Effects of the pretreatment of a cemented carbide surface on its properties and on the properties of diamond coatings deposited by oxygen-acetylene flame CVD

The influence of the pretreatment of the WC (6% Co) surface on its properti es (i.e. roughness, grain size and chemical composition) and on the propert ies of flame-deposited coatings have been studied. The surface treatments i ncluded the action of an oxidizing oxygen/acetylene flame at 1000 degrees C , scratching with diamond particles (14-20 mu m), mixture with iron (<45 mu m) in an ultrasound bath, and seeding with a nm-sized diamond suspension. An acid treatment was included in the pretreatment sequence. It is found th at the oxidizing flame and the seeding decrease the surface roughness of th e substrate as well as the diamond coatings, at the same time increasing th e adhesion of the coating. Ultrasound scratching with the diamond/iron susp ension increases the roughness of both the substrate and the diamond coatin g and decreases the adhesion of the coating. Scratching with diamond partic les shows a similar but lesser effect. Except for scratching with diamond, all the surface pretreatment procedures lead to an increase in the density of diamond particles: this increase is greatest for seeding. Our results in dicate that good adhesion and a small surface roughness are best obtained b y the use of an oxidizing flame followed by acid treatment and seeding with nanoparticles. (C) 1999 Elsevier Science S.A. All rights reserved.