The effect of Al composition on the microstructure and mechanical properties of WC-TiAlN superhard composite coating

J. S. Yoon, H. Y. Lee, J. G. Han, S. H. Yang, J. Musil

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22 Citations (Scopus)

Abstract

WC-Ti (1-x) Al x N nc-films were deposited on WC-Co and Si substrates using a multi-cathode arc ion-plating system. The microstructure and mechanical properties of the films were investigated to find out the nanostructured film growth mechanism. The microstructure of the WC-Ti (1-x) Al x N films depend on the Al concentration (x). With increasing Al in the film, the interfaces between WC and TiAIN layers loose their coherency and WC-Ti 0 .37Al 0 .57N films shows a completely nanocrystalline structure with a grain size of 10 nm, which is in agreement with the superlattice period (λ). The residual stress in WC-Ti (1-x) N films was independent of the x value and measured to be approximately 6.5 GPa. This high stress of the films was reduced to a value of 4.7G Pa by introducing Ti-WC buffer layers periodically with a thickness ratio (D buffer /D nc ) of 0.8. When the D buffer /D nc- ratio was 0.3 film adhesion strength achieved a maximum value of 45.5 N while at higher D buffer /D nc- ratios than 0.3 the film adhesion strength decreased to 25 N. The microhardness of WC-Ti (1-x) Al x N film was measured to be in the range of 38-50 GPa. The highest value of film hardness was obtained from the nanocomposite film of WC-Ti 0 .43Al 0 .57N. In the X-ray diffraction analysis (XRD) analysis, the Ti 0 .43Al 0 .57N film exhibited the same structure as the superhard (H ≥ 40 GPa) phase, which exhibits only TiAlN(111) and (200) reflections. Transmission electron microscopy (TEM) analysis also showed that WC-Ti 0 .43Al 0 .57N film was composed of very fine ( ~ 10 nm) nanocrystalline grains. So, we believe that the nanocrystalline microstructure of the film is fundamental importance for the dramatic enhancement of film hardness. The plastic deformation resistance factor (H 3 /E 2 ) of WC-Ti (1-x) Al x N films was calculated to be in a range of 0.27-0.46.

Original languageEnglish
Pages (from-to)596-602
Number of pages7
JournalSurface and Coatings Technology
Volume142-144
DOIs
Publication statusPublished - 1 Jul 2001

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Keywords

  • Composite coating
  • Microstructure and mechanical properties
  • WC-TiAlN

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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