Relationship between hardness and fracture toughness in Ti-TiB2 nanocomposite coatings

Alpana N. Ranade*, L. Rama Krishna, Zhe Li, Jane Wang, Chad S. Korach, Yip Wah Chung

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


We have synthesized Ti-TiB2 nanocomposite coatings by dual-cathode magnetron sputtering in argon onto polished titanium and silicon substrates with the TiB2 volume fraction varying between 6 and 45%. Over this volume fraction range, TiB2 is present as nanoparticles with diameter ~3 to 5nm. When deposited on titanium substrates, the coatings are relatively stress-free. Through most of the composition range, the coating hardness is enhanced over the rule-of-mixture value by 5 to 10GPa. We used two methods to determine coating fracture toughness: nanoindentation and nanoscratch. Results from these two methods are consistent and demonstrate that Ti-TiB2 nanocomposite coatings exhibit a "flatter" hardness-toughness relationship compared with metal carbide/DLC and TiN/a-Si3N4 nanocomposite coatings, i.e., the hardness decreases slower with increasing toughness. We speculate that the improved toughness of Ti-TiB2 nanocomposite coatings is due to the formation of coherent Ti-TiB2 interfaces, which in turn produce stress fields activating the motion of nearby dislocations within the Ti matrix and hence improved fracture toughness.

Original languageEnglish (US)
Pages (from-to)26-32
Number of pages7
JournalSurface and Coatings Technology
StatePublished - Dec 2012


  • Fracture toughness
  • Hardness
  • Magnetron sputtering
  • Nanoindentation
  • Nanoscratch
  • Titanium diboride

ASJC Scopus subject areas

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


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