NANOLAYERED GRADIENT STRUCTURES AS AN INTERMEDIATE LAYER FOR DIAMOND COATINGS

A molybdenum/titanium multilayered film was used as an intermediate fi lm between a diamond-like carbon (DLC) coating and steel and silicon s ubstrates. The elastic properties of the Mo/Ti intermediate layer were modified by using a gradient thickness of the titanium films. An atte mpt was thus made to obtain a smooth gradient of the elastic modulus f rom the substrate (steel, 210 GPa) to the DLC film (300 GPa). The Mo/T i multilayer was deposited in a sputter deposition unit with two sputt er targets and a rotating substrate holder. The hydrogen-free DLC coat ing was deposited with a pulsed arc discharge method. The Mo/Ti film w as characterized by several sophisticated methods, such as cross-secti on scanning force microscopy, cross-section transmission electron micr oscopy, Rutherford backscattering spectroscopy and nano-indentation. T he film has a layered structure with a columnar growth. Preliminary te sts of the mechanical properties were performed by using a scratch tes t. On silicon the Mo/Ti film detached at a slightly higher critical lo ad compared with the DLC film with no intermediate film. However, poor adhesion of the Mo/Ti film to the steel substrate prevented evaluatio n of the mechanical properties of the sample.