Poster Presentation 24th Australian Conference on Microscopy and Microanalysis 2016

The mechanical properties of carbon thin film coatings (#241)

Masturina Kracica 1 , Cenk Kocer 2 , James Partridge 1 , Desmond Lau 1 , Jodie Bradby 3 , Bianca Haberl 4 , David McKenzie 2 , Dougal McCulloch 1
  1. RMIT University, Melbourne, VIC, Australia
  2. The University of Sydney, Sydney
  3. Australia National University, Canberra
  4. Oakridge National Laboratories, Tennessee

Carbon coatings exhibit wear-resistance, low-friction, bio-compatibility and high durability in chemically harsh conditions [1]. With a high proportion of diamond-like (sp3) bonds, they are dense, mechanically hard and ideally suited to wear protection [2]. Tetrahedral amorphous carbon (ta-C) is one of the hardest known covalent network solids [3] and exhibits sp3 bonding fractions up to 85 %. In contrast, films containing a low fraction of sp3 bonds exhibit a lower modulus but a higher degree of elastic recovery from large deformations [2].

It has been reported that the hardness and/or modulus of non-crystalline carbon films correlate simply with the sp3 bonding fraction or density [2]. However, the microstructure almost certainly influences the mechanical properties and this relationship has received little attention in the literature. Knowledge gained in this area could better inform the selection of carbon coatings for particular tribological applications.

Here, we investigate the mechanical properties of non-crystalline carbon films with different densities and microstructures. The films were fabricated using a filtered cathodic vacuum arc (FCVA) deposition system. The microstructure of the films was characterised using transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). Nanoindentation was used in combination with Finite Element Modelling (FEM) to probe the mechanical properties of the films. Measurements of the reduced elastic modulus, average energy dissipation and residual penetration depth following indentation revealed the relationships between the mechanical properties, density and microstructure of the films.

1.      Bull, S.J., Tribology of carbon coatings: DLC, diamond and beyond. Diamond and Related Materials, 1995.

2.      Charitidis, C.A., Nanomechanical and nanotribological properties of carbon-based thin films: A review. 4(5–6): p. 827-836. International Journal of Refractory Metals and Hard Materials, 2010. 28(1): p. 51-70.

3.      McKenzie, D.R., D. Muller, and B.A. Pailthorpe, Compressive-stress-induced formation of thin-film tetrahedral amorphous carbon. Physical Review Letters, 1991. 67(6): p. 773-776.