Development of high-strength, damage-tolerant CVD-diamond-foil compounds

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In the second funding period, the novel PVD/CVD in-situ laminates generated in the first funding period will be further developed in terms of their properties and process technology and prepared for application on different substrates. Important starting points are the adaptation of the diamond structure and thus its residual stresses and topography in order to achieve an increase in the strength of monolithic diamond, based on a reduction in the grain and facet size. Furthermore, an adjustment of the interface adhesion strength of the diamond-metal laminates is to be achieved by a specific adjustment of the metallic interlayer thickness and the chemical composition. The new diamond-metal laminates will be mechanically characterised by means of in-situ 3- and 4-point bending and FEM modelling. A new focus is on a quantification of the interfacial adhesion, realised by 4PB peel tests, where single laminate layers are pre-damaged. With regard to a possible application, novel low-heat self-soldering in-situ solder joints with reactive nano-solder foils are investigated. Based on these findings, a separate processing of self-soldering nano-PVD interlayers directly on the laminate is being considered. The adhesion or interfacial adhesion on the substrates is also characterised via 4PB peel tests with pre-damaged bending beams. The protective effect of the optimised laminates and soldering will then be characterised by means of Rockwell-C indentation and tribological tests. Finally, a showcase study is carried out with a universal tribometer adapted to the tribological system of aluminium drawing dies in strip drawing in order to demonstrate the better performance potential of diamond-metal laminates compared to pure diamond.