Relationships between hardness, Young's modulus and elastic recovery in hard nanocomposite coatings

J. Musil, F. Kunc, H. Zeman, H. Poláková

Research output: Contribution to journalArticle

399 Citations (Scopus)

Abstract

The paper is devoted to an assessment of the mechanical behavior of hard and superhard nanocomposite coatings from loading/ unloading curves measured by a computer-controlled Fischerscope H 100 microhardness tester and a maximum depth dmax of the diamond indenter impression into the coating at a given load L. It is shown that: (1) the area between the loading/unloading curve and the value of dmax decreases with increasing (i) hardness H, (ii) effective Young's modulus E =E/(1-v2) and (iii) universal hardness HU, where E and v are the Young's modulus and the Poisson ratio, respectively; and (2) there is no simple relation between the mechanical response of the coating and H or E alone; however, this response is strongly dependent on the ratio H/E. The last fact gives a possibility of tailoring the mechanical properties of a coating for a given application, e.g. to prepare coatings with high hardness H, high resistance to plastic deformation (ΟH3 /E2), high elastic recovery Wc, but with low E and high dmax. Special attention is also given to the analysis of problems in accurately measuring the hardness of superhard (≥60 GPa) coatings. It is shown that a high elastic recovery Wc≥80% of superhard films with H≥60 GPa (1) strongly decreases the gradient dH/dL and (2) shifts the region L, where H(L) ≈ constant and the hardness H is correctly measured, to higher values of L. This means that the lowest load L used in the hardness measurement must be higher than L used in measurements of coatings with H<60 GPa to prevent the value of H measured from being significantly higher than the real hardness of the coating.

Original languageEnglish
Pages (from-to)304-313
Number of pages10
JournalSurface and Coatings Technology
Volume154
Issue number2-3
DOIs
Publication statusPublished - 15 May 2002

    Fingerprint

Keywords

  • Magnetron sputtering
  • Mechanical properties
  • Microindentation measurements
  • Nanocomposite films

ASJC Scopus subject areas

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

Cite this