A comparison of mechanical and wear properties of plasma sprayed carbon nanotube reinforced aluminum composites at nano and macro scale

Abstract

The macro- and nano-scale mechanical and wear properties of carbon nanotube (CNT) reinforced Al–Si composite coatings prepared by plasma spraying have been compared in this paper. The composite coatings show a two phase microstructure; one phase being the Al–Si matrix with well dispersed CNTs and the other being the CNT clusters. Nanoindentation testing on the matrix portion with dispersed CNTs indicated an increase in the elastic modulus by 19% and 39% and an increase in the yield strength by 17.5% and 27% by the addition of 5wt.% and 10wt.% CNTs respectively. Macro-scale compression tests indicated no improvement in the elastic modulus but an increases in the compressive yield strength by 27% and 77% respectively, by addition of 5wt.% and 10wt.% CNTs. Nanoscratch testing carried out on the Al–Si matrix with dispersed CNTs indicated a decrease in scratch volume by 34% and 71% by addition of 5wt.% and 10wt.% CNTs respectively. Macro-scale wear tests indicated a decrease in the wear volume by 68% in case of 5wt.% CNT coatings but an increase in the wear volume by 15% for the 10wt.% CNT coating. The differences in mechanical and wear properties at nano and macro scales are explained in terms of the bimodal CNT dispersion (well dispersed and clusters) in Al–Si matrix, CNT cluster size and fraction and carbide formation.