Influence of chemical pretreatment of hardmetal substrates for diamond deposition

Diamond coated cutting tools are of increasing importance in the fields of high speed cutting, dry machining or machining of special materials such as metal-matrix-composites. A well-known problem is the poor adhesion of diamond films on hard metals due to the Co- or Ni-binder that catalyzes the formation of graphite, Several methods-such as the application of intermediate layers or mechanical or chemical pretreatment of the hardmetal substrate-have been developed to overcome this effect. Usually chemical pretreatment is used in order to reduce the concentration of binder phase on the surface that is to be coated. Surprisingly pretreatment with agents such as Murakami's solution result in improved adhesion and nucleation of diamond films while the concentration of the binder phase on the surface is enhanced. This "contradiction" can be explained by proving that the surface is converted into a very thin oxide/hydroxide film. (C) 2002 Elsevier Science Ltd. All rights reserved.