Effect of upgraded field assisted sintering technology on microstructure of NiAl/CrB2 composites
Maciej Szlezynger, Łukasz Maj, Małgorzata Pomorska, Jerzy Morgiel, Katarzyna Jach, Marcin Rosinski
Quarterly No. 1, 2020 pages 7-10
DOI:
keywords: metal matrix composites, SPS, microstructure, electron microscopy
abstract The method of fabricating metal matrix composites plays a crucial role in obtaining dense materials characterized by high wear resistance. The present work describes an attempt to produce NiAl/CrB2 composites using the next-generation spark plasma sintering (SPS) method, i.e. upgraded field assisted sintering technology (U-FAST) technique. Microstructure characterization was performed by means of scanning (SEM) and transmission (TEM) electron microscopy. The SEM microstructure investigations of the NiAl model material proved practically full densification of the material sintered at 1200°C and 1300°C, even if remnants of surplus nickel were observed at the boundaries of rounded NiAl grains. The NiAl/CrB2 composites, besides fused NiAl and CrB2 grains, showed the presence of a raised level of nickel also at the grain boundaries. The TEM microstructure observations helped to establish that even if the grain boundaries were pinned by nickel-rich precipitates, some increase in grain growth took place, as evidenced by the fact that strings of smaller precipitates were also visible outside the matrix grain boundaries. All these microstructure investigations indicate that the newly elaborated U-FAST technique is evidently capable of producing compacts free of porosity at lower temperatures and during a shorter time than solid hot pressing or vacuum sintering in a semi-liquid state.