Interfacial reactions in diamond composite materials

• Applicants: Professor Dr.-Ing. Wolfgang Tillmann; Professor Dr. Metin Tolan
• Subject Area: Metallurgical, Thermal and Thermomechanical Treatment of Materials ; Glass, Ceramics and Derived Composites ; Materials in Sintering Processes and Generative Manufacturing Processes
• Term: from 2011 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 195322915

Diamond cutting segments function as abrasive elements and conduct grinding processes at drill bits, cut-off wheels, and wire saws for processing natural stone. The use of these powder metallurgically produced abrasive segments has increased since the introduction of synthetic diamonds to the market in the 1960s. Initially, they were almost exclusively used to process mineral materials. However, today they are utilized to a greater extend for high-strength composites such as for example laminate, CFRP- and GFRP components as well. Due to the quantities needed, industrial cold-pressing processes with subsequent vacuum sintering, and the much faster and thus economical hot-pressing process have proven to be most effective. However, these manufacturing processes significantly influence the strength of the interface reaction between the diamond and the metallic matrix, which in turn, is significant for the wear behavior in the later processing procedure. The mechanical bond of the diamond can be enhanced with an additional chemical interaction between the two materials (diamond vs. metal matrix). Within the scope of the proposed research project, the presence, as well as the type or the thickness of such a reaction zone, will be closely analyzed by means of radiographical investigations at the electron storage ring facility DELTA in Dortmund and interlinked with the production parameters in order to obtain specific framework conditions under which interfaces are formed. Within the first project phase, it was on the one hand possible to obtain basic knowledge about the reactivity of different one- or two-component metal matrix materials. On the other hand, two common sinter processes for diamond-metal composite materials (vacuum sintering vs. hot pressing) were compared to show the influence of the sintering time and temperature on the formation of carbide reaction zones and of graphitization phenomena. Thus, within the requested second project phase (3rd year) additional interface investigations with other carbide-forming metal powders such as vanadium and silicium are going to be carried out on the basis of the already obtained findings concerning two or three-component metal matrix materials. Furthermore, x-ray analyses with metallized diamonds as described in subtask 5 of the first application are going to be conducted. As a further work module throughout the complete third year, wear tests with diamond-metal composites on concrete are going to be conducted in order to determine the influence of different reaction zones on the diamonds with direct application-relevant experiments.

• DFG Programme: Research Grants