Thermal analyzes of the starting powders and NbC-Ni cermet with addition of TiC and W.

Reference	Presenter	Authors (Institution)	Abstract
09-068	Daniel Ayarroio Seixas	Seixas, D.A.(Universidade Federal do ABC); Yoshimura, H.N.(Universidade Federal do ABC); Santos, S.F.(Universidade Federal do ABC); Rodrigues, D.(BRATS Sintered Filters and Metallic Powders);	Cermets are applied as cutting, drilling and forming tools and NbC-Ni has potential to be used for these applications. Studying the liquid phase sintering is fundamental to understand the behavior of the additives and to determine the starting temperature of this process. In this work, the sintering temperature and shrinkage of the following compositions, in wt%, were evaluated: NbC-40Ni; NbC-12Ni-4W-4TiC; NbC-20Ni-4W-4TiC; NbC-40Ni-4W-4TiC. For the production of samples for dilatometer, the press with load cell was used to apply the pressure (48 MPa) in a matrix of 20 mm in length and 4 mm in width, being fixed the mass of powder added in 2 g. Three sintering temperatures, 1420, 1360, 1300 °C with heating rate of 15 °C/min and 30 min of holding time were studied. Differential scanning calorimetry (DSC) and termogravimetry (TG) measurements were performed on both, the initial powders and the mixtures at 1500 °C with 15 °C/min heating rate. The dilatometric analysis showed a similar shrinkage at temperatures of 1420 and 1360 °C, equal to 21%, and at 1300 °C the maximum was 10%. Furthermore, the addition of additives (W and TiC) and decreasing the Ni content retarded the cermet retraction. For the DSC/TG analyzes, the eutectic temperature of 1330 °C was obtained and that the additives are responsible for raising this temperature. Finally, the main factors responsible for mass loss were TiC and Ni evaporation, so samples with higher binder content presented about 3% of mass loss. Thus, the temperature of 1360 °C may indicate the best option for the production of these cermets.
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