Influence of formulation on structure, strength and compactibility of hardmetal press bulk

The processing of fine grained raw material enables the achievement of higher properties levels in hardness, homogeneity and functionality. Supposition for the transfer of the high potentials of the pure material via different processing steps (especially dry pressing) into the sintered end product is the optimization of the processing route in combination with the formulation. Hardmetal mixtures are processed by milling and spray drying of suspensions based on solvents (acetone, ethanol, heptane) or water. Depending on the formulation of the mixture (addition of dispersant, binder, lubricant) the properties of the press bulk can be tailored in a wide range. Besides flowability (bulk density, flow time, size distribution), characterizing properties are internal structure, distribution of granule strength and compaction behaviour of the press bulk. The paper describes the measuring techniques (ion beam preparation of granules, granule strength testing, instrumented pressing tool) and the interaction between the formulation (variation of chemical auxiliaries) and the properties of different processed material. Optimization criteria are discussed. The results can be transferred in principle from hardmetal to other fine grained metal/ceramic mixtures.