Layer adhesion and critical strain of HFCVD diamond coatings on WC-Co substrate

The extrusion of products with high demands on dimensional accuracy and surface quality, such as aluminum power bonding wires or bioabsorbable stents made of magnesium, renders high requirements on the extrusion die. With the application of HFCVD (Hot Filament Chemical Vapor Deposition) diamond coatings on cobalt-based tungsten carbide alloys, a die material with great hot strength, high surface hardness and low chemical adhesion could be provided. To identify WC-Co alloys with suitable cobalt content both for use as extrusion die and for coating with CVD diamond, investigations on ductility and hot strength as well as layer adhesion and interface stability were carried out. The mechanical properties of four WC-Co alloys containing 6 %, 9 %, 10 % and 12 % cobalt were determined by means of hot compression tests. Layer adhesion was evaluated by a standardized sandblasting test. Subsequently, hot compression tests were carried out with coated specimens to determine the critical deformation of the applied CVD diamond coatings.