A nanotribological study of thin amorphous C and Cr doped amorphous C coatings

A new rapid method of nano-scale wear testing was applied to a matrix of 150 nm amorphous C and Cr doped amorphous C coatings in order to investigate a nano-wear process under conditions which are applicable to MEMS and similar devices. The nano-wear test involved adding a method of controlled oscillation to the sample mounting of a nanoindentation system utilising a spherical ruby counter-body. At relatively low oscillation amplitude (2 μm) fretting wear was produced and classic W-shaped wear scars were generated. The degree of wear was dependent upon the applied force. At larger amplitude (14 μm) full reciprocating sliding was produced. The mode of wear was 3-body abrasive and the abrading particles were large relative to the size of the contact area producing a relatively coarse scoring of the coating surface. All coating formulations had excellent wear resistant properties compared with the Si substrate and the best formulations produced wear depths in the range 10–20 nm after 216,000 oscillations.