Microstructure examination of sintered diamond-metalmatrix tool for stone-work
Zygmunt Nitkiewicz, Maciej Świerzy Politechnika Częstochowska, Instytut Inżynierii Materiałowej, al. Armii Krajowej 19, 42-200 Częstochowa
Annals 2 No. 4, 2002 pages 233-237
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abstract The work contains results of microstructure investigation of commercially available sintered diamond-metal matrix segments being in use for stone cutting (granite). Introduction presents mode of preparation, composition, work mode of a circular sawblade as well as an abrasive wheel in particular with sintered segment (working part). 11 different materials have been examined. EDX elements analyze (Tab. 1), X-ray diffraction (Cu tube) phase composition (Figs 1 and 2 - examples of diffractograms), Rockwell hardness (Tab. 3), Vickers microhardness (Tab. 4) of certain phases have been conducted. Microphotographs of different magnification of the examined specimens have been attached (Figs 3-11). Diamond-metal sintered compacts’ matrices have usually multiphase structure, as it has been shown in the diffractograms as well as in the microphotographs. Even if the only element of the matrix is Co, it occurs in 2 allotropic forms - cubic and hexagonal. Due to their different crystalline structure and often different element composition, the phases differ in mechanical properties. It can be drawn as a conclusion that such structure properly determines work properties of the tools. During hot pressing of Co powder with addition of Sn (liquid during process) a hard intermetallic phase Co3Sn2 forms. The bond contains not only phases formed in such way but also certain hard compounds added to metal powders mix before sintering e.g. tungsten carbide WC or titanium oxide TiO. The hardness of the metal matrices of the diamond tools for granite machining comprise in a wide range from 125 to 327 HV (counted from 69 HRB to 33 HRC).