian, Assessor A (internal)
Publication statusPublished - 2007

Bibliographical note

embargoed until null

Keywords

  • AlCrVN aluminium-chromium-vanadium-nitride hard coating wear resistant coating lubricious oxide PVD arc-evaporation tribology low-friction

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