Synthesis of W-Ni composite powders from ammonium paratungstate, sintering and characterization
powder metallurgy, composite powders, tungsten -nickel, sintering, hardness
In this work, we studied the production of W-Ni powders, through high energy grinding at different grinding times (2h, 5h and 10h), followed by the reduction with hydrogen gas (H2) at a temperature of 850 ° C and with reaction time of 60 minutes, the ammonium index (APT) mixed with nickel, in the proportion of 20% p.Ni, after sintering of the post-reduced afterwards. The powders were characterized by X-ray diffraction and scanning electron microscopy - SEM. The effects of different grinding times (2h, 5h and 10h), compaction load (500 MPa and 600 MPa) and sintering temperature (1450 °C and 1550 °C) without behavior of the reduced W-Ni mixtures were investigated. The parts were sintered with heating rate of 10 °C/min. Dilatometric profiles were taxed and estimated by clothing densities by the Archimedes method. The influence of grinding times on the evolution and duration of the microstructure was also analyzed. Tungsten nickel metal particles were also selected under the same conditions for comparison purposes. From the obtained results, it was concluded that: the SEM recorded images of W-Ni mixtures revealed by The Post Morphology with measures of varied sizes, very agglomerated, as well as a good dispersion and homogenization of phases. An analysis of the X-ray diffractogram showed as phases W and Ni4W, and the reduction of the ammonium parameter was confirmed. The compacted dimensions with pressure of 500 MPa and the sintering temperature of 1450 °C presented higher density; and a 10h grinding allowed the hardening with greater microstructural homogeneity, presenting longer duration value (400.9 HV).