Synthesis of diamond coatings on tungsten carbide with photon plasmatron

In this paper, recent results on the synthesis of diamond coatings on cemented tungsten carbide substrates (WC-Co) with photon plasmatron are presented. This new plasma-CVD method for high-rate diamond synthesis in the open-air atmosphere has been described in a previous paper [S. Metev, H. Brecht, J. Schwarz, G. Sepold, New technology for high-rate synthesis of PC-diamond coatings in air with photon plasmatron, Diamond and Rel. Materials, 11 (2002), p. 472]. In the course of the work, the influence of the outstanding plasma parameters and deposition conditions (plasma temperature 15.000-20.000 degrees C, high ionization degree, operating pressure >= 1 atm, deposition rates of 12 up to 60 mu m/h) on the film properties have been investigated. Special emphasis has been laid out on the influence of the composition and the properties of the substrate material. The latter varied concerning the WC-Co ratio, grain size and surface roughness. The presence of the binder phase Co is a well-known handicap for the deposition of adhesive diamond coatings. Therefore, selected pretreatment methods (grinding, etching, ultrasonic baths, seeding) in combination with the specific deposition conditions have been used to optimize the film properties. Effects of the substrate pretreatment and the film properties have been characterized by analytical methods, including SEM, EDX, RAMAN, Profilometer and scratch testing. (c) 2004 Elsevier B.V. All rights reserved.