TiCN hard coatings: tribological performance and deposition process analysis

Marisa Rebelo de Figueiredo

Research output: ThesisDoctoral Thesis

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Within this work, a detailed investigation of the tribological phenomena behind the low-friction and moderate-wear behavior of TiC1-xNx hard coatings has been carried out. Tribological tests with a ball-on-disk configuration against Al2O3 counterparts in different testing atmospheres (ambient air, Ar, N2, dry air) revealed that the low-friction effect is tightly connected to the presence of moisture. The on-set for the steady-state low-friction regime with a coefficient of friction of 0.2 was identified to be between 15 and 25% relative humidity. An almost linear dependency of the friction on the testing temperature was observed leading to the notion that water adsorption at the surface of the wear scar is responsible for the low-friction effect. Analyses by Raman spectroscopy on the wear scars of the Al2O3 counterparts evidenced the presence of amorphous carbon in the transfer films formed for all testing atmospheres. On the other hand, only in moist atmosphere compounds containing C-H bonds were detected leading to the notion that its presence provides for the low-friction behavior. In situ optical and spectroscopic techniques were used to investigate the early stages of the tribological contact until the steady-state low-friction regime is established. The direct observation of the contact during sliding revealed that the transfer film is formed by abrasion of the coating and shearing of the removed material during the high-friction component of the running-in period. Further, the appearance and thickening of the transfer film marks the beginning of the steady-state low-friction regime where the difference in velocity between both counterparts is accommodated by interfacial sliding between the transfer film and the coating. In situ Raman analyses performed on the coating wear track during an entire test revealed the appearance of C-H bonds coincides with the establishment of the steady-state low-friction regime and build-up of the transfer film. In addition, a detailed analysis of the resources needed to deposit TiC1-xNx in a commercial deposition plant by cathodic arc evaporation was performed. The obtained information from the mass and energy balance performed during the process can serve as an instrument for its further optimization.
Translated title of the contributionTiCN Hartstoffschichten: Untersuchung der tribologischen Eigenschaften und des Beschichtungsprozesses
Original languageEnglish
  • Mitterer, Christian, Assessor A (internal)
  • Weiß, Christian, Assessor B (internal)
Publication statusPublished - 2011

Bibliographical note

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  • TiCN Hard Coating
  • Tribology
  • Self-lubricating Coating
  • Energy and Mass balance
  • Physical Vapor Deposition

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