Surface Characteristics of Plasma Treated and Titanium Nitride (TiN) Deposited Aluminum Alloy

Abstract

This investigation highlights the rationale of the magnetron sputtering technique to deposit titanium nitride (TiN) coatings on aluminum alloy 2024 (AA 2024). TiN deposition on aluminum was systematically optimized, with nitrogen flow rate (mL/min) as the varying parameter. The developed TiN coatings were compared with the atmospheric pressure plasma treated and raw (uncoated) AA 2024 aluminum substrate surface. The crystalline phase formations of TiN on the alloy surface were studied using X-ray diffractometer technique. The scanning electron microscopy imaging technique was used to study the morphology of the formed ceramic layer. Fine and pore-free grains of TiN on the alloy surface were obtained at 1.5 mL/min nitrogen flow rate (TiN layer thickness ∼ 630\xa0nm). X-ray photoelectron spectroscopy analysis was conducted on the surface in order to characterize elemental composition of the surface. Surface characteristic and wettability studies on the developed coatings were conducted using atomic force microscopy (AFM) and by measurement of contact angle, respectively. The roughness parameter (Ra) (obtained from AFM) increased by ∼72 % with TiN deposition on the AA 2024, while the contact angle value decreased by ∼18 %. The adhesion of the coating to the metal substrate (using scratch test) and the Vickers hardness measurements were also performed. Corrosion resistance imparted by the coatings was also confirmed from the electrochemical measurements. A significant positive shift in the corrosion potential (Ecorr) value from −0.96 V to −0.75 V was observed from the analysis.