Nanolayered gradient structures as an intermediate layer for diamond coatings

A molybdenum/titanium multilayered film was used as an intermediate film between a diamond-like carbon (DLC) coating and steel and silicon substrates. The elastic properties of the Mo/Ti intermediate layer were modified by using a gradient thickness of the titanium films. An attempt was thus made to obtain a smooth gradient of the elastic modulus from the substrate (steel, 210 GPa) to the DLC film (300 GPa). The Mo/Ti multilayer was deposited in a sputter deposition unit with two sputter targets and a rotating substrate holder. The hydrogen-free DLC coating was deposited with a pulsed arc discharge method. The Mo/Ti film was characterized by several sophisticated methods, such as cross-section scanning force microscopy, cross-section transmission electron microscopy. Rutherford Backscattering spectroscopy and nano-indentation. The film has a layered structure with a columnar growth. Preliminary tests of the mechanical properties were performed by using a scratch test. On silicon the Mo/Ti film detached at a slightly higher critical load compared with the DLC film with no intermediate film. However, poor adhesion of the Mo/Ti film to the steel substrate prevented evaluation of the mechanical properties of the sample.