Contribution of TiN/Ti/a-C:H multilayers architecture to biological and mechanical properties

Complex microstructure analysis of TiN/Ti/a-C:H multilayer coatings, subjected to mechanical and biological tests, were performed by means of transmission electron microscopy (TEM) and confocal scanning laser microscopy (CSLM), respectively. Influence of interface numbers and phase ratios on coating properties was studied. Thin films were fabricated by a hybrid PLD technique (PLD supported by magnetron sputtering). The a-C:H phase was characterized by an amorphous structure, while TiN was built of columnar crystallites. Multilayer coatings contained sequentially deposited TiN and a-C:H layers with thin metallic Ti inter- layers deposited at each interface. Mechanisms of mechanical wear of analyzed systems were presented focusing on the cracking propagation revealed in the scratch test. Biological tests were done basing on smooth muscle cells adhesion to coating surfaces.

An increase of TiN phase in the coating led to improvement of mechanical properties, while the carbon phase improved the biological behavior. Coatings comprising a higher rate of the carbon (a-C:H) revealed brittleness and were prone to delaminating. Optimal properties from the mechanical and biological point of view were stated for 8xTiN/Ti/a-C:H coating with 1:1 phase ratio (TiN to a-C:H).