Synthesis-Structure-Property Relations of TiAlN based Hard Coatings

Martin Josef Pfeiler

Research output: ThesisDoctoral Thesis

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Abstract

The progress in machining technology has led to an enormous variety of requirements for cutting tools. The current trend in thin film technology is the development of hard coatings with properties tailored for the respective application. Therefore, a basic understanding on the relation between the deposition process, the structure of the coating and the resulting mechanical, tribological and chemical properties is needed. The focus of this work is to establish such a scientific chain between the synthesis, the resulting structure and the properties for TiAlN-based coatings. First, the deposition process was optimized by varying the bias voltage during deposition from 40 to 160V. Second, the chemical composition was modified by forming the quaternary systems Ti-Al-V-N, Ti-Al-Ta-N, Ti-Al-Si-N and Ti-Al-B-N. And third, the architecture of the coatings was modified by the deposition of multilayered coatings with the goal of combining the most beneficial properties of different materials. An increase in bias voltage from 40 to 80V reduces the fraction of undesired hexagonal phases in the coating which is accompanied by better mechanical properties and a higher resistance to high temperature oxidation.. The high bias voltage also causes higher compressive stresses which deteriorates the coating properties for the very high bias voltages. Furthermore it was found, that high bias voltages lead to a significant reduction of surface roughness. The addition of V leads to predominant formation of cubic phases and high mechanical strength in combination with low stresses. The wear resistance at low and moderate temperatures is enhanced while at high temperatures, wear increases due to low oxidation resistance. The addition of Ta promotes the formation of cubic phases, while Si and B foster the hexagonal phase. Alloying with Ta, Si and B does not change the mechanical properties significantly, probably due to low alloying contents. However, the oxidation resistance of the coatings is found significantly improved where especially alloying with Ta and Si is found highly beneficial and resulted in improved high temperature wear resistance. The deposition of multilayered coatings resulted in the beneficial combination of properties of the individual layers, which also resulted in better performance in cutting tests.
Translated title of the contributionHerstellung-Struktur-Eigenschafts Beziehungen von TiAlN basierenden Hartstoffschichten
Original languageEnglish
QualificationDr.mont.
Supervisors/Advisors
  • Mitterer, Christian, Assessor A (internal)
  • Dehm, Gerhard, Assessor B (internal)
Publication statusPublished - 2009

Bibliographical note

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Keywords

  • TiAlN
  • Ti-Al-N
  • Ti-Al-V-N
  • Ti-Al-Ta-N
  • Ti-Al-Si-N
  • Ti-Al-B-N
  • cathodic arc evaporation
  • cutting
  • hard coating
  • thin film wear

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