Microstructure and Mechanical Characterization of Novel Al 2 O 3 -(NiAl-Al 2 O 3 ) Composites Fabricated via Pulse Plasma Sintering.

The scientific goal of this paper is to study and explain the relationship between the microstructure of a ceramic-intermetallic composite fabricated by consolidating a mixture of Al 2 O 3 and NiAl-Al 2 O 3 using the PPS technique and its basic mechanical properties. Six series of composites were manufactured. The obtained samples differed in the sintering temperature and content of compo-powder. The base powders, compo-powder, and composites were investigated using SEM equipped with an EDS and XRD. Hardness tests and K IC measurements were applied to estimate the mechanical properties of the fabricated composites. The wear resistance was evaluated using a "ball-on-disc" method. The results demonstrate that the density of the obtained composites increases with the increased temperature of the sintering. The content of NiAl + 20 wt.% Al 2 O 3 did not have a determining effect on the hardness of the manufactured composites. The highest hardness, contacting 20.9 ± 0.8 GPa, was found for the composite series sintered at 1300 °C and 2.5 vol.% of compo-powder. The highest K IC value from all the studied series equaled 8.13 ± 0.55 MPa·m 0.5 and was also achieved for the series manufactured at 1300 °C (2.5 vol.% of compo-powder). The average friction coefficient during the ball-friction test with the Si 3 N 4 ceramic counter-sample was between 0.8 and 0.95.