Abstract
Some diamond tools use iron in their composition, and it is known that iron is a strong catalyst for the graphitization of diamonds. This graphitization occurs mainly during the processing of composite materials - conventional sintering or hot pressing, and during cutting operations. This work studies the effect of TiC coating on diamond, on structure, microstructure and mechanical properties of the processed composites. Samples were prepared by mixing powders of Fe (40 μm) and diamond (425 μm), and subsequent hot pressing at 35MPa/900 °C, during 3 minutes. Microstructural aspects were observed by SEM, and iron diffusion on diamond was studied by EDS. Structural analyses were performed by X-ray diffraction and Raman spectroscopy. Compressive tests were carried out, as well as the wear resistance of the diamond composites. The importance of employing coated diamonds was stablished. It was observed that iron did not activated the graphitization of diamond crystals.
Highlights
IntroductionDiamond tools are produced by conventional sintering or hot pressing (powder metallurgy), and contain segments (diamond composites) which are responsible for the cutting action[1,2,3]
Diamond tools are produced by conventional sintering or hot pressing, and contain segments which are responsible for the cutting action[1,2,3]
The performance of diamond cutting tools produced by the powder metallurgy techniques is connected to two main steps that occur through the reaction in the diamond-matrix interface
Summary
Diamond tools are produced by conventional sintering or hot pressing (powder metallurgy), and contain segments (diamond composites) which are responsible for the cutting action[1,2,3]. A chemical reaction is usually required between the diamond surface and bonding matrix, producing adhesion through chemical bonding, as well as by mechanical anchorage The existence of this chemical reaction depends on the composition of the metal powder, its particle size and distribution, oxidation and/or reducing gases, temperature and duration of the sintering process[6]. It was found that Fe reacts with carbon atoms of diamond surfaces, forming Fe3C – cementite, and diffuses into the diamond cubic lattice, which expands to a hexagonal one – graphitic structure, promoting partial or total degradation of some diamond crystals[8] In this sense, this work investigates the thermal damage of diamonds in the presence of iron. It is studied the effect of TiC coatings on diamond in the processed composites, mainly in comparison with uncoated diamond crystals
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