Microstructure and Mechanical Characterization of Novel Al₂O₃-(NiAl-Al₂O₃) 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 Al2O3 and NiAl-Al2O3 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.% Al2O3 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 degrees 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 degrees C (2.5 vol.% of compo-powder). The average friction coefficient during the ball-friction test with the Si3N4 ceramic counter-sample was between 0.8 and 0.95.