The improved tribo-mechanical performance of MWCNT–hBN hybrid reinforced Al nanocomposites

Aluminium and its alloys are widely used in the aerospace, automotive, and electronic industries due to their low density and good corrosion resistance, but their limited strength and wear resistance restrict performance under severe loading. We have introduced a binary hybrid reinforcement of multi-walled carbon nanotubes (MWCNTs) and hexagonal boron nitride (hBN) into a pure Al matrix by ultrasonic-assisted dispersion which was consolidated using spark plasma sintering (SPS) to exploit their combined effects. MWCNTs formed a high-strength 1D framework and provided a better load transfer, while hBN provided solid lubrication through tribofilm formation. XRD confirmed the absence of harmful interfacial phases in the Al-M50B50 nanocomposite. HRTEM showed that conventionally sintered Al–1% M50B50 contained dislocation pile-ups and Al2O3 pinning particles, whereas SPS Al–3% M50B50 had uniformly dispersed reinforcements, strong interfacial bonding, and occasional Al4C3 nanocrystals, demonstrating the superior densification of SPS. Consistent with these observations, conventional sintering achieved its best properties at 1% M50B50, yielding ~92.02% relative density, ~479.31 MPa hardness, ~761.68 MPa compressive strength, and improved wear resistance compared to pure Al (~88.14% density, ~322 MPa hardness, ~422.60 MPa strength). However, higher nanofiller contents led to agglomeration and reduced performance. SPS enabled better densification and uniform filler distribution, with the Al–3% M50B50 nanocomposite attaining ~93.46% density, ~638.63 MPa hardness, ~1049.50 MPa strength, and ~26% lower wear rate than pure Al. Overall, the dual reinforcement strategy combined with SPS processing overcomes the strength–wear trade-off, offering better microstructural stability, mechanical robustness, and tribological efficiency.