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Strehler C.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Blugan G.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Ehrle B.,OERTLI Werkzeuge AG | Speisser B.,Ceratizit Luxembourg S. a r.l. | And 2 more authors.
Journal of the European Ceramic Society | Year: 2010

Si3N4/SiC cutting tools were fabricated by industrial near net shape fabrication processes. The samples were consolidated by gas-pressure sintering and pressure less sintering using three different additive systems. The mechanical and microstructural properties were compared to composites made by hot pressing. The composites fabricated by gas-pressure sintering showed 99% density, the Vickers hardness was 17.2GPa and the fracture toughness reached 4.5MPa√m. Machining trials on wood showed that a post-sintering treatment by hot isostatic pressing increases the integrity of the cutting tip due to a devitrification of the intergranular phase. © 2010 Elsevier Ltd. Source


Strehler C.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Strehler C.,TU Bergakademie Freiberg | Parlinska-Wojtan M.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Blugan G.,Empa - Swiss Federal Laboratories for Materials Science and Technology | And 6 more authors.
Journal of the European Ceramic Society | Year: 2011

Si3N4/SiC composites used for industrial wood cutting were processed by a near net shape route involving gas pressure sintering with sintering additives such as Al2O3, La2O3, Y2O3 and MgO. The cutting edge integrity of these knives was tested in a cutting trial and compared to knives made by a hot pressing route. It was found that the intergranular phase has a crucial influence on the cutting edge integrity. The boundary phase was analysed by EFTEM and EDX mapping on TEM samples: in gas pressure sintered composites the crystallisation of the apatite Y5Si3O12N phase was identified. In the hot pressed composite the boundary phase consisted only of silicates. These composites showed better edge stability than cutting tools with a Y-N-apatite phase. The formation of the type of intergranular phase was found to be determined by the amount of MgO sintering aid and the temperature of the post sintering heat treatment. © 2011 Elsevier Ltd. Source


Strehler C.,Empa - Swiss Federal Laboratories for Materials Science and Technology | Ehrle B.,TU Bergakademie Freiberg | Weinreich A.,TU Bergakademie Freiberg | Kaiser B.,TU Bergakademie Freiberg | And 4 more authors.
International Journal of Applied Ceramic Technology | Year: 2012

The introduction of ceramics into the market of wood cutting tools has been difficult because of the generally low toughness of ceramics which causes brittle failure. That is why the improvement of mechanical performance of ceramics with potential to be used as cutting tools is important. The newly developed Si 3N 4/SiC wood cutting tools have a bending strength of 740 MPa, a fracture toughness of 5.4 MPam 1/2, a hardness of 16.8 GPa and a grain size of 1 μm. These Si 3N 4/SiC tools were tested in a lifetime cutting trial on wood and showed twice as long lifecycles than standard tungsten carbide tools. Furthermore, the static corrosion resistance in tannic acid, the friction coefficients between wood and the tool material and the cutting forces were measured for both the ceramic composite and the tungsten carbide tools. © 2011 The American Ceramic Society. Source

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