Ternary Cu–CNT–AlN composite coatings consolidated by cold spray deposition of mechanically alloyed powders

Abstract

Ternary copper (Cu)–carbon nanotube (CNT)–aluminum nitride (AlN) composite coatings were consolidated by the cold gas dynamic spray (CGDS) deposition of mechanically alloyed (MA) powders. The MA powder and CGDS coating samples were characterized by weight and size measurements, optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The porosity and roughness of the coatings were examined by porosimetry and profilometry, respectively. Also, the wettability of the coatings in saturated liquid R134a refrigerant was investigated. The EDX analysis depicted the non-homogeneous dispersion of the AlN as well as the CNT. The XRD results revealed that the composite powders and coatings had undergone microstraining and grain size reduction due to deformation. Metallographic examination showed that the coating internal microstructures had lamellar and compacted features, which evidenced the severe deformation that resulted from the impact during particle deposition. Although the coatings had externally porous surfaces, they had dense and non-porous internal microstructures. Moreover, smaller pores were located inside the larger pores or craters on the surfaces. The addition of 10 vol.% and 20 vol.% AlN into the Cu–5CNT mixture produced ternary Cu–CNT–AlN composite coatings with fine pores that were directly open to the surfaces. Lastly, the coatings with AlN were more wettable in liquid R134a than the plain Cu plate and pure Cu and Cu–5CNT coatings.