The Influence of Aluminum Alloying on the Structure and Properties of TiC–Graphite–Al SHS Composites

The study investigates the possibility of using self-propagating high-temperature synthesis (SHS) in open air to produce porous titanium carbide skeletons containing free graphite, designed for spontaneous infiltration with Al–5% Cu and Al–5% Si melts prepared in a furnace at 900°C. Hybrid composites TiC–C(graphite)–(Al–5% Cu) and TiC–C(graphite)–(Al–5% Si) were obtained with relatively homogeneous structures and average densities of 3.06 and 2.94 g/cm3. The microstructure, phase composition, physical–mechanical and tribological characteristics were studied using scanning electron microscopy (SEM) with energy-dispersive spectrometry (EDS), X-ray diffraction (XRD), hydrostatic density measurement, compressive strength tests, and pin-on-disk tribometry. Secondary phases in the composites include Al4C3, Al2O3, and TiAl3. Reduced interfacial chemical activity was observed in TiC–C(graphite)–(Al–5% Cu). Tribological tests revealed enhanced wear resistance with predominantly abrasive wear mechanisms. Compared to pure Al, TiC–C composites infiltrated with Al–5% Si and Al–5% Cu exhibited significantly better tribological performance: the addition of 5% Si and 5% Cu reduced the friction coefficient by 17 and 34%, counter body wear by 21 and 71%, and composite wear by 1.8 and 3.5 times, respectively. The best tribological results were achieved for TiC–C–(Al–5% Cu). The conventional yield strength was: Al–5% Si (92.8 ± 13.1 MPa), Al–5% Cu (128.7 ± 17.2 MPa), TiC–C–(Al–5% Si) (191.0 ± 29.7 MPa), TiC–C–(Al–5% Cu) (208.3 ± 58.1 MPa). Thus, the addition of a TiC–C skeleton increased the yield strength of Al alloys by 1.6–2 times.