Optimization of the mechanical properties of magnetron sputtered diamond-like carbon coatings

Diamond-like carbon coatings containing hydrogen, a-C:H, were deposited by use of reactive DC magnetron sputtering with an industrial deposition system. The reactive gas C2H2 was used in combination with carbon targets. Using Raman spectroscopy, nanoindentation and Rockwell C indentation, the mechanical properties of the coatings were optimized. Excessively high compressive stresses, which were measured with Raman spectroscopy, were found in the coatings with high hardness, resulting in poor adhesion to the substrates. By thermal annealing, these compressive stresses were reduced without altering the hardness, resulting in diamond-like carbon coatings with good adhesion.

Research highlights
► The mechanical properties of sputtered a-C:H DLC coatings have been optimized.
► By variation of the deposition parameters, a maximum hardness of 24 GPa is found.
► Compressive stresses are reduced by thermal annealing without loss of hardness.
► Good adhesion is obtained by post-deposition thermal annealing.