Study hot pressed Fe-diamond composites graphitization

Iron (Fe) has a strong catalytic activity on diamond graphitization during the high temperature processing of diamond tools or during the cutting operation-since Fe is widely used as a metal matrix constituent of the cutting tool. Fe presents sensible influence on the performance of diamond tools produced by powder metallurgy, since its deleterious effect promotes the reduction of the tool's cutting capacity and efficiency. Aiming to avoid or minimize this deleterious effect, the use of diamond with metallic and ceramic coating materials is increased. This work studies the influence of Fe as bonding matrix, and the effect of Ti and TiC coated diamonds, on structure, microstructure and mechanical properties of the processed composites. The Fe-(4%wt)diamonds composites are processed by powder metallurgy according to the following parameters: hot pressing at 35 MPa/900 degrees C/3 min-industrial parameters. Microstructural aspects are observed by SEM and iron diffusion on diamond is studied by EDS. Structural analysis is performed by X-ray diffraction and Raman spectroscopy. Compressive tests are carried out, as well as the wear resistance of the diamond composites. The importance of employing coated diamonds is discussed. It is observed that iron has not activated graphitization of diamond crystals. Ti coated diamond composites present the best mechanical properties. (C) 2012 Elsevier Ltd. All rights reserved.