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With regards to cold spraying, wear resistant metal coatings reinforced with boron nitride nanotubes (BNNTs) have remained unexplored when compared to carbon nanotube-based composites. Using commercially pure aluminum powder, 1-3 μm B4C powder, and BNNTs, multiple reinforced metal matrix composite powders were fabricated via high energy ball milling (HEBM). The powder compositions included an Al control, a 4 vol.% B4C composition, a 4 vol.% BNNT composition, and a 2 vol.% B4C with 2 vol.% BNNT composition. The compositions were sprayed onto AZ31 substrates using helium. The coatings were evaluated using nanoindentation, micro-indentation hardness, adhesion, and tensile tests. The coatings were then qualitatively evaluated under an optical microscope and scanning electron microscopes. Good dispersion of the ceramic reinforcements throughout the Al matrix was achieved via HEBM. A 14.1% increase and a 20.8% increase in micro-indentation hardness over the control were achieved for the Al/BNNT and the Al/B4C/BNNT compositions, respectively. Adhesion testing led to the Al/B4C/BNNT composition failing cohesively and the control failing adhesively at approximately the same force. The Al/B4C adhesion tests experienced a combination of the two failure modes at a 31.2% increase in force over the control. Stress vs. strain curves from tensile testing demonstrated that the load is partially supported by the cold spray coating until the coating ruptures. Office of Naval Research (ONR) Outstanding Thesis Lieutenant, United States Navy Approved for public release. Distribution is unlimited. |
