Nano-scratch testing on thin diamond-like carbon coatings for microactuators: friction, wear and elastic-plastic deformation

In micromechanical systems the mechanical and tribological requirements for the materials in use are getting rapidly higher. The aim is to find out the fundamental frictional and wear behavior of thin coatings by using the hitherto knowledge in mechanical characterization of coatings and selective experiments. Nanoindentation and linear oscillating microwear experiments have been performed on micro-actuator components and on thin diamond-like carbon coatings, using diamond tips and loads in the range of some millinewtons. The wear depth and friction coefficients were determined as a function of load and number of wear cycles. New methods of data analysis will be discussed, which allow a separation of the different contributions of wear due to material loss, and elastic and plastic deformation. The friction coefficient shows deviations from Amonton’s law because of the dependence of the contact area on the normal load.