Cold spray deposition of mechanically alloyed ternary Cu–CNT–SiC composite powders

Ternary copper (Cu)–carbon nanotube (CNT)–silicon carbide (SiC) composite powders were prepared by mechanical alloying (MA). These MA composite powders were spray deposited as coatings on Cu plate substrates by cold gas dynamic spraying (CGDS). Characterizations of the MA powders and CGDS coatings were conducted by size and weight measurements, optical microscopy, scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The coating surfaces were also examined by mercury porosimetry and stylus profilometry. The results showed that the addition of SiC in the Cu–5CNT powder mixture led to particle size reduction after MA. The deposition efficiency of the Cu–CNT–SiC composite powders as CGDS feedstock increased when the SiC content was increased from 10 vol% to 20 vol%. The dispersion of SiC in the composite powder particles and coatings was not homogeneous as revealed by the EDX elemental mappings. As examined by XRD, the SiC as well as the CNT and the Cu had undergone microstructural changes (e.g., microstraining, grain refinement, and partial amorphization) due to the deformation caused by MA and CGDS. The addition of SiC, combined with the strain hardening due to MA and CGDS, resulted in coatings with significantly higher hardness than the coatings without SiC. Using CGDS, the MA Cu–CNT–SiC composite powders produced coatings with microporous surfaces and dense internal microstructures as evidenced by the SEM, profilometry, and porosimetry results. Lastly, the surface pores of the Cu–CNT–SiC coatings were finer than those of the pure Cu and Cu–5CNT coatings.