Mechanical Properties and Wear Resistance of  Multilayer Thin Coatings on Cutting Tools

Coatings of TiN, TiN/Ti(C,N)/TiC, TiN/Ti(C,N)/TiC/Ti(C,N)/TiC and TiN/Ti(C,N)/TiC/Ti(C,N)/TiC/ Ti(C,N)/TiC were prepared on cemented carbide substrate by chemical vapor deposition (CVD). The mechanical properties and wear  resistance of the coatings were examined with a nano  indentor equipped with an optical microscope and an atomic force microscope as the attachments. It has been found that a step appears on the loading force  displacement curves at the onset of coating fracture and a straight line segment appears on the loading force  square of indented depth curves, the latter could be used to identify the interfacial failure of the coatings. The crifical load   p    f and   p    i was proposed to be used to describe the fracture failure and the interfacial failure of the coatings, respectively. Generally speaking, multi  layer coatings have better mechanical properties and higher wear  resistance than the mono  layer counterpart. With increasing in the layer number, the fracture toughness and wear  resistance of the multi  layer coatings increase as well.