Effect of CNT content on microstructure and tribological properties of CNTs/AlSi10Mg composites by LPBF

In this study, carbon nanotubes (CNTs)/AlSi10Mg composite parts with CNTs contents ranging from 0.0 to 2.0wt.% were successfully fabricated via laser powder bed fusion (LPBF) with laser scan speeds ranging from 900 to 1,900 mm·s−1. Uniform dispersion of CNTs in the powders can be achieved when their content is below 2.0wt.%. In the LPBF samples, the morphology of the CNTs is found to be directly related to their content. Especially, the length of CNTs in samples prepared by LPBF increases as the CNT content increases. The length of CNTs is approximately 200–300 nm in the 1.0wt.% CNTs/AlSi10Mg composites and approximately 500–1,000 nm in the 2.0wt.% CNTs/AlSi10Mg composites. The hardness of the composites reaches its highest value of 143.3 HV when the CNTs content is 1.0wt.% and the laser scan speed is 1,300 mm·s−1. It is found that the self-lubricating properties of the CNTs improve the tribological properties of the composites. The coefficient of friction (CoF) and wear rate of the samples decrease with increasing CNT content. At a CNTs content of 2.0wt.%, the CoF and wear rate of the composite decrease by approximately 14% and 30%, respectively, compared to the unreinforced matrix. The presence of CNTs leads to a more complete and refined network microstructure within the samples. Both the CNTs and the aluminum carbide contribute to the Orowan mechanism and the Hall-Petch effect within the matrix.