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Modified Sinter Unit (MSU) for 125 of metal and ceramic powder compacts

  • : Roland Scholl1, Tim Slawik2, Tassilo Moritz3, Alexander Michaelis4
  • : 1Technische Universität Dresden, 2Fraunhofer IKTS Dresden, 3Fraunhofer IKTS Dresdens, 4Fraunhofer IKTS
  • : PDF Download
  • : 2014

Abstract

Powder technological manufacturing of sintered ceramic and metallic bodies is mostly accompanied by significant shrinkage in all direction in space. This yields to a bad contour accuracy or tolerance as well and causes high costs of finishing. Main reasons for failure are friction and chemical alterations between support and body. Established remedies are friction reducing coatings and inert ceramic powders, scattered on the support. These passive methods can only insufficiently remove problems. A method to prevent failure is given by a newly developed modified sintering unit (MSU), manufactured by paper technology and placed in between the body and the common sintering support. The MSU is constructed by a three-layered composite material, consisting of a mean (thicker) layer, preferably composed of same material as the body, a chemically stable and inert (thin) top layer and further a (thin) bottom layer to prevent rea¬ctions with the main sintering support. During sintering the sinter active mean layer leads to permanent tension on base of the body that reduces friction. Commonly green density of mean layer is slightly lower compared with density of body to be sintered. Results will be presented at least for two cases of sintering with high shrinkage level (15-18 % linear): (i) a cobalt alloy which conventionally sintered shows such called elephant-footing and (ii) a cobalt based tungsten carbide hard metal that sensitively reacts in the base area with lubrication additives. If issues of interaction are ignored in first case high costs of finishing can be expected, in the second one as well by changes in microstructure resp. hardness in lower edge zone.
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