作者: Wolfgang Tillmann, Miriam Gathen, Christian Kronholz
摘要: Due to their better mechanical and physical properties diamond tools have largely
replaced cemented carbide tools for machining of mineral materials like concrete and rocks. The
decomposition tendency of diamond has to be taken into consideration during the manufacturing
process as well as during their employment in machining tools. By using water cooling the diamond
decomposition is reduced, but the contamination of occupied buildings by concrete/rock-watermixture
and the need of water supply units on building sites are unfavourable. However, absence of
water cooling lead to an increased tribological and thermal wear of conventional diamond tools.
Due to the heat development the diamonds in direct contact with mineral materials as well as the
diamonds in deeper layers are deteriorated.
The Institute of Materials Engineering pursues a novel thermal protection shield concept, in which
thermal insulating materials such as Al2O3, ZrO2 or glass in diamond impregnated composite
structures act as heat shield, which protects diamonds in deeper layers against high temperature and
graphitisation. Before the effectiveness of this concept could be investigated suitable composites
have to be manufactured. In this paper the powder metallurgical production processes of diamondalumina-
cobalt-composites with varying alumina and cobalt particle sizes, their microstructures and
porosities are described. In comparison to composites with larger alumina particle sizes it could be
observed that the distribution of alumina particles with particle sizes below 70 ,m in the cobalt
matrix is uniform and the porosity of the composite decrease.
1145
作者: Luciano José de Oliveira, Marcello Filgueira
摘要: This work deals with the use of Fe-Cu alloys for use as matrix for diamonds in cutting
tools. In this case it was processed diamond beads for diamond wires - used in the
slabbing of dimension stones. Normally, diamond beads are PM processed. The beads of the
present work were manufactured using Fe-Cu alloy with addition of 1wt% of SiC as the
matrix metallic bond. It was carried out shrinkage/swelling and microstructural analyses,
Brinell hardness measurements, as well as the abrasion resistance of beads produced here
in confront with commercial ones. The results indicate that it was processed beads with
similar abrasion resistance and performance than those of the commercial diamond beads.
241
作者: Guerold Sergueevitch Bobrovinitchii, Marcello Filgueira, Sérgio Neves Monteiro, Rômulo Crespo Tardim
摘要: Powder metallurgy-based technologies of saw blades production for stone cutting normally uses cobalt as binder agent. Cobalt was chosen for that purpose because it provides improved properties, high wettability and good adhesion between dispersed diamond particles. In addition to its excellent physical properties, cobalt also shows a positive behavior associated with the control of diamond graphitization at temperatures up to 1000°C. In this work, an experimental planning method supported by a mathematical algorithm was used to study the influence of doping agents incorporated into cobalt-based binders. The consequences on the wear resistance of saw blades, as well as on other physical and mechanical properties of the “diamond-cobalt-doping agent” composites were investigated. Cr3C2, Si, Ni and Fe were used as doping agents. Experimental tests were carried out using granite as a base material for wear and cutting operations.
182
作者: P.P. Sharin, M.P. Akimova, S.P. Yakovleva
摘要: Preliminary metallization of the diamond component, which promotes the formation of chemical bonds on the diamond-matrix contact during subsequent sintering, is used to increase the strength of diamond retention and the durability of diamond-containing metal matrix composites. There are restrictions on carrying out metallization to create diamond composites with a cemented carbide matrix, since reheating the metallized coating at high sintering temperatures of carbide powders leads to its destruction, diamond graphitization and deterioration of the material properties. The structural-phase state in the diamond-matrix contact zone has been studied and the main factors providing the strength of diamond retention in diamond-cemented carbide composites obtained by hybrid technology that excludes the reheating of the metallized coating have been revealed. It was revealed, that the developed hybrid technology combining the thermal diffusion metallization of diamond and sintering according to the self-dosed impregnation scheme in one cycle ensures the production and preservation of the metallized coating by the methods of scanning electron microscopy, X-ray diffraction and X-ray phase analysis, Raman spectroscopy. Comparative tests have been carried out and it is shown that the specific productivity of experimental samples of a diamond tool (ruling pencils) with a metallized diamond component is on 39% higher than same parameter of pencils without metallization.
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