Electrodeposition Of Nickel Super Alloy From Deep Eutectic Solvent

Abstract

Nickel based super alloys are deployed for niche engineering applications due to their superior mechanical properties and are generally prepared by energy intensive and complicated routes. Herein, we report a simple, near ambient-temperature and scalable electrodeposition strategy for obtaining nickel super alloy coatings using choline chloride and urea (1:2) deep eutectic solvent. Cyclic voltammetry indicates that electrodeposition of nickel-tantalum alloy proceeds via single step, irreversible charge transfer process. Electrodeposition of Ni-Ta coatings was performed at potentiostatic (-0.3 & -0.5 V) and galvanostatic (-0.1 & -0.3 A/dm2) conditions from electrolytes containing different Ni/Ta molar ratios ranging from 1:1 to 5:1. The study reveals that electrolyte composition and elemental composition of the Ni-Ta coating does not follow a monotonic trend. Scanning electron microscopy clearly indicates that constant current electrodeposition yields smoother and uniform coatings. Elemental mapping of the samples revealed uniform distribution of nickel and tantalum all over the copper substrate. In situ high temperature X-ray studies concluded that the coatings are stable up to 300 °C. Vickers microhardness values were in the range of 120 – 180 VHN and the higher values were observed in the coatings obtained from Bath D (Ni/Ta: 4:1) which increases to 270 VHN upon annealing at 1000 °C for 1 h in inert atmosphere. At a potential of -0.5 V, nickel tantalum super alloy with the composition, 88 at% Ni and 12 at% Ta, was achieved from Bath C (Ni/Ta: 3:1).