Mechanical characterization of a functionally graded nanocomposite thin film

Functionally graded nanocomposite thin films (2D-FGM), of sub-micrometric thickness, were co-deposited from austenitic stainless steel (316L (AISI)) and poly(tetrafluoroethylene) targets by r.f. magnetron sputtering. All the deposition parameters were kept constant except for the electrical characteristics applied to polymeric target. XPS revealed in the films fluorine contents between 0 and 60 at%. The TEM analysis revealed the evolution towards a nanocomposite structure with an increase in fluorine content (from 0 to 20 at%). For the higher fluorine contents the formation of a ceramic phase, FeF2, is the main structural feature. The hardness is higher for the films with the lowest fluorine concentration due to higher chromium carbides content. The residual stresses of the 2D-FGM are essentially compressive with values up to 2.2 GPa. The values of the friction coefficient of the nanocomposite thin films are in the range of 0.66-0.71, an exception is for the highest fluorine content where the value is 0.31.