Adhesion and elasticity of plasma deposited wear resistant a-C:H coatings on nickel-titanium

A bilayer system consisting of amorphous hydrogenated carbon with an amorphous silicon interlayer has been developed to coat shape memory alloys made of nickel and titanium (NiTi) with an elastic wear resistant film. The plasma deposited film system exhibits excellent adhesion on NiTi. Tensile tests reveal high elasticity of the film system, in that it can be elongated up to 4.5% before the occurrence of fine cracks. The film system shows hardness values from 5 to 20 GPa, depending on deposition conditions. In micro scratch tests a high critical load is reached.