Investigation of the mechanisms during sintering process modifications of multi-component sputter materials and the phase specific deposition of AlCrSi(W,Ta)N

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This research project investigates interactions of sintering processes for multi-component target materials, which are subsequently used for the formation of nanocomposite structures. The AlCrSiN system, consisting of nanocrystalline grains (nc (Al,Cr)N), embedded in an amorphous matrix (a-Si3N4), is the basis for this structure. It is the aim of this project to understand the mechanisms that lead to an increase of the hardness as well as the wear and oxidation resistance by doting the coating system with tungsten and tantalum. Fundamental analyses of sintering processes for the CrSi(W, Ta) system are used to synthesize target segments with a low porosity, which are embedded in a monolithic aluminum body.Sintering parameters such as the temperature, pressure, sintering time and the stoichiometry that support diffusion and compaction, are modified while hot pressing CrSi(W, Ta). So far, the resulting diffusion and phase formation mechanisms have not been explored. Finely dispersed nanopowders are used for the refractory metals W and Ta to accelerate the diffusion velocity. Powder particle agglomerations are avoided by powder coatings, applied by means of Arc-PVD to achieve a homogenous distribution of particles in the sintered segments. Based on a simulation-assisted selection of the basic materials, sintering with solid/liquid phases is realized to foster a balanced formation of intermetallic phases in order to identify porosity-minimizing mechanisms caused by process modifications. The nanostructures of reactively deposited AlCrSi(W, Ta)N layers are correlated with the intermetallic phases in the target material by stoichiometric variations in the CrSi(W, Ta) segments as well as the number of segments in the Al target. The variations of Si, W, and Ta contents are of particular interest when investigating AlCrSi(W, Ta)N films as they enable both grain-refining as well as solid solution hardening mechanisms, thus positively influencing the hardness, wear, and oxidation resistance.The overall objective of this research project is to holistically combine the results of the analyses of the interactions between the chemical compositions and phase compositions of new target materials with the resulting tribo-mechanic coating properties of nanocomposite structures. Especially, the influence of the W and Ta contents on the oxidation behavior is closely scrutinized. Finally, the examined AlCrSi(W, Ta)N coating systems will be applied on cutting tools to analyze the influence of the doping elements and to verify these influences under real production conditions.