Electrodeposition of nanodiamond particles on aluminium alloy A319 for improved tribological properties

Nanodiamond (ND) particles (4-8-nm) have been deposited by an electrophoretic method on aluminium alloy A319 to obtain thick (20-60-m), strongly adherent coatings. The electrophoresis deposition process was carried out by dispersing ND powders in an electrolytic solution of nickel sulphate/nickel chloride solution to obtain Ni-ND composite coating and also in isopropanol to obtain Ni-free ND coating. Raman spectroscopy and scanning electron microscopy in conjunction with energy dispersive analysis were used to identify carbon phases, chemical composition, and surface texture/topography of the coatings. Nanoindentation, friction and wear tests were conducted to determine the mechanical and tribological properties. Results indicate the formation of agglomerates, soft and hard phases (200-3400-MPa) and fine network of cracks in the as-deposited Ni-ND composite coatings. In addition, the Raman peak corresponding to diamond was noted in Ni-ND composite coatings. However, there was no evidence of diamond phases in electrophoresis using isopropanol. Ni-ND coatings exhibited rougher surfaces (2.7-m, Ra value) than the aluminium substrate (1.4 m). Tests conducted with ball-on-flat microtribometer revealed an improvement of sliding wear resistance. Thus, thick tribological ND coatings obtained in this study are promising to enhance the performance of aluminium alloy A319 used for lightweight engine components.